Year
2019
Abstract
The technology for fissile assay is under development for the nuclear fuel cycle to obtain the quality assurance of recycled fissile content for fabrication of fuel rods, to assure the fissile content for the safeguards purpose, and to get the optimum design of storage site for spent fuel to maximize the safety. In the pyro-process, the major points are at the input area of spent fuel, processing area, wastes, and output area. At the output area, the enriched TRU materials through the process are accumulated for fuel rod fabrication. In the input area, spent fuel assembly is introduced which has large amount of fissile content. In the wastes, very small amount of fissile is still existing, but it has still spent fuel property. Therefore, at each area, a different environment for the measurement of fissile material is encountered.Several NDA technologies were examined for the measurement points and the different fissile composition. In the designed LSDS system, the possibility of assay for isotopic fissile content was performed. In the LSDS, the detected fission signal has the direct relationship with the mass of isotopic fissile materials. The self-shielding correction factor was applied in the assay energy range. Several assay simulations were performed on the enriched plutonium mass with uranium. The plutonium mass was changed on 11~20wt% when U235 has 1wt% in the rod. The content assay was performed on the unknown sample as well. In the fissile assay, the content of Pu239 was obtained with ~1wt% error for all the simulations. However, the accuracy on the uranium was fluctuated.The accurate plutonium assay is possible for the spent fuel and the TRU product through the pyro-process. However, the further development is necessary for large amount of TRU and assembly type of spent fuel. The accurate fissile assay will contribute to the increased safeguards system of pyro process and the quality assurance in the direct use of recycled material for fuel fabrication.