-- Residual radionuclides in air and water - Residual concentrations of
radionuclides in air shall not cause members of public to receive an effective
dose equivalent greater than 10 mrem (0.1 mSv) in one year [DOE Order
5400.5 (DOE, 1990b)]. In 40 CFR 141, National Primary Drinking Water
Regulations (EPA, 1992a), the EPA provides a limit of 4 mrem/y annual dose
equivalent to the whole body or any internal organ of any member of the public
from manmade radionuclides in drinking water.
The NRC is updating their decommissioning regulations and criteria. The new
NRC methodology is presented in NUREG/CR-5512 (Kennedy and Strenge,
1992) and is consistent with the recommendations in ICRP Publications 26 and
30 (1977, 1979). The NRC will establish a three-layered hierarchy for
developing decommissioning criteria to be used to evaluate the release of
property after D&D. The first and second layers use conservative models and
parameters, and the third layer uses site-specific models and data to provide a
more accurate approximation of actual conditions. Four criteria will be
calculated upon which to make D&D decisions: (1) a surface contamination
level for buildings and building materials (in dpm/100 cm2), (2) volume
contamination criteria for volume sources in buildings (in pCi/g), (3) soil
contamination criteria (in pCi/g), and (4) a total site inventory (in Ci).
These criteria require calculation of dose to members of the general population.
The scenarios for exposure will have to include all exposure pathways that are
credible under the proposed disposition. If the site is part of a closely guarded
government reservation, certain pathways may be eliminated, such as the use of
well water directly from the site and ingestion of significant quantities of fruits
and vegetables grown on the site. However, if the site will be released for
unrestricted use, such scenarios should be considered. The computer codes
used for calculation of dose to the public from decommissioned facilities will
include the currently accepted exposure models and site-specific or maximum
credible parameters for exposure pathways.
Finally it should be noted that a multi-agency effort has developed
measurement and decision criteria applicable to D&D projects. The Multi-
Agency Radiation Survey and Site Investigation Manual (MARSSIM) has been
published (DOE, 2000b). It provides detailed techniques applicable to the
D&D of DOE facilities.