Reactor High Fidelity Life-cycle Simulation And Precise Calculation Of Stochastic Media Based On RMC Code

With the rising concerns over the safety and economy of nuclear power system and the improvement of computational power in recent years,greater demands for the higher accuracy,efficiency and capability of reactor analysis codes were proposed.The concept of “high fidelity” simulation was attracting more and more concentrations.Meanwhile,the new design of reactors and fuels were put forward,and the dispersion fuel was one of the most attractive fuel types.The high fidelity lifecycle simulation and precise calculation of sto chastic media were two hot and difficult problems in reactor Monte Carlo research.Based on the self-developed reactor Monte Carlo code RMC,this thesis conducted research on high fidelity lifecycle simulation and stochastic media calculation.The main research contents include:(1)Coupling method of Monte Carlo neutron transport code and thermalhydraulics code.The treatments of temperature dependent cross sections were the key point of coupling calculations.Aiming to solve the problem of huge memory consumption for the multi-temperature continuous-energy cross sections,the onthe-fly cross sections treatments with high efficiency were developed for the whole energy range.For the coupling calculations,the versatile coupling of RMC/CTF codes were proposed.To solve the power oscillations problem in the Monte Carlo based coupling,the power relaxation method was used to improve the stability and the convergence of coupling.(2)Large scale burnup and refueling calculation based on Monte Carlo method.This method was the important foundation for both high fidelity simulation and stochastic media calculation.Three parts were studied: large scale burnup calculation based on integrated parallelism,the equilibrium xenon method in large scale burnup calculation and Monte Carlo refueling method.Three methods were proposed respectively,including: “domain decomposition + burnup data decomposition + hybrid parallel” integrated with batch method,modified equilibrium xenon method based on batch method and its con vergence criterion,and the built-in refueling method based on the mapping relation of “material-geometry-tally-burnup” data.(3)Precise calculation of stochastic media.The random lattice method,chord length sampling method for multiple types of particl es,chord length sampling method with packing fraction correction and explicit modeling method with pseudo mesh acceleration were proposed.The particles level precise burnup calculation was developed for assembly burnup calculation.T wo strategies of combining burnup regions based on “pseudo mesh” and “Universe” were proposed for full core burnup calculation of dispersion fuel,which were achieved by integrating the large scale burnup calculation method and combining strategies.(4)Verification and analysis of benchmark problems.The high fidelity coupling benchmarks of VERA and BEAVRS were simulated by RMC,proving its capability and accuracy of high fidelity simulations.The high temperature reactor benchmark and related burnup benchmarks were also performed to verify the capability and accuracy of transport and burnup calculations for stochastic media by RMC.This thesis achieved the innovation in methodology and a breakthrough in capability of codes for high fidelity coupling simulation and stochastic m edia calculations using Monte Carlo method.This work not only bring s RMC to advanced levels in high fidelity simulation and stochastic media calculations,but also has important value in the engineering applications.