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Game Physics

Where realistic physics, and game simplifications, are noted.

Thermodynamics Simplified

One big problem with being in outer space is that temperature extremes in both directions are very common; heavy equipment can heat an area to incredibly high temperatures, while the vacuum of space can reduce temperatures of exposed environments to less than a Kelvin. Here is a quick primer on thermodynamics, in the simplified version used in game.

1. Heat travels from hot objects to cool objects. For example, a warm body subjected to cold space will become cold very quickly, and heated air will melt an ice cube.

2. Energized machines generate waste heat as a byproduct. If the machine is hotter than the air, some of this heat travels from the hot object to the cooler air, cooling the machine and warming the air.

3. Thermogenerators use temperature differentials to convert a percentage of heat directly into electrical energy - the greater the temperature differential, the more power can be generated in this fashion.

4. Radioisotope thermogenerators use the heat generated by radioactive decay to generate power, and are used in isolated batteries that need to last for a very long time without maintenance. Their power generation rate decreases at a predictable rate as the material decays.

5. Heat can be transferred through conduction - direct flow from object to object or from object to surroundings (or surroundings to object); through convection - flow of a fluid (gas or liquid) carrying heat, either naturally due to density changes from temperature, or artificially due to mechanical pumps and other means; or through radiation, the energy emitted by matter as electromagnetic waves from any object with a temperature above absolute zero.

6. Thermal insulators can be reflectors - reflecting radiation and therefore reducing the flow of heat from radiation sources; or insulators, materials specifically designed to inhibit the flow of heat by reducing the rate of heat transfer.

7. Clothing, plating, and walls all act as insulators to delay the transfer of heat from hotter places to cooler places.

Atmospheric Representations

The atmosphere of an environment controls a number of factors – how heat transfers from objects to other objects, whether people can breathe, etc.

1 clo = Maintain temperature comfortably in 'room temperature' with standard ventilation and 50% humidity.

Complex science stuff you don't need to know:

The effectiveness of an insulator is indicated by its R-value, or resistance value. The R-value of a material is the inverse of the conduction coefficient (k) multiplied by the thickness (d) of the insulator. In most of the world, R-values are measured in SI units: square-meter kelvins per watt (m²·K/W). In the United States, R-values are customarily given in units of British thermal units per hour per square-foot degrees Fahrenheit (Btu/h·ft²·°F).

Rigid fiberglass, a common insulation material, has an R-value of four per inch, while poured concrete, a poor insulator, has an R-value of 0.08 per inch.

The tog is a measure of thermal resistance of a unit area, also known as thermal insulance, commonly used in the textile industry, and often seen quoted on, for example, duvets and carpet underlay.

The Shirley Institute in Manchester, England developed the tog as an easy-to-follow alternative to the SI unit of m2K/W. The name comes from the informal word “togs” for clothing which itself was probably derived from the word toga, a Roman garment.

The basic unit of insulation coefficient is the RSI, (1 m² K / Watt). 1 tog = 0.1 RSI. There is also a clo clothing unit equivalent to 0.155 RSI or 1.55 tog.

A tog is 0.1 m2K/W. In other words, the thermal resistance in togs is equal to ten times the temperature difference (in °C)

between the two surfaces of a material, when the flow of heat is equal to one watt per square metre.

British duvets are sold in steps of 1.5 tog from 4.5 tog (summer) to 15 tog (extra-warm). The stated values are minima, actual

values may be up to 3 tog higher.

According to British retailer John Lewis, tog guidelines for duvets are as follows:[1] Lightweight summer duvet: 3.0 - 4.5 tog Spring/Autumn weight duvet: 7.0 - 10.5 tog Winter weight duvet: 12.0 - 13.5 tog

A few manufacturers have marketed combined duvet sets consisting of two duvets; one of approximately 4.5 tog and one of

approximately 9.0 tog. These can be used individually as summer (4.5 tog) and spring/autumn (9.0 tog). When joined together

using press studs around the edges, or Velcro strips across each of the corners, they become a 13.5 tog winter duvet and as such

can be made to suit all seasons.

During cold weather, layers of insulating clothing can help keep a person warm. At the same time, if the person is doing a large amount of physical activity, lots of clothing layers can prevent heat loss and possibly lead to overheating. Generally, the thicker the garment is the greater insulating abilities it has. Depending on the type of material the clothing is made out of, air movement and relative humidity can decrease the insulating ability of the material.

The amount of clothing is measured against a standard amount that is roughly equivalent to a typical business suit, shirt, and

undergarments. Activity level is compared to being seated quietly, such as in a classroom. This standard amount of insulation

required to keep a resting person warm in a windless room at 70 °F (21.1 °C) is equal to one clo. Clo units can be converted to

R-value in SI units (m²·K/W) or RSI) by multiplying clo by 0.155 (1 clo = 0.155 RSI). (In English units, 1 clo corresponds to an

R-value of 0.88 °F·ft²·h/Btu.) ASHRAE 55-2004 mentioned a Table B1 and Table B2 for more clothing information.

Factors determining thermal comfort include:

  • Personal factors (health, psychology, sociology & situational factors)
    • Insulative clothing (Clo Value)
    • Activity levels (Met Rate)
  • General Factors
    • Air temperature
    • Mean radiant temperature
    • Relative humidity (see also perspiration)
    • Drifts and ramps in operative temperature
  • Localized factors
    • Air movement/velocity (see wind chill factor)
    • Radiant asymmetry
    • Floor surface temperatures (see underfloor heating)
    • Air temperature stratification

The concept of thermal comfort is closely related to thermal stress. This attempts to predict the impact of solar radiation, air movement, and humidity for military personnel undergoing training exercises or athletes during competitive events. Values are expressed as the Wet Bulb Globe Temperature or Discomfort Index.[16] Generally, humans do not perform well under thermal stress.

People’s performances under thermal stress is about 11% lower than their performance at normal thermal conditions. Also, human performance in relation to thermal stress varies greatly by the type of task you are completing. Some of the physiological effects of thermal heat stress include increased blood flow to the skin, sweating, and increased ventilation.

The ideal standard for thermal comfort can be defined by the operative temperature. This is the average of the air dry-bulb temperature and of the mean radiant temperature at the given place in a room. In addition, there should be low air velocities and no 'drafts,' little variation in the radiant temperatures from different directions in the room, and humidity within a comfortable range.

The operative temperature intervals varied by the type of indoor location. They also vary by the time of year.[22] ASHRAE has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ration per square meter of 0.1. In the summer the suggested temperature is between 23.5 °C (74.3 °F) and 25.5 °C (77.9 °F), and airflow velocity of 0.18 m/s. In the winter, the recommended temperature is between 21.0 and 23.0 degrees Celsius with an airflow velocity of 0.15 m/s.

Heat exchangers

A heat exchanger is a tool built for efficient heat transfer from one fluid to another, whether the fluids are separated by a solid wall so that they never mix, or the fluids are in direct contact. Heat exchangers are widely used in refrigeration, air conditioning, space heating, power generation, and chemical processing. One common example of a heat exchanger is a car's radiator, in which the hot coolant fluid is cooled by the flow of air over the radiator's surface. Common types of heat exchanger flows include parallel flow, counter flow, and cross flow. In parallel flow, both fluids move in the same direction while transferring heat; in counter flow, the fluids move in opposite directions; and in cross flow, the fluids move at right angles to each other. Common constructions for heat exchanger include shell and tube, double pipe, extruded finned pipe, spiral fin pipe, u-tube, and stacked plate.

When engineers calculate the theoretical heat transfer in a heat exchanger, they must contend with the fact that the driving temperature difference between the two fluids varies with position. To account for this in simple systems, the log mean temperature difference (LMTD) is often used as an “average” temperature. In more complex systems, direct knowledge of the LMTD is not available, and the number of transfer units (NTU) method can be used instead.

Heat dissipation

A heat sink is a component that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems, and the radiator in a car (which is also a heat exchanger). Heat sinks also help to cool electronic and optoelectronic devices such as CPUs, higher-power lasers, and light-emitting diodes (LEDs). A heat sink uses its extended surfaces to increase the surface area in contact with the cooling fluid.


In cold climates, houses with their heating systems form dissipative systems, often resulting in a loss of energy (known colloquially as “Heat Bleed”) that makes home interiors uncomfortably cool or cold.

For the comfort of the inhabitants, the interiors must be maintained out of thermal equilibrium with the external surroundings. In effect, these domestic residences are islands of warmth in a sea of cold, and the thermal gradient between the inside and outside is often quite steep. This can lead to problems such as condensation and uncomfortable air currents, which—if left unaddressed—can cause cosmetic or structural damage to the property.

Such issues can be prevented through the execution of an energy audit, and the implementation of recommended corrective

procedures (such as the installation of adequate insulation, the air sealing of structural leaks, and the addition of

energy-efficient windows and doors.

Thermal transmittance is the rate of transfer of heat through a structure divided by the difference in temperature across the

structure. It is expressed in watts per square meter per kelvin, or W/m²K. Well-insulated parts of a building have a low thermal

transmittance, whereas poorly-insulated parts of a building have a high thermal transmittance.

A thermostat is a device capable of starting the heating system when the house's interior falls below a set temperature, and of

stopping that same system when another (higher) set temperature has been achieved. Thus, the thermostat controls the flow of

energy into the house, that energy eventually being dissipated to the exterior.

Thermal energy storage

Thermal energy storage refers to technologies that store energy in a thermal reservoir for later use. They can be employed to

balance energy demand between daytime and nighttime. The thermal reservoir may be maintained at a temperature above (hotter) or

below (colder) than that of the ambient environment. Applications include later use in space heating, domestic or process hot

water, or to generate electricity. Most practical active solar heating systems have storage for a few hours to a day's worth of

heat collected in insulated hot water tanks, but this can be extended to interseasonal thermal storage using underground thermal

energy storage.

Evaporative cooling

Evaporative cooling is a physical phenomenon in which evaporation of a liquid, typically into surrounding air, cools an object or a liquid in contact with it. Latent heat describes the amount of heat that is needed to evaporate the liquid; this heat comes from the liquid itself and the surrounding gas and surfaces. The greater the difference between the two temperatures, the greater the evaporative cooling effect. When the temperatures are the same, no net evaporation of water in air occurs; thus, there is no cooling effect. A simple example of natural evaporative cooling is perspiration, or sweat, which the body secretes in order to cool itself. An evaporative cooler is a device that cools air through the simple evaporation of water.

Radiative cooling

Radiative cooling is the process by which a body loses heat by radiation. It is an important effect in the Earth's atmosphere. In the case of the Earth-atmosphere system, it refers to the process by which long-wave (infrared) radiation is emitted to balance the absorption of short-wave (visible) energy from the Sun. Convective transport of heat and evaporative transport of latent heat both remove heat from the surface and redistribute it in the atmosphere, making it available for radiative transport at higher altitudes.

Laser cooling

Laser cooling refers to techniques in which atomic and molecular samples are cooled through the interaction with one or more laser light fields. The most common method of laser cooling is Doppler cooling. In Doppler cooling, the frequency of the laser light is tuned slightly below an electronic transition in the atom. Thus, the atoms would absorb more photons if they moved towards the light source, due to the Doppler effect. If an excited atom then emits a photon spontaneously, it will be accelerated. The result of the absorption and emission process is to reduce the speed of the atom. Eventually the mean velocity, and therefore the kinetic energy of the atoms, will be reduced. Since the temperature of an ensemble of atoms is a measure of the random internal kinetic energy, this is equivalent to cooling the atoms.

Sympathetic cooling is a process in which particles of one type cool particles of another type. Typically, atomic ions that can

be directly laser-cooled are used to cool nearby ions or atoms. This technique allows cooling of ions and atoms that cannot be

laser cooled directly.

Magnetic cooling

Magnetic evaporative cooling is a technique for lowering the temperature of a group of atoms. The process confines atoms using a

magnetic field. Over time, individual atoms will become much more energetic than the others due to random collisions, and will

escape—removing energy from the system and reducing the temperature of the remaining group. This process is similar to the

familiar process by which standing water becomes water vapor.

Heat transfer in the human body

The principles of heat transfer in engineering systems can be applied to the human body in order to determine how the body

transfers heat. Heat is produced in the body by the continuous metabolism of nutrients which provides energy for the systems of

the body. The human body must maintain a consistent internal temperature in order to maintain healthy bodily functions.

Therefore, excess heat must be dissipated from the body to keep it from overheating. When a person engages in elevated levels of

physical activity, the body requires additional fuel which increases the metabolic rate and the rate of heat production. The

body must then use additional methods to remove the additional heat produced in order to keep the internal temperature at a

healthy level.

Heat transfer by convection is driven by the movement of fluids over the surface of the body. This convective fluid can be

either a liquid or a gas. For heat transfer from the outer surface of the body, the convection mechanism is dependent on the

surface area of the body, the velocity of the air, and the temperature gradient between the surface of the skin and the ambient

air. The normal temperature of the body is approximately 37°C. Heat transfer occurs more readily when the temperature of the

surroundings is significantly less than the normal body temperature. This concept explains why a person feels “cold” when not

enough covering is worn when exposed to a cold environment. Clothing can be considered an insulator which provides thermal

resistance to heat flow over the covered portion of the body.[21] This thermal resistance causes the temperature on the surface

of the clothing to be less than the temperature on the surface of the skin. This smaller temperature gradient between the

surface temperature and the ambient temperature will cause a lower rate of heat transfer than if the skin were not covered.

In order to ensure that one portion of the body is not significantly hotter than another portion, heat must be distributed

evenly through the bodily tissues. Blood flowing through blood vessels acts as a convective fluid and helps to prevent any

buildup of excess heat inside the tissues of the body. This flow of blood through the vessels can be modeled as pipe flow in an

engineering system. The heat carried by the blood is determined by the temperature of the surrounding tissue, the diameter of

the blood vessel, the thickness of the fluid, velocity of the flow, and the heat transfer coefficient of the blood. The

velocity, blood vessel diameter, and the fluid thickness can all be related with the Reynolds Number, a dimensionless number

used in fluid mechanics to characterize the flow of fluids.

Latent heat loss, also known as evaporative heat loss, accounts for a large fraction of heat loss from the body. When the core

temperature of the body increases, the body triggers sweat glands in the skin to bring additional moisture to the surface of the

skin. The liquid is then transformed into vapor which removes heat from the surface of the body.[22] The rate of evaporation

heat loss is directly related to the vapor pressure at the skin surface and the amount of moisture present on the skin.[20]

Therefore, the maximum of heat transfer will occur when the skin is completely wet. The body continuously loses water by

evaporation but the most significant amount of heat loss occurs during periods of increased physical activity.

A heat pipe is a passive device constructed in such a way that it acts as though it has extremely high thermal conductivity.

Heat pipes use latent heat and capillary action to move heat, and can carry many times as much heat as a similar-sized copper

rod. Originally invented for use in satellites, they have applications in personal computers.

A thermocouple is a junction between two different metals that produces a voltage related to a temperature difference.

Thermocouples are a widely used type of temperature sensor for measurement and control, and can also be used to convert heat

into electric power.

A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of thermocouples.

Thermopiles do not measure the absolute temperature, but generate an output voltage proportional to a temperature difference.

