Time Dependent Energy Deposition Model in RMC Kinetics Calculation

Abstract

Calculating or predicting the energy deposition in the reactor is an important task for reactor design and safety analysis. Rigorous energy deposition estimation is a difficult task because of the energy dependence, spatial dependence, and time dependence of in-core nuclear heating. This paper develops a time-dependent energy deposition model in the RMC kinetics calculation to explicitly account for the time-delay effect of delayed in-core nuclear heating. An explicit sampling method (ESM) is proposed to sample the decay time of the delayed photon and beta precursors based on a new precursor library processed from the ENDF/B-VIII.0 library. The new model is verified by comparing it with the typical equilibrium model using the Godiva experiment and the C5G7- TD benchmark. Maximum 2.5% and 5.4% relative deviations are observed in GODIVA and C5G7-TD cases respectively, which indicates that the equilibrium model underestimates the energy deposition over the transient time. The analysis of the energy deposition results demonstrates that the new model can provide more precise energy deposition estimation in the transient calculation.