aConverted from the recommendation on risk, assuming risk of 0.05 per Sv.
The NRC imposes a limit of 1 mSv/yr on the effective dose that can be received by any member of the public from a NRC-licensed facility (exempting medical treatments). EPA regulations impose a limit of 0.25 mSv/yr on the effective dose from nuclear power facilities, including nuclear reactors. They provide a still more stringent 0.15 mSv/yr for waste disposal sites under the EPA's authority.
Actual exposures to the public from nuclear power operations are lower than the regulatory limit of 0.25 mSv/yr, and the limit is not presently constraining. It is unlikely to be approached except in the case of an accident, in which case the existence of regulations might be moot. The regulatory limits may, however, provide a spur to careful operation.
Permitted occupational exposures, for nuclear workers and others, are considerably higher than those for the general publicthe present US limit is 50 mSv/yr. However, the ALARA principle also applies, and the average dose for nuclear workers is much below this limit.
The EPA has taken only an advisory, but not regulatory, position on indoor radon exposures, because it has no authority over air in private residences. For radon, the EPA suggests that remedial action be taken if the indoor concentration exceeds a level of 4 pCi/liter, corresponding roughly to an effective dose of 8 mSv/yr.
Standards for the proposed Yucca Mountain nuclear waste repository have not yet been established. However, recommendations on the nature of these standards have been made by a congressionally-mandated committee working under the auspices of the National Research Council, an agency of the National Academy of Sciences. This committee recommended a limiting risk factor of 10-5 to 10-6 per year. If one assumes the present conventional risk factor of 0.05 per Sv, this translates to effective doses of 0.2 mSv/yr to 0.02 mSv/yr. This limit is to be applied to the average member of a small "critical group" (probably numbering under 100 people) that is particularly dependent on water contaminated by radionuclide releases from the repository. In the NAS recommendation, this limit would apply for up to 1 million years. Some observers believe that it unreasonable to require this level of protection for a small group of people so far into an unpredictable future.
|last updated: August 9, 2000 webmaster|