Select Committee on Science and Technology Third Report


Glossary of Terms and Acronyms
" 10-6" Often proposed as the standard design criterion for a nuclear waste repository: the risk of death to an individual in the critical group of one in one million per year (ie 10-6). On the same basis as the criterion was derived the risk from natural background radiation is about one in ten thousand.
ACSNIAdvisory Committee on the Safety of Nuclear Installations (renamed NuSAC in July 1997).
AECLAtomic Energy of Canada Limited.
AGRAdvanced Gas cooled Reactor.
AnaerobicIn the absence of free oxygen.
BecquerelThe standard unit of radioactivity , equal to one nuclear disintegration per second. A becquerel (Bq) is a very small unit and when discussing radioactive waste the term terabecquerel is often more appropriate: one terabecquerel (TBq) = 1012 Bq; ie a million million disintegrations per second.
BGSBritish Geological Survey.
BNFLBritish Nuclear Fuels plc (previously British Nuclear Fuels Ltd).
CANDUCanadian Deuterium Uranium water-cooled reactor type. The fuel consists of un-enriched ceramic uranium oxide pellets within zirconium alloy tubes.
CmndGovernment command paper.
COLAConsortium of Opposing Local Authorities.
Committed wasteWaste which cannot be avoided. It will be created even if the entire nuclear industry were to cease operation immediately: the waste either already exists or will result from the decommissioning of existing installations.
CORECumbrians Opposed to a Radioactive Environment.
Critical groupThe group of people who, on basis of age, living habits and place of residence, receive the highest radiation dose. (This may be an existing or hypothetical group.)
DecommissioningThe term decommissioning is used in a generic sense to cover all of the procedures undertaken once a nuclear installation has ceased operating. Decommissioning therefore covers processes such as defuelling reactors, cleaning and making safe an installation (which could include a long period of safe storage on site), dismantling, removal work and waste conditioning prior to storage or disposal.
Depleted uraniumUranium consisting predominantly of non-fissile uranium.
DETRDepartment of the Environment Transport and Regions.
DTIDepartment of Trade and Industry.
EURATOMEuropean Atomic Energy Community.
FissileRefers to a radionuclide which can break into two large fragments accompanied by the release of free neutrons and large amounts of energy. A few man-made radionuclides are so unstable that they fission spontaneously; others can do so if the nucleus captures a neutron.
Fission productsThe atomic fragments resulting from nuclear fission. For instance, the two large atomic fragments produced by the fission of uranium-235 might be isotopes of tin and molybdenum, which themselves are likely to be highly radioactive.
GRAGuidance on Requirements for Authorisation (for disposal facilities on land for LLW and ILW). A document outlining safety standards for disposal.
Half lifeThe time required for half of the atoms in a sample to decay or transform. For example: the radionuclide krypton-85 has a half-life of 3,934.4 days and decays to the stable isotope rubidium-85 by emitting a beta particle; after one period of 3,934.4 days, 50 per cent of the initial krypton-85 atoms in a sample will have become rubidium-85; after ten half lives (107 years, 9½ months) the sample will contain just 0.1 per cent krypton-85, and 99.9 per cent rubidium-85.
HLWHigh Level radioactive Waste. Highly active heat generating waste that normally continues to generate heat for several centuries. A high level of shielding and heat dissipation is required during handling, transportation, and storage (and disposal). Its thermal power is above 2 kW per m3. It may take many thousands, or millions, of years for the radioactivity of HLW to decay to background levels.
HSEHealth and Safety Executive.
IAEAInternational Atomic Energy Agency.
ILWIntermediate Level radioactive Waste. Waste in which radioactivity levels exceed the upper boundaries for LLW. Some of it requires shielding. Heat generation usually less than 2kW per m3 but may require provision for heat dissipation during storage (or disposal).
Intergenerational equityThe concept that future generations should not have to bear the costs and consequences of actions which were of benefit mainly to present and previous generations.
