Not really, car accidents are one of the leading causes of deaths for a reason, and lifetime risk in that particular case is a percentage chance of a person dying from being involved in a car accident, and all the factors that entails.
Let me explain this a little more indepth. This is essentially derived from two functions, though there are more factors, these are the majors as far as NRC is concerned:
- The probability that a person living near a nuclear power plant will die soon after a nuclear accident from radiation released in the accident must be less than 0.1% of the total probability that a person will be killed by any accident.
- The probability of death from cancer for any member of the public following an accident must be less than 0.1% of the total probability that a person will die of cancer from all causes.
Numerically, the stated probability per year that a person will die is 0.04%. This number was derived from a vast variety of studies, the most extensive of which was a safety study of 5 selected nuclear power plants in 1990, and consisted of four fundamental parts: the frequency of core damage (internal and external), radioactive source term inside the containment, the probability of a containment failure, and the calculated off-site consequences. The results of the study were that the likelihood per year of an accident at a nuclear power plant large enough to cause at least one early fatality to the public is in the range of one in one million to one in one billion per year. However, the 0.04% lifetime risk number is not an average probability of all the studies they conducted - it is the most limiting of all the studies conducted, so it is the one used. This comes out to 4 in 10000, as stated previously by Kaylia. Therefore the safety goal of a plant as set by the NRC is to be 1000 times above that limit, or four people in at least ten million for a design basis casualty with radioactive release to the environment.