Development And Application Of Neutronic And Thermal-Hydraulic Coupling Code For Long Life Chlorine-cooled Fast Reactor

Based on the nuclear design,thermal hydraulic design and safety analysis requirements of a new long-life chlorine-cooled fast reactor,the neutronic and thermalhydraulic coupling research of long-life Chlorine-cooled fast reactor with code development to code verification to code application as the main technical route was carried out in this paper.Firstly,according to the fast spectral characteristics of the chlorine fast reactor,the neutron physical code of the core is developed: ThorCORE3 D,a three-dimensional space-time dynamics program for two groups with burnup calculation function,was extended to multiple groups.Two kinds of benchmark were verified for the modified ThorCORE3 D,and BN600 benchmark was used to verify ThorCORE3D's burnup calculation module,proving the reliability of the program and the applicability of fast reactor.Aiming at the characteristics of long life chlorine fast reactor,the reactor core reactivity control module and material irradiation damage calculation module are developed.Secondly,based on the single-phase flow subchannel theory,subchannel analysis code ThorSUBTH is developed for chlorine-cooled fast reactor.The code used the conservation of mass equation,conservation of energy equation,conservation of axial momentum and conservation of transverse momentum equation,and gives the corresponding boundary conditions or initial conditions to solve the equations iteratively.The high-fidelity CFD software and Subchan code developed by MIT were used for code-to-code verification,and the pressure drop model,heat transfer model and turbulence mixing model used in the chlorine-cooled fast reactor were evaluated,laying a foundation for the subsequent thermal-hydraulic research on the chlorine-cooled fast reactor.Furthermore,the neutronic and thermal-hydraulic coupling method is studied to realize the coupling of neutron physics(3d space-time dynamics module,burn up calculation module and its extension module),core thermalhydraulic code(subchannel code)and loop thermal-hydraulic module in a modular coupling way.On the grid correspondence of each coupling module,the volume or mass weight method is adopted to realize the one-to-one correspondence between neutronic and thermal-hydraulic grids,the time implicit iteration method is adopted on the timestepping scheme,and a first order perturbation method is introduced to deal with the expansion effect of fast reactor on the processing of section feedback model.The correctness and reliability of three dimensional physical-thermal coupling code(TSCH)are preliminarily verified by using the European Sodium Fast Reactor(ESFR)coolant loss accident benchmark.Finally,TSC-H coupling code was used to carry out physical and thermal steady-state design and transient safety analysis for a new type of long life small chlorine cooled fast reactor(MCCFR).The steady-state analysis results show that MCCFR can achieve the high burnup target of stable operation for 30 years without feeding or refueling.The negative feedback effect extends from the beginning of the life period to the end of the core,indicating that the core has inherent safety.An effective rod lifting scheme ensures that the residual reactivity of the core is less than $1 in different life periods.The cumulative maximum atomic dispersion(DPA)of the pressure vessel and the fuel rod cladding is within the design limits.The outlet temperature of the hottest coolant channel,the fuel rod cladding and the fuel rod center line all meet the design requirements.The transient safety analysis shows that MCCFR can realize rapid shutdown under the condition of protected overpower at the beginning of the life cycle.Under the condition of unprotected overpower at the beginning of the life cycle,the core can re-enter the stable state by relying on its own negative feedback effect,and the main thermal parameters all meet the safety limits of the accident condition.In the life of the beginning and long life are there to protect the loss of coolant flow at the end of the accident conditions,MCCFR are able to quickly shut down last will establish a natural circulation reactor core decay heat is derived,in the life of the beginning and the life of the final of the unprotected coolant flow conditions,MCCFR can also pass their own negative feedback effect back into the stable state,finally to establish natural circulation core heat export;The analysis of super power accident and coolant loss accident shows that MCCFR has strong internal safety.The relevant research results in this paper are helpful for China to master the key technologies of physical thermal design and safety analysis of small chlorine-cooled fast reactors,and improve China's independent innovation ability in the field of chlorine-cooled fast reactors.It is of great significance to provide experience accumulation and technical support for the subsequent design and development of various chlorine-cooled fast reactors.