Delay to safety upgrades at Tohoku units

Japan's Tohoku Electric Power Company has pushed back the expected completion dates of construction work to bolster safety at unit 2 of its Onagawa nuclear power plant and unit 1 of its Higashidori plant. The work must be completed before the units will be allowed to resume operation.

Japan's Tohoku Electric Power Company has pushed back the expected completion dates of construction work to bolster safety at unit 2 of its Onagawa nuclear power plant and unit 1 of its Higashidori plant. The work must be completed before the units will be allowed to resume operation.

Tohoku's Onagawa plant (Image: NRA)

Tohoku applied to the Nuclear Regulation Authority (NRA) for safety assessments of Onagawa 2 and Higashidori 1 in December 2013 and June 2014, respectively. These assessments - which will verify whether measures taken at the plant meet new safety standards - can only take place once construction of additional safety measures has been completed. The company had planned to complete this construction work at both units by April this year.

However, Tohoku said yesterday it had been forced to reassess the construction schedules, primarily because safety reviews by the NRA have taken longer than originally anticipated.

The new regulatory conformity inspections at Onagawa 2 - a 796 MWe (net) boiling water reactor (BWR) - has "progressed steadily", it said. Its design basis tsunami and ground motion evaluation of major faults at the Onagawa plant has already been evaluated "as basically valid", it added. However, plant-related examination - conducted in parallel with BWR plants owned by other utilities - "has made relatively slower progress than anticipated".

The company now expects to complete construction work at Onagawa 2 in the second half of fiscal year 2018 (between October 2018 and March 2019).

It expects the new regulatory conformity inspection at Higashidori 1 - a 1067 MWe (net) BWR - to take even longer than that at Onagawa 2. This is because the evaluation of faults at the plant site took more time than expected, it said. "Meanwhile, just like Onagawa unit 2, we should incorporate the findings obtained from other plants that are at a more advanced stage of examination in our work on design and construction," it added.

Construction work at Higashidori 1 is now scheduled to be completed in fiscal 2019 (April 2019 to March 2020).

Five Japanese nuclear power reactors have already cleared inspections confirming they meet the new regulatory safety standards and have resumed operation. Another 19 - including Onagawa 2 and Higashidori 1 - have applied to restart.

Researched and written
by World Nuclear News