Abstract
This report describes the technical basis for expanding the range of the current U.S. Nuclear Regulatory Commission regulatory guide for calculating decay heat power in an independent spent fuel storage installation (Regulatory Guide 3.54, Rev. 1) to include current high bumup fuel. As part of the expansion of the guide, a revised methodology is proposed to improve flexibility, enable increased accuracy, and cover a wider range of reactor operating histories. The methods are based more directly on the physics of decay heat generation and implement, as part of the proposed guide, procedures and data from consensus standards developed for calculating decay heat by the American National Standards Institute and the International Standards Organization, ANSUANS-5.1-2005 and ISO 10645:1992(E), respectively. The proposed guide is validated using experimental calorimeter decay heat data for 68 spent fuel assemblies measured in the United States and for 64 assemblies measured more recently in Sweden at the Interim Storage Facility for Spent Nuclear Fuel. Validation of the methods beyond the range of the decay heat measurements is supported using experimental isotopic assay measurements of the dominant decay heat-generating isotopes, obtained from destructive radiochemical analysis of spent fuel samples.
