Post-Shutdown Fission-Product Decay Heating for Plutonium-239-Fueled Fast Reactors

Fission-product decay heat rates in shutdown ²³⁹Pu-fueled fast reactors are determined by direct calculation using a modified version of the CINDER code with a fission-product library of 344 nuclides. Systematic variations in fluence, flux level, irradiation time, and the initial ²³⁸U/²³⁹pu ratio are made for the ranges of current interest, and their effects on the decay heat rate for the first ten years after reactor shutdown are investigated. Variations in irradiation history and the ²³⁸U/²³⁹Pu ratio over the ranges considered cause the total decay heat rate to vary by <18% during the first day after shutdown.