Research On Neutronics And Thermal Hydraulic And Preliminary Study On Safety Characteristics Of Molten Salt Reactor

As one of the six candidates for the Generation IV reactor types,molten salt reactor(MSR)is characterized by its use of the fluid-fuel.The advantage of MSR such as sustainability of resources,high inherent safety,good economy and reliable nuclear nonproliferation make it meet the need of sustainable development of nuclear energy.With the design of MSR presented,the first molten salt reactor experiment(MSRE)was built by Oak Ridge National Laboratory(ORNL)in the 1960 s.And many countries and research institutions have carried out relevant research on MSR and proposed a lot of conceptual designs.Focusing on the demand of national energy security and sustainable development,the “Thorium molten salt reactor nuclear energy system” was launched by the Chinese Academy of Sciences as a leading science and technology project in 2011,and the liquid thorium-molten salt reactor(TMSR)was held by the Shanghai Institute of Applied Physics(SINAP)included in the project.The main goal of this project is to develop the fourth generation advanced nuclear energy technology.Compared with solid-fuel reactors,there are some differences in physics for liquid fuel reactor.And the code for the solid-fuel reactors can not analyze liquid fuel reactor accurately.Aiming at the characteristic of the liquid fuel reactor,a new physical analysis model and program for safety analysis and calculation for liquid fuel reactor is established and developed in this dissertation.In the first chapter,the characteristics of MSR,the development and status of MSR at home and abroad are introduced and summarized.Then the calculation methods of neutronics and thermal-hydraulic for MSR are investigated.In the second chapter,the neutron kinetic equation for MSR is deduced in detail in the first,especially considering the influence of fuel flow on the distribution of the delayed neutron precursors(DNP).The neutron importance is used as a weighting function to solve effective delayed neutron fraction in the core.And the importance equations for MSR and the formulation of effective delayed neutron fraction are founded.Then the thermal-hydraulic calculation for MSR is introduced in detail.Without considering the boiling and solidification of the fuel,so in the thermal-hydraulic calculation only the single phase fluid is considered without the phase change of the fuel.Because of the fuel only connected in the upper and lower plenum,there is no flow interaction in the graphite channels,and the graphite channels can be considered as a set of parallel multi-channel.So the multi-channel can be used to solve the problem of flow distribution.And then the core temperature distribution is obtained by the single channel heat transfer model.Finally,the calculation process of the program coupling neutron and thermal-hydraulic is introduced: the steady state and the transient state.In the third chapter,the physics parameters of MSRE built by ORNL is introduced in detail.Taking MSRE as the object of calculation,physical model is established.The related experimental data in MSRE was verified by coupling calculation of neutron dynamics and thermal hydraulics.The validation results by experiment data contains: the effective loss DN in steady operation,protected fuel pump start-up,protected fuel coast-down,natural circulation experiment.In the end of third chapter,the unprotected pump driven transient and the other transients were simulated.Then the TMSR-LF1 designed by SINAP is introduced in detail,and the physical model suitable for program calculation is established.A series of transient conditions is calculated,analyzing the flow distribution and the DNP distribution in the core.The preliminary study on the TMSR-LF1 contains the effective loss DN in steady operation,protected fuel pump driven at zero-power,the unprotected pump driven transient at zero-power,the inlet temperature decrease and increase transient,step introduced reactivity transient.The main work in this dissertation is to develop a a new space-time neutron dynamics program based on the two-dimensional RZ geometry,coupling with the thermal-hydraulics program.Analyzing the relevant parameter in steady and transient condition in MSR and verifying the safety feasibility of MSR by using the program,the calculation results not only verify the reliability and correctness of the program,but also prove the feasibility and security of the TMSR-LF1 design.