Japan’s Terrifying Day Saw Unprecedented Blown Roof Expose Tepco Fuel Rods
Makoto Nagai was sitting in his third-floor office at 2:46 p.m. on March 11 when the earthquake alarm buzzed. An orange LCD screen flashed 100 and 4, telling him the number of seconds before a category 4 quake would hit the city of Sendai on Japan’s northeast coast.
The intensity warning quickly jumped to 6, said Nagai, 55, head of the emergency response team in Sendai, located 129 kilometers (80 miles) west of the epicenter of what became the strongest quake in Japan’s recorded history.
“I stood up, and my coffee cup bounced sideways off my desk,” he said. “We were in an earthquake-resistant building yet an internal wall and bookshelves collapsed. Then people started to scream.”
As the magnitude-9 earthquake erupted, Kazuma Yokota, a 39- year-old inspector from Japan’s Nuclear Industrial and Safety Agency, crawled under his desk in fear the ceiling was about to collapse. Then he watched seismic shocks rip L-shaped cabinet brackets out of the wall in his office at the Fukushima Dai-Ichi nuclear power station, 100 kilometers south of Sendai.
Under the ocean floor that day, now referred to in Japan as “san ten ichi ichi” or 3/11, two 50-mile-thick slabs of the earth’s crust heaved in a grinding 80-million-year-old conflict between tectonic plates. The quake unleashed energy 24,000 times stronger than the atomic bomb dropped on Nagasaki in 1945, wrenching part of the coastline 3.6 meters closer to the U.S.
Interviews with Tokyo Electric Power Co. engineers, technicians and contract workers who were at the company’s Fukushima Dai-Ichi plant on March 11 or handled the disaster response show how the facility stood up to the quake, only to fail when the tsunami that followed found a way through its engineering defenses.
About 15 minutes after the quake, a relieved Yokota was walking toward the west gate of the plant. He was among thousands of men and women in hard hats, orange, blue and white boiler suits, shoes crunching on broken glass streaming up a hill to emergency evacuation points spread over the site’s 864 acres, equivalent to 490 soccer fields.
Maintenance technician Kazuhiko Matsumoto, 43, was among them. He was near the seafront in the turbine building of the idle No. 6 reactor wrapping up work on air ducts when the shock waves arrived. He clung to the wall to keep from falling as the room blacked out except for green emergency exit signs. As back- up lighting came on, a loudspeaker blared evacuation orders.
“People were pushing,” he said, “Someone was shouting, ‘get out, quick, get out.’”
Koichi Imamura, a 42-year-old maintenance worker at the facility for more than 20 years, was in a changing room next to reactor 5, also shut for maintenance. He was in overalls after taking off protective clothing and a radiation dosimeter when he was knocked on all fours as lockers fell over, he said.
“People were yelling and I was just thinking I’ve got to get out of here.”
The Fukushima Dai-Ichi station had 6,415 people on site that day. More than 5,500, like Matsumoto and Imamura, were subcontractors who reported to their clusters of offices in the plant for a head count.
As Tokyo Electric compiled the numbers, officials found that 6,413 staffers were safe and accounted for. Two Tokyo Electric employees were missing.
Monitor the Situation
At this point, the crisis appeared contained. While roads inside the site had buckled and windows were shattered, the six reactor buildings, reinforced concrete and steel boxes as high as 56 meters, had withstood the earthquake.
The temblor had triggered the automatic shutdown of the Dai-Ichi’s three operating reactors as designed. The engineering defense had worked.
“We thought we’d have to monitor the situation but that was about all,” said Yokota, who headed a team of seven from the nuclear safety agency based at the plant. That day he was at a quarterly review of operations with officials from Tokyo Electric, known as Tepco.
What Yokota didn’t know was that the quake knocked out a transformer station about 10 kilometers away, severing the utility’s connection to the electricity grid and the power needed to keep reactor cooling systems operating. It would be another hour before events conspired to make the name Fukushima synonymous with the biggest nuclear disaster since Chernobyl.
After the head counts, thousands of subcontractors left to check if families were safe, including Matsumoto and Imamura.
Matsumoto’s drive didn’t last long; he was forced to abandon his car because the roads were cracked and jammed with traffic. He walked 10 kilometers to his in-laws’ house to meet up with his wife and two sons, aged nine and three.
Imamura drove to his home in the town of Okuma 5 kilometers away, also convinced the engineering had averted a nuclear accident.
“Reactors four, five and six weren’t even running and the other ones shut down when the quake hit,” he said.
Yokota and two of his team also went to Okuma, where the agency kept an emergency command office.
