BWR環境下で長期間使用されたニッケル基合金溶接部の応力腐食割れ事象から得られた知見に基づくき裂進展解析評価
Evaluation on Crack Growth Analysis Model based on the Knowledge obtained from Stress Corrosion Cracking in Ni-based Alloy used for a Long Time in a BWR
著者:
青木 孝行 Takayuki AOKI 清水 禎人 Sadato SHIMIZU 宮崎 克雅 Katsumasa MIYAZAKI 林 正明 Masaaki HAYASHI 小林 広幸 Hiroyuki KOBAYASHI
発刊日:
公開日:
Alloy 182Aspect RatioCrack Growth AnalysisCrack ModelNi-based AlloyResidual StressStress AnalysisStress Corrosion Cracking
概要
During the field work of the core shroud replacement project of Tsuruga power station unit 1 in December 1999, when it had almost 30 years operation experience since the commencement of commercial operation in March 1970, many cracks were detected visually at the shroud support to reactor pressure vessel (RPV) weld metal (Ni-based alloy: Alloy 182) and confirmed with penetrant testing as well as by metallographic observation. Almost all cracks were found to propagate in the axial direction of the RPV and concluded to be interdendritic stress corrosion cracking (IDSCC). The excavation of all the cracks revealed that they propagated within the Alloy 182 weld buttering and had larger aspect ratios than IGSCC of austenitic stainless steel. A stress analysis including residual stress due to fabrication was conducted and it was found that higher stress locations predicted by the analysis matched with the locations of the real cracks. Using this result and current available methods including JSME code, a crack growth analysis was conducted. As a result, it gave a conservative result that the crack size predicted by the current methods was larger than sizes of the real cracks found in the Tsuruga unit 1 shroud support.
