Thermal-hydraulics Design And Safety Analysis Of A100MW_th Small Natural Circulation Lead Cooled Fast Reactor SNCLFR-100

A100MWth small natural circulation lead cooled fast reactor named SNCLFR-100was proposed and studied in this thesis, which can eliminate the need of coolant pumps. The elimination of coolant pumps can largely improve the engineering feasibility and the passive safety feature of the lead cooled fast reactor (LFR). Several key technical issues about SNCLFR-100were studied, including the thermal-hydraucis analysis code development, the core thermal-hydraucis characteristics anslysis and the transient safety analysis.The single channel model code LFR-SIN and the core flow distribution calculation code LFR-DIS were developed for SNCLFR-100. Code validations were carried out for each code, and good validation results were achieved. With these thermal-hydraulics analysis codes, the thermal-hyrauclis design and core thermal-hydraucis characteristics anslysis of SNCLFR-100were carried out. The design and analysis results show that the thermal-hydraucis design scheme of SNCLFR-100is feasible and acceptable.The CFD base neutronics/thermal-hdraulics coupled safety analysis code FLUENT/PK was developed for SNCLFR-100. FLUEN/PK is a CFD/neutronics coupled code by coupling a commercial CFD code named FLUENT with the point kinetics model (PKM) and the pin thermal model (PTM), which can simulate multi-dimensional thermal-hydraulics problems of nuclear reactors and increase the accuracy of safety analyses. A code-to-code validation was conducted between FLUENT/PK and SIMMER-III, and good agreements are achieved for various characteristic parameters.The safety analysis of SNCLFR-100is performed with FLUENT/PK, including protected transient of over power(PTOP), unprotected transient of over power(UTOP), protected loss of heat sink(PLOHS), and unprotected loss of heat sink(ULOHS). The detail coolant behaviors during each accident were presented by means of animation and figures, which can help people to better understand the real physical phenomena in the reactor system during the accident. The SNCLFR-100safety analysis results show that all safety parameters are under safety limit values, and SNCLFR-100shows excellent passive and inherent safety features.