Residual Radioactivity Levels - Continued

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

annual dose has not yet been determined, but values of 50, 10, 1, and 0.1 mrem/y are being

considered by the EPA as the "de facto de minimis" levels for the disposal of contaminated

material.

Section 4 of DOE Order 5400.5, Ch. 2, Radiation Protection of the Public and Environment

(DOE, 1993c), provides the following DOE guidelines for cleanup of residual radioactive

material, management of the resulting wastes, and release of property. The basic public dose

limits for exposure to residual radioactive material in addition to natural background

exposures is a 100-mrem (1-mSv) effective dose equivalent in a year. The effective dose

equivalent in a year is the sum of the effective dose equivalent from exposures to radiation

sources external to the body during the year plus the cumulative effective dose equivalent

(CEDE) from radionuclides taken into the body during the year.

DOE Order 5400.5, Ch. 2 (DOE, 1993c) also provides the following guidelines for

(1) residual concentrations of radionuclides in soil, (2) concentrations of airborne radon

decay products, (3) external gamma radiation, (4) surface contamination, and

(5) radionuclide concentrations in air or water:

-- Residual radionuclides in soil - Generic guidelines for thorium and radium (226Ra, 228Ra,

230

Th, and 232Th) are 5 pCi/g averaged over the first 15 cm of soil below the surface and

15 pCi/g averaged over 15-cm-thick layers of soil more than 15 cm below the surface.

For other radionuclides in soil (e.g., plutonium), specific guidelines should be derived

from the basic dose limit by means of an environmental pathway analysis using specific

property data where available. Residual concentrations of radioactive material in soil are

defined as those in excess of background concentrations averaged over an area of 100 m2.

-- Airborne radon decay products - Applicable generic guidelines are found in 40 CFR

192 (EPA, 1992b). In any occupied or habitable building, the objective of remedial

action should be, and a reasonable effort should be made to achieve, an annual average

(or equivalent) radon decay product concentration (including background) not to exceed

0.02 WL. Remedial actions by DOE are not required to comply with this guideline when

there is reasonable assurance that residual radioactive material is not the source of the

radon concentration.

-- External gamma radiation - The average level of gamma radiation inside a building or

habitable structure on a site to be released without restrictions should not exceed the

background level by more than 20 R/h.

-- Surface contamination - The DOE guidelines on transuranic surface contamination

levels are given in a DOE memorandum dated November 17, 1995, "Application of

10-4