Technical Evaluation Results Concerning Hamaoka Nuclear Power Station Unit 4's Aging State

Chubu Electric Power has completed the technical evaluation of an aging state (Note 1) of Hamaoka Nuclear Power Station Unit 4 which will mark its 30th year of operation on September 3, 2023.

In accordance with ordinances on the technical evaluation of aging states (Note 2), Chubu Electric Power conducted an assessment assuming Unit 4 to retain its cold shutdown (Note 3), and thereby concluded that continuing the ongoing maintenance initiatives would allow for maintaining the integrity of the Unit's facilities.

In view of this evaluation result, Chubu Electric Power today submitted to the Nuclear Regulation Authority an application for approval of changes in regards to the Technical Specifications for Nuclear Reactor Facility related to the Long-Term Maintenance Management Policy (Note 4).

Unit 4 will start undergoing examinations by the Nuclear Regulation Authority. Assessments for the operation of the Unit will be performed when the timing is appropriate.

（Note 1）A technical evaluation of an aging state involves identifying, from all aging degradation events that might or have occurred on safety function-equipped components/structures, incidents to focus on for the sake of countering age-related deteriorations, and in turn assessing the integrity of components/structures corresponding to these events. The evaluation process also includes checking if the present maintenance management is effective, and, when necessary, identifying maintenance measures that should be added.

（Note 2）"Ordinances" refer to "Article 43, Paragraph 3-22-1 of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors," "Article 82 of the Rule for the Installation, Operation, etc., of Commercial Nuclear Power Reactors," and "Guidelines in Implementing Measures for Aging Management at Commercial Nuclear Installations."

• "Article 43, Paragraph 3-22-1 of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors"
  As per the Nuclear Regulation Authority regulations, this ordinance mandates to take steps required for achieving operational safety (this includes items involving steps to take in the event of severe accidents) in regards to maintaining nuclear power reactor facilities.
• "Article 82 of the Rule for the Installation, Operation, etc., of Commercial Nuclear Power Reactors"
  This ordinance mandates technical evaluations to be conducted on the aging degradation of components/structures prescribed as critical in ensuring the safety of nuclear power reactor facilities by the Nuclear Regulation Authority. Evaluations must be completed by the day in which the nuclear reactor marks its 30th year of operation. This ordinance also requires harnessing evaluation results and accordingly drawing up a policy for maintenance management that must be performed within 10 years for relevant nuclear power reactor facilities.
• "Guidelines in Implementing Measures for Aging Management at Commercial Nuclear Installations (hereinafter "Implementation Guidelines")" This ordinance prescribes basic requirements on both aging state technical evaluations performed by reactor licensees to counter aging, as well as the Long-Term Maintenance Management Policy.
  1.Performing and reviewing the technical evaluation of aging states
  2.Drawing up and changing the Long-Term Maintenance Management Policy
  3.Reflecting the Long-Term Maintenance Management Policy into Technical Specifications
  4.Performing maintenance management based on the Long-Term Maintenance Management Policy

（Note 3）The evaluation based on the assumption that the cold shutdown condition is maintained refers to the technical evaluation of an aging state of components/structures with safety functions that are necessary to maintain the cold shutdown condition, and is defined in the Implementation Guidelines. (According to the Implementation Guidelines, "The evaluation of an aging state shall be conducted only on the assumption of maintaining cold shutdown if any of the components/structures do not comply with the criteria specified in the Technical Standards for Commercial Nuclear Power Reactors and their Ancillary Facilities on the day when 30 years have elapsed since the start of operation.)

（Note 4）The Long-Term Maintenance Management Policy is a plan for maintenance management based on results of aging state technical evaluations, which must be performed within ten years for relevant nuclear power reactor facilities.