Research On Neutronics/Thermal-coupled Systematic Analysis Technology For Liquid Metal Cooled Fast Breeder Reactor

In order to understand three dimensional dynamic characteristics and safety features of reactor transient condition accurately,it is necessary to research the accidents in which the neutronic/thermal coupling effect is strong and the distribution of power changes obviously by the way of coupling three dimensional neutronic code and thermal-hydraulic code.In this paper,the three dimensional neutronic/thermal-coupled systematic analysis technology for Liquid Metal Cooled Fast Breeder Reactor(LMFBR)is researched.The technologies consist of fast reactor systematic analysis technology,technology for solving three dimensional neutron kinetics equation and neutronic/thermal coupling technology.On the basis of these technologies,fast reactor system analysis code,three dimensional neutronic code and three dimensional neutronic/thermal coupled code for fast reactor were developed.At first,fast reactor systematic analysis technology is researched in this paper.The physical model for system analysis is studied and system analysis code for Sodium cooled Fast Reactor(SFR)is developed.The physical parameters of coolant and heat transfer correlations used for Lead cooled Fast Reactor(LFR)is studied.On the basis of the existing models,the system analysis code for LFR was developed.The unprotected loss of flow and loss of heat sink accident in EBR-II fast reactor were analyzed by system analysis code for SFR.The calculation results coincide well with the experimental data and the effectiveness of the code and inherent safety feature of EBR-II were validated.The steady state condition,power variation condition and accident condition were analyzed by system analysis code for LFR and the code was validated.Secondly,the technology for solving three dimensional neutron kinetics equation is studied in this paper.The high order nodal expansion method is proposed to solve the three dimensional neutron kinetics equation under hexagonal-z geometry and calculation precision of spatial discretization is improved.The Diagonally implicit Runge-Kutta method(DIRK)is used to improve the calculation precision of time discretization.On the basis of this method,the three-dimensional steady neutronic code and three-dimensional neutron kinetics code were developed.These two code were validated by the corresponding steady-state benchmark problem and the transient benchmark.At last,three dimensional neutronic/thermal coupling technology which consists of steady and transient neutronic/thermal coupling technology for fast reactor is studied in this paper.In the steady neutronic/thermal coupling technology,the system analysis code neutronic code conduct calculation in turn and transfer data to each other.Three-dimensional power distribution and thermal hydraulic parameters are obtained by iterative computations between two codes.In the transient neutronic/thermal coupling technology,the internal coupling is chosen as the coupling way and the improved semi-implicit coupling is chosen as the time discrete method.Multiple time step strategy is chosen as time step control method.The neutronic code and thermal/hydraulic code adopt different timestep.On the basis of the coupling method,the three dimensional neutronic code and system analysis co de are coupled by way of modular coupling.The three dimensional neutronic/thermal coupled code for fast reactor was developed and validated by VVER440 and SNR benchmark problem.