We investigated the relationship between magnetic properties and the accumulation of fatigue damage at elevated temperature for SUS304 stainless steel. The strain-controlled push-pull fatigue tests at 923 K under total str ain range conditions of 0.4%, 0.5% and 0.7% were implemented. The leakage magnetic flux density was also measured before and after each fatigue test. As result, it was shown that the maximum differences in leakage magnetic flux density before and after the fatigue test subsequently incre...
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Evaluation of Initial Fatigue Damage of SUS304 Stainless Steel at Elevated Temperature by a Magnetic Method

Two magnetic methods are proposed for the evaluation of initial degradations of type 304 stainless steel in stress corrosion cracking (SCC). The first one is the measurement of the distribution of chromium depletion by means of a magnetic force microscope (MEM). MEM observations are performed for some samples sensitized in various conditions, and the obtained results coincide with the expected ones from the chromium behavior. Moreover, the phase distributions in the solution-annealed and sensitized states a...
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Evaluation of Initial Degradation in Stress Corrosion Cracking by Magnetic Methods

To realize long-life fast breeder reactor (FBR) plants, it is important to develop a precise estimation method of metallurgical microstruct ure change before crack initiation. For estimating the metallurgical microstructure change related to degradation in commercial FBR plants, the change of magnetic property is focused on. Austenitic stainless steel is paramagnetic, but the magnetic flux density changes as creep damage at 773K or 823K. Finally, it is possible to detect the metallurgical microstructure c...
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Magnetic change in austenitic stainless steels subjected to long term creep damage

In order to achieve both safety and economic efficiency of a nuclear power plant, it is necessary to realize rational maintenance based on characteristics of the plant. The fast breeder prototype reactor, Monju, spent most of the year for the maintenance. It is important to identify causes of the prolonged maintenance of Monju and to investigate countermeasures for implementation of rational maintenance of a next fast reactor. In this study, causes of the prolonged maintenance of Monju during reactor cold s...
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Analysis of issues related to maintenance period of the fast breeder prototype reactor Monju (1) Analysis of plant operation for maintenance of cold shutdown Monju

In order to achieve both safety and economic efficiency of a nuclear power plant, it is necessary to realize rational maintenance based on characteristics of the plant. The fast breeder prototype reactor, Monju, spent most of the year for the maintenance. It is important to identify causes of the prolonged maintenance of Monju and to investigate countermeasures for implementation of rational maintenance of a next fast reactor. In this study, causes of the prolonged maintenance of Monju during reactor cold s...
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Analysis of issues related to maintenance period in the fast breeder prototype reactor Monju (2) Analysis of plant maintenance plan

To achieve the reasonable and effective maintenance of nuclear power plants, it is essential to optimize the aging management from the viewpoints of both safety and efficiency. We propose an inspection-process-scheduling model that minimizes the number of inspection activities in a fast reactor. In this study, we formulate the inspection-process-scheduling problem as mixed integer programming and 0- integer programming problem....
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Fundamental Study on Optimal Scheduling of Inspection Process for Fast Reactor

Maintenance scheduling is currently manually handled, which is a time-consuming process because of the large number of components and constraints that must be taken into account when creating a schedule. Besides, to develop next-generation power plants with excellent operability, it is necessary to make it possible to evaluate operability and maintainability in advance at the design stage. Our objective is to develop and implement an automatic scheduling system using the mathematical technique of Operations...
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Development of Inspection Process Scheduling System for Analyzing Operability of Fast Reactor

State of microstructure in metallic materials can be expressed as numerical values based on a concept of system free energy, and the energy value is used as a measure of damage analysis of the materials. In this study, change in the system free energy of the FG-HAZ in 9Cr heat resistant ferritic steels during creep is evaluated as summation of chemical free energy, strain energy and surface energy, which are obtained by a series of experiments, i.e., chemical analysis using extracted residues, X-ray d...
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Microstructural analysis of HAZ in the welded joints of 9Cr heat resistant ferritic steels for fast reactor

Microstructural states of metallic materials can be expressed by system free energy, and the estimation of the system free energy is useful for damage analysis of the materials. In this study, chang e with creep time in the system free energy of the FG-HAZ in 9Cr heat resistant ferritic steels is estimated on the basis of a series of experiments such as chemical analysis by using extracted resid ues, X-ray diffraction, and scanning transmission observations. The change in the system free energy is expresse...
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Microstructural analysis of HAZ in the welded joints of 9Cr heat resistantferritic steels for fast reactor