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Characterization of Remote-Handled Transuranic Waste for the Waste Isolation Pilot Plant: Final Report Appendix H Waste Dose Rates and Characterization Cost Estimates The committee provides the following worker dose and characterization cost estimates as examples of the type of assessments that could be presented in the three implementation plans (from Battelle Columbus Laboratories, Energy Technology Engineering Center, and Oak Ridge National Laboratory) that the U.S. Department of Energy (DOE) is planning to submit to the U.S. Environmental Protection Agency and the New Mexico Environment Department along with its characterization plan for remote-handled transuranic (RH-TRU) waste. The committee’s assessment is based on the information gathered during the study. It is not to be considered complete and is not meant to replace DOE’s own assessment of worker doses and costs. The predominant exposure pathways for workers from routine waste handling activities are direct exposure to external penetrating radiation or inhalation from surface contamination, and inhalation of airborne radioactive material generated during characterization and handling activities. The radiogenic health effects associated with TRU waste are due primarily to alpha and gamma radiation. Beta particles and neurons may also pose health concerns for RH-TRU waste if the container is breached or waste is exposed during handling or characterization. H.1 Committee’s Example of Estimate for Waste Dose Rates Because of the high surface dose rates, all of the handling operations involving RH-TRU waste are performed in hot cells, where available, and/or by remote-handling equipment. Good radiological safety practices require that all radiological activities must maintain worker dose levels ALARA (as low as reasonably achievable). In the absence of appropriate radiological safety measures, the potential for significant radiation exposure is high. The estimated volume-weighted mean RH drum surface dose rate at individual generator sites is 470 mSv per hour (47,000 mrem per hour) (Wu, 2001). Therefore, the cost associated with the handling of RH-TRU waste may be substantial. Doses from handling RH-TRU waste are expected to be less than contact-handled transuranic (CH-TRU) waste due to requirements for remote handling. For instance, the DOE-Carlsbad Field Office estimated for the period 1999–2001 that the collective dose for handling CH-TRU waste at the Waste Isolation Pilot Plant (WIPP) is approximately 0.08 person-mSv (0.008 person-rem) per transportation cask type TRUPAC-II. According to Wu (2001), this is about two times higher than the estimated collective dose to workers handling a RH72-B type cask of RH-TRU waste. Doses to workers depends on several factors including the number of drums characterized and handled, types of sampling and measurements conducted, number of workers involved in the characterization and drum handling, worker experience and training, and facilities, equipment and shielding. Table H.1 compares estimated
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Characterization of Remote-Handled Transuranic Waste for the Waste Isolation Pilot Plant: Final Report collective doses to workers at three different sites. Because these data are from different sites they may not be comparable. TABLE H.1 Committee’s Estimates of Worker Doses at Selected Sites Site Collective Dose Comment Battelle Columbus Laboratories 1.0 person-mSv (100 person-mrem) per container This dose corresponds to an average of five workers handling the containers and includes waste characterization and handling containers for storage.1 Argonne National Laboratory-East 0.22–0.64 person-mSv (22–64 person-mrem) per container Range of collective doses for four different location and storage scenarios.2 Waste Isolation Pilot Plant (WIPP) 0.02 person-mSv (2 person-mrem) per container Waste is shipped to WIPP in RH72-B waste canisters (assume each canister contains 3 containers of 55 gallons). Waste handlers receive 80 percent of the dose.3 NOTE: Collective doses may not be representative of all RH-TRU waste generator sites. This table was compiled by the committee as an example of worker dose estimates on the basis of information gathered during the study. It is not intended to be complete and may contain inaccuracies. 1Memorandum from Dr. Rigley at Battelle Columbus Laboratories (BCL, 2000). 2Radiological risk assessment at Argonne National Laboratory-East (Cheng et al., 2002). 3Information presented to the committee during the second meeting (Wu, 2001). The Battelle Columbus Laboratories in Ohio developed its own RH-TRU waste characterization plan, which involves visual examination of the waste during repackaging. The re-packaging step, which occurs in a hot cell, is necessary because the this site’s RH-TRU waste containers do not meet transportation requirements. At this site, the worker dose per container (100 person-mrem per 5 persons corresponds to 20 mrem) is within the range of worker doses for CH-TRU waste characterization (Wu, 2001). It is unclear how representative Battelle Columbus Laboratories worker exposure data are for other RH-TRU waste generators. However, the Battelle data are informative because this is the only site actively characterizing RH-TRU waste. A radiological risk assessment for RH-TRU waste has been performed for storage options at Argonne National Laboratory-East (Cheng et al. 2002). Although characterization of RH-TRU waste has not begun at this site, risk assessments have been conducted to analyze potential radiation exposures associated with various on-site storage scenarios. Detailed analyses of container handling activities at the Alpha Gamma Hot Cell Facility show that the major determinants of worker collective dose are manipulation of containers for waste loading and placing and securing container lids. These two activities account for 75 percent of the collective dose to workers (Cheng et al., 2002).
