Hopes Rise for Hokkaido N-reactor Restart after Clearing Major Safety Hurdle; Power Company Still Needs Approval from Residents

By Yuki Kanahori and Ryoya Kato / Yomiuri Shimbun Staff Writers

20:00 JST, May 1, 2025

Almost 12 years after applying for a safety screening, the No. 3 reactor at Hokkaido Electric Power Co. Inc.’s Tomari nuclear power plant has effectively been given the green light to resume operations by Japan’s nuclear safety watchdog.

The Nuclear Regulation Authority approved a draft report on Wednesday that concluded the reactor had met safety standards introduced after the March 2011 accident at the Fukushima No. 1 nuclear power plant.

The reactor was shut down in May 2012, more than a year after the Great East Japan Earthquake triggered the accident at Tokyo Electric Power Company Holdings, Inc.’s Fukushima No. 1 plant.

One reason for the Tomari reactor’s protracted screening process was a shortage of Hokkaido Electric employees with expertise in geology and natural disasters such as earthquakes. Consequently, the company spent a lot of time and effort crafting detailed explanations based on scientific evidence.

In 2019, the NRA pointed out that it “could not rule out” the possibility that a fault under the Tomari nuclear plant was active. Hokkaido Electric, which was forced to conduct further investigations into the matter, struggled to accumulate data on volcanic ash and other factors needed as evidence. It ultimately took about two years until the NRA finally accepted the fault in question was not active.

In 2020, then NRA chief Toyoshi Fuketa even expressed his concerns to the company’s senior management.

“Unless you have staff with the necessary expertise, I don’t think this screening will get completed,” Fuketa said.

The NRA introduced new regulatory standards for nuclear power reactors in 2013 as a result of the 2011 nuclear accident. A high degree of expertise is required to ensure these requirements are met.

After this was pointed out by the NRA, Hokkaido Electric accepted external specialists and also hired new recruits. The company initially had about 60 staff handling the screening procedures, but this was increased and peaked at about 220.

The NRA also extended a helping hand at times. At each screening meeting since March 2022, the watchdog presented written documents outlining discussion items and its questions. This made it easier for Hokkaido Electric to respond to these issues.

“This was highly unusual, given the NRA’s position that responsibility for demonstrating safety rests with the company,” said Nagaoka University of Technology Prof. Hiroshi Yamagata, an expert on safety engineering.

Cost soars

As the screening dragged on, Hokkaido Electric finished most of the new construction that was required to meet the safety standards.

To prevent hydrogen explosions like those that occurred at the Fukushima No. 1 plant, equipment that can recombine leaked hydrogen with oxygen to form water has been fitted inside the reactor’s containment vessel. Multiple power-supply vehicles have also been stationed on higher ground as a precaution for emergency situations such as power outages caused by a tsunami.

The construction of a 19-meter-high seawall is the main safety measure yet to be completed at the Tomari nuclear plant. Hokkaido Electric estimated the maximum height of tsunami that might strike the plant would be 15.68 meters and began constructing the seawall last year. As a safeguard against the possibility that a tsunami could spill over this wall, the company installed doors and other such safety measures that will prevent seawater from flooding the reactor building.

The total construction cost of these safety measures has climbed to about ¥510 billion, which is at least 17 times more expensive than the ¥20 billion to ¥30 billion that was initially estimated in 2011.

“These costs snowballed as a result of steadily dealing with each step of the construction and screening process,” a Hokkaido Electric official told The Yomiuri Shimbun.

Local consent needed

Hokkaido Electric is preparing to restart the Tomari No. 3 reactor in early 2027, a move prompted in part by the need to recoup some of the massive construction costs.

If the NRA officially declares the reactor has passed the safety screening, focus will shift to whether the company can gain the consent of local authorities.

Hokkaido Gov. Naomichi Suzuki, who assumed the post in 2019, also has avoided making any clear-cut statements on the issue.

“The process is still ongoing,” Suzuki said to reporters after the NRA approved the draft report on Wednesday. “At this stage, I can’t comment with any preconceived notions.”

At a press conference on the day, Hokkaido Electric President Susumu Saito emphasized that the company would work closely with local authorities.

“We will diligently explain the safety steps we’ve taken so we can gain wide support from Hokkaido residents, especially from those living in the area where the nuclear plant stands,” Saito said.