Thermopiles are widely used, e.g., they are the key component of infrared thermometers, such as those used to measure body

temperature via the ear.

A thermal diode or thermal rectifier is a device that preferentially passes heat in one direction: a “one-way valve” for heat.

Fusion Reactor:

A fusion reactor uses a plasma field contained within a laser grid in which heat created from the fusion of hydrogen gases is used to generate power.

“As a consequence, most fusion reactions combine isotopes of hydrogen (“protium”, deuterium, or tritium) to form isotopes of helium (3He or 4He) as the fusion end product.”

Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in 6,420 of hydrogen (~156.25 ppm on an atom basis). Deuterium accounts for approximately 0.0156% (or on a mass basis: 0.0312%) of all naturally occurring hydrogen in Earth's oceans, while the most common isotope (hydrogen-1 or protium) accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see VSMOW).

The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen isotope, protium, has no neutron in the nucleus. The deuterium isotope's name is formed from the Greek deuteros meaning “second”, to denote the two particles composing the nucleus.[1] Deuterium was discovered and named in 1931 by Harold Urey, earning him a Nobel Prize in 1934 after the discovery of the neutron in 1932 made the structure of deuterium obvious. Soon after deuterium's discovery, Urey and others produced samples of water in which deuterium has been highly concentrated with respect to protium, a substance popularly known as heavy water.

Because deuterium is destroyed in the interiors of stars faster than it is produced, and because other natural processes are thought to produce only an insignificant amount of deuterium, it is presently thought that nearly all deuterium found in nature was produced in the Big Bang 13.7 billion years ago, and that the basic or primordial ratio of hydrogen-1 (protium) to deuterium (about 26 atoms of deuterium per million hydrogen) has its origin from that time. This is the ratio found in the gas giant planets, such as Jupiter. However, different astronomical bodies are found to have different ratios of deuterium to hydrogen-1, and this is thought to be as a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water-cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium. In fact, the discovery of deuterium/protium ratios in a number of comets very similar to the mean ratio in Earth's oceans has led to theories that much of Earth's ocean water has a cometary origin.[2][3]

Differences between deuterium and common hydrogen (protium) Chemical symbol Deuterium discharge tube A vial of glowing deuterium.

Deuterium is frequently represented by the chemical symbol D. Since it is an isotope of hydrogen with mass number 2, it is also represented by 2H. IUPAC allows both D and 2H, although 2H is preferred.[4] A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes. Also, its large mass difference with protium (1H) (deuterium has a mass of 2.014102 u, compared to the mean hydrogen atomic weight of 1.007947 u, and protium's mass of 1.007825 u) confers non-negligible chemical dissimilarities with protium-containing compounds, whereas the isotope weight ratios within other chemical elements are largely insignificant in this regard. Natural abundance Main article: Big Bang nucleosynthesis

Deuterium occurs in trace amounts naturally as deuterium gas, written 2H2 or D2, but most natural occurrence in the universe is bonded with a typical 1H atom, a gas called hydrogen deuteride (HD or 1H2H).[5]

The existence of deuterium on Earth, elsewhere in the solar system (as confirmed by planetary probes), and in the spectra of stars, is an important datum in cosmology. Gamma radiation from ordinary nuclear fusion dissociates deuterium into protons and neutrons, and there are no known natural processes other than the Big Bang nucleosynthesis, which might have produced deuterium at anything close to the observed natural abundance of deuterium (deuterium is produced by the rare cluster decay, and occasional absorption of naturally occurring neutrons by light hydrogen, but these are trivial sources). There is thought to be little deuterium in the interior of the Sun and other stars, as at temperatures there nuclear fusion reactions that consume deuterium happen much faster than the proton-proton reaction that creates deuterium. However, deuterium persists in the outer solar atmosphere at roughly the same concentration as in Jupiter, and this has probably been unchanged since the beginning of the Solar System. The natural deuterium abundance seems to be a very similar fraction of hydrogen, wherever hydrogen is found, unless there are obvious processes at work that concentrate it.

Thus, the existence of deuterium at a low but constant primordial fraction in all hydrogen, is one of the arguments in favor of the Big Bang theory over the Steady State theory of the universe. It is estimated that the abundances of deuterium have not evolved significantly since their production about 13.7 bya.[6]

Deuterium abundance on Jupiter has been directly measured at 26 atoms D per million hydrogens by the Galileo entry probe; ISO-SWS observations find 22 atoms of D per million H atoms in Jupiter.[7] and this abundance is thought to represent close to the primordial solar system ratio.[3] This is about 17% of the terrestrial deuterium-to-hydrogen ratio of 156 deuterium atoms per million hydrogen atoms.

Cometary bodies such as Comet Hale Bopp and Halley's Comet have been measured to contain relatively more deuterium (about 200 atoms D per million hydrogens), ratios which are enriched with respect to the presumed protosolar nebula ratio, probably due to heating, and which are similar to the ratios found in Earth seawater. The recent measurement of deuterium amounts of 161 atoms D per million hydrogen in Comet 103P/Hartley (a former Kuiper belt object), a ratio almost exactly that in Earth's oceans, emphasizes the theory that Earth's surface water may be largely comet-derived.[2][3] Concentrating natural abundance deuterium

Deuterium is concentrated for industrial, scientific and military purposes as heavy water from ordinary water. The world's leading supplier of deuterium was Atomic Energy of Canada Limited, in Canada, until 1997, when the last heavy water plant was shut down. Canada uses heavy water as a neutron moderator for the operation of the CANDU reactor design. Properties Physical properties

The physical properties of deuterium compounds can exhibit significant kinetic isotope effects and other physical and chemical property differences from the hydrogen analogs; for example, D2O is more viscous than H2O.[8] Chemically, deuterium behaves similarly to ordinary hydrogen, but there are differences in bond energy and length for compounds of heavy hydrogen isotopes which are larger than the isotopic differences in any other element. Bonds involving deuterium and tritium are somewhat stronger than the corresponding bonds in hydrogen, and these differences are enough to make significant changes in biological reactions.

Deuterium can replace the normal hydrogen in water molecules to form heavy water (D2O), which is about 10.6% denser than normal water (enough that ice made from it sinks in ordinary water). Heavy water is slightly toxic in eukaryotic animals, with 25% substitution of the body water causing cell division problems and sterility, and 50% substitution causing death by cytotoxic syndrome (bone marrow failure and gastrointestinal lining failure). Prokaryotic organisms, however, can survive and grow in pure heavy water (though they grow more slowly).[9] Consumption of heavy water does not pose a health threat to humans, it is estimated that a 70 kg person might drink 4.8 liters of heavy water without serious consequences.[10] Small doses of heavy water (a few grams in humans, containing an amount of deuterium comparable to that normally present in the body) are routinely used as harmless metabolic tracers in humans and animals. Quantum properties

The deuteron has spin +1 (“triplet”) and is thus a boson. The NMR frequency of deuterium is significantly different from common light hydrogen. Infrared spectroscopy also easily differentiates many deuterated compounds, due to the large difference in IR absorption frequency seen in the vibration of a chemical bond containing deuterium, versus light hydrogen. The two stable isotopes of hydrogen can also be distinguished by using mass spectrometry.

The triplet deuteron nucleon barely is bound at EB = 2.23 MeV, so all the higher energy states are not bound. The singlet deuteron is a virtual state, with a negative binding energy of ~60 keV. There is no such stable particle, but this virtual particle transiently exists during neutron-proton inelastic scattering, accounting for the unusually large neutron scattering cross-section of the proton.[11] Nuclear properties (the deuteron) Deuteron mass and radius

The nucleus of deuterium is called a deuteron. It has a mass of 2.013553212724(78) u[12] The charge radius of the deuteron is 2.1402(28) fm[13] Spin and energy

Deuterium is one of only four stable nuclides with an odd number of protons and odd number of neutrons. (2H, 6Li, 10B, 14N; also, the long-lived radioactive nuclides 40K, 50V, 138La, 180mTa occur naturally.) Most odd-odd nuclei are unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. Deuterium, however, benefits from having its proton and neutron coupled to a spin-1 state, which gives a stronger nuclear attraction; the corresponding spin-1 state does not exist in the two-neutron or two-proton system, due to the Pauli exclusion principle which would require one or the other identical particle with the same spin to have some other different quantum number, such as orbital angular momentum. But orbital angular momentum of either particle gives a lower binding energy for the system, primarily due to increasing distance of the particles in the steep gradient of the nuclear force. In both cases, this causes the diproton and dineutron nucleus to be unstable.

The proton and neutron making up deuterium can be dissociated through neutral current interactions with neutrinos. The cross section for this interaction is comparatively large, and deuterium was successfully used as a neutrino target in the Sudbury Neutrino Observatory experiment. Isospin singlet state of the deuteron

Due to the similarity in mass and nuclear properties between the proton and neutron, they are sometimes considered as two symmetric types of the same object, a nucleon. While only the proton has an electric charge, this is often negligible due of the weakness of the electromagnetic interaction relative to the strong nuclear interaction. The symmetry relating the proton and neutron is known as isospin and denoted I (or sometimes T).

Isospin is an SU(2) symmetry, like ordinary spin, so is completely analogous to it. The proton and neutron form an isospin doublet, with a “down” state (?) being a neutron, and an “up” state (?) being a proton.

A pair of nucleons can either be in an antisymmetric state of isospin called singlet, or in a symmetric state called triplet. In terms of the “down” state and “up” state, the singlet is

  \frac{1}{\sqrt{2}}\Big( |\uparrow \downarrow \rangle - |\downarrow \uparrow \rangle\Big).

This is a nucleus with one proton and one neutron, i.e. a deuterium nucleus. The triplet is

  \left( \begin{array}{ll} |\uparrow\uparrow\rangle\\ \frac{1}{\sqrt{2}}( |\uparrow\downarrow\rangle + |\downarrow\uparrow\rangle )\\ |\downarrow\downarrow\rangle \end{array} \right) 

and thus consists of three types of nuclei, which are supposed to be symmetric: a deuterium nucleus (actually a highly excited state of it), a nucleus with two protons, and a nucleus with two neutrons. The latter two nuclei are not stable or nearly stable, and therefore so is this type of deuterium (meaning that it is indeed a highly excited state of deuterium). Approximated wavefunction of the deuteron

The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, the wavefunction need not be antisymmetric in general). Apart from their isospin, the two nucleons also have spin and spatial distributions of their wavefunction. The latter is symmetric if the deuteron is symmetric under parity (i.e. have an “even” or “positive” parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. have an “odd” or “negative” parity). The parity is fully determined by the total orbital angular momentum of the two nucleons: if it is even then the parity is even (positive), and if it is odd then the parity is odd (negative).

The deuteron, being an isospin singlet, is antisymmetric under nucleons exchange due to isospin, and therefore must be symmetric under the double exchange of their spin and location. Therefore it can be in either of the following two different states:

  Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (-1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (-1) as needed for antisymmetry.
  Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (-1) from isospin exchange, (-1) from spin exchange and (-1) from parity (location exchange), again for a total of (-1) as needed for antisymmetry.

In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l ; The lower its orbital angular momentum, the lower its energy. Therefore the lowest possible energy state has s = 1, l = 0.

In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore the lowest possible energy state has s = 0, l = 1.

Since s = 1 gives a stronger nuclear attraction, the deuterium ground state is in the s =1, l = 0 state.

The same considerations lead to the possible states of an isospin triplet having s = 0, l = even or s = 1, l = odd. Thus the state of lowest energy has s = 1, l = 1, higher than that of the isospin singlet.

The analysis just given is in fact only approximate, both because isospin is not an exact symmetry, and more importantly because the strong nuclear interaction between the two nucleons is related to angular momentum in spin-orbit interaction that mixes different s and l states. That is, s and l are not constant in time (they do not commute with the Hamiltonian), and over time a state such as s = 1, l = 0 may become a state of s = 1, l = 2. Parity is still constant in time so these do not mix with odd l states (such as s = 0, l = 1). Therefore the quantum state of the deuterium is a superposition (a linear combination) of the s = 1, l = 0 state and the s = 1, l = 2 state, even though the first component is much bigger. Since the total angular momentum j is also a good quantum number (it is a constant in time), both components must have the same j, and therefore j = 1. This is the total spin of the deuterium nucleus.

To summarize, the deuterium nucleus is antisymmetric in terms of isospin, and has spin 1 and even (+1) parity. The relative angular momentum of its nucleons l is not well defined, and the deuteron is a superposition of mostly l = 0 with some l = 2. Magnetic and electric multipoles

In order to find theoretically the deuterium magnetic dipole moment µ, one uses the formula for a nuclear magnetic moment

  \mu = {1\over (j+1)}\langle(l,s),j,m_j=j|\overrightarrow{\mu}\cdot \overrightarrow{j}|(l,s),j,m_j=j\rangle


  \overrightarrow{\mu} = g^{(l)}\overrightarrow{l} + g^{(s)}\overrightarrow{s} 

g(l) and g(s) are g-factors of the nucleons.

Since the proton and neutron have different values for g(l) and g(s), one must separate their contributions. Each gets half of the deuterium orbital angular momentum \overrightarrow{l} and spin \overrightarrow{s}. One arrives at

  \mu = {1\over (j+1)}\langle(l,s),j,m_j=j|\left({1\over 2}\overrightarrow{l} {g^{(l)}}_p + {1\over 2}\overrightarrow{s} ({g^{(s)}}_p + {g^{(s)}}_n)\right)\cdot \overrightarrow{j}|(l,s),j,m_j=j\rangle

where subscripts p and n stand for the proton and neutron, and g(l)n = 0.

By using the same identities as here and using the value g(l)p = 1 µ N, we arrive at the following result, in nuclear magneton units

  \mu = {1\over 4 (j+1)}\left[({g^{(s)}}_p + {g^{(s)}}_n)\big(j(j+1) - l(l+1) + s(s+1)\big) + \big(j(j+1) + l(l+1) - s(s+1)\big)\right]

For the s = 1, l = 0 state (j = 1), we obtain

  \mu = {1\over 2}({g^{(s)}}_p + {g^{(s)}}_n) = 0.879

For the s = 1, l = 2 state (j = 1), we obtain

  \mu = -{1\over 4}({g^{(s)}}_p + {g^{(s)}}_n) + {3\over 4} = 0.310

The measured value of the deuterium magnetic dipole moment, is 0.857 µ N. This suggests that the state of the deuterium is indeed only approximately s = 1, l = 0 state, and is actually a linear combination of (mostly) this state with s = 1, l = 2 state.

The electric dipole is zero as usual.

The measured electric quadrupole of the deuterium is 0.2859 e·fm2. While the order of magnitude is reasonable, since the deuterium radius is of order of 1 femtometer (see below) and its electric charge is e, the above model does not suffice for its computation. More specifically, the electric quadrupole does not get a contribution from the l =0 state (which is the dominant one) and does get a contribution from a term mixing the l =0 and the l =2 states, because the electric quadrupole operator does not commute with angular momentum. The latter contribution is dominant in the absence of a pure l = 0 contribution, but cannot be calculated without knowing the exact spatial form of the nucleons wavefunction inside the deuterium.

