Publications Details

Thermal management of wastes from advanced fuel cycles

Hardin, Ernest H.; Price, Laura L.; Swift, Peter N.

Waste heat generation, repository temperature, and waste radiotoxicity were evaluated using three idealized fuel cycle cases (Table I) in addition to reference UNF. Heat output was normalized to electrical energy produced, simplifying thermal analysis of alternative fuel cycles, especially if waste mass and volume can be accommodated using various container and engineered barrier system configurations. Using a reference repository thermal model, the peak near-field temperature for these cases is shown to be in the range 100 to 130°C, indicating that any of the cases considered can be thermally "fine tuned" (line loading density, decay storage) to limit temperatures as required. Whereas transmutation of TRUs has been proposed to limit repository temperatures after decay of short-lived fission products, the repository concept of operations (drift spacing, decay storage, waste packaging, active ventilation, etc.) can be readily adjusted to accomplish the same effect. The potential radiotoxicity from long-lived fission products, normalized to electricity produced, is effectively the same for all three fuel cycle cases. This is especially important for a repository in clay or shale, where LLFPs are the major contributors to projected dose. Thus, burning of TRUs (conversion to fission products) may decrease overall radiotoxicity, but without significantly changing the toxicity of fission products, or the projected dose for a clay/shale repository, if electrical energy is produced and taken into account (Figure 5). Separation of long-lived fission products, and direct transmutation, have limited applicability with attendant technical and economic challenges.11 Whatever approach is taken to manage long-lived fission products, it should consider the entire system including geologic disposal, and the impacts should be normalized to the benefits, i.e., to the useable energy produced.