LLWLow Level radioactive Waste. Radioactive materials other than those suitable for disposal with ordinary refuse, but containing less than 4 x109 Bq per tonne of alpha activity or less than 12 x 109 Bq per tonne of beta/gamma activity. Does not require shielding during normal handling and transportation.
MagnoxReactor type using uranium metal fuel rods enclosed in a cladding of magnesium alloy.
MoDMinistry of Defence.
MOXMixed Oxide Fuel (a mixture of plutonium oxide and uranium oxides).
MTRMaterials Testing Reactor.
NCNINational Campaign for the Nuclear Industry.
NEAOECD Nuclear Energy Agency.
NERCNatural Environment Research Council.
NGONon Governmental Organisation.
NIINuclear Installations Inspectorate (part of the HSE).
NIMBYNot In My Back Yard. Referring to objections to activities nearby, e.g. planned nuclear installations, or motorways.
NirexUnited Kingdom Nuclear Industry Radioactive Waste Management Executive.
NRPBNational Radiological Protection Board.
NSCNational Steering Council for Nuclear Free Local Authorities.
NuSACNuclear Safety Advisory Committee (originally ACSNI).
OECDOrganisation for Economic Co-operation and Development.
PalaeoclimaticConcerned with the climate in the geological past.
PartitioningSpecifically the separation of certain radionuclides from other wastes so that they may be subjected to transmutation.
Probabilistic assessmentIn the case of a repository, a safety assessment that takes into account the probabilities and consequences of events and processes that could lead to radionuclide releases, or influence release rates, and also takes account of uncertainties in estimating probabilities and consequences.
POSTParliamentary Office of Science and Technology.
PWRPressurised Water Reactor.
R&DResearch and Development.
RadionuclideAny nuclide (isotope of an element) which exhibits radioactivity (ie can undergo spontaneous disintegration, releasing an alpha-particle, a beta-particle or a gamma-ray).
RCEPRoyal Commission on Environmental Pollution.
RCFRock Characterisation Facility (specifically the one planned in Cumbria).
RWMACRadioactive Waste Management Advisory Committee.
RWPGRadioactive Waste Policy Group (in the DETR).
SAPSafety Assessment Principles (for nuclear plants).
SEPAScottish Environment Protection Agency.
SievertA measure of radiation dose which takes into account the type of radiation involved, the energy deposited in the tissues irradiated, and the sensitivity of the different body tissues to radiation. Typically, doses are expressed in terms of micro sieverts (µSv). 1 sievert = 1 million µSv. A dose of around 6.5 Sv, delivered over a few minutes or hours, will lead to death from acute radiation sickness within a few weeks. The annual average dose to an individual in the United Kingdom is 2,200 µSv from natural radiation and 400 µSv from man-made radiation, (of which 370 µSv is from medical uses of radiation and radioactive materials).
SKBSvensk Kärnbränslehantering AB (Swedish nuclear fuel and waste management company).
Subduction zoneArea of the Earth's surface where one tectonic plate is over-ridden by another: typically an oceanic plate will subduct beneath a continental plate. It has been suggested that depositing nuclear waste in or on a plate that is being subducted will lead to it being transported into the mantle and thus out of the biosphere.
Terabecquerel1012 Becquerels.
THORPThermal Oxide Reprocessing Plant (at Sellafield). Oxide fuel is used in AGRs, PWRs and other light water reactors.
TransmutationProcess by which radionuclides are bombarded with neutrons (either in a reactor or a particle accelerator) and are converted into shorter-lived or stable nuclides.
UKAEAUnited Kingdom Atomic Energy Authority, now known only by its acronym.
URLUnderground Research Laboratory.
VitrificationThe process by which radioactive waste (typically HLW) is immobilised in borosilicate glass.
VLLWVery Low Level radioactive Waste. Formally defined as material in which each 0.1 m3 contains less than 4 x 105 Bq of beta/gamma activity or single items which contain less than 4 x 104 Bq of beta/gamma activity. This waste can be disposed of at landfill sites without special treatment.
WIPPWaste Isolation Pilot Plant. An underground waste repository built in salt deposits in New Mexico US for military nuclear waste.

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