We have developed a new index called Resilience index, which evaluate the reliability of system safety of nuclear power plant under severe accident by considering the capability to recover from the situation the system safety function was lost. In this paper, a detailed evaluation procedure for the Resilience index was described. System safety of a PWR plant under severe accident was then assessed according to the Resilience index concept to discuss applicability of the index. We found that the Resilie...
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Fundamental Study on Applicability of Resilience Index for System Safety Assessment

We have proposed new indices for evaluating resilience, that is, the response margin and response reliability of a nuclear power plant during an accident and detailed procedure for assessing those indices. In this study, the resilience of a simple fast reactor plant model is evaluated according to the indices. The applicability of the resilience evaluation method to fast reactor plants is then discussed from the viewpoints of reflecting the characteristics of each reactor type....
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Fundamental Study on Applicability of Resilience Evaluation Method to Fast Reactor Plants

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 ...
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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. ...
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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)

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)

In order to realize reasonable and effective maintenance of nuclear power plants, it is essential to optimize aging management from the viewpoint of safety and efficiency. We propose maintenance scheduling model considering that effective maintenance activities are different for each failure cause. Our model creates a schedule that minimizes the number of maintenance activities while ensuring the reliability of functions important to safety. In this paper, we formulate the maintenance scheduling model as a ...
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Maintenance Scheduling Considering Relationship between Failure Cause and Maintenance Type

In nuclear power plants, a lot of failure cases by high cycle thermal fatigue are reported, which is induced by temperature fluctuation of the coolant. To ensure the safety of nuclear power plants, thermal fatigue should be evaluated adequately. To evaluate thermal fatigue, frequency response functions were developed by Kasahara et al... These functions were derived theoretically to calculate thermal stress caused by thermal striping and thermal stratification oscillation, which are main causes of high...
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Development of thermal stress evaluation method and fatigue damage evaluation method for thermal stratification oscillation

In nuclear power plants, a lot of failure cases by high cycle thermal fatigue have been reported, which is induced by temperature fluctuation of the coolant. To ensure the safety of the nuclear power plants, the thermal fatigue failure should be prevented adequately. Thus The Japan Society of Mechanical Engineers (JSME) published the high cycle thermal fatigue evaluation guideline. In the guideline, it is proposed that the structural integrity can be judged by the location of thermal stratification, which...
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Study on the mechanism of stress generation of straight pipe and elbow pipe which has thermal stratification