Improvement of the Simplified Hybrid Method for Seismic Risk Assessment of Nuclear Fuel Facilities

hybrid method proposed by Kennedy is referred to （ e.g., in the Atomic Energy Society of Japan standard （ draft ） on the risk assessment method for nuclear fuel facilities ） as one of the seismic probabilistic risk assessment methods for nuclear fuel facilities. Although this method enables us to easily evaluate a plant ʼ s annual probability of failure, the evaluated probability may occasionally be overestimated or underestimated depending on the analysis case. Such a tenden-cy is a major obstacle to judging the appropriateness of the evaluation results of the method. In this paper, the cause of overestimation and underestimation is analyzed, and ways to improve the simplified hybrid method are studied and proposed to enable evaluation results within an acceptable range, which is defined in this paper, to be obtained.