When quasi-laminar defects are detected in the RPV shell, these defects are modeled to single circular crack with a diameter of 2a and an angle of ? from RPV wall enveloping these micro-defects like as the model used in the structural integrity assessment for Doel-3. An acceptable crack size is investigated for fracture assessment and initial crack size considering the fatigue crack growth by 60 years operation due to the JSME Fitness-for-Service (FFS) code. It was found that the initial crack with 2a of 4%...
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Structural Integrity Assessment for Internal Crack in RPV Shell

Flaw evaluation method for riser brace arm weld was investigated in case of a flaw is detected in in-service inspection. Weld residual stress was evaluated using 3-D finite element model considering structure of riser brace. Fatigue and SCC crack growth evaluation was performed using evaluated residual stress and stress due to normal operation. Two methods, which are JSME fitness-for-service code and influence function method, were applied to estimation of stress intensity factor to investigate effect of st...
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Structural Integrity Assessment for Riser Brace Arm Weld

Pulsed Eddy Current Testing (Pulsed ECT) has a potential to reduce costs and time for pipe wall thickness measurement because it can be applied from outside of heat insulation material. Artificial defects on pipe specimen and actual piping at a power plant were inspected by Pulsed ECT. Detected positions of artificial defects were coincided well with the actual positions. It was possible to map the wall thickness of the actual power plant piping without removing wire mesh on the surface and to identify rema...
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Wall thickness measurement of thinning pipe by Pulsed Eddy Current Testing device through heat insulation

The purpose in this research is to verify whether risk recognition can be explained not only by the subjective evaluation methods but also by the objective evaluation based on autonomic nervous activity. In the present study, a fundamental method to realize objective risk recognition evaluation has been proposed using heartbeat data in the safety education at experiential training facilities. Based on the results obtained in this research, it has been confirmed that risk-taking behavior characteristics can ...
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Evaluation of risk sensitivity and risk taking behavior based on objective measurements

Principles of Nuclear Power Station's maintenance was established as Code for Maintenance at Nuclear Power Plants (JEAC 4209) in 2003 and revised in 2007,2014 And also Guide for Maintenance at Nuclear Power Plants was established in 2007 and revised in 2014. Recently these Code & Guide were revised accordingly and published as JEAC4209-2016 and as JEAG 4210-2016. Revising these Code & Guide are now under review. Points of the revision is to implement the new regulatory inspection system enforced in 2020 ref...
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Progress report of Revising Code and Guide for Maintenance at Nuclear Power Plants

New nuclear regulation inspections will begin in April 2020. For the preparation of them, Trial use will begin on October this year, and we have assigned Kashiwazaki-Kariwa Nuclear Power Station as a pilot plant for it. This report describes the status about Corrective Action Program (CAP) improvement and Configuration Management (CM) development for the trial use and implementation of a new nuclear regulation inspection, cooperating with NRA study of it....
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Preparation Status of Trial Use for Nuclear Regulation Inspection

New nuclear regulation inspections will begin in April 2020. For the preparation of them, Trial use will begin on October this year, and we have assigned Kashiwazaki-Kariwa Nuclear Power Station as a pilot plant for it. This report describes the status about Corrective Action Program (CAP) improvement and Configuration Management (CM) development for the trial use and implementation of a new nuclear regulation inspection, cooperating with NRA study of it....
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Status of Trial Use for Nuclear Regulation Inspection

One of the most important lessons learned from the Fukushima accident is the lack of technical proficiency. From that perspective, a strategic plan was developed to establish an organization of knowledgeable engineers who are familiar with and accountable for the performance and reliability of important plant systems. The System Engineering Group was founded in Kashiwazaki-Kariwa NPS in 2013 and started system performance monitoring as one of its core activities in 2016. In this report, the process used for...
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System monitoring activity at Kashiwazaki-Kariwa Nuclear Power Station

Large amount of sea water intruded Reactor Buildings including controlled area of Fukushima-Daini Nuclear Power Plant (NPP) at the Tsunami disaster 11th May 2011 and the sea water was contaminated by some radioactive substances. Although the concentration of the radioactive substances was low enough to meet the criteria of technical specification for discharge to the sea、we decided to decontaminate it under the limit of the detection for more safe. Then the result of the discussion with local government and...
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The Safety Handling Technic of the Sea Water that intruded Fukushima-Daini NPP at the Tsunami Disaster 2011

In the application for approval of nuclear power plant operation period extension, it is required to carry out two surveillance tests separately from the conventional plan. At this time, it is necessary to compensate for the surveillance test piece by reconstitution bonding of the used test specimen, since the shortage of the test specimen is expected. Although the used test piece of the welded part is used for the reconstitution bonding of the heat affected zone (HAZ) test piece, the test piece collection ...
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Applicability of Reconstituted Surveillance Test Piece for RPV Embrittlement Evaluation