Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs :2015 (AESJ-SC-P005E：2015）

内容紹介

＜FOREWORDより＞

The “Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs 2015” was established by the Atomic Energy Society of Japan (AESJ) through discussions in PLM Subcommittee followed by deliberations in System Safety Technical Committee and then in Standards Committee. The Code sets forth the method for implementation of ageing management measures to be adopted by Japan’s electric utilities which are in charge of 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 taking into consideration long-term plant operation through 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 regulatory inspections conducted by the Ministry of Economy, Trade and Industry in accordance with the Electricity Business Act (It was decided in July 2013 that the Nuclear Regulation Authority would perform regulatory inspections according to the “Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors”) and voluntary inspections implemented by 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.

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 the revised version started immediately after issuance of the original Code in conjunction with the work toward establishment of a new inspection system for nuclear power plants. This new version of the Code specifies the details of ageing management measures to be taken from the early stage of operation, when the plant marks its 10^th and 20^th year of operation, and enhances ageing management measures to be implemented every 10 years after a plant marks its 30^th year of operation.

AESJ-SC-P005:2008 which was issued in February 2009 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 number of operating years to determine the details of an ageing management program in conjunction with the maintenance program. In addition, “summary sheet of ageing phenomena” were formulated showing expected ageing phenomena according to nuclear power plant component based on knowledge obtained by nuclear power plants which had implemented an ageing management technical evaluation. The summary sheet of ageing phenomena is attached to this Code as a regulatory requirement and this Code requires 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 a plant marks its 10^th and 20^th year of operation and enhances ageing management measures to be implemented every 10 years after the plant marks its 30^th year of operation by specifying the standardized methods for evaluation of individual ageing phenomena.

The summary sheet of ageing phenomena in AESJ-SC-P005: 2010 (Amendment 1), 2011 (Amendment 2) and 2012 (Amendment 3) include the results of ageing management technical evaluation for the 8 units (i.e., Turuga-1, Fukushima Daiichi-4, 6, Hamaoka-2, Tokai Daini, Mihama-1 and Ohi-1, 2) as the latest knowledge, which were described in the reports submitted to Nuclear Safety Commission of Japan from November 2007 to the end of October 2010.

AESJ-SC-P005:2015 includes the following major changes:

• Incorporating the “Regulatory Guide for the Implementation of Ageing Management Program for Commercial Nuclear Power Generation Facilities” (issued by the Nuclear Regulation Authority, December 6, 2013) and lessons learned from the Great East Japan Earthquake, the scope of components subject to the evaluation and the evaluation period were reviewed and modified, and descriptions about technical evaluation of plants in a long-term shutdown state, tsunami safety evaluation and evaluation of the effectiveness of the Assessment of ageing management measures were added.
• The findings obtained from the International Generic Ageing Lessons Learned (IGALL) were incorporated into Attachment E (Reference) “List of Ageing Phenomena”.
• Attachment C (Provisions) “Methods for Implementing Technical Evaluation of Ageing Phenomena” and Attachment D (Provisions) “Method for Implementing Seismic Safety Evaluation” were modified incorporating the latest knowledge.
• The Summary Sheet of Ageing Phenomena included in Attachment A (Provisions) was revised to include the results of ageing management technical evaluation for the 5 units (i.e., Fukushima Daiichi-1, Fukushima Daini-1, Genkai-2, Ikata-2 and Mihama-2), which were described in the reports submitted to Nuclear Safety Commission of Japan from November 2010 to the end of October, 2012 as well as operating experience in nuclear power plants as the latest knowledge. In addition, the combinations of component portions and ageing phenomena, which should be subject to seismic safety evaluations taking into account ageing phenomena, were identified in the Summary Sheet of Ageing Phenomena for each plant component based on the knowledge obtained by nuclear power plants which had implemented an ageing management technical evaluation.

AESJ-SC-P005:2015 includes following Attachments, but the Attachments E and F (Reference) are not an integral part of the provisions.

Attachment A (Provisions): Ageing Management According to Summary Sheet of Ageing Phenomena

Attachment B (Provisions): Method for Implementing Ageing Management Program every Ten years

Attachment C (Provisions): Methods for Implementing Technical Evaluation of Ageing Phenomena

Attachment D (Provisions): Method for Implementing Seismic Safety Evaluation

Attachment E (Reference): List of Ageing phenomena

Attachment F (Reference): Philosophy for Ageing Management Based on Ageing Phenomenon Characteristics