Research On Critical Boron Concentration And Critical Control Rod Position Search Method Based On Adjoint Flux

Monte Carlo method has been widely used in the design and analysis of advanced nuclear system for its flexible geometric description and accurate simulation.Critical boron concentration and critical control rod position search are considered as an important part of reactor design and analysis.In the traditional search method,multiple criticality calculations are required,thus the slow convergence rate of Monte Carlo method results in the low search efficiency.In this work,based on Super Multi-functional Calculation Program for Nuclear Design and Safety Evaluation(SuperMC),a highly efficient Monte Carlo critical boron concentration and critical control rod position search method are studied based on adjoint flux.1)Critical boron concentration search method based on adjoint flux is developed.For the problem of adjoint flux computation,based on iterated fission probability method and source merge strategy,more accurate calculation method is developed without memory increase.For the problem of critical boron concentration search.Starting from the neutron transport equation and perturbation equation,the effective multiplication factor on the boron concentration response coefficient of the initial state can be obtained,the variable quantity of boron concentration which can meet the needs of reactor system criticality can be computed.The correctness of this function has been verified by a standard Westinghouse 17×17 PWR assembly model.2)Critical control rod position search method based on axial dispersed is developed.For the problem of critical control rod position search,taking an axial segmentation strategy,calculating the effect of each control rod on the effective multiplication factor,the effective multiplication factor on the control rod position response coefficient of the initial state can be obtained.The correctness of this function has been verified by a benchmark C5G7-UOX assembly.The criticality search method studied by this work has been applied to a full core Hoogenboom benchmark and IAEA BN-600 benchmark.For each application,by only one criticality calculation,the results of critical boron concentration of Hoogenboom benchmark and critical control rod position of IAEA BN-600 benchmark tallied with results published by other institutes,which preliminary indicated that this method could provide support for nuclear design and analysis.