Higher magnetic and electric multipole moments cannot be calculated by the above model, for similar reasons. Applications Ionized deuterium in an IEC fusion reactor giving off its characteristic pinkish-red glow. Emission spectrum of an ultraviolet deuterium arc lamp.

Deuterium has a number of commercial and scientific uses. These include: Nuclear reactors

Deuterium is useful in nuclear fusion reactions, especially in combination with tritium, because of the large reaction rate (or nuclear cross section) and high energy yield of the D–T reaction. There is an even higher-yield D–3He fusion reaction, though the breakeven point of D–3He is higher than that of most other fusion reactions; together with the scarcity of 3He, this makes it implausible as a practical power source until at least D–T and D–D fusion reactions have been performed on a commercial scale.

Deuterium is used in heavy water moderated fission reactors, usually as liquid D2O, to slow neutrons without high neutron absorption of ordinary hydrogen.[14] In research reactors, liquid D2 is used in cold sources to moderate neutrons to very low energies and wave lengthes appropriate for scattering experiments. NMR spectroscopy Main article: Deuterium NMR

Deuterium NMR spectra are especially informative in the solid state because of its relatively small quadrupole moment in comparison with those of bigger quadrupolar nuclei such as chlorine-35, for example. Tracing

In chemistry, biochemistry and environmental sciences, deuterium is used as a non-radioactive, stable isotopic tracer, for example, in the doubly labeled water test. In chemical reactions and metabolic pathways, deuterium behaves somewhat similarly to ordinary hydrogen (with a few chemical differences, as noted). It can be distinguished from ordinary hydrogen most easily by its mass, using mass spectrometry or infrared spectrometry. Deuterium can be detected by femtosecond infrared spectroscopy, since the mass difference drastically affects the frequency of molecular vibrations; deuterium-carbon bond vibrations are found in locations free of other signals.

Measurements of small variations in the natural abundances of deuterium, along with those of the stable heavy oxygen isotopes 17O and 18O, are of importance in hydrology, to trace the geographic origin of Earth's waters. The heavy isotopes of hydrogen and oxygen in rainwater (so-called meteoric water) are enriched as a function of the environmental temperature of the region in which the precipitation falls (and thus enrichment is related to mean latitude). The relative enrichment of the heavy isotopes in rainwater (as referenced to mean ocean water), when plotted against temperature falls predictably along a line called the global meteoric water line (GMWL). This plot allows samples of precipitation-originated water to be identified along with general information about the climate in which it originated. Evaporative and other processes in bodies of water, and also ground water processes, also differentially alter the ratios of heavy hydrogen and oxygen isotopes in fresh and salt waters, in characteristic and often regionally-distinctive ways.[15] Contrast properties

Neutron scattering techniques particularly profit from availability of deuterated samples: The H and D cross sections are very distinct and different in sign, which allows contrast variation in such experiments. Further, a nuisance problem of ordinary hydrogen is its large incoherent neutron cross section, which is nil for D. The substitution of deuterium atoms for hydrogen atoms thus reduces scattering noise.

Hydrogen is an important and major component in all materials of organic chemistry and life science, but it barely interacts with X-rays. As hydrogen (and deuterium) interact strongly with neutrons, neutron scattering techniques, together with a modern deuteration facility,[16] fills a niche in many studies of macromolecules in biology and many other areas. Nuclear resonance spectroscopy

Deuterium is useful in hydrogen nuclear magnetic resonance spectroscopy (proton NMR). NMR ordinarily requires compounds of interest to be analyzed as dissolved in solution. Because of deuterium's nuclear spin properties which differ from the light hydrogen usually present in organic molecules, NMR spectra of hydrogen/protium are highly differentiable from that of deuterium, and in practice deuterium is not “seen” by an NMR instrument tuned to light-hydrogen. Deuterated solvents (including heavy water, but also compounds like deuterated chloroform, CDCl3) are therefore routinely used in NMR spectroscopy, in order to allow only the light-hydrogen spectra of the compound of interest to be measured, without solvent-signal interference. History Suspicion of lighter element isotopes

The existence of nonradioactive isotopes of lighter elements had been suspected in studies of neon as early as 1913, and proven by mass spectrometry of light elements in 1920. The prevailing theory at the time, however, was that the isotopes were due to the existence of differing numbers of “nuclear electrons” in different atoms of an element. It was expected that hydrogen, with a measured average atomic mass very close to 1 u, the known mass of the proton, always had a nucleus composed of a single proton (a known particle), and therefore could not contain any nuclear electrons without losing its charge entirely. Thus, hydrogen could have no heavy isotopes. Deuterium predicted and finally detected Harold Urey

It was first detected spectroscopically in late 1931 by Harold Urey, a chemist at Columbia University. Urey's collaborator, Ferdinand Brickwedde, distilled five liters of cryogenically produced liquid hydrogen to 1 mL of liquid, using the low-temperature physics laboratory that had recently been established at the National Bureau of Standards in Washington, D.C. (now the National Institute of Standards and Technology). This concentrated the fraction of the mass-2 isotope of hydrogen to a degree that made its spectroscopic identification unambiguous.[17][18] Naming of the isotope and Nobel Prize

Urey created the names protium, deuterium, and tritium in an article published in 1934. The name is based in part on advice from G. N. Lewis who had proposed the name “deutium”. The name is derived from the Greek deuteros (second), and the nucleus to be called “deuteron” or “deuton”. Isotopes and new elements were traditionally given the name that their discoverer decided. Some British chemists, like Ernest Rutherford, wanted the isotope to be called “diplogen”, from the Greek diploos (double), and the nucleus to be called diplon.[1]

The amount inferred for normal abundance of this heavy isotope of hydrogen was so small (only about 1 atom in 6400 hydrogen atoms in ocean water) that it had not noticeably affected previous measurements of (average) hydrogen atomic mass. This explained why it hadn't been experimentally suspected before. Urey was able to concentrate water to show partial enrichment of deuterium. Lewis had prepared the first samples of pure heavy water in 1933. The discovery of deuterium, coming before the discovery of the neutron in 1932, was an experimental shock to theory, but when the neutron was reported, making deuterium's existence more explainable, deuterium won Urey the Nobel Prize in chemistry in 1934. Lewis was embittered by being passed over for this recognition given to his former student.[1] “Heavy water” experiments in World War II Main article: Heavy water

Shortly before the war, Hans von Halban and Lew Kowarski moved their research on neutron moderation from France to England, smuggling the entire global supply of heavy water (which had been made in Norway) across in twenty-six steel drums.[19][20]

During World War II, Nazi Germany was known to be conducting experiments using heavy water as moderator for a nuclear reactor design. Such experiments were a source of concern because they might allow them to produce plutonium for an atomic bomb. Ultimately it led to the Allied operation called the “Norwegian heavy water sabotage”, the purpose of which was to destroy the Vemork deuterium production/enrichment facility in Norway. At the time this was considered important to the potential progress of the war.

After World War II ended, the Allies discovered that Germany was not putting as much serious effort into the program as had been previously thought.[citation needed] The Germans had completed only a small, partly built experimental reactor (which had been hidden away). By the end of the war, the Germans did not even have a fifth of the amount of heavy water needed to run the reactor, partially due to the Norwegian heavy water sabotage operation.[citation needed] However, even had the Germans succeeded in getting a reactor operational (as the U.S. did with a graphite reactor in late 1942), they would still have been at least several years away from development of an atomic bomb with maximal effort. The engineering process, even with maximal effort and funding, required about two and a half years (from first critical reactor to bomb) in both the U.S. and U.S.S.R, for example. Deuterium in thermonuclear weapons Main articles: Teller-Ulam design and thermonuclear weapon A view of the Sausage device casing of the Ivy Mike hydrogen bomb, with its instrumentation and cryogenic equipment attached. The bomb held a crygenic dewar containing on the order of 100 kg of liquid deuterium. The bomb is 20 feet tall; note seated man at photo-right for scale

The 62-ton Ivy Mike device built by the United States and exploded November 1, 1953, was the first fully successful “hydrogen bomb” or thermonuclear bomb. In this context, it was the first bomb in which most of the energy was derived from stages after the primary fission stage of the atomic bomb. It was assembled in essentially a building that resembled a factory rather than a weapon. At its center, a very large cylindrical thermos flask or cryostat, held cryogenic liquid deuterium fusion fuel in an amount of less than 1000 liters (162 kg). A regular fission bomb (the “primary”) at one end was used to create the conditions needed to initiate the fusion reaction.

Later, “dry bombs” were developed which did not require cryogenic deuterium, but all modern thermonuclear weapons are thought to contain deuterium salts in the secondary stages, the deuterium containing material being principally lithium deuteride. Data

  Density: 0.180 kg/m3 at STP (0 °C, 101.325 kPa).
  Atomic weight: 2.0141017926 u.
  Mean abundance in ocean water (from VSMOW) 155.76 ±0.1 ppm (a ratio of 1 part per approximately 6420 parts), that is, about 0.015% of the atoms in a sample (by number, not weight)

Data at approximately 18 K for D2 (triple point):

      Liquid: 162.4 kg/m3
      Gas: 0.452 kg/m3
  Viscosity: 12.6 µPa·s at 300 K (gas phase)
  Specific heat capacity at constant pressure cp:
      Solid: 2,950 J/(kg·K)
      Gas: 5,200 J/(kg·K)


An antideuteron is the antiparticle of the nucleus of deuterium, consisting of an antiproton and an antineutron. The antideuteron was first produced in 1965 at the Proton Synchrotron at CERN[21] and the Alternating Gradient Synchrotron at Brookhaven National Laboratory.[22] A complete atom, with a positron orbiting the nucleus, would be called antideuterium, but as of 2005 antideuterium has not yet been created. The proposed symbol for antideuterium is D, that is, D with an overbar.[23] Pycnodeuterium

Deuterium atoms can be absorbed into a palladium (Pd) lattice. They are effectively solidified as an ultrahigh density deuterium lump (Pycnodeuterium) inside each octahedral space within the unit cell of the palladium host lattice. It was once reported that deuterium absorbed into palladium enabled nuclear cold fusion.[24] However, cold fusion by this mechanism has not been generally accepted by the scientific community.[25] Ultra-dense deuterium

The existence of ultra-dense deuterium is suggested by experiment. This material, at a density of 140 kg/cm3, would be a million times more dense than regular deuterium, denser than the core of the Sun. This ultra-dense form of deuterium may facilitate achieving laser-induced fusion.[26] Only minute amounts of ultra-dense deuterium have been produced thus far.[27][28] At the moment, it is not known how the material is produced or if it remains stable without applied pressure, however, there is conjecture that it is possible to produce a new stable state of matter by compressing ultra-cold deuterium in a Rydberg state.[29]

Tritium (play /'tr?ti?m/ or /'tr??i?m/; symbol T or 3H, also known as hydrogen-3) is a radioactive isotope of hydrogen. The nucleus of tritium (sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of protium (by far the most abundant hydrogen isotope) contains one proton and no neutrons. Naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. The name of this isotope is formed from the Greek word “tritos” meaning “third”.

While tritium has several different experimentally determined values of its half-life, the National Institute of Standards and Technology lists 4,500±8 days (approximately 12.32 years).[1] It decays into helium-3 by beta decay as in this nuclear equation:

  1T  	?  	3
  2He1+  	+  	e-  	+  	?

and it releases 18.6 keV of energy in the process. The electron's kinetic energy varies, with an average of 5.7 keV, while the remaining energy is carried off by the nearly undetectable electron antineutrino. Beta particles from tritium can penetrate only about 6.0 mm of air, and they are incapable of passing through the dead outermost layer of human skin.[2] The unusually low energy released in the tritium beta decay makes the decay (along with that of rhenium-187) an appropriate laboratory for absolute neutrino mass measurements (the most recent experiment being KATRIN).


The low energy of tritium's radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting.

Production Lithium

Tritium is produced in nuclear reactors by neutron activation of lithium-6. This is possible with neutrons of any energy, and is an exothermic reaction yielding 4.8 MeV. In comparison, the fusion of deuterium with tritium releases about 17.6 MeV of energy.

  3Li  	+  	n  	?  	4
  2He  	(  	2.05 MeV  	)  	+  	3
  1T  	(  	2.75 MeV  	)

High-energy neutrons can also produce tritium from lithium-7 in an endothermic reaction, consuming 2.466 MeV. This was discovered when the 1954 Castle Bravo nuclear test produced an unexpectedly high yield.[3]

  3Li  	+  	n  	?  	4
  2He  	+  	3
  1T  	+  	n

High-energy neutrons irradiating boron-10 will also occasionally produce tritium.[4] The more common result of boron-10 neutron capture is 7Li and a single alpha particle.[5]

  5B  	+  	n  	?  	2 4
  2He  	+  	3

The reactions requiring high neutron energies are not attractive production methods. Deuterium See also: Heavy water#Tritium production

Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron. This reaction has a quite small absorption cross section, making heavy water a good neutron moderator, and relatively little tritium is produced. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. The Ontario Power Generation's “Tritium Removal Facility” processes up to 2,500 long tons (2,500,000 kg) of heavy water a year, and it separates out about 2.5 kg (5.5 lb) of tritium, making it available for other uses.[6]

Deuterium's absorption cross section for thermal neutrons is about 0.52 millibarns, whereas that of oxygen-16 (16 8O) is about 0.19 millibarns and that of oxygen-17 (17 8O) is about 240 millibarns. 17 8O makes up about 0.038% of all naturally occurring oxygen, hence oxygen has an overall absorption cross section of about 0.28 millibarns. Therefore, in deuterium oxide made with natural oxygen, 21% of neutron captures are by oxygen nuclei, a proportion that may rise further since the percentage of 17 8O increases from neutron captures by 16 8O. Also, 17 8O splits when bombarded by the alpha particles emitted by decaying uranium, producing radioactive carbon-14 (14 6C), a dangerous by-product, by the equation.

  8O + 4
  2He ? 14
  6C + assorted smalled products


Tritium is an uncommon product of the nuclear fission of uranium-235, plutonium-239, and uranium-233, with a production of about one per each 10,000 fissions.[7][8] This means that the release or recovery of tritium needs to be considered in the operation of nuclear reactors, especially in the reprocessing of nuclear fuels and in the storage of spent nuclear fuel. The production of tritium was not a goal, but is rather just a side-effect. Helium-3 and tritium

Tritium's decay product, helium-3, has a very large cross section for reacting with thermal neutrons, expelling a proton, hence it is rapidly converted back to tritium in nuclear reactors.[9]

3 2He + n ? 1 1H + 3 1H Cosmic rays

Tritium occurs naturally due to cosmic rays interacting with atmospheric gases. In the most important reaction for natural production, a fast neutron (which must have energy greater than 4.0 MeV[10]) interacts with atmospheric nitrogen:

  7N  	+  	n  	?  	12
  6C  	+  	3

The global equilibrium inventory of tritium is approximately constant due to a fixed production rate and losses proportional to the inventory. Production history

According to the Institute for Energy and Environmental Research report in 1996 about the U.S. Department of Energy, only 225 kg (500 lb) of tritium has been produced in the United States since 1955. Since it continually decays into helium-3, the total amount remaining was about 75 kg (170 lb) at the time of the report.[3]

Tritium for American nuclear weapons was produced in special heavy water reactors at the Savannah River Site until their close-downs in 1988. With the Strategic Arms Reduction Treaty (START) after the end of the Cold War, the existing supplies were sufficient for the new, smaller number of nuclear weapons for some time.

