Classification of LLW for Near-Surface Disposal

DOE-STD-6003-96

(75 mrem) to the thyroid, and 0.25 mSv (25 mrem) to any other organ of the body (10 CFR

61.41) were used to establish radionuclide concentration limits based on several exposure

scenarios (NRC 1981 and NRC 1982). The intruder construction scenario produced the highest

dose to individuals. This scenario begins with the construction of a house on the waste disposal

site after the period of institutional control, assumed to be 100 yr. Construction workers are

exposed to direct gamma radiation from the waste and inhale waste particles while digging the

foundation. If the waste is still recognizable as being radioactive, construction is assumed to

stop after 6 h. Class C waste is assumed to be stable for 500 yr.

If the waste is not recognizable as being radioactive, construction is assumed to continue

for 500 h. The completed house is occupied, and the inhabitants inhale suspended waste parti-

cles and are exposed to direct gamma radiation from the waste. In addition, they are assumed

to grow one-half of all their food on the waste site. The inhabitants there ingest radionuclides

deposited on the leaves of plants and absorbed through their roots, either directly in the case of

vegetables or indirectly through the meat and milk of cows in the case of grass. 10 CFR 61 lim-

its the specific activity of radionuclides so that the 50-yr whole-body dose commitment ("intruder

dose") to workers from construction or the 50-yr dose commitment to inhabitants from exposure

during the first year does not exceed 5 mSv (0.5 rem), which is currently the maximum permis-

sible annual dose for members of the public.

7. 4.1.1 Classification of LLW for Near-Surface Disposal

Determination of the classification of radioactive waste involves two considerations. First,

consideration must be given to the concentration of long-lived radionuclides (and their shorter-

lived precursors) whose potential hazard will persist long after such precautions as institutional

controls, improved waste form, and deeper disposal have ceased to be effective.

These precautions delay the time when long-lived radionuclides could cause exposures.

In addition, the magnitude of the potential dose is limited by the concentration and availability of

the radionuclide at the time of exposure. Second, consideration must be given to the concentra-

tion of shorter-lived radionuclides for which requirements on institutional controls, waste form,

and disposal methods are effective.

7. 4.1.2 Classes of Waste

Class A waste is waste that is usually segregated from other waste classes at the dis-

posal site. The physical form and characteristics of Class A waste must meet the minimum

requirements set forth in 10 CFR 61.56(a). If Class A waste also meets the stability require-

ments set forth in 10 CFR 61.56(b), it is not necessary to segregate the waste for disposal.

Class B waste is waste that must meet more rigorous requirements on waste form to

ensure stability after disposal. The physical form and characteristics of Class B waste must

meet both the minimum and stability requirements set forth in 10 CFR 61.56.

Class C waste is waste that not only must meet more rigorous requirements on waste

form to ensure stability but also requires additional measures at the disposal facility to protect

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