In order to improve safety of major equipments in nuclear power plants, an advanced FMEA (Failure Mode and Effect Analysis) was developed which was integrated PFM (probabilistic fracture mechanics) into the proven FMEA by evaluating the risk priority number in maintenance management based on a trio of anomaly occurrences in equipments (O), their severity (S) and their detectability (D). The results of equipement risk evaluation were visualized by evaluating the triangle area in the radar chart of three para...
英字タイトル:
Development of Visualization Method of Risk for Maintenance Management

Abstract: Shape changing robot was developed for a narrow space installation and a rough plane stable movement in severe environment. This robot consists of three parts of the slim main body and two crawlers attached to the both ends. When this robot moves a narrow space, three parts lie in a straight line like “I” shape and when the robot moves on a rough plane, three parts are formed like “U” shape. We minimized the use of electric parts in the main body against high temperature and high radiation en...
英字タイトル:
Result of Site Test for Investigation Robot for inside Primary Containment Vessel of 1F-1 - Shape Changing Robot -

1. 概要 原子炉格納容器内部調査装置の 開発および実証 ~ 形状変化形ロボット ~ 日立 GE ニュークリア・エナジー(株) 岡田 聡 Satoshi OKADA 石澤 幸治 Koji ISHIZAWA 高橋 良知 Yoshinori TAKAHASHI 国際廃炉研究開発機構(IRID) 遠藤 洋 Hiroshi ENDO 福島第一原子力発電所の廃止措置に向け、 原子炉格 納容器 (PCV) 内部を調査するための装置を開発した [1] [2]。 PCV 内は放射線量が高く、 放射性物質飛散防止の観 点か......

The structural integrity for Pressurized Thermal Shock (PTS) was evaluated for the RPVs of Japanese Boiling Water Reactors (BWRs). It has been clarified that the BWR RPVs have the sufficient margin of fracture toughness by calculating the stress intensity factor in transitional condition and the acceptance criteria for RPV shell plate which is assumed to be neutron-irradiated in core region for 60 years. ...
英字タイトル:
Evaluation of Pressurized Thermal Shock in transitional condition for Boiling Water Reactor pressure vessel

This study proposes an innovative method for arresting SCC, fatigue and hydrogen assisted cracks, and making harmless the cracks by overload. By overloading, compressive residual stress is introduced ahead of the crack. The residual stress reduces K values and arrests the crack. By the method, KISCC, KIHE and ?Kth increase with increasing Kov (K value by overload) and the notional threshold values were given by　the equation: NKISCC, NKIHE and ? NKth=Ｃ + ＤKov. Where Ｃ is KISCC, KIHE and ?Kth(in the case of ...
英字タイトル:
Arrest of SCC, Fatigue and Hydrogen Assisted Cracks, and Make Harmless the Cracks by Overload

This study proposes an innovative method for arresting SCC, fatigue and hydrogen assisted cracks, and making harmless the cracks by overload. By overloading, compressive residual stress is introduced ahead of the crack. The residual stress reduce K values and arrest the crack. By theory, Kiscc, Kjhe and Kth increase with increasing Kov (K value by overload) and the nominal threshold values were given the equation: “Kuscc, NKjhe and NK th=C + D Kov. Where C is Kiscc, Kihe and Kth, respectively, and D is a p...
英字タイトル:
Arrest of SCC, Fatigue and Hydrogen Assisted Cracks, and Make Harmlessthe Cracks by Overload