The production of tritium was resumed with irradiation of rods containing lithium (replacing the usual control rods containing boron, cadmium, or hafnium), at the reactors of the commercial Watts Bar Nuclear Generating Station in 2003–2005 followed by extraction of tritium from the rods at the new Tritium Extraction Facility[11] at the Savannah River Site beginning in November 2006.[12] Tritium leakage from the TPBARs during reactor operations limits the number that can be used in any reactor without exceeding the maximum allowed tritium levels in the coolant.[13] Properties

Tritium has an atomic mass of 3.0160492. It is a gas (T2 or 3H2) at standard temperature and pressure. It combines with oxygen to form a liquid called tritiated water, THO.

Tritium's radioactivity is 9650 curies per gram.[14] (357 TBq/g)

Tritium figures prominently in studies of nuclear fusion because of its favorable reaction cross section and the large amount of energy (17.6 MeV) produced through its reaction with deuterium:

  1T  	+  	2
  1D  	?  	4
  2He  	+  	n



The same is true, albeit to a lesser extent, of deuterium. This is why brown dwarfs (so-called failed stars) cannot utilize ordinary hydrogen, but they do fuse the small minority of deuterium nuclei. Radioluminescent 1.8 curies (67 GBq) 6 by 0.2 inches (150 × 5.1 mm) tritium vials are thin, tritium-gas-filled glass vials whose inner surfaces are coated with a phosphor. The vial shown here is brand-new.

Like hydrogen, tritium is difficult to confine. Rubber, plastic, and some kinds of steel are all somewhat permeable. This has raised concerns that if tritium were used in large quantities, in particular for fusion reactors, it may contribute to radioactive contamination, although its short half-life should prevent significant long-term accumulation in the atmosphere.

The high levels of atmospheric nuclear weapons testing that took place prior to the enactment of the Partial Test Ban Treaty proved to be unexpectedly useful to oceanographers. The high levels of tritium oxide introduced into upper layers of the oceans have been used in the years since then to measure the rate of mixing of the upper layers of the oceans with their lower levels. Health risks

Tritium is an isotope of hydrogen, which allows it to readily bind to hydroxyl radicals, forming tritiated water (HTO), and to carbon atoms. Since tritium is a low energy beta emitter, it is not dangerous externally (its beta particles are unable to penetrate the skin), but it is a radiation hazard when inhaled, ingested via food or water, or absorbed through the skin.[15][16][17][18] HTO has a short biological half-life in the human body of 7 to 14 days, which both reduces the total effects of single-incident ingestion and precludes long-term bioaccumulation of HTO from the environment.[17][19]

Tritium has leaked from 48 of 65 nuclear sites in the US. In one case it was detected in groundwater at levels exceeding the United States Environmental Protection Agency (EPA) drinking water standards by up to 375 times.[20]

The US Nuclear Regulatory Commission states that in normal operation in 2003, 56 pressurized water reactors released 40,600 curies of tritium (maximum: 2,080; minimum: 0.1; average: 725) and 24 boiling water reactors released 665 curies (maximum: 174; minimum: 0; average: 27.7), in liquid effluents.[21] Regulatory limits

The legal limits for tritium in drinking water vary from country-to-country and from continent-to-continent. Some figures are given below.

  Canada: 7,000 becquerel per liter (Bq/L).
  United States: 740 Bq/L or 20,000 picocurie per liter (pCi/L) (Safe Drinking Water Act)
  World Health Organization: 10,000 Bq/L.
  European Union: "investigative" limit of 100 Bq/L.

The American limit is calculated to yield a dose of 4.0 millirems (or 40 microsieverts in SI units) per year.[22] This is about 1.3% of the natural background radiation (roughly 3000 microsieverts). Usage Self-powered lighting Watch with tritium-illuminated face Main article: Tritium illumination

The emitted electrons from the radioactive decay of small amounts of tritium cause phosphors to glow so as to make self-powered lighting devices called betalights, which are now used in firearm night sights, watches (see Luminox for example), exit signs, map lights, and a variety of other devices. This takes the place of radium, which can cause bone cancer and has been banned in most countries for decades. Commercial demand for tritium is 400 grams per year[3] and the cost is approximately US $30,000 per gram.[23] Nuclear weapons

Tritium is an important component in nuclear weapons. It is used to enhance the efficiency and yield of fission bombs and the fission stages of hydrogen bombs in a process known as “boosting” as well as in external neutron initiators for such weapons. Neutron initiator

Actuated by an ultrafast switch like a krytron, a small particle accelerator drives ions of tritium and deuterium to energies above the 15 kilo-electron-volts or so needed for deuterium-tritium fusion and directs them into a metal target where the tritium and deuterium are adsorbed as hydrides. High-energy fusion neutrons from the resulting fusion radiate in all directions. Some of these strike plutonium or uranium nuclei in the primary's pit, initiating nuclear chain reaction. The quantity of neutrons produced is large in absolute numbers, allowing the pit to quickly achieve neutron levels that would otherwise need many more generations of chain reaction, though still small compared to the total number of nuclei in the pit. Boosting

This section needs additional citations for verification. (February 2010)

Main article: Boosted fission weapon

Before detonation, a few grams of tritium-deuterium gas are injected into the hollow “pit” of fissile plutonium or uranium. The early stages of the fission chain reaction supply enough heat and compression to start deuterium-tritium fusion, then both fission and fusion proceed in parallel, the fission assisting the fusion by continuing heating and compression, and the fusion assisting the fission with highly energetic (14.1 MeV) neutrons. As the fission fuel depletes and also explodes outward, it falls below the density needed to stay critical by itself, but the fusion neutrons make the fission process progress faster and continue longer than it would without boosting. Increased yield comes overwhelmingly from the increase in fission. The energy released by the fusion itself is much smaller because the amount of fusion fuel is so much smaller. The effects of boosting include:

  increased yield (for the same amount of fission fuel, compared to detonation without boosting)
  the possibility of variable yield by varying the amount of fusion fuel
  allowing the bomb to require a smaller amount of the very expensive fissile material – and also eliminating the risk of predetonation by nearby nuclear explosions
  allowing the primary to quickly release most of its power before it has expanded to a larger size difficult to retain within a so-called "radiation case" (??).
  not so stringent requirements on the implosion setup, allowing for a smaller and lighter amount of high-explosives to be used

The tritium in a warhead is continually undergoing radioactive decay, hence becoming unavailable for fusion. Furthermore its decay product, helium-3, absorbs neutrons if exposed to the ones emitted by nuclear fission. This potentially offsets or reverses the intended effect of the tritium, which was to generate many free neutrons, if too much helium-3 has accumulated from the decay of tritium. Therefore, it is necessary to replenish tritium in boosted bombs periodically. The estimated quantity needed is 4 grams per warhead.[3] To maintain constant levels of tritium, about 0.20 grams per warhead per year must be supplied to the bomb.

One mole of deuterium-tritium gas would contain about 3.0 grams of tritium and 2.0 grams of deuterium. In comparison, the 4.5 kilograms of plutonium-239 in a nuclear bomb consists of about 20 moles of plutonium. Tritium in hydrogen bomb secondaries See also: nuclear weapon design

Since tritium undergoes radioactive decay, and it is also difficult to confine physically, the much-larger secondary charge of heavy hydrogen isotopes needed in a true hydrogen bomb uses solid lithium deuteride as its source of deuterium and tritium, where the lithium is all in the form of the lithium-6 isotope.

During the detonation of the primary fission bomb stage, excess neutrons released by the chain reaction split lithium-6 into tritium plus helium-4. In the extreme heat and pressure of the explosion, some of the tritium is then forced into fusion with deuterium, and that reaction releases even more neutrons.

Since this fusion process requires an extremely higher temperature for ignition, and it produces fewer and less energetic neutrons (only fission, deuterium-tritium fusion, and 7 3Li splitting are net neutron producers), lithium deuteride is not used in boosted bombs, but rather, for multistage hydrogen bombs. Controlled nuclear fusion

Tritium is an important fuel for controlled nuclear fusion in both magnetic confinement and inertial confinement fusion reactor designs. The experimental fusion reactor ITER and the National Ignition Facility (NIF) will use deuterium-tritium fuel. The deuterium-tritium reaction is favorable since it has the largest fusion cross-section (about 5.0 barns) and it reaches this maximum cross-section at the lowest energy (about 65 keV center-of-mass) of any potential fusion fuel.

The Tritium Systems Test Assembly (TSTA) was a facility at the Los Alamos National Laboratory dedicated to the development and demonstration of technologies required for fusion-relevant deuterium-tritium processing. Analytical chemistry


Aside from chlorofluorocarbons, tritium can act as a transient tracer and has the ability to “outline” the biological, chemical, and physical paths throughout the world oceans because of its evolving distribution.[24] Tritium has thus been used as a tool to examine ocean circulation and ventilation and, for such purposes, is usually measured in Tritium Units where 1 TU is defined as the ratio of 1 tritium atom to 1018 hydrogen atoms.[24] As noted earlier, nuclear weapons testing, primarily in the high-latitude regions of the Northern Hemisphere, throughout the late 1950s and early 1960s introduced large amounts of tritium into the atmosphere, especially the stratosphere. Before these nuclear tests, there were only about 3 to 4 kilograms of tritium on the Earth's surface; but these amounts rose by 2 or 3 orders of magnitude during the post-test period.[24] North Atlantic Ocean

While in the stratosphere (post-test period), the tritium interacted with and oxidized to water molecules and was present in much of the rapidly produced rainfall, making tritium a prognostic tool for studying the evolution and structure of the hydrologic cycle as well as the ventilation and formation of water masses in the North Atlantic Ocean.[24] In fact, bomb-tritium data were utilized from the Transient Tracers in the Ocean (TTO) program in order to quantify the replenishment and overturning rates for deep water located in the North Atlantic.[25] Most of the bomb tritiated water (HTO) throughout the atmosphere can enter the ocean through the following processes: a) precipitation, b) vapor exchange, and c) river runoff – these processes make HTO a great tracer for time-scales up to a few decades.[25] Using the data from these processes for the year 1981, the 1 TU isosurface lies between 500 and 1,000 meters deep in the subtropical regions and then extends to 1,500–2,000 meters south of the Gulf Stream due to recirculation and ventilation in the upper portion of the Atlantic Ocean.[24] To the north, the isosurface deepens and reaches the floor of the abyssal plain which is directly related to the ventilation of the ocean floor over 10 to 20 year time-scales.[24]

Also evident in the Atlantic Ocean is the tritium profile near Bermuda between the late 1960s and late 1980s. There is a downward propagation of the tritium maximum from the surface (1960s) to 400 meters (1980s), which corresponds to a deepening rate of approximately 18 meters per year.[24] There are also tritium increases at 1,500 meters depth in the late 1970s and 2,500 meters in the middle of the 1980s, both of which correspond to cooling events in the deep water and associated deep water ventilation.[24]

From a study in 1991, the tritium profile was used as a tool for studying the mixing and spreading of newly formed North Atlantic Deep Water (NADW), corresponding to tritium increases to 4 TU.[25] This NADW tends to spill over sills that divide the Norwegian Sea from the North Atlantic Ocean and then flows to the west and equatorward in deep boundary currents. This process was explained via the large-scale tritium distribution in the deep North Atlantic between 1981 and 1983.[25] The sub-polar gyre tends to be freshened (ventilated) by the NADW and is directly related to the high tritium values (> 1.5 TU). Also evident was the decrease in tritium in the deep western boundary current by a factor of 10 from the Labrador Sea to the Tropics, which is indicative of loss to ocean interior due to turbulent mixing and recirculation.[25] Pacific and Indian Oceans

In a 1998 study, tritium concentrations in surface seawater and atmospheric water vapor (10 meters above the surface) were sampled at the following locations: the Sulu Sea, the Fremantle Bay, the Bay of Bengal, the Penang Bay, and the Strait of Malacca.[26] Results indicated that the tritium concentration in surface seawater was highest at the Fremantle Bay (approximately 0.40 Bq/liter), which could be accredited to the mixing of runoff of freshwater from nearby lands due to large amounts found in coastal waters.[26] Typically, lower concentrations were found between 35 and 45 degrees south latitude and near the equator. Results also indicated that (in general) tritium has decreased over the years (up to 1997) due to the physical decay of bomb tritium in the Indian Ocean. As for water vapor, the tritium concentration was approximately one order of magnitude greater than surface seawater concentrations (ranging from 0.46 to 1.15 Bq/liter).[26] Therefore, the water vapor tritium is not affected by the surface seawater concentration; thus, the high tritium concentrations in the vapor were concluded to be a direct consequence of the downward movement of natural tritium from the stratosphere to the troposphere (therefore, the ocean air showed a dependence on latitudinal change)[26]

In the North Pacific Ocean, the tritium (introduced as bomb tritium in the Northern Hemisphere) spread in three dimensions. There were subsurface maxima in the middle and low latitude regions, which is indicative of lateral mixing (advection) and diffusion processes along lines of constant potential density (isopycnals) in the upper ocean.[27] Some of these maxima even correlate well with salinity extrema.[27] In order to obtain the structure for ocean circulation, the tritium concentrations were mapped on 3 surfaces of constant potential density (23.90, 26.02, and 26.81).[27] Results indicated that the tritium was well-mixed (at 6 to 7 TU) on the 26.81 isopycnal in the subarctic cyclonic gyre and there appeared to be a slow exchange of tritium (relative to shallower isopycnals) between this gyre and the anticyclonic gyre to the south; also, the tritium on the 23.90 and 26.02 surfaces appeared to be exchanged at a slower rate between the central gyre of the North Pacific and the equatorial regions.[27]

The depth penetration of bomb tritium can be separated into 3 distinct layers. Layer 1 is the shallowest layer and includes the deepest, ventilated layer in winter; it has received tritium via radioactive fallout and lost some due to advection and/or vertical diffusion and contains approximately 28 % of the total amount of tritium.[27] Layer 2 is below the first layer but above the 26.81 isopycnal and is no longer part of the mixed layer. Its 2 sources are diffusion downward from the mixed layer and lateral expansions outcropping strata (poleward); it contains about 58 % of the total tritium.[27] Layer 3 is representative of waters that are deeper than the outcrop isopycnal and can only receive tritium via vertical diffusion; it contains the remaining 14 % of the total tritium.[27] Mississippi River System

The impacts of the nuclear fallout were even felt in the United States throughout the Mississippi River System. Tritium concentrations can be used to understand the residence times of continental hydrologic systems (as opposed to the usual oceanic hydrologic systems) which include surface waters such as lakes, streams, and rivers.[28] Studying these systems can also provide societies and municipals with information for agricultural purposes and overall river water quality.

