Irradiation-assisted stress corrosion cracking or IASCC is a well-known result of age-related degradation of baffle former bolts which are an integral compo- nent of PWR core internals. However, methods for analyzing the causes and assessing IASCC have yet to be established and are being studied. The baffle former bolts are components of the baffle structure and in order to maintain the integrity of the baffle structure, an effective approach for maintaining the bolts must be provided. This paper prop...
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maintenance method for Irradiation Assisted Stress Corrosion Cracking of PWR core

Temper bead welding (TBW) is one effective repair welding method for the large-scale nuclear power plants instead of post weld heat treatment (PWHT). Consistent Layer (CSL) technique is the theoretically most authoritative method among the five temper bead welding techniques. For TBW, toughness is the key criteria to evaluate the tempering effect. A neural network-based method for toughness prediction in heat affected zone (HAZ) of low-alloy steel has been investigated to evaluate the tempering effect...
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Prediction of Toughness in HAZ produced by Temper Bead Welding of Consistent Layer Technique

In this study, a predictive simulation model coupling weld bead formation and thermal conduction was developed for construction of the method of predicting or evaluating the temperature distribution during temper bead welding. Welding parameters used in the analysis were estimated from experimental welding conditions based on the thermal conduction theory and numerical simulations of previous works. The simulation results were compared with the experimental results under the same welding conditions to ...
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Predictive Simulation Model of Bead Shape and Temperature Distribution during Temper Bead Welding

規格基準動向1．はじめにAlloy600はPWR環境でSCC（以下PWSCC）の感受性があることから保全対策と関連規格の整備はPWR（加圧水型原子炉）の課題の一つとして認識されている。近年、Alloy600が使用されているPWR上蓋に海外で損傷事例が見られていたため、万一の場合の補修工法の確立は優先度の高い課題として検討されてきた。上蓋の補修にはき裂の存在する開先面に遠隔操作により３次元制御で健全な溶接を行う高度な技術を要する。さらに、規格についても、複雑形状のバウンダリ部におけるき裂進展評価、延性破壊評......

In this study, the effects of seal welding conditions, such as welding heat input, depth of crack, and plate thickness, on the welding-induced residual stress and the stress intensity factor (SIF) around the remaining crack were investigated by finite element analysis. In addition, the parameter Q/√a (Q: welding heat input, a: depth of crack) was theoretically derived from welding thermal conduction theory as representative of the temperature distribution along the crack direction. As the results, it w...
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Study on Welding Procedure Parameter Influencing Structural Soundness at Seal Weld

In this study, a fast simulation technique of Iterative Substructure Method (ISM) was applied for numerical analysis of the distribution of residual stress by J-weld and repair weld of Bottom Mounted Instrument (BMI) nozzle in reactor vessel penetration. The calculated results were compared with the measured values to validate the constructed residual stress analysis model. The effect of BMI mounting angles on distribution of residual stress at J-welds was investigated. Based on the results, similarity and...
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Numerical Analysis of Residual Stress by J-weld and Repair Weld of Bottom Mounted Instrument Nozzles in Reactor Vessel Penetration