According to the past edition of “Guideline of Inspection and Evaluation for Core Internals (Core Spray Sparger & Piping Jet Pum p]” issued by Japan Nuclear Technology Institute (JANTI), fully penetrated flaw should be assumed for uninspected region, for ev aluating their integrity. This assumption was considered to be too conservative. Then, this study was performed on the better as sumption of flaw existence in the uninspected region to develop more appropriate flaw modeling by using statistical evaluati...
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The Guideline of BWR Inspection Program Study on Flaw Characterization of Core Internals Piping for Uninspected Region

Seal welding is a repair method when crack by Stress Corrosion Cracking (SCC) is found in weld rtion of core internals including pressure b oundary component in nuclear power plant. Seal lding is welded directly on surface of existing SCC crack and prevents SCC propagation by la ting SCC crack from reactor water environment. In this study, development of seal welding hnology using automatic TIG Welding was executed, and the applicability of seal welding method CRD stub-tube weld portion was confirmed by ex...
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Development of Seal Welding Repair Technology for CRD Stub-tube

For the commercialization of fast breeder reactors (FBR), it is essential to enhance the economic competitiveness by reduction of total cost by elongation of plant service period. In this point of view, it is important to establish the assessment method of integrity of aged weld joint and repair welding for the components of future long life FBR. In the present study, evolution of microstructure is evaluated for the 304SS-304SS weld joint which was used for 88,000h at 526-545°C in the French proto-typ...
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Influence of FBR plant service and repair welding on microstructure and residual stress of austenitic stainless steel weld joint

The reasons of accidents are reported frequently that “I was too busy to avoid an error“ or “I had no time to make a check“. Though there is a view on that personnel reduction and increase in quantity of occupations heighten the feeling of busyness of workers, there are few previous studies on the factors that affect the feeling of busyness. Then, the questionnaire about the feeling of busyness is developed. In this study, in order to make clear the background factors influencing the feeling of busyness, ...
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A Study of the Background Factors Influencing the Feeling of Busyness of Plant Workers

For the commercialization of fast breeder reactors (FBR), it is essential to enhance the economic competitiveness by reduction of total cost by elongation of plant service period. For this reason, it is needed to establish the aged weld joint integrity assessment method for future FBR compon ents. Additionally, since it is expected to employ the repair weld for aged structural components, it is essential to investigate the effect of repair weld. To investigate the influence of high temperature-long service...
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Basic investigation of aging weld joint and repair weld joint integrity assessmentusing neutron residual stress measurement method

“Guidelines for Inspection and Evaluation of Reactor Internals”, published by Thermal and Nuclear Power Engineering Society (TENPES) and taken over by Japan Nuclear Technology Institute (JANTI), adopted a very conservative assumption on flaw characterization for uninspected region of cylindrical components. Fully penetrated flaw should be assumed for uninspected region, when SCC is found and flaw evaluation is performed on cylindrical core internals such as core shroud. The authors suggested a modified me...
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Technical Basis for Revision of Guidelines for Inspection and Evaluation of Reactor Internals on Flaw Characterization for Uninspected Region of Cylindrical Components

In order to grasp efficiency of risk information, we tried to apply an insight of PRA to considering of severe accidents; TMI, Chernobyl, and Fukushima Dai-ichi. Based on this analysis, three points are disclosed. At first, PRA can product adequate countermeasures for low-likelihood events; huge earthquake or Tsunami. Next, PRA can prove weak points in design or operation reasonably. Third point is safety culture. PRA and safety culture are seemed to be connected deeply. These analyses revealed PRA is on...
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-For Discussions with the Public for the Safety of Nuclear Power -Applying Risk Information to Prevention/Mitigation of SA-

Target of PRA is not calculating PRA to get CDF/CFF, but providing significant and useful information from PRA results for risk-informed activities. Lot of risk applications have been implemented these about 20 years in US. After Fukushima Dai-ichi accidents, Japanese Nuclear Regulation Authority provided new regulatory requirements about external events and beyond design events. And Risk Application faces full-scale implementation. In this report, several methods of risk application are showed with adeq...
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- For Discussions with the Public for the Safety of Nuclear Power -Various Patterns of Risk Application Method and Examples-

After Fukushima daiichi nuclear accident, it becomes more important risk communication with the public. In discussions with the public in nuclear safety, communication and discussions on risks that not only nuclear risks also social risks are important. Differences in viewpoints, understanding, and thought about risks become communication difficult. We need to discuss risks fairly, appropriately with the public and reduce total social risks. ...
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For Discussions with the Public for the Safety of Nuclear Power -Discussion with the Public -

In considering nuclear safety, it is an important task to clarify the relationship with peace of mind that is the heart of people. What is the state that scientific safety is something that people feel safe. We considered the relationship between quantified risk and safety, and ways to acquire peace of mind. We analyzed the thresholds of safety risks as a social common sense, showed a safe condition, and showed the importance of forming a consensus to obtain peace of mind. ...
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For Discussions with the Public for the Safety of Nuclear Power -Safety and Secure-