In a 2004 study, several rivers were taken into account during the examination of tritium concentrations (starting in the 1960s) throughout the Mississippi River Basin: Ohio River (largest input to the Mississippi River flow), Missouri River, and Arkansas River.[28] The largest tritium concentrations were found in 1963 at all the sampled locations throughout these rivers and correlate well with the peak concentrations in precipitation due to the nuclear bomb tests in 1962. The overall highest concentrations occurred in the Missouri River (1963) and were greater than 1,200 TU while the lowest concentrations were found in the Arkansas River (never greater than 850 TU and less than 10 TU in the mid-1980s).[28]

Several processes can be identified using the tritium data from the rivers: direct runoff and outflow of water from groundwater reservoirs.[28] Using these processes, it becomes possible to model the response of the river basins to the transient tritium tracer. Two of the most common models are the following:

  Piston-flow approach – tritium signal appears immediately; and
  Well-mixed reservoir approach – outflow concentration depends upon the residence time of the basin water[28]



As for the mass flux of tritium through the main stem of the Mississippi River into the Gulf of Mexico, data indicated that approximately 780 grams of tritium has flowed out of the River and into the Gulf between 1961 and 1997.[28] And current fluxes through the Mississippi River are about 1 to 2 grams per year as opposed to the pre-bomb period fluxes of roughly 0.4 grams per year.[28] History

This section needs additional citations for verification. (August 2007)

Tritium was first predicted in the late 1920s by Walter Russell, using his “spiral” periodic table,[29][citation needed] then produced in 1934 from deuterium, another isotope of hydrogen, by Ernest Rutherford, working with Mark Oliphant and Paul Harteck. Rutherford was unable to isolate the tritium, a job that was left to Luis Alvarez and Robert Cornog, who correctly deduced that the substance was radioactive.[30] Willard F. Libby discovered that tritium could be used for dating water, and therefore wine.[31]

'Plasma Ore' / 'Plasma Gas' – Ultradense deuterium or tritium?

Electronvolt From Wikipedia, the free encyclopedia

(Redirected from KeV)

Jump to: navigation, search meV, keV, MeV, GeV, TeV, PeV, and BeV redirect here. For other uses, see MEV, KEV, GEV, TEV, PEV, and BEV.

In physics, the electron volt (symbol eV; also written electronvolt[1][2]) is a unit of energy equal to approximately 1.602×10-19 joule (symbol J). By definition, it is the amount of energy gained by the charge of a single electron moved across an electric potential difference of one volt. Thus it is 1 volt (1 joule per coulomb, 1 J/C) multiplied by the electron charge (1 e, or 1.602176565(35)×10-19 C). Therefore, one electron volt is equal to 1.602176565(35)×10-19 J.[3] Historically, the electron volt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences because a particle with charge q has an energy E=qV after passing through the potential V; if q is quoted in integer units of the elementary charge and the terminal bias in volts, one gets an energy in eV.

The electron volt is not an SI unit and its value must be obtained experimentally.[4] Like the elementary charge on which it is based, it is not an independent quantity but is equal to (1 J/C)(2 h a / µ0 c0)0.5 It is a common unit of energy within physics, widely used in solid state, atomic, nuclear, and particle physics. It is commonly used with the SI prefixes milli-, kilo-, mega-, giga-, tera-, or peta- (meV, keV, MeV, GeV, TeV and PeV respectively). Thus meV stands for milli-electron volt.

Atomic properties like the ionization energy are often quoted in electron volts.

In chemistry, it is often useful to have the molar equivalent, that is the energy that would be produced by one mole of charge (6.02214129(27)×1023) passing through a potential difference of one volt. This is equal to 96.4853365(21) kJ/mol.[3] Contents

  1 Energy
  2 Momentum
  3 Mass
  4 Distance
  5 Temperature
  6 Properties
  7 Scattering experiments
  8 See also
  9 References
  10 External links


Conversion factors:

  1 eV = 1.602176487(40)×10-19 J (the conversion factor is numerically equal to the elementary charge expressed in coulombs).
  1 eV (per atom) is 96.4853365(21) kJ/mol.[3]

For comparison:

  5.25×1032 eV: Total energy released from a 20 kt Nuclear Fission Device.
  ~624 EeV (6.24×1020 eV): energy needed to power a single 100 watt light bulb for one second. (100 W = 100 J/s = ~6.24×1020 eV/s).
  300 EeV (3×1020 eV) = (50 J) :[5] the so-called Oh-My-God particle (the most energetic cosmic ray particle ever observed).
  1 TeV: A trillion electronvolts, or 1.602×10-7 J, about the kinetic energy of a flying mosquito.[6]
  210 MeV: The average energy released in fission of one Pu-239 atom.
  200 MeV: The average energy released in nuclear fission of one U-235 atom .
  17.6 MeV: The average energy released in the fusion of deuterium and tritium to form He-4; this is 0.41 PJ per kilogram of product produced.
  1 MeV: Or, 1.602×10-13 J, about twice the rest mass-energy of an electron.
  13.6 eV: The energy required to ionize atomic hydrogen. Molecular bond energies are on the order of one eV per molecule.
  1.6 to 3.4 eV: the photon energy of visible light.
  1/40 eV: The thermal energy at room temperature. A single molecule in the air has an average kinetic energy 3/80 eV.
  125.3 +/- 0.6 GeV: The energy emitted by the decay of the Higgs Boson as measured by two separate detectors at the LHC to an accuracy of 5 sigma[7]


In high-energy physics, electron-volt is often used as a unit of momentum. A potential difference of 1 volt causes an electron to gain a discrete amount of energy (i.e., 1 eV). This gives rise to usage of eV (and keV, MeV, GeV or TeV) as units of momentum, for the energy supplied results in acceleration of the particle.

The dimensions of momentum units are M 1 L 1 T -1 . The dimensions of energy units are M 1 L 2 T -2 . Then, dividing the units of energy (such as eV) by a fundamental constant that has units of velocity (M 0 L 1 T -1 ), facilitates the required conversion of using energy units to describe momentum. In the field of high-energy particle physics, the fundamental velocity unit is the speed of light c. Thus, dividing energy in eV by the speed of light in vacuum, one can describe the momentum of an electron in units of eV/c.[8] [9]


p = 1\; \text{GeV}/c = \frac{(1 \cdot 10^{9}) \cdot (1.60217646 \cdot 10^{-19} \; \text{C})\;\cdot\; \text{V}}{(2.99792458 \cdot 10^{8}\; \text{m}/\text{s})} = 5.344286\cdot 10^{-19}\; \text{kg}\cdot \text{m}/\text{s} Mass

By mass-energy equivalence, the electron volt is also a unit of mass. It is common in particle physics, where mass and energy are often interchanged, to express mass in units of eV/c2, where c is the speed of light in a vacuum (from E = mc2). It is often common to simply express mass in terms of “eV” as a unit of mass, effectively using a system of natural units with c set to 1 (hence, E = m).


      1 GeV/c2 = 1.783×10-27 kg


      1 amu = 931.46 MeV/c2 = 0.93146 GeV/c2
      1 MeV/c2 = 1.074×10-3 amu


In particle physics, a system of units in which the speed of light in a vacuum c and the reduced Planck constant h are dimensionless and equal to unity is widely used: c = h = 1. In these units, both distances and times are expressed in inverse energy units (while energy and mass are expressed in the same units, see Mass–energy equivalence). In particular, particle scattering lengths are often presented in units of inverse particle masses.



The above relations also allow expressing the mean lifetime t of an unstable particle (in seconds) in terms of its decay width G (in eV) via G = h/t. For example, the B0 meson has a lifetime of 1.530(9) picoseconds, mean decay length is ct = 459.7 µm, or a decay width of 4.302±25×10-4 eV.

Conversely, the tiny meson mass mass differences responsible for meson oscillations are often expressed in the more convenient inverse picoseconds. Temperature

In certain fields, such as plasma physics, it is convenient to use the electronvolt as a unit of temperature. The conversion to kelvins (symbol: uppercase K) is defined by using kB, the Boltzmann constant:

  {1 \mbox{ eV} \over k_{\mathrm{B}}} = {1.602\,176\,53(14) \times 10^{-19} \mbox{ J} \over 1.380\,6505(24) \times 10^{-23} \mbox{ J/K}} = 11\,604.505(20) \mbox{ K}.

For example, a typical magnetic confinement fusion plasma is 15 keV, or 170 megakelvins. Properties Energy of photons in the visible spectrum EV to nm vis.png

The energy E, frequency v, and wavelength ? of a photon are related by

  E=h\nu=\frac{hc}{\lambda}=\frac{(4.135 667 33\times 10^{-15}\,\mbox{eV}\,\mbox{s})(299\,792\,458\,\mbox{m/s})}{\lambda}


  E\mbox{(eV)}=\frac{1239.84187\,\mbox{eV}\,\mbox{nm}}{\lambda\ \mbox{(nm)}}

A photon with a wavelength of 532 nm (green light) would have an energy of approximately 2.33 eV. Similarly, 1 eV would correspond to an infrared photon of wavelength 1240 nm, and so on. Scattering experiments


Orders of magnitude (energy) From Wikipedia, the free encyclopedia Jump to: navigation, search Different orders of magnitude of natural energy production for solar, wind and geothermal versus average global consumption rate (1 W = 1 J/s)

This list compares various energies in joules (J), organized by order of magnitude. List of orders of magnitude for energy Factor (Joules) SI prefix Value Item 10-31 3.0×10-31 J average kinetic energy of a molecule at the lowest temperature reached as of 2003[citation needed] 10-28 6.6×10-28 J energy of a typical AM radio photon (1 MHz) (4×10-9 eV)[1] 10-24 yocto- (yJ) 1.6×10-24 J energy of a typical microwave oven photon (2.45 GHz) (1×10-5 eV)[2][3] 10-23 1.5×10-23 J average kinetic energy[citation needed] of a molecule in the Boomerang Nebula, the coldest place known outside of a laboratory, at a temperature of 1 kelvin[4] 10-22 2-3000×10-22 J energy of infrared light photons[5] 10-21 zepto- (zJ) 1.7×10-21 J 1 kJ/mol, converted to energy per molecule[6] 2.1×10-21 J thermal energy in each degree of freedom of a molecule at 25 °C (kT/2) (0.01 eV)[7] 3-7×10-21 J energy of a van der Waals interaction between atoms (0.02-0.04 eV)[8][9] 4.1×10-21 J “kT” at 25 °C, a common rough approximation for the total thermal energy of each molecule in a system (0.03 eV)[10] 7-22×10-21 J energy of a hydrogen bond (0.04 to 0.13 eV)[8][11] 10-20 4.5×10-20 J upper bound of the mass-energy of a neutrino in particle physics (0.28 eV)[12][13] 10-19 1.6×10-19 J ˜1 electronvolt (eV)[14] 3–5×10-19 J energy range of photons in visible light[15][16] 3-14×10-19 J energy of a covalent bond (2-9 eV)[8][17] 5-200×10-19 J energy of ultraviolet light photons[5] 10-18 atto- (aJ) 10-17 2-2000×10-17 J energy range of X-ray photons[5] 10-16 10-15 femto- (fJ) 10-14 > 2×10-14 J energy of gamma ray photons[5] 2.7×10-14 J upper bound of the mass-energy of a muon neutrino[18][19] 8.2×10-14 J rest mass-energy of an electron[20] 10-13 1.6×10-13 J 1 megaelectronvolt (MeV)[21] 10-12 pico- (pJ) 2.3×10-12 J kinetic energy of neutrons produced by D-T fusion, used to trigger fission (14.1 MeV)[22][23] 10-11 3.4×10-11 J average total energy released in the nuclear fission of one uranium-235 atom (215 MeV)[24][25] 10-10 1.503×10-10 J rest mass-energy of a proton[26] 1.505×10-10 J rest mass-energy of a neutron[27] 1.6×10-10 J 1 gigaelectronvolt (GeV)[28] 3.0×10-10 J rest mass-energy of a deuteron[29] 6.0×10-10 J rest mass-energy of an alpha particle[30] 10-9 nano- (nJ) 1.6×10-9 J 10 GeV[31] 8×10-9 J initial operating energy per beam of the CERN Large Electron Positron Collider in 1989 (50 GeV)[32][33] 10-8 1.3×10-8 J mass-energy of a W boson (80.4 GeV)[34][35] 1.5×10-8 J mass-energy of a Z boson (91.2 GeV)[36][37] 1.6×10-8 J 100 GeV[38] 6.4×10-8 J operating energy per proton of the CERN Super Proton Synchrotron accelerator in 1976[39][40] 10-7 1×10-7 J = 1 erg[41] 1.6×10-7 J 1 TeV (teraelectronvolt)[42], about the kinetic energy of a flying mosquito[43] 5.6×10-7 J energy per proton beam in the CERN Large Hadron Collider in 2011 (3.5 TeV)[44][45] 10-6 micro- (µJ) 10-5 10-4 10-3 milli- (mJ) 10-2 centi- (cJ) 10-1 deci- (dJ) 1×10-1 J energy of an American half-dollar falling 1 metre[46][47] 100 J 1 J = 1 N·m (newton–metre) 1 J = 1 W·s (watt-second) 1 J kinetic energy produced as an extra small apple (~100 grams[48]) falls 1 meter against Earth's gravity[49] 1 J energy required to heat 1 gram of dry, cool air by 1 degree Celsius[50] 1.4 J ˜ 1 ft·lbf (foot-pound force)[41] 4.184 J = 1 thermochemical calorie (small calorie)[41] 4.1868 J = 1 International (Steam) Table calorie[51] 8 J Greisen-Zatsepin-Kuzmin theoretical upper limit for the energy of a cosmic ray coming from a distant source[52][53] 101 deca- (daJ) 1×101 J flash energy of a typical pocket camera photoflash capacitor (100-400 µF @ 330 V)[54] 5×101 J most energetic cosmic ray ever detected, in 1991[55] 102 hecto- (hJ) 3×102 J energy of a lethal dose of X-rays[56] 3×102 J kinetic energy of an average person jumping as high as they can[57][58][59]

3.6×102 J kinetic energy of 800 g[60] standard men's javelin thrown at > 30 m/s[61] by elite javelin throwers[62]

