Fukushima: The Story of a Nuclear Disaster

by David Lochbaum

  Reaching even further back in seismic time, however, one potential counterexample stood out: the 869 A.D. Jogan earthquake and tsunami. The exact origin of the earthquake, believed to have been a magnitude 8.6, was unknown, but scientists had found evidence of geologic deposits from the tsunami well inland in areas not that far north of Fukushima Daiichi. Could such a devastating earthquake occur close to Fukushima after all? Concerned, TEPCO ran another calculation assuming an earthquake as large as Jogan and found it might produce a tsunami as high as thirty feet. The utility then surveyed tsunami deposits around Fukushima Prefecture and located some just north of the Daiichi site, but it found their patterns to be inconsistent with its model. TEPCO’s conclusion: further research was needed.

  A tugboat that was swept inland by the March 11 tsunami and left to rest in the devastated town of Ofunato, north of Sendai. Similar scenes of destruction could be found along the battered coastline of northeastern Japan. U.S. Navy

  TEPCO managers discussed the new wave projections internally and considered countermeasures. But ultimately the company did not see a need to prepare for what it still regarded as a highly improbable event. It didn’t move its backup diesel generators out of the turbine building basements. Nor did it enhance protection by constructing a large seawall. Although the Sanriku Coast ranks as one of the most “engineered” in the world—with tsunami barriers stretching for miles—TEPCO management feared that a tall barricade in front of a nuclear plant would send the wrong message to the public. “Building embankments as tsunami countermeasures may end up sacrificing nearby villages for the sake of protecting nuclear power stations,” according to a TEPCO document. “It may not be socially acceptable.”

  NISA conducted hearings on earthquake and tsunami hazards at nuclear plants in June 2009. The panel examining Fukushima Daiichi didn’t include a tsunami expert. Earthquakes were regarded as a more probable threat, and that’s what the committee focused on. But when the panel’s findings were presented, a respected seismologist warned NISA that a tsunami at the plant could be as devastating as an earthquake. When he asked why the 869 A.D. Jogan earthquake, which sent water more than two miles inland, was not incorporated into the panel’s assessment, a TEPCO official dismissed it as a “historic” event not relevant to the deliberations. Although NISA promised to follow up on the issue, at the next meeting Fukushima Daiichi’s existing preparations were deemed sufficient. Without pressure from regulators, TEPCO continued to investigate the Jogan issue on a slow track. TEPCO did eventually get around to reporting new tsunami damage assessments to NISA—on March 7, 2011.

  Four days later, at the U.S. NRC, the prediction that things could get “really ugly” at Fukushima Daiichi was coming true. Inside the Operations Center at White Flint, experts watched the crisis develop with growing alarm—and frustration at the lack of information or the ability to respond. The NRC’s early offer of engineering assistance to Japan had been met with silence, and the NRC staff, like ordinary members of the public, had access to nothing but spotty and confusing media reports. “This is not our event,” NRC chairman Gregory Jaczko warned his impatient team.

  But that didn’t preclude the agency’s experts from parsing every detail trickling out of Japan. In the early hours of March 12, Daniel Dorman, a deputy director working in the Operations Center, called Jaczko at home to alert him to the explosion at Unit 1. Dorman and his colleagues were watching it replayed on a television screen.

  “It’s an initial short duration pulse,” Dorman told his boss, “like an explosion, followed by a large cloud, and then there is some subsequent footage showing what appears to be the frames of the building that—the upper walls around the—what would be the metal framework above the refueling level, it’s been opened up to the I beams.” He continued, “We’re still working off of what we got on the media. But it is a very disturbing image.”

  Dorman wasn’t alone in his concern.

  At 5:12 a.m. Washington time, the NRC’s Robert Hardies e-mailed his colleague Matthew Mitchell: “My dog woke me up to go out. I turned on CNN. They had breaking video they could not explain. To me it looked like a containment building disappearing in an explosive cloud. WTF.”