The three men reached the center in 15 minutes and found the office wrecked, power down and no working communications, the first indication to Yokota that emergency procedures were unraveling.
“We couldn’t contact anybody for one or two hours,” he said. “I thought, this means trouble.”
Back at the Fukushima site, the head of the Dai-Ichi operation Masao Yoshida and two deputies, Masatoshi Fukura and Atsufumi Yoshizawa, set up a disaster control center in an earthquake-proofed bunker. Yoshida, 56, had taken up the position in June, his fourth stint at the 40-year-old atomic power station.
Linked by a hot line to Tepco headquarters in central Tokyo, the three-story, white bunker had extra-thick walls and two filtration systems designed to keep out radiation. It was to become their new home.
Yoshida knew Dai-Ichi “inside out” and was ready to take charge, said Yokota, who later joined him in the bunker.
“It’s our mission to keep the power plant stable, putting safety as the top priority,” Yoshida said in a Jan. 4 New Year video greeting posted on Tepco’s website. Wearing glasses and dressed in blue overalls, he is flanked by two “kadomatsu” bamboo decorations that symbolize good fortune for the coming year.
Yoshida had been vice chairman of the Japan Society of Maintenology, a group that studies how to safely extend the lifespan of nuclear power facilities.
“Yoshida isn’t afraid to deliver bad news,” said Kenzo Miya, 70, an honorary professor at the University of Tokyo who chairs the society.
The Dai-Ichi chief’s priority was to manage the power failure after the earthquake cut the utility’s connection to the electricity grid.
Yoshida could get replacement electricity from 13 back-up diesel generators to run emergency water pumps for cooling reactors. Each generator is the size of a train locomotive and capable of delivering 6,000 kilowatt hours of power, enough to run 14,400 Japanese homes for that period. Again, the engineering was working.
“When the generators are running, the noise is so loud you can’t go near them without earplugs,” said Yasuo Arai, who trained as an engineer and now works at community relations for Tepco.
“Most are located in generator rooms in basement 1 of the turbine buildings,” Arai said, pointing to a diagram in a Tepco brochure of the Dai-Ichi plant. The turbine buildings holding eight of the generators are about 140 meters from the seafront, another two generators were on the ground floor behind reactor 4, which was offline for maintenance. Three others were in and around reactor 6, which was also offline.
As Yoshida’s Tepco engineers fanned out to control rooms to check for earthquake damage and monitor procedures as the reactors shut down, 25 kilometers up the coast in Minami Soma, Mayor Katsunobu Sakurai was realizing the earthquake was only part of the unfolding disaster.
Sakurai had raced to the fifth-floor rooftop of the government office, one of the highest in the city of 70,000 people. He looked toward the sea and saw what looked like a wall of sand pummeling and splintering through rows of houses and bellowing clouds of smoke and dust.
“In those first moments we couldn’t comprehend what we were seeing,” Sakurai, 55, said. The tsunami he was witnessing surged 2.4 kilometers inland, swallowing everyone in its path. Almost 1,500 town residents were killed or are listed as missing, out of a national toll exceeding 26,000.
The seabed off Japan had buckled along a 300-kilometer stretch of fault line. The upheaval hurled about 67 cubic kilometers of ocean at Japan’s coast, or enough to flood all of Manhattan a mile deep, according to estimates by Roger Bilham, a seismologist at the University of Colorado.
Within an hour the tsunami would smash into 860 kilometers of Japan’s coastline at heights the U.S. National Oceanic and Atmospheric Administration estimated as high as 24 meters.
Akira Tamura, a 35-year-old control room manager at Dai- Ichi’s No. 2 reactor, was home on March 11 in Minami Soma on a day off. He was surfing Internet news sites dressed in sweat pants and a T-shirt, when the quake reached his area.
“Roof tiles went flying and crashing in the street,” he said.
After checking on elderly neighbors, Tamura jumped in the car and picked up his wife at the flower shop where she worked. He was forced to change route because main roads were flooded. His apartment was on higher ground out of the tsunami’s reach.
At Tamura’s Dai-Ichi workplace, the tsunami crashed over a 2.5-kilometer breakwater of 60,000 concrete blocks and 25-ton tetra pods as well as a 5.6-meter-high wall in the seabed in front of the site.
The plant, built on a layer of rock 10 meters above sea level, was pummeled by a wave as high as 15 meters that flooded parts of the facility in six meters of seawater before flowing back to the ocean, according to Tepco estimates.
