Criticality Studies for UREX Processes

The completion of criticality experiments for mixtures of transuranic actinides (TRU; includes neptunium, plutonium, americium, and curium) that will be created during the separation of used nuclear fuel may be a requirement in order to construct prototype plants for the Global Nuclear Energy Partnership (GNEP). In this program and the Advanced Fuel Cycle Research and Development (AFC R&D) program that supports it, economic and environmental methods are being developed to reduce the impact of waste from commercial nuclear fuel cycles. Recycling of used fuel by chemically separating it into U, fission products, and TRU would be the first step in this new fuel cycle. Proposed mixtures and concentrations of TRU covering a wide range of conditions must be examined theoretically and experimentally to demonstrate criticality safety in advance of construction of a processing facility. Theoretical studies may be limited because of insufficient nuclear data for the rarer isotopes of Np, Pu, Am, and Cm. These data limitations include reaction cross sections in some energy regimes, thermal feedback coefficients, and delayed neutron fractions