Surveys of Wastes from Nuclear Reactor Facilities Before Disposal
See IE Information Notice 85-92 entitled as above and dated December 2, 1985.
This document supplements IE Circular 81-07 (IEC-81-07) as it applies to surveys of solid wastes before disposal from nuclear reactor facilities. It also discusses typical surveys that could be made to preclude unintentional release of radioactive materials.
The health physics position was written in the context of 10 CFR 20.201 and 20.301, but it also applies to the "new" 10 CFR Part 20, Sections 20.1501 and 20.2001. HPPOS-071 and HPPOS-072 contain related topics.
IEC-81-07 was issued by NRC in 1981 (see HPPOS-071) and provided guidance on the control of radioactively contaminated material and identified the extent licensees should survey for contamination (see HPPOS-072).
The criteria in IEC-81-07 addressed surface contamination levels based on the best information available at the time and were related to the detection capability of portable survey instruments equipped with thin-window "pancake" Geiger-Mueller (GM) probes responding primarily to beta radiation. The monitoring of aggregated, packaged material was not addressed. There was no major emphasis on segregating waste from designated contamination areas in 1981. As a result, large volumes of monitored wastes were not being released for unrestricted disposal. However, because of the recent emphasis on minimizing the volume of radioactive waste, current practices at many nuclear power facilities results in large volumes of segregated, monitored wastes with large total surface areas being released as "clean" waste.
When scanning surfaces with hand-held pancake probes, there is a chance that some contamination will not be detected or the total surface area will not be completely scanned. [See papers by J. F. Sommers, "Sensitivity of Portable Beta-Gamma Survey Instruments," Nuclear Safety 16 (4), pp. 452-457 (1975), and "Sensitivity of GM and Ion-Chamber Beta-Gamma Survey Instruments," Health Physics 28 (6), pp. 775-761 (1975).] Thus, when numerous items of "clean" material are combined, the accumulation of small amounts of contamination that escaped pancake probe detection may be detected using detectors sensitive to gamma radiation (e.g., by using a sensitive scintillation detector in a low-background area). Such measurements of packaged clean waste before disposal can reduce the likelihood that contaminated waste will be disposed of as clean waste.
To avoid the unintentional release of radioactive materials from nuclear reactor facilities, a good monitoring program that includes the following is recommended.
Surveys made with methods for detecting very low levels of radioactivity to discriminate between materials that are contaminated and those that can be disposed of as clean waste. The survey methods should provide licensees with reasonable assurance that licensed material is not released from their control.
Surveys using portable survey instruments with small pancake GM probes should be done only on small items and small areas. Because these instruments and probes lose detection sensitivity when moved and because of the difficulties in completely scanning large areas, this method of survey should be supplemented with other techniques for larger items.
Final measurements on each package of aggregated wastes should be done to ensure that an accumulation of licensed material resulting from the buildup of multiple, nondetectable quantities has not occurred (e.g., final measurements using sensitive scintillation detectors in low-background areas).
Regulatory references: 10 CFR 20.201, 10 CFR 20.301, 10 CFR 20.1501, 10 CFR 20.2001
Subject codes: 7.1, 7.6, 9.7