Interviews with workers at Dai-Ichi that day indicate that as most staff had left and many of the Tepco technicians were inside buildings checking on reactors, few saw the waves arrive.
Witnesses say from higher ground behind the plant, the view was blocked by buildings. A Tepco engineer, who’d worked for the company for 30 years, was in reactors 5 and 6 after the earthquake and said he didn’t realize the tsunami had hit.
What the earthquake had failed to do, the tsunami now achieved: It overwhelmed the engineering defenses at Dai-Ichi.
Seawater flooded the basements of turbine buildings and other sites, disabling 12 of the 13 back-up generators and destroying electrical switching units. Salt water shorted electric circuitry, depriving the reactors of power for cooling and triggering a nuclear disaster that Tepco was forced to combat with fire hoses and makeshift pumps.
“The level of flooding differed by building, but it was as high as 1.5 meters in one turbine room,” said Hikaru Kuroda, chief of Tepco’s nuclear facility management group.
At about 3:41 p.m., almost an hour after the quake, Dai- Ichi lost alternating-current power at the three operational reactors as the generators failed. Tepco immediately informed the government it had experienced “station blackout” as required by nuclear emergency regulations.
Eighteen days later Prime Minister Naoto Kan slammed the sea defenses as inadequate. “It’s undeniable their assumptions about tsunamis were greatly mistaken,” he told lawmakers.
The unfolding crisis and the radiation leaks that followed shook a nation that sends 300,000 school children each year to visit the Hiroshima memorial for victims of the first atomic bombing and those killed by radiation poisoning.
The only defenses left to prevent Dai-Ichi’s nuclear fuel rods from overheating and spewing radiation were banks of so- called “coping” batteries designed to last no more than half a day. Once those were deployed to power emergency cooling, a nuclear plant would be, in the parlance of the industry, “12- hours coping.”
“What that means is the clock has started ticking on restoring power before the batteries run out,” said Edward Morse, a professor of nuclear engineering at the University of California at Berkeley. Batteries buy several hours to “work miracles,” he said. ``Once the batteries start failing, if the cavalry isn’t there to bail you out, then you know you are really in trouble.''
Without cooling, nuclear reactors are like giant kettles left to boil. Water covering the fuel rods inside begins to turn to steam, exposing the rods that melt and emit radiation upon contact with air.
Tepco’s engineers couldn’t determine if the batteries were working because monitoring equipment malfunctioned, leaving them blind to what was happening inside the reactors.
“We lost the ability to assess the performance of the emergency core cooling system because meters designed to check the water flow rates in the No. 1 and No. 2 reactors failed,” Kuroda said. “We still don’t know why they died, that will be part of the accident investigation.”
At 4:36 p.m., less than two hours after the quake, Tepco was forced to acknowledge it had lost control of the reactors. Nine minutes later, the company notified the government.
At 7:03 p.m., Kan declared a nuclear emergency, prompting an evacuation of residents living around the Fukushima facility that would extend to a 20-kilometer radius within 24 hours.
Tepco engineers were unable for the next two hours to get readings for how much water was covering the fuel rods in the No. 1 and No. 2 reactors, according to a data sheet obtained by Bloomberg News. Once readings were available, they showed that water levels held steady through the night, an indication the batteries were working.
At the No. 1 reactor, water levels began dropping in the early morning of March 12. At 8:36 a.m., the reading showed zero centimeters as the fuel rods began to emerge and come into contact with the air. Within four hours, 1.7 meters of fuel rods were exposed.
By this time, Tepco had begun to vent radioactive steam into the atmosphere to reduce pressure in the reactor.
“They were choosing the lesser of two evils,” said Yokota. “If pressure built up too much inside, it would explode and could have thrown a lot more radioactive material into the environment.”
Outside the Playbook
Professor Morse at Berkeley agreed, saying releasing the pressure by venting steam is “in the playbook,” referring to procedures for dealing with nuclear accidents.
That afternoon, about 24 hours after the quake, a hydrogen explosion inside the No. 1 reactor building caused radiation levels to rise. The explosion caused “blow out” panels in the concrete building around the reactor to do what they’re designed to do -- blow out under pressure.
A second threat emerged from spent-fuel pools, about 40- feet deep and located at the top of the reactors. The spent fuel rods also need to be cooled and covered with water to prevent them melting and emitting radiation.
After two further blasts in the next 62 hours, it was a March 15 fire around the spent fuel pool in reactor 4 that told Berkeley’s Morse that Tepco engineers were entering territory outside the nuclear playbook.
With reactor 4 shut down for maintenance, more than 1,300 fuel rods were stored at the top of the reactor building where an unexplained explosion had destroyed the roof.
