Effect evaluation on performance issues of passive safety system-Part I. Passive heat removal system

The passive safety system has advantages over active safety system since it has low dependence on the operator and external power supply. However, because the passive safety system operates with natural phenomena such as gravity, density difference, pressure difference, etc., the driving force is very low compared with active safety system. Therefore, the change of the internal/external environment of the system can have an effect on the performance of system. For this reason, it is necessary to evaluate whether the system can sufficiently perform the safety function in various accident situations. Since the existing safety standards for safety system have been developed for active safety systems, it is required to develop standards for performance evaluation of passive safety systems. For this reason, in this study, performance evaluation method for passive safety system is being developed. Since the identifying major performance issues is important for developing methodology, performance issues that can affect the natural circulation flow of the system, such as friction and heat loss of pipe within the system, are investigated and selected through the research related to safety regulation of passive safety systems. The effect of each performance issue on the system has analyzed by using conceptual problem for PHRS type passive safety system. For the effect analysis, passive safety systems using single/two phase natural circulation flow are conceptually designed by referring to the concept of the existing systems. For the effect evaluation, MARS-KS, which is system analysis code developed by KAERI, is used in this study. The main conclusions on the effect of each performance issues are drawn through the analysis. In addition, after the individual effect analysis of performance issues on passive safety system, a comprehensive assessment has performed to analyze the performance of system when several issues acted simultaneously.