Approval of Changes to the Decommissioning Plan of Hamaoka Nuclear Power Station Units No. 1 and 2

On December 21, Chubu Electric Power received an approval from the Nuclear Regulation Authority (NRA) on the application for approval of changes (partially amended on October 23 and December 14, 2023) to the Hamaoka Nuclear Power Station Units No. 1 and 2 Decommissioning Plan (“Decommissioning Plan”) (Note 1), submitted on March 13, 2023.

Also on December 21, Chubu Electric Power received an approval from the NRA for the June 19, 2023 application of changes the company made to the Operational Safety Program of Nuclear Facilities (Note 2).

Chubu Electric Power will continue to steadfastly decommission Units No. 1 and 2 while both securing transparency and giving overriding priority to ensuring safety.

【Overview of application for approval of changes】

1. Decommissioning Plan

(1) Postponement of the start of Stage 3
The start of the dismantling and removal of the reactor zone (Note 3) (Stage 3) will be changed from FY2023 to FY2024.

(2) Addition of reactor zone peripheral equipment (Note 4) to be dismantled
The suppression chamber (Note 5) as well as the primary containment vessel equipment hatch and its shielding wall will be added to the list of equipment to be dismantled.

2. Technical Specifications for Nuclear Facilities

(1) Change resulting from revisions in the Decommissioning Plan
Dismantling-subject equipment will be added, and changes will be made to the capacity of the radioactive solid waste storage area and the release control target values of radioactive gaseous waste.

(Note 1) The Hamaoka Nuclear Power Station Units No. 1 and 2 Decommissioning Plan provides an overall plan for the safe and reliable dismantling of Units No. 1 and 2’s reactor facilities, and also sets forth factors including the content of work carried out in the decommissioning and measures for ensuring safety. The decommissioning of Units No. 1 and 2 is divided and conducted into four steps, ranging from Step 1 (i.e., the “dismantling work preparation period”) to Step 4 (i.e., “building dismantling and removal period”).

(Note 2) The Technical Specifications for Nuclear Facilities, based on the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, sets forth items the nuclear power reactor installer should observe to safely operate and decommission a nuclear power station (e.g., safety organization, safety measures).

(Note 3) A reactor zone is an area including the reactor pressure vessel and its surrounding radiation shielding.

(Note 4) Reactor zone peripheral equipment refers to such elements as the exhaust stack, turbine body, main condenser, feed water and condensate system equipment, standby liquid control system equipment, and main steam pipes, and indicates equipment excluding the reactor zone.

(Note 5) A suppression chamber is equipment at the bottom of the reactor containment vessel and stores water. It features a function to direct steam stored inside the reactor or reactor containment vessel in an accident into water, and cool or condense it to suppress pressure increase.