  3

  MARCH 12 THROUGH 14, 2011: “WHAT THE HELL IS GOING ON?”

  At first, plant boss Masao Yoshida thought the violent motion beneath his feet at 3:36 p.m. March 12 was another earthquake. Then came potentially worse news: the top of the Unit 1 reactor building had blown off; only the steel framework remained.

  Four minutes later, the harried team in the plant’s emergency response center joined the rest of the world watching the explosion replayed on TV screens. A huge billow of white smoke and debris expanded skyward, drifting away on the prevailing winds.

  A check of the jury-rigged gauge showed that the water level inside the Unit 1 reactor had not changed: 5.5 feet below the top of the fuel, or about 21.5 feet below normal. The fuel had started melting about twenty-one hours earlier. Also, the pressure within the reactor vessel had not dropped, suggesting that the worst-case scenario—that the explosion had damaged the reactor vessel itself—had not occurred.

  This looked to personnel at the plant and at TEPCO’s emergency operations center like a hydrogen explosion. But from what source? Prime Minister Kan had asked the Nuclear Safety Commission chief, Haruki Madarame, that morning about the likelihood of hydrogen igniting, and had been assured that this was unlikely.

  During normal reactor operations, nitrogen gas is added to the drywell—part of the primary containment structure—to preclude an explosion of hydrogen should any accident occur. Hydrogen cannot ignite unless oxygen is present, so substituting nitrogen for oxygen—a process called “inerting”—eliminates the possibility of a volatile mix forming inside the drywell. The atmosphere in the reactor building itself was not inerted because regulators never thought it would be necessary; protecting the containment from rupture would be sufficient to prevent radiation leaks. Now, somehow, hydrogen gas had apparently migrated to an area where no one had expected it to be.

  The initial reaction among the startled workers was denial that the hydrogen was generated from damaged nuclear fuel. Yoshida first thought the explosion might involve the turbine generators, which use hydrogen gas as a cooling medium in their operation. However, this was ruled out when reports indicated that the Unit 1 turbine building had not been damaged in the blast.

  Unit 1 after a hydrogen explosion blew off the top of the reactor building. Tokyo Electric Power Company

  Another theory suggested that the spent fuel pool in the “attic” of the reactor building was boiling and the fuel there was no longer completely immersed. If so, the overheated cladding of the fuel rods could have reacted with steam to generate the hydrogen gas that ignited. Without working instruments, there was no way to check the water level or temperature of the pool. But it was not clear how so much of it could have boiled away in such a short time, given what the operators knew about the amount of heat generated by the relatively small quantity of fuel in the pool: only 292 spent fuel assemblies and 100 new assemblies. (The new assemblies were there to await the next refueling.)

  Then another hypothesis was put forward: the extreme pressure and heat that had built up before venting had loosened bolts and seals in the reactor’s drywell, allowing radioactive steam and hydrogen to leak into the reactor building, where a spark or static electricity triggered the blast. Or perhaps when the containment was vented, hydrogen under enormous pressure had leaked out of the vent pipe into the reactor building before it could be expelled through the tall exhaust stack shared with Unit 2. Normally, ventilation fans within the reactor building might have helped to draw any hydrogen up and out of the building, but the fans couldn’t work without electricity. Instead, the gas would have accumulated until it became concentrated enough to explode. No matter what the hypothesis, though, one thing was clear: if the containment had been vented sooner to reduce its pressure, this might have preve
nted hydrogen—and fission products—from leaking into the reactor building.

  For the hapless crew in the plant’s emergency response center, there was more bad news: falling debris had damaged the electric cable that workers had spent hours laying and were within minutes of energizing to restore power to Units 1 and 2. The explosion had also damaged the fire hoses that workers had carefully arranged to inject seawater into Unit 1. Although radioactive litter was now scattered around the Unit 1 reactor building, Yoshida ordered his employees to get the hoses working. The fire engines injecting freshwater into Unit 1 had used up their supply nearly an hour earlier. The need to get water into the core was still imperative, and the workers had been very close to being able to supply it. The explosion set them back by several hours, but despite the hazardous conditions they repaired the damage by 7:00 p.m.

