Residual Radioactivity Levels - Continued

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

DOE 5400.5 requirements for release and control of property containing residual

radioactive materials," the guideline values are as follows:

Guidelines

20 dpm/100 cm2

Removable Contamination

500 dpm/100 cm2

Total (Fixed plus Removable Contamination)

-- 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

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