Impact of Isotope Fidelity on Fuel Cycle Calculations

The purpose of this study is to examine the importance of the isotopic composition of plutonium on PWR MOX fuel fabrication as part of a multi-tiered fuel cycle, and the effect of its evolution during a transition. Two main effects can modify the isotopic composition of the plutonium used to build the PWR-MOX fuel: decay and depletion. This analysis is based on a transition of the nuclear fuel cycle to a configuration identified as 'Evaluation Group 29' or 'EG29', in the recently-published Evaluation and Screening (E and S) report. The EG29 fuel cycle corresponds to a double strata fleet. The first stratum is composed of sodium-cooled fast reactors (SFRs) multi-recycling plutonium. Surplus plutonium is sent to the second stratum composed of pressurized water reactors with full mixed oxide (U/Pu)O₂ cores (MOX-PWRs). The PWR stratum is also multi-recycling its plutonium. The target energy generation ratio for the final EG29 system is 70:30 (SFR:PWR), with a 1% annual growth in nuclear energy demand. All the calculation of this study have been performed using the Cyclus fuel cycle simulator framework. The facility models are from the Cycamore package, developed by the Cyclus team, and containing a Pu-equivalent fuel fabrication model as well as a simple fixed mixing ratio fuel fabrication model. A new neural network model has also been contributed to the Cyclus environment using the cyCLASS tool, allowing the use of the fuel fabrication and depletion models from the CLASS tool in Cyclus. (authors)