Np-237 Transmutation On PWR Burnable Poison Rods

Minor actinides are the primary contributors to long term radiotoxicity in spent fuel.The majority of commercial reactors in operation in the world are PWRs,so to study the minor actinide transmutation characteristics in the PWRs and ultimately realize the successful minor actinide transmutation in PWRs are crucial problem in the area of the nuclear waste disposal.The key issues associated with the minor actinide transmutation are the appropriate loading patterns when introducing minor actinides to the PWR core.As Np-237 is the most abundant of all the minor actinides,focus of this research is transinutation of Np-237.Two different minor actinide transmutation materials loading patterns on the PWR burnable poison rods are studied in MIT released BEAVRS benchmark.One is that Np-237 substitute for burnable poison directly within burnable poison rods,another oneis to coat a thin layer of Np-237 in the water gap between the zircaloy cladding and the stainless steel which is filled with water.Simulation calculation indicates that the two loading patterns can load approximately equivalent to 5-6 PWR annual Np-237 yields without disturbing the PWR keff markedly.Both Np-237 loading patterns are technically feasible;most importantly do not need to modifythe configuration of the PWR core and composition of nuclear fuel.Furthermore,the two Np-237 loading patterns completely isolate Np-237 transmutation materials from nuclear fuel,so it alsofacilitates fuel reprocessing after discharged from PWR core.We believe that loading Np-237 toPWR burnable poison rods for transmutation is an optimal minor actinide loading pattern.Fuel Cycle ofreactor is reduced with the introduction of Np-237 to burnable poison rods which can be improved by adjusting boron letdown curve during burnup.Simulation results show that finding a compromise between two loading patterns can yield to minilal disturbance to the normal operating conditions of the reactor and high transmutation rate of Np-237.