Kansai details upgrade work at oldest Takahama units

Kansai Electric Power Company has released a plan of safety improvement works it will carry out to extend the operating periods of units 1 and 2 of its Takahama nuclear power plant in Japan's Fukui prefecture beyond 40 years. Regulatory approval for operating the units for up to 60 years has already been granted.

Kansai Electric Power Company has released a plan of safety improvement works it will carry out to extend the operating periods of units 1 and 2 of its Takahama nuclear power plant in Japan's Fukui prefecture beyond 40 years. Regulatory approval for operating the units for up to 60 years has already been granted.

Takahama 1 and 2 to the right, with units 3 and 4 to the left (Image: NRA)

Under revised regulations which came into force in July 2013, Japanese reactors have a nominal operating period of 40 years. Extensions can be granted once only and are limited to a maximum of 20 years, contingent on exacting safety requirements.

In June this year, the Nuclear Regulation Authority (NRA) approved a 20-year operating extension for Takahama units 1 and 2 - both 780 MWe (net) pressurized water reactors which began operating in 1974 and 1975, respectively. They become the first Japanese units to be granted a licence extension beyond 40 years under the revised regulations.

Plant owner Kansai yesterday presented a schedule for the safety improvement works that will enable the two units to continue operating beyond 40 years.

The utility said work to improve fire protection at the two units would begin this month and will be completed by August 2019. The work will involve the replacement of fire-resistant cabling and the installation of fire protection sheeting, as well as the installation of additional fire detectors and fire extinguishing facilities.

Work to replace the refueling water tank is also set to begin this month, with installation of the new tank and construction of a protective wall around the tank due to be completed by August 2019.

Kansai will also reinforce the existing concrete wall surrounding the containment vessel of each unit and will also install a secondary dome on their containment buildings. This work will begin in February 2017, with completion scheduled for August 2019 at unit 1 and November 2019 at unit 2.

The seawater intake facility of unit 2 is also to be relocated. Excavation of a new tunnel into the bedrock will begin in May 2017, following by the installation of piping. A protective wall will also be built around the new seawater intake facility, with work due to be completed in March 2020.

The existing central control panels of both units will also be replaced between April 2018 and August 2019.

Kansai said it will "proceed with implementation of the work plan - which was made up today place the top priority on safety - to allow for operation for 60 years."

Takahama 1 and 2 have been offline for periodic inspections since January 2011 and November 2011, respectively, and are progressing through the restart process. In April, the NRA confirmed the units meet new safety regulations. The units are the oldest of the seven reactors so far deemed to conform to the new safety standards.

Unit 3 of the Takahama plant resumed operation on 29 January. Takahama 4 was restarted on 26 February, but was taken offline again three days later following an automatic shutdown due to a "main transformer/generator internal failure". An injunction imposed by a district court on 9 March has kept both units idle.

Researched and written
by World Nuclear News