ESTIMATION OF RECOVERABLE ENERGIES IN NEUTRON-INDUCED FISSION AND CAPTURE WITH ASSOCIATED UNCERTAINTIES

Developing extended modeling and simulation capabilities for the advanced nuclear fuel design concepts requires an integration of the current knowledge-base built upon decades of light water reactor (LWR) experience with the novel design objectives of new fuel design concepts. Such objectives include the increase in burnable poison loading in the high burnup fuels (HBUs) and with it, the increased importance of the recoverable energy value for certain neutron absorbers. As such, the isotope dependent energy deposition model must be evaluated to obtain a more accurate representation of the heat generation in the new fuel design. This paper documents work to improve the energy deposition model and data (nominal value and its associated uncertainty) for the recoverable energy. This includes adding other sources of energy deposition to the fission and capture reactions such as the (n, α) capture reaction as well as the subsequent decay of the compound nucleus resulting from these capture reactions. A simple sampling procedure for propagating the uncertainties caused by energies is also implemented in the SCALE package. The results show that for major actinides, there is a minimal difference in the recoverable energy in comparison with current SCALE values. However, for the ²³⁸U, there is a slightly elevated 26% relative difference in the capture energy as a result of the addition of decay energy. The impact of these updated energy values is demonstrated on selected transport/depletion calculations based on LWR models.