Residual radionuclides in air and water

DOE-STD-1128-98

-- 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.

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