A study on the effects of ESFAS STI modification on the unavailability of ESF actuated components |
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| Authors: | Yoon-Hwan Lee Seung-Cheol Jang |
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| Affiliation: | a Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong, Daejeon, South Korea
b Chungnam National University, 79 Daehangno, Yuseong, Daejeon, South Korea |
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| Abstract: | The nuclear industry has made so great efforts to attain safe and economically viable Nuclear Power Plants all over the world. Probabilistic Safety Assessment (PSA) applications are required now more than ever in order to operate Nuclear Power Plants.In this paper, the unavailability model of Engineered Safety Feature (ESF) actuated components, which is part of the Korean Standard Nuclear Power Plant (KSNPP) PSA model, is used to analyze the effects of Surveillance Test Interval (STI) extension of Engineered Safety Feature Actuation System (ESFAS) on the unavailability of the ESF actuated components.To develop a more accurate and realistic PSA model, the loop controller modules of Plant Control System (PCS) are also modeled on the KSNPP PSA model. The fault tree developed by each ESF actuated component includes the component failure, ESFAS signal failure, and loop controller module failure of PCS. When the ESFAS STI is extended from one month to three months, the unavailability of ESF actuated components partially increased by 10%. This shows the STI extension of ESFAS has minor effects on the unavailability of the ESF actuated components. The effects of ESFAS STI extension of KSNPP on the unavailability of the ESF actuated components as well as Core Damage Frequency (CDF) and Large Early Release Frequency (LERF) is less than expected. That result indirectly indicates that the ESFAS in KSNPP is designed well enough to extend the ESFAS STI. |
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| Keywords: | AFAS, Auxiliary Feedwater Actuation Signal AFW, Auxiliary Feed Water AIMS, Advanced Information Management System AOT, Allowed Outage Time AOV, Air Operated Valve ARC, Auxiliary Relay Cabinet BURD, Bayesian Update for Reliability Data CCF, Common Cause Failure CCW, Component Cooling Water CDF, Core Damage Frequency CIAS, Containment Isolation Actuation Signal CS, Containment Spray CSAS, Containment Spray Actuation Signal CVCS, Chemical Volume and Control System DAFAS, Diverse Auxiliary Feedwater Actuation Signal DPS, Diverse Protection System EER, Electrical Equipment Room EPRI, Electric Power Research Institute ESF, Engineered Safety Feature ESFAS, Engineered Safety Feature Actuation System FTREX, Fault Tree Reliability Evaluation eXpert FV, Fussell Vesely GW, Gaseous Waste HPSI, High Pressure Safety Injection I& C, Instrumentation and Control KAERI, Korea Atomic Energy Research Institute KSNPP, Korean Standard Nuclear Power Plant LCO, Limiting Conditions for Operation LERF, Large Early Release Frequency LOCA, Loss of Coolant Accident LPSI, Low Pressure Safety Injection MCB, Main Control Board MCR, Main Control Room MCSs, Minimal Cut Sets MSIS, Main Steam Isolation Signal MTTR, Mean Time To Repair NPP, Nuclear Power Plant NRC, Nuclear Regulatory Commission PCS, Plant Control System PSA, Probabilistic Safety Assessment RAS, Recirculation Actuation Signal SIAS, Safety Injection Actuation Signal STI, Surveillance Test Interval SRs, Surveillance Requirements |
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