Kansai reschedules restarts of three reactors

05 February 2019

Kansai Electric Power Company has informed Fukui Prefecture that the restart of units 1 and 2 of the Takahama nuclear power plant and unit 3 of the Mihama plant has been delayed as work to bolster safety measures will now take longer than originally expected.

Containment building reinforcement work at Takahama unit 1 (Image: Kansai)

Kansai said yesterday that it had completed a review of construction work needed for the units to meet revised safety standards and concluded the schedule needed revising. The upgrades are aimed at preparing the three units for operation beyond 40 years.

At Takahama 1 and 2, work is being carried out to reinforce their containment buildings. Kansai is reinforcing the existing concrete wall surrounding the containment vessel of each unit and as well as installing secondary domes.

Kansai said completion of this work will be postponed by about nine months. The construction work at unit 1 is now scheduled to be completed in May 2020, instead of this August, while at unit 2 it will be finished in January 2021, instead of March 2020.

The utility is also improving fire protection at the two units by replacing fire-resistant cabling and installing fire protection sheeting, as well as installing additional fire detectors and fire extinguishing facilities. It is also replacing the refueling water tank and constructing an anti-tornado wall around the tank. The seawater intake facility of unit 2 is also being relocated by excavating a new tunnel in the bedrock. An anti-tornado wall is also to be built around the new seawater intake facility. The existing central control panels of both units are also being replaced.

Takahama units 1 and 2 are both 780 MWe (net) pressurised water reactors (PWRs) which began operating in 1974 and 1975, respectively. In June 2016, they became the first Japanese units to be granted a licence extension beyond 40 years under the revised regulations.

Most of the work at Mihama 3 is related to improving the unit's seismic resistance. Kansai is reinforcing the used fuel storage pool and replacing its fuel assembly rack. It is also replacing the internal structure of the reactor core and improving the seismic resistance of the reactor containment vessel. The company said this work is now expected to be completed in July 2020, instead of January 2020, as drilling work was taking longer than planned because the supporting bedrock had been found to be deeper than expected.

Other work at Mihama includes improving fire protection work, including replacing old cables with fire-resistant cabling, installing fire protection panels and fire detectors, as well as installing new fire extinguishing equipment. A new, higher tidal barrier is also being constructed at the plant.

Mihama 3 - also a 780 MWe PWR - entered commercial operation in 1976. In November 2016, the Nuclear Regulation Authority approved an extension to the operating period for the unit until 2036.

So far, nine of Japan's 39 operable reactors have cleared inspections confirming they meet the new regulatory safety standards and have resumed operation. These are: Kyushu's Sendai units 1 and 2 and Genkai units 3 and 4; Shikoku's Ikata unit 3; and Kansai's Takahama units 3 and 4 and Ohi units 3 and 4. Another 16 reactors have applied to restart.

Researched and written by World Nuclear News