This paper describes the methods and results of an uncertainty evaluation of a significant plant response analysis of reactor trip failure events,specifically anticipated transients without scram in the Japanese proto...This paper describes the methods and results of an uncertainty evaluation of a significant plant response analysis of reactor trip failure events,specifically anticipated transients without scram in the Japanese prototype fast breeder reactor Monju.Unprotected loss of heat sink(ULOHS)has a relatively large contribution to the core damage frequency due to reactor trip failure.The uncertainty in the allowable time to core damage in this event has so far been estimated by considering the range of reactivity coefficients.There are some cases where it is considered that core damage will be avoided.Specifically,if the primary heat transport system(PHTS)pump inlet sodium temperature stays below 650℃for 1 h,the avoidance of core damage due to a ULOHS event is assumed.This is the temperature at which the probability of cavitation in the static pressure bearing begins to increase.In this study,a success scenario was investigated in two aspects:identification of influential input parameters and estimation of the probability of success.In the parameter identification,input parameters that satisfy the pump inlet temperature being below 650°C are clarified by treating the reactivity coefficients and reactor kinetics parameters as variables that can be taken to be within the design range.In the probability estimation,the results are fitted to a lognormal distribution function,from which the output variable was found to fall between 640 and 679℃with a probability of 90%,the probability of the temperature being 650℃or lower was 0.23,and the average and mode value was 659℃.展开更多
Thermal expansion behavior was investigated in detail for evaluation of the core support plate expansion reactivity in the ULOHS(Unprotected Loss of Heat Sink)reactor trip failure event.The core support plate expansio...Thermal expansion behavior was investigated in detail for evaluation of the core support plate expansion reactivity in the ULOHS(Unprotected Loss of Heat Sink)reactor trip failure event.The core support plate expansion reactivity plays an important role in the safety evaluation of the ULOHS event.In this paper,a possibility of mechanical restraint was investigated in thermal expansion of the core structure for the prototype FBR(Fast Breeder Reactor)Monju.The reactor core expansion was simulated in a three-dimensional FEA(Finite Element Analysis)model of the RV(Reactor Vessel)considering detailed temperature distribution of the sodium coolant based on the thermal-hydraulic analysis result of the whole core model.It was found that the thermal expansion of the core was not restrained in the ULOHS event,although part of the core structure is mechanically restrained.展开更多
文摘This paper describes the methods and results of an uncertainty evaluation of a significant plant response analysis of reactor trip failure events,specifically anticipated transients without scram in the Japanese prototype fast breeder reactor Monju.Unprotected loss of heat sink(ULOHS)has a relatively large contribution to the core damage frequency due to reactor trip failure.The uncertainty in the allowable time to core damage in this event has so far been estimated by considering the range of reactivity coefficients.There are some cases where it is considered that core damage will be avoided.Specifically,if the primary heat transport system(PHTS)pump inlet sodium temperature stays below 650℃for 1 h,the avoidance of core damage due to a ULOHS event is assumed.This is the temperature at which the probability of cavitation in the static pressure bearing begins to increase.In this study,a success scenario was investigated in two aspects:identification of influential input parameters and estimation of the probability of success.In the parameter identification,input parameters that satisfy the pump inlet temperature being below 650°C are clarified by treating the reactivity coefficients and reactor kinetics parameters as variables that can be taken to be within the design range.In the probability estimation,the results are fitted to a lognormal distribution function,from which the output variable was found to fall between 640 and 679℃with a probability of 90%,the probability of the temperature being 650℃or lower was 0.23,and the average and mode value was 659℃.
基金The authors would like to recognize the contribution of Hiroki Yada for the thermal expansion analysis,and also Masaki Minami and Kousuke Araki of NESI for the thermal-hydraulic analysis in this paper.
文摘Thermal expansion behavior was investigated in detail for evaluation of the core support plate expansion reactivity in the ULOHS(Unprotected Loss of Heat Sink)reactor trip failure event.The core support plate expansion reactivity plays an important role in the safety evaluation of the ULOHS event.In this paper,a possibility of mechanical restraint was investigated in thermal expansion of the core structure for the prototype FBR(Fast Breeder Reactor)Monju.The reactor core expansion was simulated in a three-dimensional FEA(Finite Element Analysis)model of the RV(Reactor Vessel)considering detailed temperature distribution of the sodium coolant based on the thermal-hydraulic analysis result of the whole core model.It was found that the thermal expansion of the core was not restrained in the ULOHS event,although part of the core structure is mechanically restrained.
