TOKYO — There was no avoiding fearful memories of the Japanese nuclear disaster of 2011 on Tuesday after a powerful earthquake off the coast of Fukushima caused a cooling system in a nuclear plant to stop, leaving more than 2,500 spent uranium fuel rods at risk of overheating.
But this time, the Tokyo Electric Power Co., the utility that operates three nuclear plants, restored the cooling pump at the Fukushima Daini plant in about an hour and a half. The Daini plant is about 7 miles south of Fukushima Daiichi, the ruined plant where three reactors melted down five years ago after tsunami waves inundated the power station and knocked out backup generators.
Tokyo Electric reported that it never lost power at either the Daini plant or its neighbor to the north after the Tuesday quake, which had a magnitude of 7.4, according to the Japanese weather service.
“We took the regular actions that we should take when handling troubles,” Yuichi Okamura, acting general manager of the nuclear power division at Tokyo Electric, said at a news conference Tuesday.
The company was prepared for big tsunamis, having built sea walls rising to about 46 feet at the Fukushima plants and enclosing backup generators in waterproof facilities, Okamura said.
Critics of Tokyo Electric, which struggled to keep on top of a crisis that unfolded over the weeks that followed the calamity in 2011, said they were relieved that there had been no immediate damage. But they said they remained skeptical that the company had done enough to prepare for a disaster on the scale of the earthquake five years ago. That quake, which had a magnitude of 8.9, set off tsunami waves as high as 130 feet in some places. (The highest waves Tuesday reached about 55 inches.)
“It looks like the right things have been done,” said Azby Brown, director of the Future Design Institute at the Kanazawa Institute of Technology and a volunteer researcher with SafeCast, an independent radiation-monitoring group. “But you never know until something happens. As far as this morning goes, they did a decent job, but mainly because it wasn’t that big of an earthquake or that big of a tsunami.”
Building higher sea walls, for example, “is all good, but that is like fighting the last war,” Brown said. “It remains to be seen how well prepared they would be for some other unusual combination of disasters.”
Compared with five years ago, Tokyo Electric has improved its communication with the public, reporting information about the cooling pump at Daini almost as it happened Tuesday.
The company also quickly said that it had suspended the treatment and transfer of contaminated water from the Daiichi plant, where an extensive cleanup and decommissioning process is underway. By the evening, those operations had been restored.
“What I can say is today’s response was decent, and they seemed to be confident,” said Tatsujiro Suzuki, director of the Research Center for Nuclear Weapons Abolition at Nagasaki University. But, he said, it would be difficult to independently verify Tokyo Electric’s claims because the Japanese Nuclear Regulation Authority depends on the company to release information.
He added that he was not convinced that Tokyo Electric was being fully transparent about its decisions, particularly about the cleanup at the Daiichi plant.
“We should be informed fully whether this operation is reasonably done with cost effectiveness and safety and making sure that the best technology is being used,” Suzuki said.
Daisuke Maeda, a spokesman for the Nuclear Regulation Authority, said the agency had offices on the sites of the nuclear plants and worked with Tokyo Electric and other utility companies on Tuesday to confirm that the power stations were safe after the earthquake.
Regarding the longer-term situation, nuclear experts expressed concern about the safety of the cleanup operation at the Daiichi plant.
The melted cores of three reactors have yet to be removed as they are still too radioactive for workers to approach. Since the 2011 disaster, ground water seeps into the reactors daily. The water, contaminated by the melted fuel rods, needs to be treated and stored on site. So far, Tokyo Electric has built more than 880 tanks of about 1,000 tons each.
The tanks are inspected four times a day to confirm that they do not leak, said Okamura of Tokyo Electric. And in an effort to halt the flood of ground water into the damaged buildings, the company has built an underground wall of frozen dirt nearly a mile in length encircling the reactors. The wall is not yet fully frozen, though, and ground water continues to flow into the reactors.
Critics worry that the sea walls or storage tanks might not withstand a more powerful earthquake or tsunami. And Tuesday’s incident at the Daini reactor showed that quakes can set off problems even at plants that are not operating.
Most of the country’s 54 plants remain closed since the 2011 disaster, but the administration of Prime Minister Shinzo Abe wants to restart most of them.
Kiyoshi Kurokawa, who oversaw an independent investigation on the Fukushima nuclear accident for the Japanese parliament, said that building walls and storage tanks failed to solve the underlying problem of an earthquake-prone country relying on nuclear power. Instead, he said, both the government and utility companies should invest in developing alternative sources of power like solar or wind technology.
“I think we expect more of such readjusting plate movements and that has been reasonably predicted, and many volcanic activity and earthquakes have been rampant over the last five years,” said Kurokawa, an adjunct professor at the National Graduate Institute for Policy Studies. “So why are we continuing to restart nuclear plants?”