報告書番号

Q15003

タイトル（和文）

復元抽出による確率論的破壊力学解析コードの開発

タイトル（英文）

Development of Probabilistic Fracture Mechanics Analysis Code Based On Sampling with Replacement

概要 （図表や脚注は「報告書全文」に掲載しております）

確率論的破壊力学（PFM）は，原子力発電プラントの構造健全性評価を合理的に行える手法として，これまでに複数のPFM解析コードが開発されている．通常のPFM解析では，亀裂寸法や物性値のような実測データの統計的なばらつきを確率密度関数により表し，同関数から抽出した値を用いて破損確率を評価している．十分な数の実測データは統計的なばらつきに物理的な上限および下限を有していると考えられるが，実測データに基づきモデル化した確率密度関数に含まれる保守性は十分に評価されていない．本研究では，破損確率を合理的に評価するため，復元抽出によるPFM解析コードPEDESTRIANを開発した．また，実測データの復元抽出による解析と確率密度関数による解析とで，破損確率にどのような違いが生じるかを評価した．

概要 （英文）

Probabilistic Fracture Mechanics (PFM) is a rational methodology in structural integrity evaluation for nuclear power plants, and several PFM analysis codes have been developed. In general, statistical distributions of random variables such as initial crack sizes and material properties are expressed as probability density functions (PDFs), and a set of random variables are sampled from those functions for each time of repeated failure analysis to get the cumulative failure probability. Since most of random variables are considered to have physical upper and lower limits in their distribution, it is essential to set the reasonable cut-offs in the functions to avoid the improper samplings. If a sufficient number of measured data are available, their population is supposed to intrinsically include the information comes from such the limits. In this study, PFM analysis code named PEDESTRIAN was developed. PEDESTRIAN can sample the variables based on the direct sampling of measured data by means of sampling with replacement in order to evaluate failure probability in a rational manner. The difference in failure probability was discussed between the general sampling procedure, which uses PDFS, and PEDESTRIAN's direct sampling procedure. Consequently, the failure probability obtained by PEDESTRIAN's direct sampling procedure was about an order of magnitude lower than that obtained by the general sampling procedure.

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