5-20×102 J energy output of a typical photography studio strobe light in a single flash[63] 6.0×102 J kinetic energy of 2 kg[64] standard men's discus thrown at 24.4 m/s[citation needed] by the world record holder Jürgen Schult[65] 6×102 J use of a 10-watt flashlight for 1 minute 7.5×102 J a power of 1 horsepower applied for 1 second[41] 7.8×102 J kinetic energy of 7.26 kg[66] standard men's shot thrown at 14.7 m/s[citation needed] by the world record holder Randy Barnes[67] 103 kilo- (kJ) 1.1×103 J ˜ 1 British thermal unit (BTU), depending on the temperature[41] 1.4×103 J total solar radiation received from the Sun by 1 square meter at the altitude of Earth's orbit per second (solar constant)[68] 1.8×103 J kinetic energy of M16 rifle bullet (5.56x45mm NATO M855, 4.1 g fired at 930 m/s)[69] 3×103 J Lorentz force can crusher pinch[70] 3.4×103 J kinetic energy of world-record men's hammer throw (7.26 kg[71] thrown at 30.7 m/s[72] in 1986)[73] 3.6×103 J = 1 W·h (watt-hour)[41] 4.2×103 J energy released by explosion of 1 gram of TNT[41][74] 4.2×103 J ˜ 1 food Calorie (large calorie) ~7×103 J muzzle energy of an elephant gun, e.g. firing a .458 Winchester Magnum[75] 9×103 J energy in an alkaline AA battery[76] 104 1.7×104 J energy released by the metabolism of 1 gram of carbohydrates[77] or protein[78] 3.8×104 J energy released by the metabolism of 1 gram of fat[79] 4-5×104 J energy released by the combustion of 1 gram of gasoline[80] 5×104 J kinetic energy of 1 gram of matter moving at 10 km/s[81] 105 3×105 J—15×105 J kinetic energy of an automobile at highway speeds (1 to 5 tons[82] at 89 km/h or 55 mph)[83] 5×105 J kinetic energy of 1 gram of a meteor hitting Earth[84] 106 mega- (MJ) 1×106 J kinetic energy of a 2 tonne[82] vehicle at 32 metres per second (72 miles per hour)[85] 1.2×106 J approximate food energy of a snack such as a Snickers bar (280 food calories)[86] 3.6×106 J = 1 kW·h (kilowatt-hour) (used for electricity)[41] 8.4×106 J recommended food energy intake per day for a moderately active woman (2000 food calories)[87][88] 107 1×107 J kinetic energy of the armor-piercing round fired by the assault guns of the ISU-152 tank[89][citation needed] 1.1×107 J recommended food energy intake per day for a moderately active man (2600 food calories)[87][90] 3.7×107 J $1 of electricity at a cost of $0.10/kWh (the US average retail cost in 2009)[91][92][93] 4×107 J energy from the combustion of 1 cubic meter of natural gas[94] 4.2×107 J caloric energy consumed by Olympian Michael Phelps on a daily basis during Olympic training[95] 6.3×107 J theoretical minimum energy required to accelerate 1 kg of matter to escape velocity from Earth's surface (ignoring atmosphere)[96] 108 1×108 J kinetic energy of a 55 tonne aircraft at typical landing speed (59 m/s or 115 knots)[citation needed] 1.1×108 J ˜ 1 therm, depending on the temperature[41] 1.1×108 J ˜ 1 Tour de France, or ~90 hours[97] ridden at 5 W/kg[98] by a 65 kg rider[99] 7.3×108 J ˜ energy from burning 16 kilograms of oil (using 135 kg per barrel of light crude)[citation needed] 109 giga- (GJ) 1 .. 10×109 J energy in an average lightning bolt[100] (thunder) 1.1×109 J magnetic stored energy in the world's largest toroidal superconducting magnet for the ATLAS experiment at CERN, Geneva[101] 1.4×109 J theoretical minimum amount of energy required to melt a tonne of steel (380 kW·h)[102][103] 2.0x109 J Energy of an ordinary 61 liter gasoline tank of a car.[80][104][105] 2.0×109 J Planck energy, the unit of energy in Planck units[106] 3.3×109 J approximate average amount of energy expended by a human heart muscle over an 80-year lifetime[107][108] 4.5×109 J average annual energy usage of a standard refrigerator[109][110] 6.1×109 J ˜ 1 bboe (barrel of oil equivalent)[111] 1010 2.3×1010 J kinetic energy of an Airbus A380 at cruising speed (560 tonnes at 562 knots or 289 m/s)[citation needed] 4.2×1010 J ˜ 1 toe (ton of oil equivalent)[111] 5×1010 J yield energy of a Massive Ordnance Air Blast bomb, the second most powerful non-nuclear weapon ever designed[112][113] 7.3×1010 J energy consumed by the average U.S. automobile in the year 2000[114][115][116] 8.6×1010 J ˜ 1 MW·d (megawatt-day), used in the context of power plants[117] 8.8×1010 J total energy released in the nuclear fission of one gram of uranium-235[118][119][120] 1011 1012 tera- (TJ) 3.4×1012 J max fuel energy of an Airbus A330-300 (97,530 liters[121] of Jet A-1[122])[123] 3.6×1012 J 1 GW·h (gigawatt-hour)[124] 4×1012 J electricity generated by one 20-kg CANDU fuel bundle assuming ~29%[125] thermal efficiency of reactor[126][127] 6.4×1012 J energy contained in jet fuel in a Boeing 747-100B aircraft at max fuel capacity (183,380 liters[128] of Jet A-1[122])[129] 1013 1.1×1013 J energy of the maximum fuel an Airbus A380 can carry (320,000 liters[130] of Jet A-1[122])[131] 1.2×1013 J orbital kinetic energy of the International Space Station (417 tonnes[132] at 7.7 km/s[133])[134] 8.8×1013 J yield of the Fat Man atomic bomb used in World War II (21 kilotons)[135][136] 9.0×1013 J theoretical total mass-energy of 1 gram of matter[137] 1014 6×1014 J energy released by an average hurricane in 1 second[138] 1015 peta- (PJ) > 1015 J energy released by a severe thunderstorm[139] 1.0×1015 J yearly electricity consumption in Greenland as of 2008[140][141] 4.2×1015 J energy released by explosion of 1 megaton of TNT[41][142] 1016 1×1016 J estimated impact energy released in forming Meteor Crater[citation needed] 1.1×1016 J yearly electricity consumption in Mongolia as of 2010[140][143] 9.0×1016 J mass-energy in 1 kilogram of antimatter (or matter)[144] 1017 1×1017 J energy released on the Earth's surface by the magnitude 9.1-9.3 2004 Indian Ocean earthquake[145] 1.7×1017 J total energy from the Sun that strikes the face of the Earth each second[146] 2.1×1017 J yield of the Tsar Bomba, the largest nuclear weapon ever tested (50 megatons)[147][148] 4.2×1017 J yearly electricity consumption of Norway as of 2008[140][149] 8×1017 J estimated energy released by the eruption of the Indonesian volcano, Krakatoa, in 1883[150][151] 1018 exa- (EJ) 1.4×1018 J yearly electricity consumption of South Korea as of 2009[140][152] 1019 1.4×1019 J yearly electricity consumption in the U.S. as of 2009[140][153] 1.4×1019J yearly electricity production in the U.S. as of 2009[154][155] 5×1019 J energy released in 1 day by an average hurricane in producing rain (400 times greater than the wind energy)[138] 6.4×1019 J yearly electricity consumption of the world as of 2008[156][157] 6.8×1019 J yearly electricity generation of the world as of 2008[156][158] 1020 5.0x1020 J total world annual energy consumption in 2010[159][160] 8.0×1020 J estimated global uranium resources for generating electricity 2005[161][162][163][164] 1021 zetta- (ZJ) 6.9×1021 J estimated energy contained in the world's natural gas reserves as of 2010[159][165] 7.9×1021 J estimated energy contained in the world's petroleum reserves as of 2010[159][166] 1022 1.5×1022J total energy from the Sun that strikes the face of the Earth each day[146][167] 2.4×1022 J estimated energy contained in the world's coal reserves as of 2010[159][168] 2.9×1022 J identified global uranium-238 resources using fast reactor technology[161] 3.9×1022 J estimated energy contained in the world's fossil fuel reserves as of 2010[159][169] 4×1022 J estimated total energy released by the magnitude 9.1-9.3 2004 Indian Ocean Earthquake[170] 1023 2.2×1023 J total global uranium-238 resources using fast reactor technology[161] 5×1023 J approximate energy released in the formation of the Chicxulub Crater in the Yucatán Peninsula[171] 1024 yotta- (YJ) 5.5×1024 J total energy from the Sun that strikes the face of the Earth each year[146][172] 1025 1026 1.3×1026 J conservative estimate of the energy released by the impact that created the Caloris basin on Mercury[citation needed] 3.8×1026 J total energy output of the Sun each second[173] 1027 1028 3.8×1028 J kinetic energy of the Moon in its orbit around the Earth (counting only its velocity relative to the Earth)[174][175] 1029 2.1×1029 J rotational energy of the Earth[176][177][178] 1030 1.8×1030 J gravitational binding energy of Mercury 1031 3.3×1031 J total energy output of the Sun each day[173][179] 1032 2×1032 J gravitational binding energy of the Earth[180] 1033 2.7×1033 J Earth's kinetic energy in its orbit[181] 1034 1.2×1034 J total energy output of the Sun each year[173][182] 1039 6.6×1039 J theoretical total mass-energy of the Moon 1041 5.4×1041 J theoretical total mass-energy of the Earth[183][184] 6.9×1041 J gravitational binding energy of the Sun[185] 1043 5×1043 J total energy of all gamma rays in a typical gamma-ray burst[186][187] 1044 1-2×1044 J estimated energy released in a supernova;[188] sometimes referred to as a foe 1046 1×1046 J estimated energy released in a hypernova[189] 1047 1.8×1047 J theoretical total mass-energy of the Sun[190][191] 1058 4×1058 J visible mass-energy in our galaxy, the Milky Way[192][193] 1059 1×1059 J total mass-energy of the galaxy, including dark matter and dark energy[194][195] 1062 1-2×1062 J total mass-energy of the Local Supercluster, including dark matter[196] 1069 4×1069 J estimated total mass-energy of the observable universe[197] SI multiples SI multiples for joule (J) Submultiples Multiples Value Symbol Name Value Symbol Name 10-1 J dJ decijoule 101 J daJ decajoule 10-2 J cJ centijoule 102 J hJ hectojoule 10-3 J mJ millijoule 103 J kJ kilojoule 10-6 J µJ microjoule 106 J MJ megajoule 10-9 J nJ nanojoule 109 J GJ gigajoule 10-12 J pJ picojoule 1012 J TJ terajoule 10-15 J fJ femtojoule 1015 J PJ petajoule 10-18 J aJ attojoule 1018 J EJ exajoule 10-21 J zJ zeptojoule 1021 J ZJ zettajoule 10-24 J yJ yoctojoule 1024 J YJ yottajoule

This SI unit is named after James Prescott Joule. As with every International System of Units (SI) unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (J). When an SI unit is spelled out in English, it should always begin with a lower case letter (joule), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that “degree Celsius” conforms to this rule because the “d” is lowercase. —Based on The International System of Units, section 5.2.

Energy conversion efficiency From Wikipedia, the free encyclopedia Jump to: navigation, search


Output energy is always lower than input energy Efficiency of Power Plant, World total 2008

Energy conversion efficiency (?) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat. Contents

  1 Overview
  2 Fuel heating values and efficiency
  3 Example of energy conversion efficiency
  4 See also
  5 References
  6 External links


Energy conversion efficiency is not defined uniquely, but instead depends on the usefulness of the output. All or part of the heat produced from burning a fuel may become rejected waste heat if, for example, work is the desired output from a thermodynamic cycle.Energy converter is an example of an energy transformation. For example a light bulb falls into the categories energy converter.

  \eta = \frac{P_\mathrm{out}}{P_\mathrm{in}} 

Even though the definition includes the notion of usefulness, efficiency is considered a technical or physical term. Goal or mission oriented terms include effectiveness and efficacy.

Generally, energy conversion efficiency is a dimensionless number between 0 and 1.0, or 0 to 100%. Efficiencies may not exceed 100%, e.g., for a perpetual motion machine. However, other effectiveness measures that can exceed 1.0 are used for heat pumps and other devices that move heat rather than convert it.

When talking about the efficiency of heat engines and power stations the convention should be stated, i.e., HHV (aka Gross Heating Value etc.) or LCV (aka Net Heating value), and whether gross output (at the generator terminals) or net output (at the power station fence) are being considered. The two are separate but both must be stated. Failure to do so causes endless confusion.

Related, more specific terms include

  Electrical efficiency, useful power output per electrical power consumed;
  Mechanical efficiency, where one form of mechanical energy (e.g. potential energy of water) is converted to mechanical energy (work);
  Thermal efficiency or Fuel efficiency, useful heat and/or work output per input energy such as the fuel consumed;
  'Total efficiency', e.g., for cogeneration, useful electric power and heat output per fuel energy consumed. Same as the thermal efficiency.
  Luminous efficiency, that portion of the emitted electromagnetic radiation is usable for human vision.

Fuel heating values and efficiency

In Europe the usable energy content of fuel is typically calculated using the lower heating value (LHV) of that fuel, which definition assumes that the water vapor produced during fuel combustion (oxidation), remains gaseous, and is not condensed to liquid water so the latent heat of vaporization of that water is not usable. Using the LHV, a condensing boiler can achieve a “heating efficiency” in excess of 100% ( this does not violate the first law of thermodynamics as long as the LHV convention is understood, but does cause confusion). This is because the apparatus recovers part of the heat of vaporization, which is not included in the definition of the lower heating value of fuel. In the U.S. and elsewhere, the higher heating value (HHV) is used, which includes the latent heat for condensing the water vapor, and thus the thermodynamic maximum of 100% efficiency cannot be exceeded with HHV's use. Example of energy conversion efficiency

This article is missing information about clear definition of the energy conversion efficiency for light sources. The lighting efficiency is given by the luminous efficacy which does not allow to give a simple percentage without specifying what "100%" would be. If there is an ISO standard or another reliable source defining the energy conversion efficiency in lighting, please cite it. . This concern has been noted on the talk page where whether or not to include such information may be discussed. (May 2012)

Conversion process Energy efficiency Electricity generation Gas turbine up to 40% Gas turbine plus steam turbine (combined cycle) up to 60% Water turbine up to 90% (practically achieved) Wind turbine up to 59% (theoretical limit) Solar cell 6–40% (technology dependent, 15% most often, 85–90% theoretical limit) Fuel cell up to 85% World Electricity generation 2008 Gross output 39%, Net output 33%.[1] Engine/Motor Combustion engine 10–50%[2] Electric motors 70–99.99% (above 200W); 50–90% (between 10–200W); 30–60% (small ones < 10W) Natural process Photosynthesis up to 6% [3] Muscle 14–27% Appliance Household refrigerators low-end systems ~ 20%; high end systems ~ 40–50% Incandescent light bulb 0.7–5.1%,[4] 5–10%[citation needed] Light-emitting diode (LED) 4.2–14.9%,[4] up to 35% [5][dead link] Fluorescent lamps 8.0–15.6%,[4] 28% [6] Low-pressure sodium lamps 15.0–29.0%,[4] 40.5% [6] Metal halide lamps 9.5–17.0%,[4] 24% [6] Switched-mode power supply currently up to 95% practically Electric shower 90–95% ( Overall it would be more efficient to use a heat pump, requiring less electric energy[citation needed]) Electric heaters ~100% (essentially all energy is converted into heat) others Firearm ~30% (.300 Hawk ammunition) Electrolysis of water 50–70% (80–94% theoretical maximum)

TNT equivalent From Wikipedia, the free encyclopedia Jump to: navigation, search “Kiloton” redirects here. For the similarly named weight measurements, see Tonne. Diagram of explosive yield vs mushroom cloud height, illustrating the difference between 22 kiloton Fat Man and 15 megaton Castle Bravo explosions

TNT equivalent is a method of quantifying the energy released in explosions. The ton (or tonne, i.e. metric ton) of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT. The megaton of TNT is a unit of energy equal to 4.184 petajoules.[1]

The kiloton and megaton of TNT have traditionally been used to rate the energy output, and hence destructive power, of nuclear weapons (see nuclear weapon yield). This unit is written into various nuclear weapon control treaties, and gives a sense of destructiveness as compared with ordinary explosives, like TNT. More recently, it has been used to describe the energy released in other highly destructive events, such as asteroid impacts. However, TNT is not the most energetic of conventional explosives. Dynamite, for example, has more than 60% more energy density (approximately 7.5 MJ/kg, compared to 4.7 MJ/kg for TNT). Contents

  1 Value
  2 Examples
  3 See also
  4 References
  5 External links


A gram of TNT releases 4100–4602 Joules upon explosion. To define the tonne of TNT, this was arbitrarily standardized by letting 1 gram TNT = 4184 J (exactly). This conveniently defined the energy liberated by one gram of TNT as exactly one kilocalorie.

