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

This is to announce that today, Chubu Electric Power submitted an application for approval of changes to the "Hamaoka Nuclear Power Station Units No.1 and 2 Decommissioning Plan" (Note 1) ("Decommissioning Plan") to the Nuclear Regulation Authority in keeping with the stipulations of Article 43, Paragraph 3-34-3, of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors.

On the basis of the Decommissioning Plan which was submitted to the national government on March 16, 2015 and approved on February 3, 2016, Chubu Electric Power has shifted to Stage 2 of decommissioning to dismantle the exhaust stack, turbine and other reactor zone peripheral equipment (Note 2) as well as decontaminate the reactor pressure vessel and survey the contamination status.

The application for approval of changes to the Decommissioning Plan was submitted this time due to the following changes that arose as decommissioning work progressed.

1 Postponement of the start of Stage 3

For Japan’s first dismantling and removal of the reactor zone (Note 3) of a commercial light water reactor (Stage 3), safe and efficient dismantling methods and methods to reduce radioactive waste generated from dismantling as much as possible have been steadily reviewed.

In order to continue reviewing safety measures to further reduce exposure dose during dismantling work and methods to more efficiently dismantle and store dismantled and removed materials, based on the results of contamination surveys to date, the start of Stage 3 will be changed from FY2023 to FY2024.

2 Addition of reactor zone peripheral equipment to be dismantled

For the dismantling of reactor zone peripheral equipment, application for approval of changes to the Decommissioning Plan is submitted upon adding equipment for which dismantling and removal plan has been developed to the list of equipment to be dismantled as appropriate.

This time, suppression chamber (Note 4) for which dismantling and removal plan has been newly developed, as well as primary containment vessel equipment hatch and its shielding wall will be added to the list of equipment to be dismantled.

3 Other

Due to the addition of equipment to be dismantled, exposure assessment conditions were updated, wording was revised and descriptions were optimized.

Chubu Electric Power will continue to steadily advance the decommissioning of Units 1 and 2 while both securing transparency and giving utmost priority on ensuring safety.

(Note 1) Hamaoka Nuclear Power Station Units No.1 and 2 Decommissioning Plan provides the overall plan for safely and reliably dismantling the reactor facilities of Units 1 and 2, and it also gives details for the work carried out during decommissioning and measures for ensuring safety. The decommissioning of Units 1 and 2 is divided into four steps from step 1, i.e. "dismantling work preparation period" to step 4, i.e. "building dismantling and removal period" and will be conducted in this order.

(Note 2) Reactor zone peripheral equipment is equipment excluding reactor zones, such as the exhaust stack, turbine body, main condenser, condensate and feed water system equipment, standby liquid control system equipment and main steam pipes.

(Note 3) Reactor zone is the area encompassing the reactor pressure vessel and radiation shielding surrounding the reactor pressure vessel.

(Note 4) Suppression chamber is the facility that is located at the lower part of the primary containment vessel and stores water. Its function is to direct steam inside the reactor or primary containment vessel to its stored water during an accident and cool or condense it to control pressure increase.