Bernard L. Cohen, Sc.D.
Professor at the University of Pittsburgh


The principal risks associated with nuclear power arise from health effects of radiation. This radiation consists of subatomic particles traveling at or near the velocity of light---186,000 miles per second. They can penetrate deep inside the human body where they can damage biological cells and thereby initiate a cancer. If they strike sex cells, they can cause genetic diseases in progeny.

Radiation occurs naturally in our environment; a typical person is, and always has been struck by 15,000 particles of radiation every second from natural sources, and an average medical X-ray involves being struck by 100 billion. While this may seem to be very dangerous, it is not, because the probability for a particle of radiation entering a human body to cause a cancer or a genetic disease is only one chance in 30 million billion (30 quintillion).

Nuclear power technology produces materials that are active in emitting radiation and are therefore called "radioactive". These materials can come into contact with people principally through small releases during routine plant operation, accidents in nuclear power plants, accidents in transporting radioactive materials, and escape of radioactive wastes from confinement systems. We will discuss these separately, but all of them taken together, with accidents treated probabilistically, will eventually expose the average American to about 0.2% of his exposure from natural radiation. Since natural radiation is estimated to cause about 1% of all cancers, radiation due to nuclear technology should eventually increase our cancer risk by 0.002% (one part in 50,000), reducing our life expectancy by less than one hour. By comparison, our loss of life expectancy from competitive electricity generation technologies, burning coal, oil, or gas, is estimated to range from 3 to 40 days.

There has been much misunderstanding on genetic diseases due to radiation. The risks are somewhat less than the cancer risks; for example, among the Japanese A-bomb survivors from Hiroshima and Nagasaki, there have been about 400 extra cancer deaths among the 100,000 people in the follow-up group, but there have been no extra genetic diseases among their progeny. Since there is no possible way for the cells in our bodies to distinguish between natural radiation and radiation from the nuclear industry, the latter cannot cause new types of genetic diseases or deformities (e.g., bionic man), or threaten the "human race". Other causes of genetic disease include delayed parenthood (children of older parents have higher incidence) and men wearing pants (this warms the gonads, increasing the frequency of spontaneous mutations). The genetic risks of nuclear power are equivalent to delaying parenthood by 2.5 days, or of men wearing pants an extra 8 hours per year. Much can be done to avert genetic diseases utilizing currently available technology; if 1% of the taxes paid by the nuclear industry were used to further implement this technology, 80 cases of genetic disease would be averted for each case caused by the nuclear industry.

Reactor accidents

The nuclear power plant design strategy for preventing accidents and mitigating their potential effects is "defense in depth"--- if something fails, there is a back-up system to limit the harm done, if that system should also fail there is another back-up system for it, etc., etc. Of course it is possible that each system in this series of back-ups might fail one after the other, but the probability for that is exceedingly small. The Media often publicize a failure of some particular system in some plant, implying that it was a close call" on disaster; they completely miss the point of defense in depth which easily takes care of such failures. Even in the Three Mile Island accident where at least two equipment failures were severely compounded by human errors, two lines of defense were still not breached--- essentially all of the radioactivity remained sealed in the thick steel reactor vessel, and that vessel was sealed inside the heavily reinforced concrete and steel lined "containment" building which was never even challenged. It was clearly not a close call on disaster to the surrounding population. The Soviet Chernobyl reactor, built on a much less safe design concept, did not have such a containment structure; if it did, that disaster would have been averted.

Risks from reactor accidents are estimated by the rapidly developing science of "probabilistic risk analysis" (PRA). A PRA must be done separately for each power plant (at a cost of $5 million) but we give typical results here: A fuel melt-down might be expected once in 20,000 years of reactor operation. In 2 out of 3 melt-downs there would be no deaths, in 1 out of 5 there would be over 1000 deaths, and in 1 out of 100,000 there would be 50,000 deaths. The average for all meltdowns would be 400 deaths. Since air pollution from coal burning is estimated to be causing 10,000 deaths per year, there would have to be 25 melt-downs each year for nuclear power to be as dangerous as coal burning.

Of course deaths from coal burning air pollution are not noticeable, but the same is true for the cancer deaths from reactor accidents. In the worst accident considered, expected once in 100,000 melt-downs (once in 2 billion years of reactor operation), the cancer deaths would be among 10 million people, increasing their cancer risk typically from 20% (the current U.S. average) to 20.5%. This is much less than the geographical variation--- 22% in New England to 17% in the Rocky Mountain states.

Very high radiation doses can destroy body functions and lead to death within 60 days, but such "noticeable" deaths would be expected in only 2% of reactor melt-down accidents; there would be over 100 in 0.2% of meltdowns, and 3500 in 1 out of 100,000 melt-downs. To date, the largest number of noticeable deaths from coal burning was in an air pollution incident (London, 1952) where there were 3500 extra deaths in one week. Of course the nuclear accidents are hypothetical and there are many much worse hypothetical accidents in other electricity generation technologies; e.g., there are hydroelectric dams in California whose sudden failure could cause 200,000 deaths.

Radioactive Waste

The radioactive waste products from the nuclear industry must be isolated from contact with people for very long time periods. The bulk of the radioactivity is contained in the spent fuel, which is quite small in volume and therefore easily handled with great care. This "high level waste" will be converted to a rock-like form and emplaced in the natural habitat of rocks, deep underground. The average lifetime of a rock in that environment is one billion years. If the waste behaves like other rock, it is easily shown that the waste generated by one nuclear power plant will eventually, over millions of years (if there is no cure found for cancer), cause one death from 50 years of operation. By comparison, the wastes from coal burning plants that end up in the ground will eventually cause several thousand deaths from generating the same amount of electricity.

The much larger volume of much less radioactive (low level) waste from nuclear plants will be buried at shallow depths (typically 20 feet) in soil. If we assume that this material immediately becomes dispersed through the soil between the surface and ground water depth (despite elaborate measures to maintain waste package integrity) and behaves like the same materials that are present naturally in soil (there is extensive evidence confirming such behavior), the death toll from this low level waste would be 5% of that from the high level waste discussed in the previous paragraph.

Other Radiation Problems

The effects of routine releases of radioactivity from nuclear plants depend somewhat on how the spent fuel is handled. A typical estimate is that they may reduce our life expectancy by 15 minutes.

Potential problems from accidents in transport of radioactive materials are largely neutralized by elaborate packaging. A great deal of such transport has taken place over the past 50 years and there have been numerous accidents, including fatal ones. However, from all of these accidents combined, there is less than a 1% chance that even a single death will ever result from radiation exposure. Probabilistic risk analyses indicate that we can expect less than one death per century in U.S. from this source.

Mining uranium to fuel nuclear power plants leaves "mill tailings", the residues from chemical processing of the ore, which lead to radon exposures to the public. However, these effects are grossly over-compensated by the fact that mining uranium out of the ground reduces future radon exposures. By comparison, coal burning leaves ashes that increase future radon exposures. The all-inclusive estimates of radon effects are that one nuclear power plant operating for one year will eventually avert a few hundred deaths, while an equivalent coal burning plant will eventually cause 30 deaths.

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