The implementation standard for internal fire probabilistic risk assessment of Nuclear Power Plants

Internal Fire PRA (IFPRA) is an analysis method which can quantitatively evaluate plant damage states, including core damage frequency. Because PRA results can be used for identifying the causes of end states, such as simultaneous multiple components failures (SMCF) of safety significant components induced by the effect of fire, by analyzing the results systematically, it is utilized worldwide. Because the Implementation Standard for IFPRA has not yet been developed in Japan, Japanese utilities have not evaluated fire consequences sufficiently. Considering the circumstances, the Atomic Energy Society of Japan (AESJ) has been working on development of the "Implementation Standard for Internal Fire Probabilistic Risk Assessment of Nuclear Power Plants" since fiscal year 2012. This IFPRA standard prescribes the requirements and specific methods to implement Level 1 PRA for accidents initiated by internal fire at NPPs during power operation. This standard is being finished at the Fire PRA subcommittee under the Risk Technical Committee for the Standards Committee of AESJ, and is expected to be published in fiscal year 2014. This standard will give great support to PRA engineers for performing the IFPRA with adequate quality, by identifying vulnerabilities associated with internal fire, and moreover will contribute to further improvement of the NPPs' safety.