| The accelerator-driven subcritical system（ADS）is a powerful tool for transmuting high-level and long-lived nuclear wastes.The impact of beam transients on the subcritical reactor is a key issue affecting the reliable operation of the ADS system.The ADS subcritical reactor has a high heterogeneity of neutron flux in time-space and deep subcriticality,which makes it difficult for traditional neutron dynamics models and analysis methods to be directly used in the dynamic characteristics of accelerator-driven subcritical reactor.This brings challenges to the study of the beam transient dynamic characteristics of the ADS subcritical reactor.Therefore,the research on the neutron dynamics and analysis methods of the ADS subcritical reactor under beam transients with high heterogeneity of neutron flux in time-space is of great academic significance for improving the neutron dynamics theory and promoting the research and development of ADS engineering.Based on the neutron space-time dynamics method of the ADS subcritical reactor,this thesis studies the development method of the"multi-mode"core few-group constant library suitable for the strong"time-space"heterogeneity of the ADS subcritical reactor.Proposing a set of a highly adaptable ADS subcritical reactor beam transient neutron space-time dynamics method,and developed the ADS subcritical reactor neutron dynamics improved quasi-static core diffusion program（the TRIONES program）,applied to the analysis and study of the impact of the ADS subcritical reactor dynamic characteristics under beam transients.In order to solve the problem that the existing single"two-step method"core few-group constant library cannot describe the strong"time-space"heterogeneity of the ADS subcritical reactor beam transient neutron flux.This study proposes a method to generate a"multi-mode"core few-group constant library suitable for the strong"time-space"heterogeneity of the ADS subcritical reactor.This research focuses on the neutronics characteristics of the ADS subcritical reactor,and carries out the research based on the high-efficiency ADS subcritical reactor neutron space-time kinetics method,including the improvement of the quasi-static method:by adjusting the time step of the shape function and the amplitude function,to improve calculation efficiency;selection of shape function:consider three modes ofλfundamental neutron flux,ADS subcritical reactor steady-state neutron flux and promptαfundamental neutron flux;selection of weight function:consider the adjointλfundamental wave neutron flux;and the direct numerical calculation method of ADS neutron space-time dynamics using the difference method.Developed the ADS subcritical reactor neutron kinetics improved quasi-static core diffusion program TRIONES,and explained its calculation process and calculation methods of related calculation modules.The OpenMC program was used to construct a three-dimensional heterogeneity calculation model of the ADS sub-critical reactor core,to generate a homogenized 12-group constant library of the ADS sub-critical reactor,and apply it to the TRIONES program to develop the lambda eigenvalue fundamental wave（λmode）,ADS subcritical reactor steady state（S mode）and time eigenvalue fundamental wave（αmode）three modes of neutron flux calculation,merging and fitting to produce a precise characterization of strong"time-space"heterogeneity"multi-mode"few-group constant library,improve the existing single"two-step method"group constant quasi-static model,and realize self-adapting beam transients.Based on the time-space related"multi-mode"core few-group constants of beam transients,a strong"time-space"inhomogeneous ADS subcritical reactor beam transient neutron space-time dynamics method was established,and the beam transient neutron dynamics method was developed.Analyzing the influence of the beam transient"multi-mode"core few-group constant library on the dynamic characteristics of the ADS subcritical reactor.Analyzing the neutron dynamics results of the ADS subcritical reactor at different beam transient conditions（beam trip,starting process and beam trip and recovery after beam trip）,different positions（four typical positions）and different subcritical degrees(keff=0.99,0.96,and 0.93).The results show that for the beam transient condition,the error of the neutron dynamics results of the multi-mode core few-group constant library,S mode adopted for the starting process and theαmode under the beam trip conditions,is the smallest.Compared with the existing single"two-step method"core few-group constant library,it can more accurately characterize the temporal and spatial evolution characteristics of neutron dynamics in the ADS subcritical reactor.Based on the improved quasi-static model of“multi-mode”core few group constants under beam transient conditions,this study proposes a set of a highly adaptable ADS subcritical reactor beam transient neutron space-time dynamics method.It can more accurately characterize the temporal and spatial evolution characteristics of neutron dynamics in the ADS subcritical reactor with strong"time-space"inhomogeneous,perfect the neutron dynamics theory,and promote the research and development of ADS engineering. |