This definition is a conventional one. The explosive's energy is normally calculated using the thermodynamic work energy of detonation, which for TNT has been accurately measured at 4686 J/g from large numbers of air blast experiments and theoretically calculated to be 4853 J/g.

The measured pure heat output of a gram of TNT is only 2724 J, but this is not the important value for explosive blast effect calculations.

Alternative TNT equivalency can be calculated depending upon when in the detonation the value is measured and which property is being compared.

A kiloton of TNT can be visualized as a cube of TNT of 8.46 metres (27.8 ft) on a side.

Grams TNT Symbol Tons TNT Symbol Energy

gram of TNT g microton of TNT µt 4.184×10^3 J

kilogram of TNT kg milliton of TNT mt 4.184×10^6 J

megagram of TNT Mg ton of TNT t 4.184×10^9 J

gigagram of TNT Gg kiloton of TNT kt 4.184×10^12 J

teragram of TNT Tg megaton of TNT Mt 4.184×10^15 J

petagram of TNT Pg gigaton of TNT Gt 4.184×10^18 J


  Conventional bombs yield range from less than 1 ton to FOAB's 44 tonnes.
  Minor Scale, a 1985 United States conventional explosion utilizing 4,400 tonnes of ANFO explosive to simulate a 4 kilotons of TNT (17 TJ) nuclear explosion, is believed to be the largest planned detonation of conventional explosives in history.
  The Little Boy atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about 15 kilotons of TNT (63 TJ). The nuclear weapons currently in the arsenal of the United States range in yield from 0.3 kt (1.3 TJ) to 1.2 Mt (5.0 PJ) equivalent, for the B83 strategic bomb.
  During the Cold War, the United States developed hydrogen bombs with a maximum theoretical yield of 25 megatons of TNT (100 PJ); the Soviet Union developed a prototype weapon, nicknamed the Tsar Bomba, which was tested at 50 Mt (210 PJ), but had a maximum theoretical yield of 100 Mt (420 PJ).[9] The actual destructive potential of such weapons can vary greatly depending on conditions, such as the altitude at which they are detonated, the nature of the target they are detonated against, and the physical features of the landscape where they are detonated.
  The energy contained in 1 megaton of TNT (4.2 PJ) is enough to power the average American household (in the year 2007) for 103,474 years.[10] For example, the 30 Mt (130 PJ) estimated upper limit blast power of the Tunguska event could power the aforementioned home for just over 3,104,226 years. To put that in perspective: the blast energy could power the entire United States for 3.27 days.[11]
  Megathrust earthquakes record huge MW values, or total energy released. The 2004 Indian Ocean Earthquake released 9,560 gigatons of TNT (40,000 EJ) equivalent, but its ME (surface rupture energy, or potential for damage) was far smaller at 26.3 megatons of TNT (110 PJ).
  The total global nuclear arsenal is about 30,000 nuclear warheads with a destructive capacity of 5,000 megatons or 5 gigatons (5,000 million tons) of TNT.
  The approximate energy released when the largest fragment of Comet Shoemaker-Levy 9 impacted Jupiter was estimated to be equal to 6 million megatons (or 6 trillion tons) of TNT.
  The maximum theoretical yield from 1 kg of matter would be produced by annihilating it with an equal amount of antimatter, converting all of the mass into energy equal (by mass-energy equivalence) to 43 megatons of TNT (180PJ). However, in the case of proton-antiproton annihilation, ~50% of the released energy will escape in the form of almost-undetectable neutrinos.[12] Electron-positron annihilation events emit their energy entirely as gamma rays.
  The approximate energy released when the Chicxulub impact caused the mass extinction 65 million years ago was estimated to be equal to 96 million megatons of TNT.
  The amount of energy given in the 2011 Tohoku earthquake and tsunami was more than 200,000 times the surface energy and was calculated by the USGS at 3.9×10^22 joules, slightly less than the 2004 Indian Ocean quake. This is equivalent to 9,320 gigatons of TNT, or approximately 600 million times the energy of the Hiroshima bomb.
  On a much grander scale, supernova explosions give off about 10^44 joules of energy, which is about ten octillion (10^28) megatons of TNT, a quantity equivalent to the explosive force of a quantity of TNT one and two-thirds the size of the planet Earth.

Helium-4 From Wikipedia, the free encyclopedia Jump to: navigation, search Helium-4 Full table General Name, symbol Helium-4, He-4,4He Neutrons 2 Protons 2 Nuclide data Natural abundance 99.999863% Half-life stable Isotope mass 4.002602 u Spin 0 Binding energy 28300.7 keV Picture of a diffuse gray sphere with grayscale density decreasing from the center. Length scale about 1 Angstrom. An inset outlines the structure of the core, with two red and two blue atoms at the length scale of 1 femtometer. The helium atom. Depicted are the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.

Helium-4 (4 2He or 4He) is a non-radioactive isotope of helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on earth. Its nucleus is the same as an alpha particle, consisting of two protons and two neutrons. Alpha decay of heavy elements in the Earth's crust is the source of most naturally occurring helium-4 on Earth. Helium-4 is also produced by nuclear fusion in stars. Most of the helium-4 in the universe, however (including most of the helium in the Sun), was thought to have been produced by the Big Bang. Helium-4 makes up about a quarter of the ordinary matter in the universe, with almost all of the rest being hydrogen. However, this primordial helium is largely absent from the Earth, having escaped during the high temperature phase of Earth's formation, leaving radioactive decay to produce most helium on Earth, after the planet cooled and solidified.

When helium-4 is cooled to below 2.17 kelvins (–271 °C), it becomes a superfluid, with properties that are very unlike those of an ordinary liquid. For example, if helium-4 is kept in an open vessel, a thin film will climb up the sides of the vessel and overflow. Another name for this property of helium is Rollin film. This strange behaviour is a result of the Clausius-Clapeyron relation and cannot be explained by the current model of classical mechanics nor by nuclear or electrical models; it is only understood as a quantum mechanical phenomenon. The total spin of the nucleus (zero) is an integer, so it is a boson, as are neutral atoms of helium-4. The superfluid behavior is now understood to be a manifestation of Bose-Einstein condensation, which occurs only with bosons.

Helium-4 also exists on the moon, and as with on Earth, is the most abundant helium isotope. The helium-4 atom Main article: Helium atom

The helium atom is the next least complicated atom after hydrogen, but the extra electron introduces a third body, so that solution becomes a three body problem which has no analytic solution. However, numerical approximations of the equations of quantum mechanics have given a good estimate of the key atomic properties (such as size and ionization energy) of helium-4. The related stability of the helium-4 nucleus and electron shell

The nucleus of the helium-4 atom is identical with an alpha particle. High energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud. This symmetry reflects similar underlying physics: the pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. Adding another of any of these particles would require angular momentum and would release substantially less energy (in fact, no nucleus with five nucleons is stable). This arrangement is thus energetically extremely stable for all these particles, and this stability accounts for many crucial facts regarding helium in nature.

For example, the stability and low energy of the electron cloud state in helium accounts for the element's chemical inertness (the most extreme of all the elements), and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements.

In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions involving both heavy-particle emission, and fusion. Some stable helium-3 is produced in fusion reactions from hydrogen, but it is a very small fraction, compared with the highly favorable helium-4. The stability of helium-4 is the reason hydrogen is converted to helium-4 (not deuterium or helium-3 or heavier elements) in the Sun. It is also partly responsible for the fact that the alpha particle is by far the most common type of baryonic particle to be ejected from atomic nuclei; in other words, alpha decay is far more common than cluster decay. Binding energy per nucleon of common isotopes. The binding energy per particle of helium-4 is significantly larger than all nearby nuclides.

The unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the Big Bang, as the “soup” of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. So tight was helium-4 binding that helium-4 production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and also leaving few to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy) and thus no energetic drive was available, once helium had been formed, to make elements 3, 4 and 5. It was barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon. However, due to lack of intermediate elements, this process requires three helium nuclei striking each other nearly simultaneously (see triple alpha process). There was thus no time for significant carbon to be formed in the few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4.

All heavier elements (including those necessary for rocky planets like the Earth, and for carbon-based or other life), have thus had to be created since the Big Bang, in stars which were hot enough to fuse not just hydrogen (for this produces only more helium), but to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Helium-4, by contrast, makes up about 23% of the universe's ordinary matter—nearly all the ordinary matter that isn't hydrogen.

Tritium is not dangerous externally, but is a radiation hazard when inhaled, ingested, or absorbed. Tritiated water has a biological half-life of 7 to 14 days, reducing the total effects of ingestion and precluding long-term accumulation from the environment.

Tritium illumination makes self-lighting devices (replacing radium).

Neutron Initiator - a particle accelerator launches ions of tritium and deuterium to the 15 keV point required for fusion, then directs them into a metal target, resulting in high-energy fusion.

Tritium Ore: The legendary plasma ore?

Helium-3 Refrigerator

A helium-3 refrigerator is a simple device used in experimental physics for obtaining temperatures down to about 0.2 kelvins. By evaporative cooling of helium-4 (the more common isotope of helium), a 1-K pot liquefies a small amount of helium-3 in a small vessel called a helium-3 pot. Evaporative cooling of the liquid helium-3, usually driven by adsorption since due to its high price the helium-3 is usually contained in a closed system to avoid losses, cools the helium-3 pot to a fraction of a kelvin.

Nanomaterial turns radiation directly into electricity

  16:31 27 March 2008 by Phil McKenna
  For similar stories, visit the Energy and Fuels and Nanotechnology Topic Guides

Materials that directly convert radiation into electricity could produce a new era of spacecraft and even Earth-based vehicles powered by high-powered nuclear batteries, say US researchers.

Electricity is usually made using nuclear power by heating steam to rotate turbines that generate electricity.

But beginning in the 1960s, the US and Soviet Union used thermoelectric materials that convert heat into electricity to power spacecraft using nuclear fission or decaying radioactive material. The Pioneer missions were among those using the latter, “nuclear battery” approach.

Dispensing with the steam and turbines makes those systems smaller and less complicated. But thermoelectric materials have very low efficiency. Now US researchers say they have developed highly efficient materials that can convert the radiation, not heat, from nuclear materials and reactions into electricity. Power boost



Tests of layered tiles of carbon nanotubes packed with gold and surrounded by lithium hydride are under way. Radioactive particles that slam into the gold push out a shower of high-energy electrons. They pass through carbon nanotubes and pass into the lithium hydride from where they move into electrodes, allowing current to flow.

“You load the material with nuclear energy and unload an electric current,” says Popa-Simil. Space probes

The tiles would be best used to create electricity using a radioactive material, says Popa-Simil, because they could be embedded directly where radiation is greatest. But they could also harvest power directly from a fission reactor's radiation.

Devices based on the material could be small enough to power anything from interplanetary probes to aircraft and land vehicles, he adds.

“I believe this work is innovative and could have a significant impact on the future of nuclear power,” says David Poston, of the US Department of Energy's Los Alamos National Laboratory. However perfecting new nuclear technologies requires years of development, he adds.

Popa-Simil agrees, saying it will be at least a decade before final designs of the radiation-to-electricity concept are built.

A paper on the new nuclear power materials was presented on 25 March, at the Materials Research Society Spring Meeting 2008 , San Francisco, California, US.

Brahmin Milk - Removes radiation, is a disturbing shade of yellow green

Brahmin Cheese - Travels better but less benefits due to processing

Smoothies - Milk + Fruit! Cheesecake - hmmm, cheesecake…

Alprazolam causes extreme muscle relaxation, sedation and mental slowness. EFFECTS: Increased Damage Resistance 25%, Increased Fire Resistance 25%, AP -20, Agility -2 ADDICTIVE: Moderately WITHDRAWAL: Endurance -3, Strength -3 (Benzodiazepene Withdrawal) WEAPON: Cripple legs, Unconsciousness for 10 seconds

Amphetamine causes enhanced focus and CNS stimulation. EFFECTS: Repair & Science +15, AP +15 ADDICTIVE: Mildly WITHDRAWAL: Perception -2 (Amphetamine Withdrawal)

Aspirin dulls pain. EFFECTS: Increased Damage Resistance 5% ADDICTIVE: Not

2CB is a powerful empathogen causing visual distortions and euphoria. EFFECTS: Visuals, +3 luck, +2 Intelligence, +1 Perception ADDICTIVE: Mildly WITHDRAWAL: Reduce Radiation Resistance 10% (Serotonin Sickness) WEAPON: Fear

Ceremonial Herbs for your ceremonial rituals. EFFECTS: +1 Luck, -1 Intelligence, Ignore Crippled Limb Effect ADDICTIVE: Not

Coldturkene is that “pre-war stuff” the doctors talk about. EFFECTS: Cures addictions. ADDICTIVE: Not

Clonazepam causes moderate muscle relaxation and mental slowness. EFFECTS: Increased Damage Resistance 20%, Agility -1, AP -10, Steady Aim ADDICTIVE: Moderately WITHDRAWAL: Endurance -3, Strength -3 (Benzo Withdrawal)

Cocaine speeds the metabolism and stimulates the brain's reward center. EFFECTS: Damage Head 10, Agility +3, AP +10 ADDICTIVE: Very WITHDRAWAL: Charisma -3

Dextromethorphan is a dissociative anesthetic similar to PCP when taken in high doses. EFFECTS: Increased Carry Weight +50, Agility -2, Perception -2, visuals ADDICTIVE: Mildly WITHDRAWAL: Endurance -1, Strength -1 (DXM Withdrawal)

Diazepam is a habit-forming muscle relaxant. EFFECTS: AP -10, Damage Resist 10%, Steady Aim ADDICTIVE: Mildly WITHDRAWAL: Endurance -3, Strength -3 (Benzo Withdrawal)

Diet Mentats are made with aspartame instead of sugar. I dunno. Regular Mentats look sugary to me. EFFECTS: Intelligence & Perception +2, Rads +5 ADDICTIVE: Mildly WITHDRAWAL: Intelligence -2, Perception -2 (Mentats Withdrawal)

Heroin is a potent and highly addictive painkiller. EFFECTS: Agility -2, Strength -2, Damage Resistance 50% ADDICTIVE: Extremely WITHDRAWAL: Charisma -2, Strength -1, Endurance -1 (Opiate Withdrawal) WEAPON: Massive poison

