Performance Assessment and Sensitivity Analyses of Disposal of Plutonium as Can-in-Canister Ceramic, Rev. 00
The TSPA-SR nominal-case model (CRWMS M&O 2000d) was used in this analysis, incorporating the radionuclide inventory and physical characteristics of the plutonium can-in-canister ceramic waste form into the nominal, 100-realization TSPA-SR model (DTN: MO0009MWDNM601.018) and into the nominal, median-value TSPA-SR model (DTN: MO0009MWDMED01.020). The nominal, median-value TSPA-SR model (DTN: MO0009MWDMED01.020) was superceded by DTN: MO0012MWDMED01.032 that was not available at the onset of this analysis. The two models produce the same results, except for the 242Pu dose rate, for which the BDCF was corrected in DTN: MO0012MWDMED01.032. In this analysis, the BDCF of 242Pu was corrected in the TSPA-SR model (MO0009MWDMED01.020), such that it produces identical results when compared with the results using the corrected data set, DTN: MO0012MWDMED01.032 (see assumption 5.6). Performance assessment and sensitivity analyses of the can-in-canister ceramic were conducted to evaluate the potential use of HLW as a surrogate for the immobilized plutonium waste form in the TSPA-SR model (DTN: MO0101MWDPLU03.001, MO0101MWDPLU03.002). For the evaluation, the dose-rate histories for the can-in-canister ceramic were compared to the same number of HLW canisters and sensitivity analyses were conducted in areas where uncertainty exists to determine whether the inclusion of the plutonium can-in-canister ceramic waste form as HLW is appropriate. The following conclusions can be made: (1) The dose from the immobilized plutonium waste form, can-in-canister ceramic is significantly higher (about a factor of five) than that from an equivalent number of canisters of high-level waste. This higher dose is primarily due to 239Pu colloids from the ceramic and to a larger amount of 237Np in the surplus plutonium than is contained in the high-level waste. (2) The use of HLW as surrogate for immobilized plutonium in the TSPA-SR model is not strictly justified, because the current analysis indicated a noticeably higher dose rate than the equivalent number of HLW canisters. On the other hand, the total dose rate from the immobilized plutonium is more than one order of magnitude lower than the total dose rate from the TSPA-SR nominal case and does not significantly contribute to the total dose from the repository. Because of its relatively small contribution to total dose, the HLW could be used as a surrogate for the immobilized plutonium for all practical purposes, recognizing that the peak dose rates from HLW are somewhat lower than from the equivalent amount of immobilized plutonium. The higher peak dose from immobilized plutonium is due to significantly higher dose rates from waste-form colloids. The colloid model used in the TSPA-SR model will be subject to further refinement in the future. (3) The peak dose from the 17-ton case of can-in-canister ceramic is approximately a factor of 15 below that of the nominal, median-value TSPA-SR case (DTN: MO0009MWDMED01.020). (4) The dissolution rate using the LLNL ceramic model is more than one order of magnitude below that of high-level waste glass. The dissolution model used previously for ceramic (based on Synroc) has dose releases between that assuming the LLNL ceramic dissolution model and that assuming a high-level waste glass-dissolution model. (5) Comparison of dose history using different dissolution models for the ceramic shows little difference. The models used in the comparison include LLNL ceramic, Synroc ceramic, high-level waste glass, and instantaneous dissolution. The reason that the dissolution model has little affect on dose history is that the dose is controlled by colloid release and by solubility controlled release from the waste packages. (6) The uncertainty in the ceramic surface area has no significant affect on dose history. The uncertainty in the rate of formation of colloids has a significant effect on the dose rate history. This effect is due to colloids being a primary contributor to the total dose rate from can-in-canister ceramic. (7) Uncertainty in radionuclide inventory in the surplus plutonium does not translate directly into uncertainty in total dose rate. For example, an increase of a factor of five in radionuclide inventory only doubles the peak dose rate while decreasing the radionuclide inventory by a factor of five decreases the peak total dose rate by a factor of seven. This result is because the peak dose from the can-in-canister ceramic is largely controlled by the amount of 239Pu colloids that are released from the waste package. (8) A change in the number of waste packages used for disposal of the can-in-canister ceramic translates directly into a change in dose rate history. For a factor of five decrease in the number of waste packages there is an approximate factor of five decrease in dose rate.
- Research Organization:
- Yucca Mountain Project, Las Vegas, NV (United States)
- Sponsoring Organization:
- USDOE Office of Civilian Radioactive Waste Management (RW) (US)
- DOE Contract Number:
- AC08-91RW00134
- OSTI ID:
- 784520
- Report Number(s):
- MOL.20010205.0015; ANL-WIS-PA-000003,Rev 00, DC # 23390; ANL-WIS-PA-000003,Rev 00, DC # 23390; TRN: US0108304
- Resource Relation:
- Other Information: PBD: 31 Jan 2001
- Country of Publication:
- United States
- Language:
- English
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