Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs: 2008 (AESJ-SC- P005: 2008)
- Published Title
- Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs: 2008 (AESJ-SC- P005: 2008)
- Responsible Subcommittee
- PLM Subcommittee
- 2009/02/28(Japanese-Language Edition)
*English-Language Edition in Preparation.
(Remarks) This document is translated from the original Japanese-language version. In case any misunderstanding or misinterpretation arise herefrom, the original Japanese text alone is valid.
"Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs 2008"was established by Atomic Energy Society of Japan (AESJ) through discussions by PLM Working Group followed by deliberations by Power Reactor Technical Committee and then by Standards Committee. The Code sets forth the method for the implementation of ageing management measures to be adopted by the Japan’s electric utilities which are in charge of the operation and management of light water reactor type nuclear power plants.
For the purpose of this Code, ageing management of nuclear power plants means the implementation of activities considering a long-term plant operation through the evaluation of the effects of ageing phenomena, which are expected to occur in structures, systems and components constituting a nuclear power plant, on their safety functions.
In order to ensure safe and stable operation, Japan’s nuclear power plants are subjected to the regulatory inspections conducted by the Ministry of Economy, Trade and Industry in accordance with the Electricity Enterprises Law and voluntary inspections implemented by the electric utilities by shutting operation at regular intervals. These inspections are intended to verify the consistency with the technical standards specified in the ministerial ordinances and notifications. At the same time the electric utilities are implementing the maintenance programs for plant structures, systems and components to confirm their integrity, maintain their intended safety functions and maintain and improve their reliability.
In addition, while the plant is operating, the electric utilities carry out condition monitoring, including trend monitoring, plant walkdowns and surveillance tests, to identify abnormal indications of plant structures, systems and components.
To assure safety and reliability of a nuclear power plant for a long period of time, it is essential to carry out technical evaluations focusing on ageing phenomena which may initiate and develop as operating years increase and take necessary actions.
In this regard, the electric utilities are required to move on the measures in accordance with the guideline, “Improvement of Ageing Management for Commercial Power Reactors”, which was published by Facility Obsolescence Review Panel, Nuclear and Industrial Safety Subcommittee, Advisory Committee for Natural Resources and Energy on August 31, 2005.
On the other hand, the Japanese Government issued the revised Rules on the Installation and Operation of Commercial Power Reactors on December 26, 2005 incorporating a requirement for the electric utilities to submit a report regarding the results of plant life management evaluation. In addition, the government released the “Ageing Management Implementation Guideline for Nuclear Power Plants” and the “Standard Review Plan for PLM Activities at Commercial Nuclear Power Plants”.
Meanwhile, possible improvements of the current inspection system for nuclear power plants are being discussed. As part of the activities toward the establishment of the new inspection system, the possibility of improving the current maintenance activities based on the “maintenance program”, which definitely states the system of implementing maintenance activities, scope of structures, systems and components subject to the maintenance, and implementation plan of maintenance activities, is being investigated.
In the course of the improvement of maintenance activities, a consensus that the ageing management program, which is one of the pillars constituting the basic principles of maintenance program, should be incorporated into the maintenance activities from the early stage of plant operation, is being built.
In this regard, it is necessary to clearly understand the characteristics of the development of each ageing phenomenon and then implement maintenance activities to address such development.
The original version of Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs was issued in March 2007. The original version set forth the method of implementing ageing management measures for plants operating more than 30 years. Drafting work of the revised version started immediately after the issuance of the original Code in conjunction with the work toward the establishment of the new inspection system for nuclear power plants. This new version of Code specifies the details of ageing management measures to be taken from the early stage of operation, when the plant marks its 10th and 20th year of operation, and enhanced ageing management measures to be implemented every 10 years after the plant marked its 30th year of operation.
This Code includes major changes; first, the definition of ageing management measures was reviewed and maintenance activities to be conducted to address ageing phenomena were identified according to the operating years to determine the details of ageing management program in conjunction with the maintenance program.
In addition, a “summary sheet of ageing phenomena” was formulated showing expected ageing phenomena according to nuclear power plant components based on the knowledge obtained by the nuclear power plants which had implemented the plant life management technical evaluation. The summary sheet of ageing phenomena is attached to this Code as a regulatory requirement and this Code requires the electric utilities to perform ageing management from the early stage of plant operation according to the summary sheet of ageing phenomena.
This Code also includes another attachment which identifies the ageing management measures to be taken when the plant marks its 10th and 20th year of operation and enhanced ageing management measures to be implemented every 10 years after the plant marks its 30th year of operation by specifying the standardized methods for the evaluation of individual ageing phenomena.