Recently, preventive maintenance tasks for welding of safe-end nozzles of reactor vessels and steam generators of PWRs in Japan had been carried out sequentially. Before the maintenance tasks, inspection services were carried out and several crack indications were found by eddy current testing (ECT). These indications were found in the welding which made b y 600 series nickel base alloy and evaluated as stress corrosion cracks which were oriented to the axial direction of the nozzle. Then investigations to...
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Development of the advanced phased array UT technique for accurate sizing of cracks in the nozzlewelding

Japanese government has recently addressed a policy to increase capacity factor of existing nuclear PPs to achieve the goal to decrease the emission of CO2. Numerous preventive measures have taken in nuclear power plants to minimize the risk of unexpected long shutdown. Newly developed mitigation measures or repair methods need to be qualified to satisfy regulatory standards, before it is implemented to nuclear power plants. The qualification process needs to comply regulatory standards though it may consum...
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R/D and implement of temper bead welding as newly developed maintenance technique in nuclear power plant

Abstract For the last couple of years, issue of defects in Alloy 600 weld lowered the capacity factor of nuclear power plants. To apply newly developed repair technique, like temper-bead welding that has not been prescribed in technical standards, it is necessary to evaluate its technical applicability to the requirement. In the previous cases, this process has been completed by issuance of no action letter for specific area and condition, utilizing implementation process, such as confirm testing by J...
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Study on implementing newly developed repair welding technique within a limited time frame for nuclear power plant

In order to reutilize nuclear power generation and maintain their presence, it is important to take actions based on assumptions beyond "safety myth". For example, in the field of SCC, long term reliability may be further assured based on evaluation under severer condition than the usual operating environment. Since such severe conditions cannot be reasonably simulated by the experiment in the laboratory, it is effective to utilize numerical simulation as reported in the previous paper. This paper rep...
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Development of an evaluation method utilizing numerical simulation to assure long-term reliability of residual stress improvement by surface treatment

?本報では、予ひずみを付与して原子炉の中性子照射による硬化を模擬した低合金製試験片を対象として、実験室X線を用いた高温その場測定技術（以後、その場測定技術）を活用した熱回復挙動の詳細な観察を行い、熱回復パラメータによる熱回復挙動の推定方法の有用性を改めて確認するとともに、溶接熱サイクルを想定した熱回復挙動の推定方法の高度化について考察する。...
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A Discussion about Thermal Recovery Zone Estimation Based on Lab X-ray In-situ Observation of Thermal Recovery Behavior of Neutron Irradiation-Simulated Materials?

Abstract Various research projects have been conducted on the residual stress distribution in the pipe weld since it is important to evaluate SCC initiation, or to evaluate structural integrity. Our previous report noted the necessity of considering the influence of complicated residual stresses in multi-path weld joint in order to enhance the evaluation of long-term reliability of mitigated stress. This paper describes the evaluation result about the changes in residual stress caused by variations in...
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Evaluation of varying extent on the residual stress distribution by effect of varied welding application and repair welding

Abstract Surface finishing methods, such as Water Jet Peening (WJP), have been applied to welds in some major components of nuclear power plants as a counter measure to Primary Water Stress Corrosion Cracking (PWSCC). In addition, the methods of surface finishing (buffing treatment) is being standardized, and thus the buffing treatment has been also recognized as the well-established method of improving stress. On the other hand, the long-term stability of peening techniques has been confirmed by acc...
英字タイトル:
Prediction method of long-term reliability in improving residual stresses by means of surface finishing