In nuclear power plants, the structural components that are in contact with coolant are susceptible to thermal loads due to the change in the fluid temperature. If the heating and cooling processes are cyclic, the structure will endure thermal fatigue that may lead to failure. Thermal stratification is one of the main loads that can lead to high cycle thermal fatigue damage. The Japan Society of Mechanical Engineers, (JSME) have published the evaluation guideline for high cycle thermal fatigue. It treat...
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Stress Generation Mechanism of Elbow Pipes Due to Thermal Stratification

Abstract: Preparation for DEC (design extension condition) is one of the lesson learned from Fukushima nuclear accident. From the structural point of view, it is needed to know the failure modes of the pipe structure to make adequate preparation against excessive seismic loading. But the failure modes under seismic loading are still not clear. Low cycle fatigue is one of the major failure modes observed at seismic experiments. Ratcheting is also observed at some other experiments. And collapse is assum...
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Failure modes investigation of pipe structure under excessive seismic loading

Preparation for DEC (design extension condition) is one of the lessons learned from Fukushima Daiichi nuclear accident. Best estimation is required for DEC. For best estimation of structural strength against seismic load, it is needed to know the failure modes of the piping to make adequate preparation against excessive seismic loading. Ratcheting, collapse and fatigue are the probable failure modes of piping due to seismic loading. But the occurrence conditions of these failure modes under seismic loadi...
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Numerical study on piping failure modes under seismic loading - ratcheting and collapse

Abstract Thermal fatigue crack may initiate at mixing tee where high and low temperature fluids flow in and mix. In order to prevent piping failure caused by thermal fatigue, an evaluation procedure of fluid temperature fluctuation at mixing tee using numerical simulation has been de veloped. This paper compared results of three computational grids of different resolution and discussed the effect of the grids resolution on predictions. The same simulation conditions were set same as WATLON experiments perf...
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Numerical Simulation of Temperature Fluctuation Downstream from a T-Junction-Evaluation of Computational Grid Influence Using LES Dynamic Model

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

Abstract In recent years, there are so many systems using movie. So, we propose a new method to predict the near-future images using movie. To predict the movi e, the Principal Component Analysis (PCA) and Multi-Channel Singular Spectrum Analysis (MSSA) are used in this method. Predicted movie obtained from this metho d is almost the same as the original movie, but improvement is required to reduce the calculation time and to increase the precision of the prediction for real -time image prediction. So, in ...
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Technological Improvement of Movie Prediction Method by PCA and MSSA

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)

Progressive deformation (ratcheting) is one of the failure modes by excessive seismic loadings. These occurrence conditions seem to be similar to the conditions for thermal ratcheting which is called Bree’s diagram. After experiments for ratcheting have done, there were similar results with Bree diagram in some frequency of input waves and not in other frequency. This paper shows detail results by numerical analysis and gives three frequency regions to clarify different characteristics in dynamic load...
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Progressive deformation by dynamic loadings and effects of frequency

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)