A Short-Scale Time-Dependent Model for Decay Heat Analysis Following Reactor Shutdown

Abstract

Acquiring adequate information on the nuclear fuel decay heat is one of the major topics in nuclear research. In this work, we investigate the decay heat of Low Enriched Uranium (LEU) fuel (U₃Si₂-Al, 19.75% enriched) for a fictitious mini-core reactor using the Serpent-2 Monte Carlo code. The results were compared relatively to a previous measurement that was carried out with the same fuel composition and geometry. The decay heat of the simulation was analyzed for the first nine hours following the reactor shutdown. The study covers decay heat for four different fuel depletion sets: 0.25% (quasi-fresh fuel), 10%, 20% and 30% U-235 depletion. Predominant radioactive fission products are also present in this investigation. The decay heat differences between the low-burnup and the high-burnup cores are significantly higher for the long-lived radioactive products than for the short-lived radioactive sources.