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Characterization of Remote-Handled Transuranic Waste for the Waste Isolation Pilot Plant: Final Report The WIPP facility has estimated worker doses for the handling and emplacement of RH-TRU waste (Wu, 2001). WIPP is currently not authorized to receive RH-TRU waste; estimates of worker doses are based on calculated average container surface dose rates, shielding characteristics of the RH72-B canister, and remote-handling of waste canisters. Worker doses are substantially lower than doses estimated at the generator sites primarily because of RH72-B canister shielding. As shown in Table H.1, collective dose may vary widely between and within sites. For instance, container handling methods and procedures (the key determinant of worker dose) may differ. Further, the relative importance of worker exposures incurred during the characterization phase compared to that incurred in other handling operations will likely differ at the generator sites. Accordingly, it is important that ALARA programs be site-specific. H.2 Committee’s Example of Cost Estimates Characterization costs including facilities and instrumentation for RH TRU waste sampling and measurements are significant. According to DOE and the generator sites, the characterization of an RH-TRU waste container under the CH-TRU waste characterization requirements is estimated to cost in the range of $20,000 to $300,000 per container (Restrepo and Millard, 2001). In contrast, the cost of characterizing CH-TRU waste is about $3,800 per container (DOE-EM, 2001). The large range in RH-TRU characterization cost estimates is due to the variability in the waste content and the characterization processes among the sites. In addition, these cost estimates are not site-specific and take into account only a few characterization scenarios. Associated infrastructure costs in support of full characterization of RH-TRU waste have been estimated to be $100,000 per container (Restrepo and Millard, 2001). The Committee has not verified these cost estimates. REFERENCES BCL. 2000. Battelle Columbus Laboratory Memorandum from D.Ridgley. April 12. Wu, C-F. 2001. TRU Waste Dosimetry. Presentation to the National Research Council Committee, 3–5 October. Albuquerque, N.Mex. Cheng, J-J, H.Avci, D.Hecker, W.Bray, T.Bray, and C.Grandy. 2002. Radiological Risk Assessment for the Remote-Handled Transuranic Waste Storage Options at Argonne National Laboratory-East. Proceedings of the WM’02 Conference, February 24–28, Tucson, Ariz. DOE-EM. 2001. Transuranic Waste Characterization Cost Analysis. U.S. Department of Energy-Office of Environmental Management. Memorandum from L.Wade, Director of the Waste Isolation Pilot Plant Office. February 23. Washington, D.C. Restrepo, L.F. and J.B.Millard. 2001. A Risk/Cost Impact Analysis of Various Options for Characterizing Department of Energy Generated Remote-Handled Transuranic Waste. June 30. Omicron-01–012. Albuquerque, N.Mex. Presented in Notification of Proposed Change to the EPA’s Waste Isolation Pilot Plant 40 CFR 194 Certification. July 16, 2001. Draft. Revision 1. Carlsbad, N.Mex.
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