A Ni-base alloy weld, including cracks due to stress corrosion cracking found in the reactor internal of the oldest BWR in Japan, Tsuruga unit 1, in 1999, was examined by three (3) types of UT method. After this examination, a depth of each crack was confirmed by carrying out a little excavation with a grinder and PT examination by turns until each crack Hisappeared. Then, the depth measured by the former method was comp ared with the one measured by the latter method. n this fashion, performances of the ...
英字タイトル:
Evaluation on Ultrasonic Examination Methods applied to Ni-base Alloy Weld including Cracks dueto Stress Corrosion Cracking found in BWR Reactor Internal

In recent years, several cases have been reported that SCC was found in reac- tor internals and reactor nozzle safe-end and penetrations of BWR. Therefore, it is getting more important to understand what kind of characteristics Ni-base alloy used for a long time in BWR have. In this study, the results of the investiga- tion on SCC found in the shroud support (Ni-base alloy) of the oldest BWR in Japan, Tsuruga unit 1, in 1999 are discussed. Based on the discussion, the conclusions are summarized as fol...
英字タイトル:
Stress Corrosion Cracking in Ni-base Alloy Used for a Long Time in a BWR

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 ...
英字タイトル:
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

The 2011 off the Pacific coast of Tohoku Pacific Earthquake and the Tsunami gave the serious damage to the Fukushima-Daiichi Nuclear Power Plants (NPPs). The lessons from the accidents, IAEA’s Integrated Regulatory Review Service (IRRS) team conducted review for NRA. The mission provided recommendations and suggestions for improvements in most of the areas covered by the review. include: 1) The NRA should work to attract competent and experienced staff, and enhance staff skills relevant to nuclear and r...
英字タイトル:
Improvement of NRA’s Inspection by IRRS recommendation and Innovative Integrated New Maintenance System for NPPs

Abstract This study proposes the systematization of plant maintenance and establishment of Maintenology or “Maintenance Engineering“. In this paper, it is shown that “Inspection System Engineering”, which consists of a part of Maintenance En gineering, is necessary to incorporate a scientific approach or rationality into maintenance planning and can provide ho w to optimize inspection planning by considering the structural strength and aging degradation of equipment or component....
英字タイトル:
Approach to the Construction of “Maintenance Engineering"

It is important for maintenance of nuclear power station facilities in the future to promote mathematical techniques which support judgement to modify maintenance practices, such as maintenance tasks, maintenance implementation timing, and so on. Mathematical Maintenance Working Group, which has been established by Maintenance Standardization Committee since July 6, 2018, is investigating application examples of such mathematical techniques in maintenance planning as influence evaluation of changing maint...
英字タイトル:
Investigation on application examples of mathematical techniques to support judgement to modify maintenance practices

1．はじめに：普遍性と階層構造原子力発電設備でとられている保全の基本原理の中に「階層性」と「階層原理」を導入できないかという命題は検討に値する。階層原理とは、例えば原子力プラントが電力を生産するまでにたどるプロセスは、設計と建設と運転管理、の三つの部分からなり、それらが階層的な役割を果たしながら全体として電力の安定供給という機能を果たしている仕組みを言う。階層性が存在し階層原理が正常に機能すれば、設計、建設、運転管理の三つの行為が適切に機能し、その結果電力は正常に国民に供給される、という目標が達成される。......

1．はじめに原子力発電に関わらず、プラントの保全は設計・運転・管理に携わるエキスパートによってその内容が立案され実施されている。計画立案の際に最も有効な情報は実はエキスパートの業務経験に基づく知識であり、過去のトラブル等の運転実績である。特に原子力の場合、他の産業に比べて日が浅いことから、現場の人たちの試行錯誤によって保全計画の改善がなされてきた側面が強い。しかしながら、運転経験の蓄積にともない従来の経験に基づく保全から理論に基づいた保全へと移行する機運が高まってきた。保全の体系化とはこの一連の流れにおい......

1．はじめにプラントシステムの保全計画は、体系化された学問に基づき立案・実施されるというよりも、現場で実務に携わる専門家の経験に基づき、多くの試行錯誤を経て段階的にその精度を高めていくという手法が、これまで一般的にとられてきている。これは、原子力発電プラントの保全計画についても同様であり、プラントの安全性・信頼性確保を目標に、運転経験と技術知見の蓄積を可能な限り保全計画に反映してきた結果として現在の完成度の高い保全計画が構築されているものの、まだまだ定量的な要素も少なく、そのため論理的な要素の導入にも限界......

1．はじめに保全は、機械、電気、制御などの機器から成る、いわゆる「機械系」とそれを保全する「人間系」から構成されている。これまでの保全はこの２つの要素が渾然一体となって取り扱われ、両者を明確に分離して分析評価する手法が十分には取られて来なかった。これには社会的状況や規制などの影響もあったと考えられるが、いずれにしても保全の体系化や保全学の構築など、学術的アプローチを積極的に進めようとする気運が希薄であった。しかしながら、近年、保全を学術として捉え、それを体系化することによって、合理的効率的に保全の最適解が......