Reactor pressure vessel (RPV) of the light water reactor is the most important safety related component. To prevent non-ductile fracture of RPVs during operation, the degree of irradiation embrittlement of RPV steels is monitored by surveillance tests, and structural integrity assessment of RPVs is conducted based on the test results. The assessment method based on probabilistic fracture mechanics (PFM) is known as a rational one in assessing the integrity of RPVs, and efforts for practical applications of ...
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Study on Practical Application of Probabilistic Structural Integrity Assessment Method for Reactor Pressure Vessels

Assuring the structural integrity of a reactor pressure vessel (RPV) is known as one of the critical issues to maintain the safe long-term operation of a nuclear power plant. Authors have been conducting extensive research on the improvement of structural integrity assessment methods of RPVs. In this paper, we describe some research results obtained from the recent activity including the review on the technical background of the methods and study on probabilistic methods for the applicability to the cu...
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Study on Structural Integrity Assessment of Reactor Pressure Vessels

Residual stress by welding would be one of the most significant factors in evaluating failure probabilities of PLR piping since the SCC growth behavior is strongly affected by residual stress distribution. The residual stress distribution is well known to ch ange caused by varying of welding conditions such as groove shape, electrical voltage and current, inter-pass temperature, etc. Therefore, to evaluate the scatter of welding condition and their influence on residual stress is important to assess the st...
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Probabilistic Structural Integrity Assessment of Reactor Coolant Pressure Boundary Piping-1- The Scatter of Welding Conditions and Welding Residual Stress -

Stress corrosion cracking (SCC) in primary loop recirculation piping made of austenitic stainless steel has been observed near welding joints. The SCC grows near the welding zone mainly due to high tensile residual stress by welding as well as the other contributing f actors of material and environment. The residual stress analysis due to welding of austenitic stainless piping is important and has been already conducted by many researchers. In present work, the effect of scatters of welding conditions such...
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Probabilistic Structural Integrity Assessment of Reactor Coolant Pressure Boundary Piping-2- Residual Stress Analyses of the Effect of Scatter of Welding Conditions -

A probabilistic fracture mechanics (PFM) analysis code PASCAL-SP, which evaluates failure probabilities at welded joints in piping where being susceptible to stress corrosion cracking (SCC), h as been developed. This code is based on Monte Carlo simulation technique and Japanese code related to the SCC evaluation. Uncertainties and scatters of welding residual stress distribution we re modeled using database obtained from parametric FEM analyses. Sensitivity analyses concerning uncertainties and scatters o...
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Probabilistic Structural Integrity Assessment of Reactor Coolant Pressure Boundary Piping-3 - Probabilistic Fracture Mechanics Analyses Concerning Welding Residual Stress Distribution -

In nuclear power plants, stress corrosion cracking has been observed near the weld zone of the primary loop recirculation pipes made of low-carbon austenitic stainless steel Type 316L. Residual stress is important factor in the occurrence and propagation of SCC. The joining process of pipes usually includes surface machining and welding, and both processes induce residual stresses. In this study, FEM was used to estimate residual stress distributions generated by butt welding and surface machining. In addi...
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Evaluation of Residual Stress Distribution due to Welding and Surface Machining and Crack Growth Behavior

This study proposes a numerical analysis method for evaluation of strength properties related with mater ial control and material maintenance. The method using generalized Voronoi diagram for modeling of hete rogeneity of grain shape is proposed. Effect of grain shape on strength properties is analyzed by the fi nite element method. ...
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Investigation of Material Control and Material Maintenance Method by Evaluation of Strength Properties Considering Grain Shape

To clarify the effects of residual stress and hardening on intergranular stress corrosion cracking (IGSCC) behavior in welds of low-carbon austenitic stainless steels with surface machining, residual stress and hardness were evaluated by 3-dimentional thermo elastic-plastic analysis and grain boundary sliding behavior was examined using a constant strain rate tensile test. It was revealed that grain boundary sliding occurred in the material at 561K by the tensile test with the numerically simulated t...
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Effect of Residual Stress and Hardening on Grain Boundary Sliding in Welds of Low-carbon Stainless Steels with Surface Machining

Abstract To assure the structural integrity of a reactor pressure vessel (RPV) is known as one of the critical issues to maintain the safe long-term operation of a nuclear power plant. In Japan, the assessment meth ods for RPV integrity, stipulated in the codes and standards, have been endorsed by the regulatory body. Authors have initiated extensive research on the improvement of structural integrity assessment methods of RP Vs. In this paper, we describe some research results obtained from the first-year...
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Study of System Safety Evaluation on LTO of National ProjectStructural Integrity Assessment of Reactor Pressure Vessels

To assure the structural integrity of a reactor pressure vessel (RPV) is known as one of the critical issu es to maintain the safe long-term operation of a nuclear power plant. In Japan, the assessment methods for RPV integrity, stipulated in the codes and standards, have been endorsed by the regulatory body. Authors h ave initiated extensive research on the improvement of structural integrity assessment methods of RPVs. I this paper, we describe some research results obtained from the second-year activity...
英字タイトル:
Study of System Safety Evaluation on LTO of National Project Structural Integrity Assessment of Reactor Pressure Vessels