The Risk Impact from the Instrumentation Air System Modeling in Probabilistic Safety Assessment for a BWR-4 plant
Recently, Probabilistic Safety Assessment (PSA) has been widely used in various riskinformed applications. This paper describes a risk-informed decision-making approach used to address the instrumentation air (IA) system issue at a BWR-4 nuclear power plant (NPP) in Taiwan. The function of the IA system is to provide clean, oil free, compressed and dried air to plant instruments and valves. Instrument and service air is provided by three motor-driven compressors which are located in the turbine building basement. Normally one air compressor is in standby, while the others are in operation. The instrument air is discharged from the dryer and splits into two main instrument headers. The IA system is normally set up with two compressors to meet the loads of the instrumentation air and service air. The compressed air load shared between two units will be connected when system pressure drops to 85 psig and will be isolated when system pressure reaches further to 75 psig. The emergency operation of the IA system by two compressors is to continue adequate supply of air for the successful operation of air operated components. The related risk measures in CDF (core damage frequency) and LERF (large early release frequency) of the IA system can be determined by calculating the difference in plant risks between the alternative cases that met the various configurations. In some alternative cases, re-distributing the load of IA system under specific transients is required. The initiating event frequency of loss of IA system is re-evaluated more detailed by analyzing the fault tree structure. The risk insights of IA system analysis provide a safety significance perspective of the operational experience on this NPP. The paper will discuss the lesson learned from the process and results of the IA system analysis. However, areas of safety improvement will be suggested through detailed review of IA system.
Probabilistic Safety Assessment (PSA) instrumentation air
Ching-Hui Wu Po-Jung Chiu Jyh-Der Lin
Institute of Nuclear Energy Research No. 1000, Wenhua Rd., Jiian Village, Longtan Township, Taoyuan Institute of Nuclear Energy Research No. 1000, Wenhua Rd., Jiian Village, Longtan Township,Taoyuan C
国际会议
上海
英文
885-889
2010-10-10（万方平台首次上网日期，不代表论文的发表时间）