Ibuprofen dulls aches. EFFECTS: Increased Damage Resistance 5% ADDICTIVE: Not

MDMA provides euhporia, focus, and a sense of oneness. EFFECTS: Luck +5, Visuals ADDICTIVE: Mildly WITHDRAWAL: Reduce Radiation Resistance 10% (Serotonin Sickness) WEAPON: Calm

Methamphetamine is a dangerously potent stimulant. EFFECTS: AP+30, Damage Health 10 ADDICTIVE: Very WITHDRAWAL: Endurance -1, Perception -3 (Meth Psychosis) WEAPON: Poison, rage

Morphine is what Med-X was called before the Australian government went all Psycho on Bethesda. EFFECTS: Damage Resistance 25%, Agility -2, ignores crippled limb effects ADDICTIVE: Very WITHDRAWAL: Charisma -2, Strength -1, Endurance -1 (Opiate Withdrawal)

Methadone is an opioid often used to manage Heroin addiction. EFFECTS: Restore health +10, +1 Endurance ADDICTIVE: Not

Multi-vitamin Pills for a balanced diet. EFFECTS: Damage Resistance 10, AP -10, Agility -1 ADDICTIVE: Mildly WITHDRAWAL: Charisma -2, Strength -1, Endurance -1 (Opiate Withdrawal)

Phencyclidine is a dissociative anesthetic used first on humans medically, then on animals, and then by humans recreationally. EFFECTS: Damage Resistance 25%, Endurance +2, Stentgh +2, Perception -3, Visuals ADDICTIVE: Mildly WITHDRAWAL: Strength -1, Endurance -1, Intelligence -1 (PCP Withdrawal) WEAPON: Frenzy

RedEye NoDoze Pills keeps you up all night, and all day, and all night EFFECTS: Temporarily grants you the “well-rested” perk. ADDICTIVE: Not

Sativex provides euphoric relief for radiation symptoms. EFFECTS: Charisma +1, Rad Resist +25, mild visuals ADDICTIVE: Mildly WITHDRAWAL: Charisma -1

Tobacco is cheap, common, and well-known for its deleterious effects. EFFECTS: Charisma +1, Rads +10, AP +5, Speech + 10, smoking effect ADDICTIVE: Extremely WITHDRAWAL: Charisma -3, Endurance -1

Thorazine is an antipsychotic sedative with a paralytic effect. EFFECTS: Ends hallucinations, 15 second paralysis, AP -20. Thorazine lasts one minute longer than all other chems. ADDICTIVE: Not WEAPON: Paralysis for 20 seconds

Tribal Healing Powder can fix you up! EFFECTS: -2 Perception, Restores 1 health per second for 45 seconds. Counts as “medicine” so higher medicine skills heals for

more. ADDICTIVE: Not

“Weed” provides good vibes. EFFECTS: Charisma +1, Radiation Resistance +25%, Euphoria, smoking effect ADDICTIVE: Habit forming WITHDRAWAL: Charisma -1 (THC Withdrawal)

Many chems can be used as a weapon by finding and “filling” an empty syringe with the chemical [credit: Better Living Thru

Chemistry]. To fill the a syringe, drop into the gameworld and click on it. A message box will prompt you to fill the syringe

with a chem from your inventory. You can now smoke cigarettes and joints. New alcohol types [credit: FDA Mod], including Grandpa's Brain Tonic, Mad Macho Tequila, Mutfruit Rotgut, and Wasteland

Moonshine. All achohol now provides a slight rad reduction effect as in prior fallout games. Removes 20 rads over 10 seconds per drink. New visual effects for many drugs. These visual effects are configurable and can be turned on or off in the FWE Control Panel

under “FWE Settings > Drug Visuals.” Revamp of addiction and withdrawal effects for existing chems, consistent with the BLTC/FDA mod. Some “medicine” type chems are now addictive, including rad-x and radaway. The duration of most drugs and chems is increased to 600 seconds (game time). Stimpacks now heal over time (5 seconds). Consuming multiple stimpacks does not let you heal faster, so watch out! Morphine (Med-x) and Ceremonial Herbs (added by the FDAMod) now provide an “ignore crippled effects” property, letting you

temporarily fight through crippling injuries and ignore their penalties. All chems and drugs now have weight. The value of most chems and drugs have been adjusted.

Crippled Effects

Crippled injuries are more severe and greatly impact your ability to fight in battle [Credit: RI - Healing]

  Wounded arms affects your aiming accuracy more (60% reduction rather than 50%).
  Cripple leg movement speed reduced significantly (60% with one leg, 30% with two broken)
  Crippled torsos results in a random chance (85%) to stagger and fall over and reduced endurance.
  Crippled heads induces a nasty blurring effect to vision and concussion effects (reduces PER).
  Damage multiplier to crippled limbs increased to .66 (was .5), so limbs tend to get crippled more easily. 

Healing + Recovery [Credit: Triage by Kearsage]

FWE integrates a modified version of the “Triage” mod that changes the way you heal crippled limbs and recover from injuries.

FWE adds a Control Panel option to enable or disable the Triage healing system if you do not like it. To access this option,

open the control panel and select “FWE Settings > Triage.” By default, triage is enabled.


You are no longer able to apply stimpaks directly to injured limbs, but instead must use the triage menu item (under the armor

tab) to open the healing options. If you apply stimpaks directly to crippled limbs in the pip-boy, they will be consumed and

contribute towards healing your overall health, but they will not restore that limbs condition.

In addition, two new perks, Wasteland Doctor [requires 40 medicine, 5 INT] and Wasteland Surgeon [requires 60 medicine, 6 INT],

control your ability to recover wounds more effectively. By default, these perks require you to choose them during the normal

level up perk selection process. However, you can change this so the perks are automatically awarded when you meet the

requirements in the FWE Control Panel under “FWE Settings > Triage > Free Perks On.”

When opening the triage menu, you will have three choices depending on what perks you have, how injured your limbs are, and

whether you are in combat or not.


  Used without the doctor or surgeon perks or during combat.
  Restores crippled limbs by regaining +5 condition.
  Requires brace (for limbs) or surgical supplies (for head/chest injuries) with no chance to recover the brace/supplies. 


  Used with doctor or surgeon perks when out of combat
  The surgeon perk is required to triage chest and head injuries.
  Restores crippled limbs to full condition from crippled status over time (100 seconds with doctor perk, 50 seconds with 


  Requires brace / surgical supplies with a chance to recover equipment dependent on your medical skill. 

Injured Limb Healing

  Used with doctor or surgeon perk when out of combat to heal limbs with over 5% health (i.e. not crippled)
  Restores injured limbs to full condition
  Does NOT require brace / surgical supplies 

Note, that resting no longer automatically heals you after a single of hour of sleep. This changed is described more below under

the Primary Needs section.

CRAFTING Medical Braces + Surgical Supplies

Added an option to CRAFT medical braces and surgical supplies, IF you have the wasteland doctor perk, courtesy of razorwire. You

can make a medical brace from 1 leather belt and 1 scrap metal, and surgical supplies from 1 abraxo cleaner and 3 empty bottles.


FWE greatly increases the rate that radiation is gained by default [credits: XFO]

  Radiation accumulated 5x the normal rate
  Swiming and wading increases rads even faster
  Radiation no longer decays over time, you have to use rad-away or visit a doctor to reduce it.
  Radiation accumulation rates are configurable in to the FWE Control Panel: 

Radiation Rates Control Panel Options ( Combat > Radiation )

Option 1 - Low Rads (Vanilla), 100% radiation decay

Option 2 - Moderate Rads, 2.5x accumulation, 10% decay rate

Option 3 - High Rads (FWE Default), no rad decay

  More severe radiation sickness effects [credits: Radiation Revamp] You suffer more SPECIAL penalties and other ill effects 

from increasing levels of radiation poisoning. At higher rad levels, you begin to glow with radiation!

Home Lab + Infirmary

Tweaked the costs of the home lab + infirmary upgrades down to 750 from 1200.

The lab requires ONE stimpak to heal addictions.

The infirmary requires 1 stimpak to restore you to full health. Limb healing requires 1 stimpak and you must have 1 medical

brace and 1 surgical supplies in your inventory. The medical brace and surgical supplies are not consumed, only the stimpak.

Lastly, curing rads requires 1 radaway. There is still an advantage to using these features, as regardless of your medicine

skill, it only takes 1 stimpak to heal to full health and all of your limbs, and to remove all rads.

Portable Lab + Infirmary

  Integration of FF Portable Laboratory + Infirmary (by Fritz_Fretz). This adds a purchasable lab and infirmary to the game, 

so you can get those services even if you don't live in Megaton or Tenpenny tower. Includes cool new models .

  To set up either piece, drop it from your inventory and position it as desired on a level surface. The set up has fairly 

tight angular restrictions, so a table or floor work best. Activate the placer to to enter the set up menu. Once placed the

model will change, i.e. the med-kit opens and a chemistry set is placed on the locker. A delay (default 3 days) is built into

the set up of each item.

  The items must remain set up for the duration of the delay in order to be used. This was done to make placement of these 

items more semi-permanent in an effort to avoid using them as an exploit. Activating the item prior to the expiration of the

delay will allow you to check how many hours are left prior to its being usable.

  After the delay has expired, performing this check will enable the item's use. Once enabled, activate the contents of the 

med-kit/chemistry set to use the infirmary/laboratory. Activating the lid/locker will allow you to pack the infirmary/laboratory

for transport.

Primary Needs (by K.Schenk and FritZ_FretZ)

FWE features a fully customizable (and disable'able) primary needs mod for hunger, thirst, and sleep. In addition to controlling

how often (and how much) you need to eat, drink, or sleep, the mod also controls how sleeping affects health recovery and how

food and water restores health (or not). When the game loads, the configuration menu will run. You can re-access this menu by

HOLDING the keypad enter key for a few seconds or through the FWE Control Panel under the “Primary Needs” option on the main

menu. The configuration menu allows you to choose health recovery on rest, food and drink healing, the rate of how quickly you

get hungry/thirsty/sleepy, and how much you need to eat/drink/sleep to reduce your needs levels.

Default Needs

By default, you are required to eat and drink a few times (3-4) each day or else you will suffer increasingly severe penalties

to your SPECIAL stats. Different types of food provide different amounts of hunger satisfaction, typically in-line with their

weight (i.e. 1 WG of meat provides more food value than 0.1 WG item of junk food). If you eat too much too quickly, you will get

“full” and suffer a minor Agility penalty. When eating or drinking, pause a second or two to allow your status condition to be

updated. You will typically need 6-8 hours of sleep per day to be well rested.

In addition, by default, food and water sources do not heal your health, again this can be changed in the Primary Needs section

of the control panel if desired. In addition, you do not automatically heal limbs + health when resting. Instead you heal health

slowly overtime (based on endurance and strength) and you cannot heal crippled limbs during sleep.

In the control panel, you can disable the entire primary needs system, or enable disable each of the components (hunger, thirst,

and sleep) independently.

Bottle Water

Primary Needs allows you to bottle water from most water sources. You will see empty bottles in your misc tab of the pip-boy

after drinking collected liquid items. To fill an empty bottle, activate a water source while in sneak mode. A menu will pop up

asking you how many of your bottles you would like to fill.

Portable bedroll, water purifier, and grill

In addition, Primary Needs adds new items to the main vendors, including a portable bed roll, a water purifier, and cooking

oven. The water pruifier uses RadAway packets to turn “dirty” water in to cleaner types (although never as good as purified

water). The bedroll allows you to sleep nearly anywhere, and the cooking oven lets you make “grilled” meats that are more light

weight but nutritious rations. However, cooking some food items will remove their unique properties (i.e. deathclaw meat special

bonuses). In order to re-pickup these items, hold the “use” key (z) and then hit activate key.

Darn's UI Support

Integrated support for Darn's UI with primary needs, so that the x-panels display your current hunger, thirst, and sleep levels

from primary needs.

Starting at 80% condition, there is a 0.1% chance of a weapon jamming, to 10% at 10% condition. When reloading, there is a chance the weapon will jam. 1% at 50% condition, to 25% at 10% condition. Weapon condition has a slightly greater effect on fire rate for automatic weapons, with slower rates of fire at progressively

lower conditions.

Repairing power armor uses other suits of power armor or fusion batteries (for the suit) and sensor modules (for the helm).In

addition, you can CRAFT a power armor repair kit at a workbench. These repair kits are made from 3 scrap metals, 1 abraxo

cleaner, and 1 conductor, and will yield two power armor repair kits. You need at LEAST 50 repair skill in order to CRAFT the

repair kit.

Ammo now has weight [Credit: Weighted Ammo Mod] when held in your inventory. Now you can't carry an entire ammo supply dump

around with you. Ammo weight is applied to used CALIBR ammo types as well. Ammo weight is as follows:

  0.01 lbs : Darts; BB Ammo; 5mm
  0.03 lbs : 10mm; .32 Caliber; Small Energy Cell; Alien Power Cell; 5.56mm; Microfusion Cell; Electron Charges; Flamer Fuel
  0.05 lbs : 44 Magnum; .308 Caliber; Rail Spikes
  0.10 lbs : Shotgun Shell; Mesmetron Cell
  1.00 lbs : Missile
  3.00 lbs : Mini Nuke 

Various items of medical equipment now provides a bonus to your medicine skill when combined at a workbench into a medical kit.

Combining a Bonesaw, Scalpal, Forcepts, Tweezers, and a Toolkit at the workbench creates a “Medical Kit” misc item that provides

+10 to your medical skill when in your inventory.

Cross Repair

The range of items available to repair armor and weapons is greatly expanded [credits: Repair Rethought].

  Many weapons and armor are now cross-repairable with logical counterparts.
  Schematic-built weapons repairable with original parts
  Clothing and leather armor repairable with fabric items and wonderglue
  Weapons and metal armors repairable with scrap metal
  Wooden stuff repairable with wooden stuff 

Scrap Metal

Changed the role of scrap metal for use in repairing weapons and armor. Scrap metal is no longer used in the repair lists. Instead, you must use the workbench to CRAFT “repair parts” out of scrap metal. You will gain this ability once your repair skill reaches level 50, at which point TWO scrap metals will yield TWO repair parts. At repair skill 75, two scrap metals will yield three repair parts, and at skill 100 four repair parts. The weight of scrap metal has been increased from 1.0 to 1.5. Repair parts weigh 0.5, so converting scrap metal into repair parts is a weight effecient solution.


You can now CRAFT a tool-kit at a workbench by combing a lunchbox with a hammer, wrench, scissors, and iron. The “toolbox” will provide +10 to your repair skill when held in your inventory.

Other Repair Changes

Standing next to a workbench provides an addition +10 to your repair skill [credits: Haldur's Improved Workbench].

Tweaked the repair gamesettings. You can now repair weapon armor condition the same level as your repair skill. For example, in the original fallout, 50 repair skill let you repair things to 70% condition, and in prior FWE versions only to 30% condition. Now with 50 repair skill you can repair to 50% condition.

The repair skill of vendors has been increased to provide an alternative to those who do not specialize in repair.

The base cost for repair has been reduced, from 2x down to 1.25x base weapon cost. In conjunction with the broad price reductions for weapons and armor, it should be more feasible to use vendors to repair.

1b/lugs/maxwell13/physics.txt · Last modified: 2012/07/24 15:17 (external edit)