Yasuhiro Kanto

Recent Japanese Probabilistic Fracture Mechanics Researches Related to Failure Probability of Aged RPV

In order to prepare for the need of probabilistic methodology in design, inspection and maintenance of nuclear components, JAERI (The Japan Atomic Energy Research Institute) has conducted PFM (Probabilistic Fracture Mechanics) researches of Phase 1 and Phase 2 since late 1980s. In order to establish the standard procedure, Phase 1 had been conducted from 1988 to 1994 by entrusting contract researches to JWES (The Japan Welding Engineering Society), MRI (Mitsubishi Research Institute Incorporation) and JSME (The Japan Society of Mechanical Engineers). Subsequently, JAERI initiated Phase 2 in 1996 aiming at more practical application. JAERI had entrusted contract researches from 1996 to 2000 to JWES. JAERI also initiated a development of a PFM Code PASCAL (PFM Analysis of Structural Components in Aging LWR) as well as the contract research. The development of PASCAL-Ver.1 was completed in 2000. PASCAL-Ver.1 was released in 2001. Using PASCAL-Ver. 1, round robin analyses on the usability of the code, the effect of annealing on the failure probability of an RPV, the probabilistic evaluation of the flaw acceptance standard in ASME ( or JSME) Code have been performed within the contract research. This paper presents the overview of activities related to RPV and some results of round robin analyses conducted in PFM Sub-Committee in JWES. In addition, the outline of PASCAL-Ver.1 is also introduced.

Numerical Analysis of Kidney Stone Fragmentation by Short Pulse Impingement: Effect of Geometry

To better understand the behavior of stresses generated inside a kidney stone by direct pulse impingement during extracorporeal shock wave lithotripsy (ESWL), numerical analyses are performed in this work. LS-DYNA, an explicit Finite Element code for non-linear dynamic analysis is employed to investigate the effect of stone geometry to the stress field evolution inside the stone when subjected to short pulse wave. Circular disks with parts removed from the front and the back are used to model the stones that assumed have already had initial fracture. The other variation of spherical geometry such as ellipse is also considered in the numerical calculation.

A Prototype Tactile Mouse for GUI Presentation

Graphical user interface is widely used in PC applications, but it becomes a big drawback for persons with visual disability. Tactile displays have been already developed for them, but they are usually large and expensive. Here a prototype of tactile mouse, which is a mouse with smallsized tactile display, was developed and evaluated in shape recognition. A neural network program, n-Design, was used for compiling experimental data.

Verification of Probabilistic Fracture Mechanics Analysis Code PASCAL

1. 緒言 国内において確率論的破壊力学 (PFM) の適用性向上を図るためには、破損頻度の算出に用いら れる PFM 解析コードの検証が不可欠である。著者らは、原子力機構が整備を進めている原子炉圧力容器 (RPV) に対する PFM 解析コード PASCAL に対する検証の一環として、PASCAL に導入した機能の検証を 行うとともに、米国の PFM 解析コード FAVORとのベンチマーク解析を実施した。 2. PASCALの機能整備 PASCALの適用性向上を目的として、条件付亀裂進展確率 (CPI) 及び条件付亀裂 貫通確率 (CPF) に関する低損傷確率評価機能、認識論的不確実さを考慮した信頼度評価機能等を PASCAL に導入した。例えば、信頼度評価機能の整備では、これまで不確実さの分類を考慮せずにモンテカルロ法 により CPI 及び CPFを算出していたのに対し、二重ループ化する改良を行った。具体的には、内側のルー プで偶然的不確実さのみを考慮して求めた CPIと CPFを、外側のループで認識論的不確実さに基づき統計 処理することにより、前報で示したとおり破損頻度の信頼度を評価できるようにした。また、整備した全 ての機能について検証を実施し、適切に動作していることを確認した。 3.ベンチマーク解析 PASCAL の信頼性向上を図る ため、FAVOR との比較計算を実施した。PASCALと FAVOR の機能の相違を確認した上で、単一亀裂に対 する CPI及び CPF の比較、RPV 炉心領域に対する亀 裂進展頻度 (FCI) 及び亀裂貫通頻度 (TWCF) の比 較等を実施した。PASCAL と FAVOR とでは開発機 関が異なるため、個々の機能には違いがあるが、本 比較計算を通じて、RPV 寸法や化学成分、応力拡大 係数等の条件を合わせた場合にはほぼ同等の結果が 得られることを確認した (図1)。 4. 結論 PASCAL に整備した個々の機能検証、及び PASCAL と FAVOR のベンチマーク解析を通じて、 PASCALの信頼性を検証し、実用性の向上を図った。 5. 謝辞 本報告は、原子力規制庁からの受託事業「平成28年度高経年化技術評価高度化事業(原子炉一 次系機器の健全性評価手法の高度化)」で得られた成果である。関係各位に謝意を表する。

Sensitive Analyses of Probabilistic Fracture Mechanics for Reactor Pressure Vessel during Pressurized Thermal Shock and Comparison with the Results of International Round Robin Analyses in Asian Countries

This paper demonstrates sensitive analyses of probabilistic fracture mechanics (PFM) for reactor pressure vessel (RPV) during pressurized thermal shock (PTS) loading, and comparison of our calculation with the results of the international round robin (RR) analyses in Asian countries (Korea, Taiwan and Japan). The international Round Robin activity was performed in PFM sub-committees in the Atomic Energy Research Committee of Japan Welding Engineering Society (JWES) in conjunction with Korea and Taiwan research groups. The purposes of this program are to establish reliable procedures to evaluate fracture probability of reactor pressure vessels during pressurized thermal shock and to maintain the continuous cooperation among Asian institutes in the probabilistic approach to nuclear safety. Some parameters to RPV failure probabilities are chosen to evaluate their significance quantatively. The differences caused by selection of analyzing programs and some input parameters will be discussed.

A Hermitian Type Triangular Element only with Corner Nodes and its Application to XFEM

A new triangular element of Hermitian type, i.e., the degrees of freedom includes differentiation of value as well as value itself, is proposed and XFEM formulation is demonstrated. Some numerical examples are also shown.

General Post Processing Program for J-Integral Calculation around Arbitrary Shaped Cracks

In this paper, a general post processing program for J-integral calculation is developed to apply to arbitrary shaped cracks in a three dimensional body. Usually J-integral calculation programs are options for specific stress analysis programs and they are not applicable to results from different analysis programs. In most cases, there are many limitations in analysis models or shapes of cracks. This situation is not favorable for users. This paper will demonstrate a development of a post-processing program to calculate J-integral for arbitrary shaped cracks in a three dimensional body. This program requires only discrete data of displacements and stresses at nodal or numerical integration points. Users can use their own programs for stress analyses and calculate J-integral after that. In this paper, errors in approximation will be discussed as the first stage of the development.

Time and Frequency Domains Iterative Regularization for Inverse Analysis of an Instrumented One-Point Bend Specimen

This paper proposes an application of the inverse analysis to estimate the elastic response ahead of the crack-tip of a one-point bend specimen. The difficulty of the problem lies on determination of the impulse response function that relates the elastic response to a unit applied impact force which is numerically ill-posed. Two iterative numerical regularization schemes are proposed, first is a time-domain regularization based on the conjugate-gradient method and second is a frequency-domain regularization based on an optimal filter approach. Both schemes are evaluated by using the data obtained from an impact experiment. The result shows that the estimation error is about 18.0%.