In this research, a new index “The Resilience Index” was proposed to evaluate the capability of nuclear power plant to recover from the situation of safety function lost. Three elements assumed to evaluate the resilience index are the achievement rate, necessary time, and probability of success of each accident management activity. The resilience index is expected to visualize the improvement of safety of each nuclear power plant against severe accidents. ...
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Development of Resilience Evaluation Method for Nuclear Power Plant (Part 1: Proposal of Resilience Index for Assessment of Safety of Nuclear Power Plant under Severe Accident)

We have developed a new index, called the resilience index, that evaluates the dynamic stability of the system safety of a nuclear power plant during a severe accident by considering the ability to recover system safety functions that have become lost in the situation. In this paper, a detailed evaluation procedure for the resilience index is described. The system safety of a PWR plant during a severe accident is then assessed according to the resilience index in order to discuss the applicability of ...
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Development of Resilience Evaluation Method for Nuclear Power Plants (Part 3: Study on Evaluation Method and Applicability of Resilience Index)

We have developed a new index, called the resilience index, that evaluates the dynamic stability of the system safety of a nuclear power plant during a severe accident by considering the ability to recover system safety functions that have become lost in the situation. In this paper, a detailed evaluation procedure for the resilience index is described. The system safety of a PWR plant during a severe accident is then assessed according to the resilience index in order to discuss the applicability of ...
英字タイトル:
Development of Resilience Evaluation Method for Nuclear Power Plants (Part 3: Study on Evaluation Method and Applicability of Resilience Index)

In this research, a new index “The Resilience Index” was proposed to evaluate the capability of nuclear power plant to recover from the situation of safety function lost. Three elements assumed to evaluate the resilience index are the achievement rate, necessary time, and probability of success of each accident management activity. The resilience index is expected to visualize the improvement of safety of each nuclear power plant against severe accidents. ...
英字タイトル:
Development of Resilience Evaluation Method for Nuclear Power Plant (Part.1: Proposal of Resilience Index for Assessment of Safety of Nuclear Power Plant under Severe Accident)

The resilience index has been proposed to evaluate the capability for recovering safety performance of systems subjected severe accident for nuclear power plants. In this study, a failure probability assessment model was developed for the resilience evaluation of static components in nuclear power plants. This model took into consideration the effect of material degradation caused by low-cycle fatigue. Crack initiation due to fatigue damage was assumed and its depth was determined from the magnitude of f...
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Development of Evaluation Method for Resilience Index in Nuclear Power Plant (Part 2: Development of Reliability Assessment Model Considering Degradation of Static Components)

Resilience index is proposed to be applied to evaluate the capability to recover safety performance of systems under severe accident of nuclear power plant. This study developed the failure probability model of equipment by low-cycle fatigue and applied the model to the reliability analysis for degradation of static components in resilience index, ...
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Development of Resilience Evaluation Method for Nuclear Power Plant (Part 2: Study on Reliability Analytical Method for Degradation of Static Components)

The total system design on Nuclear Plant ensures “Nuclear safety” with making practically achievable efforts to prevent and mitigate nuclear and radiological accidents. The performance based system design with “Defence in depth (D-I-D)” has been laid out as the key means in “preventing accidents”, “controlling escalation to serious consequences”, and “preventing harmful consequences to the public”. D-I-D is extended to the management of severe accidents, and is an approach intended to provide protection...
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Development of Resilience Evaluation Method for Nuclear Power Plant (Part4: Concept of System Safety on Operating Nuclear Power Plants)

It has been clarified that the fatigue life is reduced in the fatigue test of high-temperature and high-pressure water that simulates PWR reactor coolant environment compared to that in the tmosphere, and temperature, strain rate，etc. affect the decrease of fatigue life. In this study, the influence of crack growth behavior on fatigue life of SUS316 in simulated PWR reactor coolant environment of different temperature was investigated. Fatigue tests were conducted under different temperatures (325℃ and 200℃...
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Influence of Temperature on the Fatigue Crack Initiation and Growth in Reactor Coolant Environment

The fatigue tests were conducted under different temperature (325℃ and 200℃) in simulated PWR reactor coolant condition with interrupting tests and replica-observation. By observing fatigue crack on the specimen surface, the effect of temperature on crack initiation and growth were studied. From the results of the fatigue tests, the followings were confirmed; ・The number of cycles that fatigue cracks initiate is almost the same in different temperature. On the other hand, the number of cracks that initiate ...
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Influence of Temperature on the Fatigue Crack Initiation and Growth in Reactor Coolant Environment

Abstract: After Fukushima-Daiichi NPP accident, improvement of nuclear safety is highly requested in order to prevent re-occurrence of severe accident. New sc me of fatigue evaluation to confirm system safety in NPPs is enhanced to be established based on Defense-in-Depth concept. In step 1, grand design of fatigue evaluation is reviewed on the viewpoint of fatigue management in long-term safe operation of NPPs, which is required after Fukushima-Daiichi NPP accident. Thi study focuses on the direction to r...
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Reconstruction of Grand Design for Fatigue Evaluation (Step-2) -Fatigue failure analysis of Japanese NPPs-