Radiation:

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.
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.

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.

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 meltdown might be expected once in 20,000 years of reactor operation. In 2 out of 3 meltdowns 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 meltdowns each year for nuclear power to be as dangerous as coal burning.

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.
Elaborate packaging largely neutralizes potential problems from accidents in transport of radioactive materials. 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.