Research On Calculation Of Source Term In Spent Fuel Reprocessing Equipment

The spent fuel reprocessing can reduce the amount of radioactive waste,the hazards of long-lived nuclides,and recycle nuclear resources,is an important link in the realization of a closed cycle of nuclear fuel.It is a certain amount of fissile nuclides and a large number of convertible nuclides,transuranic nuclides,and fission-debris nuclides in spent fuel that make process-related systems and equipments becoming radiation sources having radiation hazards during the reprocessing process.The source item calculation of spent fuel reprocessing equipments,which has important engineering application requirements,provides data basis for material composition analysis,equipment radiation protection,shielding structure design,etc.At present,there is no systematic calculation and analysis program for the radiation protection source items of the main systems and equipments for the reprocessing plant.Therefore,it is significant to study the calculation of the radiation protection source items of the main systems and equipments in combination with the design characteristics of the process system of the spent fuel reprocessing plant.The process of spent fuel reprocessing usually involves the extraction and separation of some nuclides.Taking into account the simultaneous nuclear reactions,the calculation of the nuclide inventory is a nonhomogeneous burnup calculation problem.This paper conducts research on the Chebyshev rational approximation method(CRAM),which is the mainstream in the field of nuclide inventory calculation,and derives the matrix index representation of the nonhomogeneous burnup calculation problem(including constant mobility,polynomial mobility,and exponential mobility).So that the CRAM method can be used for the calculation of nuclide inventory in the process of spent fuel reprocessing.Subsequently,typical examples were selected to verify the use of the CRAM method in the calculation of the nuclide inventory in the reprocessing process,and the analytical solution of the examples were deduced.The results show that the calculation accuracy of the CRAM method is similar to the transmutation track analysis for the problem of nonhomogeneous burnup calculation,and the CRAM can calculate the nuclide inventory in the reprocessing process accurately.Subsequently,based on the research on the process flow of the reprocessing plant and the characteristics of the main systems and equipments,it was established that the calculation model of the equipment source term and the source term of the ventilation filter system of the reprocessing plant,and the corresponding source term calculation and analysis program was developed.The program can calculate not only the equipment energy spectrum data including the 18-group Gamma energy spectrum,the 22-group neutron energy spectrum,and the 7-group Gamma energy spectrum by merging,according to different source item data types and equipment volume types,but also the sedimentation source item of the filtering equipment and the pipeline and its energy spectrum in ventilation filter system.In this paper,it has been studied that method and model for the calculation of nuclide inventory and equipment source term in the process of spent fuel reprocessing,developed the calculation and analysis program for radiation protection source term of main systems and equipments in the reprocessing plant,and carried out tests of the program.The research results of this paper are helpful to improve the source term analysis ability in the spent fuel reprocessing process,and have certain engineering application value.