Design Studies for the Optimization of ~(238)Pu Production in NpO_2 Targets Irradiated at the High Flux Isotope Reactor

摘要

Efforts to reestablish a domestic ~(238)Pu production capability in support of National Aeronautics and Space Administration mission objectives are ongoing throughout the U.S. Department of Energy complex. The Plutonium-238 Supply Project (PSP) was initiated in response to a report published by the National Research Council in 2011 stating that "without a restart of ~(238)Pu production, it will be impossible for the United States, or any other country, to conduct certain important types of planetary missions after this decade." The PSP is targeting a sustained, constant production rate of 1.5 kg/year of heat source PuO_2 for several years. Design and optimization studies of ~(237)Np-bearing targets are underway at Oak Ridge National Laboratory (ORNL). It is anticipated that targets will be irradiated in ORNL's High Flux Isotope Reactor (HFIR) and in the Advanced Test Reactor (ATR) at Idaho National Laboratory. A variety of target materials, containments, arrangements, and irradiation histories have been analyzed, and the results indicate that a sufficient quantity of~(238)Pu can be produced in HFIR and ATR to fulfill the PSP's constant production rate target. This paper focuses on the design and optimization of new target configurations containing pellets that are (1) -93% of the theoretical density of NpO_2, (2) loaded into pins of cladding materials that can be handled as solid waste following postirradiation ~(238)Pu recovery operations, (3) irradiated in various vertical experiment facility (VXF) locations in the HFIR permanent beryllium reflector, and (4) rotated within and/or moved to another VXF location following each HFIR operational cycle to maximize ~(238)Pu production and minimize peak heat generation rates.