Year
2016
Abstract
A project to research the application of non-destructive assay (NDA) to spent fuel assemblies is underway among a team comprised of the European Commission, DG Energy, Directorate Safeguards; the Swedish Nuclear Fuel and Waste Management Company; Uppsala University; and US national laboratories (Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and Oak Ride National Laboratory). The research goals of this project combine safeguards goals (detection of missing/substituted fuel pins and verification of operator declarations) and non-safeguards goals (estimation of decay heat and reactivity of each assembly). The final objective of this project is to quantify the capability of several integrated NDA instruments being developed to meet the aforementioned safeguards and non-safeguards goals using combined signatures of neutron, gamma-ray, and decay heat. In support of these goals, passive gamma and neutron measurements were made on 50 spent fuel assemblies at the Swedish Central Interim Storage Facility for Spent Nuclear Fuel (Clab) using high- purity germanium and Fork detectors. The Oak Ridge National Laboratory (ORNL) Inverse Depletion Theory (INDEPTH) code was used to reconstruct the spent fuel parameters (initial enrichment, burnup, and cooling time) for each assembly. INDEPTH uses a gradient-based search technique—combined with the ORIGEN code for forward depletion calculations—to find the spent fuel parameters that result in passive gamma and neutron outputs that best match the measurements. The results of the INDEPTH calculations are presented and compared to the operator declarations (trusted in this case) in order to assess how accurately these parameters can be determined using current passive gamma and neutron measurements. These results will provide a baseline which can be used to assess whether and by how much new safeguards instruments being developed for NDA measurements can improve the accuracy of reconstructed fuel parameter values.