“Before the spent fuel pool ignited, I could put my thumbs under my suspenders and say, ‘yeah that’s a small-break LOCA,’” Morse said, using the industry jargon for “loss of cooling accidents” similar to what occurred at Three Mile Island, Pennsylvania, in 1979.
“That turned out to be the most terrifying event throughout the whole ordeal,” Morse said. “Now they have no containment structure whatsoever, they don’t even have a roof. I thought that could have been a game changer.”
Tepco now had three reactors without cooling systems and a fourth with a fire spewing radiation into the air.
The danger now was an increase in radiation from the spent fuel pool would force workers to withdraw from trying to get the three reactors under control, threatening multiple reactor meltdowns.
With no means to circulate cooling fluid inside the reactors, the company drafted in fire engines, Chinook helicopters, concrete-pouring trucks and crowd-control water cannons to inject, spray and dump thousands of tons of water onto the spent-fuel pools and into the reactor vessels.
“In the worse-case scenario, if we imagine there’s no water in the spent fuel pool and there is a source of fire that’s strong enough to melt the rods, a gaseous release of radioactive nuclides takes place,” said Gennady Pshakin, a nuclear physicist based in Obninsk, site of Russia’s first nuclear power plant. “Naturally, the fresher the fuel, the higher the radiation volume, especially of iodine and cesium.”
The radioactive gases contain heavy elements so while winds could blow them some 20 kilometers, they wouldn’t reach Tokyo, Pshakin said.
On two occasions radiation levels at Dai-Ichi reached 1 sievert an hour. Thirty minutes of exposure to that dose would trigger nausea. Contamination for four hours might lead to death within four months, according to the U.S. Environmental Protection Agency.
Five kilometers away at the nuclear safety agency’s offsite center, Yokota said radiation levels set off a constant warning ping at detectors in the office, so he put on his DuPont Co. Tyvek protective suit and a face mask.
On March 15, Yokota, who sports a wispy mustache and thin, graying sideburns, moved the office to Fukushima city, the prefectural capital about 60 kilometers from the plant, because of radiation spikes.
He shuttled between the offsite and the Dai-Ichi bunker. When the No. 3 reactor housing exploded on the morning of March 14, levels inside the bunker jumped as much as 12-fold, he said, checking dates and times in a pocket diary.
“I was so tired I didn’t have trouble sleeping. We ate crackers and cheese for breakfast, for dinner we had canned rations. I lost weight. My belt is one hole tighter.”
Tamura, the reactor control room manager from Minami Soma, attempted to return to Dai-Ichi two days after the quake, only to find the roads blocked. It was March 18 before the 16-year Tepco veteran, who attended a company-run vocational high school and played for the rugby team, was able to enter the reactor site.
He worked on helping repair electrical equipment and restore cooling systems. Much of his time was spent trying to get diesel for emergency generators, he said.
“When I told my family that I’m going to Dai-Ichi my wife begged me to stop. She was dead set against it,” Tamura said in a March 24 interview at the port of Onahama about 55 kilometers south of the plant. He was speaking during his first break in a week outside the Kaiwo Maru, a four-masted sailing ship used to accommodate exhausted workers.
At first there were no blankets at Dai-Ichi so Tamura grabbed what sleep he could on the floor. On board the Kaiwo Maru, he took a bath and ate his first hot meal in a week, teriyaki chicken.
“I wanted to have seconds but after eating so little all this time I just couldn’t,” he said.
The stopgap methods to cool the reactors and spent-fuel rods were having little effect, he said, with the use of salt water adding a further complication from corrosion.
“Even as firefighters pumped water into the reactors, the levels wouldn’t rise, and you can’t determine the reason without getting inside,” Tamura said.
“Now, I just want to see my wife. At work, you leave all personal belonging outside, so I don’t even have a picture to look at,” he said before leaving for another shift.
“I kept remembering her face while I worked. She loves flowers. I like seeing my wife working with flowers, because she looks happy.”
On March 29, Tepco was able to restore lighting in the control room of the No. 4 reactor as engineers slowly made progress in fighting the crisis.
The next day in the adjoining turbine building, the bodies of the two missing Tepco workers, Kazuhiko Kokubo, 24, and Yoshiki Terashima, 21, were found in the basement.
To contact the reporters on this story: Jason Clenfield in Tokyo at firstname.lastname@example.org Takahiko Hyuga in Tokyo at email@example.com Yuji Okada at firstname.lastname@example.org Pavel Alpeyev in Tokyo at email@example.com
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