Transuranic Waste Facility: Evaluation of Material-at-Risk Limits
The purpose of this analysis was to provide an evaluation and justification of the differences in the safety-basis parameters of Area G and the proposed TRU Waste Facility (TWF) in response to a request from the Los Alamos Field Office. Many of the differences in safety parameters stem from physical attributes such as facility location, size, and updated safety-basis requirements, etc. However, the primary safety-basis parameter that LANL and the Los Alamos Field Office can control for the proposed TWF is the required MAR limit. Based on the following analysis, LANL has proposed to reduce the overall facility MAR from 30,000 PE Ci to 21,400 PE Ci, and the waste storage buildings from 4,550 PE Ci to 3,200 PE Ci. The recommendation balances program requirements, operational considerations, facility construction cost, and container costs. To implement the reduced MAR strategy above, the Los Alamos Field Office and LANL will need to work with WIPP to ensure two characterization/shipment campaigns are scheduled each year. The analysis in this document included a review of historical trends and potential future scenarios in activity for enduring waste containers to define the expected normal operating range. The first part of the MAR analysis resulted in a newly defined range of activity of 10.5-18.0 PE Ci per DE2= expected for the design life of the new TWF. However, for accident scenario analysis, containers will use the WIPP WAC limits because there are no other individual container controls. Specifically, accident scenarios involving less than the building MAR will use the 80-PE Ci WIPP-WAC limit for drums. The accident analyses are intended to bound the potential impacts, and are not intended to be based on normal operational ranges. The Field Office also requested that LANL evaluate a potential reduction of the waste storage building MAR Limit by a factor of two to three. LANL used the newly defined MAR range of 10.5-18.0 PE Ci/DE to define upper and lower MAR boundary requirements using three containerization scenarios. The result of the analysis showed that the most probable scenario of future operations that balances costs, drum packaging efficiency, and shipment efficiency will routinely require the use of one-third to two-thirds of the MAR limit for each building. This result, paired with scenarios that could potentially provide short-term MAR increases, demonstrates that the MAR cannot be reduced by a factor as large as two to three, but can be reduced from 4,550 PE Ci to 3,200 PE Ci for waste storage buildings (a reduction of 30%). The TWF PDSA submittal contained combustibility values for enduring waste that appeared relatively large compared to Area G. The analysis provided the basis for the initial combustibility values established in the PDSA. Although the recent data provided combustibility values that were much lower than the PDSA assumptions (27% versus 80% in PDSA), the analysis shows that there is variability in combustible loading over time. For safety-basis accident scenarios, the material composition distribution for waste containers will be included in the MAR requirement by assuming all waste is combustible instead of applying a control for combustible loading. For operations and programs, it is better to assume 100% combustibles and maintain flexibility for waste generator containerization rather than to maintain a requirement for administrative controls of combustible loading. Controlling MAR through administrative controls is difficult for both the generator and waste management operations.