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......

Abstract: This study tries to clarify the maintenance activities that can be applied risk information to, and determine priority of the application. For that purpose, first, we investigated the maintenance activities themselves, and broke them down into 75 “Maintenance Elements”. Second, we evaluated whether each “ Maintenance Element” could be applied risk information to. Third, we determined the priority of the risk application on “application merit” and “possibility” aspects. This study has revealed t...
英字タイトル:
Study of Application of Risk Information to Maintenance Management

Japanese government has recently addressed a policy to increase capacity factor of existing nuclear PPs to achieve the goal to decrease the emission of CO2. Numerous preventive measures have taken in nuclear power plants to minimize the risk of unexpected long shutdown. Newly developed mitigation measures or repair methods need to be qualified to satisfy regulatory standards, before it is implemented to nuclear power plants. The qualification process needs to comply regulatory standards though it may consum...
英字タイトル:
R/D and implement of temper bead welding as newly developed maintenance technique in nuclear power plant

Abstract For the last couple of years, issue of defects in Alloy 600 weld lowered the capacity factor of nuclear power plants. To apply newly developed repair technique, like temper-bead welding that has not been prescribed in technical standards, it is necessary to evaluate its technical applicability to the requirement. In the previous cases, this process has been completed by issuance of no action letter for specific area and condition, utilizing implementation process, such as confirm testing by J...
英字タイトル:
Study on implementing newly developed repair welding technique within a limited time frame for nuclear power plant

Although performance of nuclear power stations has been increased dramatically due to high reliability of the plant system and equipment in recent years, the troubles related to human performance are still reported at present. It becomes therefore, important to analyze the trouble experiences related to human performance and to share those lessons learned among maintenance personnel in order to secure the safety of nuclear power stations. In this study, error management analysis was carried out using trou...
英字タイトル:
Study on analysis method and its application for effective utilization of trouble experiences in maintenance work at nuclear power stations

Stress corrosion cracking (SCC) is one of serious aging degradation problems for the Alloy 600 components of pressurized water reactors (PWRs). In order to prevent SCC, various methods such as water jet peening (WJP), laser peening (LP), surface polishing have been used to introduce compressive stresses at the surfaces of the PWR components. However, it has been reported that such compressive residual stress introduced by these methods might be relaxed during the practical operation, because of high te...
英字タイトル:
Kinetic analysis on the long term stability of the effect obtained by various residual stress improvement methods ― Evaluation for long term stability of residual stress improving treatment on Ni base alloy (report 2) ―

In order to reutilize nuclear power generation and maintain their presence, it is important to take actions based on assumptions beyond "safety myth". For example, in the field of SCC, long term reliability may be further assured based on evaluation under severer condition than the usual operating environment. Since such severe conditions cannot be reasonably simulated by the experiment in the laboratory, it is effective to utilize numerical simulation as reported in the previous paper. This paper rep...
英字タイトル:
Development of an evaluation method utilizing numerical simulation to assure long-term reliability of residual stress improvement by surface treatment

In order to estimate the stability of the stress improving effect by water jet peening (WJP) residual stress improvement methods during the long-term operation of nuclear power plants, the residual stress in nickel-based alloy 600 has been studied through the kinetics of hardness reduction behavior in practical operation temperatures. Based on the relationship between the residual stress relaxation and the hardness reduction rates, it has been found that in actual operating condition, when the hardness decr...
英字タイトル:
Prediction of Residual Stress Stability Introduced by Water Jet Peening Residual Stress Improvement Method to Ni-based Alloy during Long-Term Operation

In order to compare the stability of the stress improvement effect introduced by laser peening (LP), water jet peening (WJP) and buffing residual stress improvement methods during the long-term operation of nuclear power plants, the hardness in nickel-based alloy 600 has been studied through the kinetics of hardness reduction behavior in practical operation temperatures. The predicted hardness results show that in actual operating condition, the time required to reduce the hardness to 180HV is 1268 years fo...
英字タイトル:
Long-Term Stability Comparison of LP, WJP and Buffing Residual Stress Improvement Methods under Actual Operating Condition