  Meanwhile, just beyond the six-mile (ten-kilometer) evacuation zone, residents of the coastal town of Namie thought they had finally reached safety. Earlier that morning they had been rousted from the evacuation centers to which they had fled to escape the tsunami; now those centers were too close to a new danger: Fukushima Daiichi. Their next haven was a school. Children played in the schoolyard. Adults, dressed in heavy winter coats, sat together on the gymnasium floor or cooked a meal outside. While the world watched images of the giant cloud billowing from Unit 1, those closest to it were unaware because of the loss of cell phone and television service.

  As the Namie evacuees would later learn, merely being farther from the damaged reactors would not necessarily protect them. Luck was on their side that night, however, because the emissions from Unit 1 were relatively small, and the prevailing winds blew them primarily northward along the coast and then out to sea.

  Almost from the beginning of the accident, an early-warning system had been making ominous predictions about the danger that the Namie evacuees and other people near Fukushima Daiichi could face should conditions worsen at the plant. The System for Prediction of Environmental Emergency Dose Information, or SPEEDI, was developed by the Japanese after the Three Mile Island accident. It went into operation in 1986. If radiation is released in an accident, SPEEDI uses real-time measurements from the nuclear plant together with meteorological data to predict where the radioactivity will spread and how intense it will be. When actual radiation release data are available, the system is far more useful in assessing risks and defining evacuation areas than the concentric zones arbitrarily drawn around a plant. The system is continually updated and monitored from an office in the capital.

  The day before, when TEPCO declared a nuclear emergency, SPEEDI had switched to emergency mode, ready to track any releases from Fukushima Daiichi and guide decisions about evacuations based on the location of radiation plumes. There was one problem: Fukushima Daiichi had no power. As a result, when radiation was released, the plant’s on-site measuring devices were unable to gather and transmit data about it to SPEEDI. Without such data, all SPEEDI could do was indicate the direction in which the radiation would travel.1

  Those projections were duly passed from the Education Ministry, where SPEEDI is housed, to NISA, which forwarded them to the prime minister’s office. But they came with a caveat: their reliability could not be guaranteed because no one knew how much radiation was actually being released. As a result, the readouts were never shown to the prime minister.

  Four days into the accident, the news media began asking for the SPEEDI data. That prompted a meeting of top Education Ministry officials who worried that “a release of the predictions could cause people unnecessary confusion.” With that, responsibility for SPEEDI data was handed off to the NSC, whose chief, Madarame, dismissed the calculations as no better than “a mere weather report.”

  The Namie evacuees at the school had no inkling they were at risk until a TEPCO employee showed up late on the afternoon of March 12 in protective clothing, carrying a dosimeter. Less than an hour after the Unit 1 explosion, radiation readings at the plant boundary had soared. But the employee reassured the worried families that they were safe because they were outside the official evacuation zone—and then he jumped in his car and left. About 6:30 p.m., military trucks arrived at the school. With little official explanation, the occupants were made to pack up their few belongings and head out into the night, once again in search of safety. Other evacuees weren’t as lucky; some remained in areas that were in the path of radiation plumes until March 16 before being told to leave.

  In Tokyo the evening of March 12, officials gathered in the prime minister’s office, struggling to figure out what was happening at Fukushima Daiichi. Just before 6:30 p.m., a decision was made to double the evacuation zone to a 12.4-mile (twenty-kilometer) radius around the plant. Kan announced the decision on national television, telling his audience that Japan was facing an “unprecedented crisis.” Joining him was Cabinet Secretary Edano, who reassured the public that although an explosion had occurred in the Unit 1 reactor building, the primary containment remained intact and there would be no major escape of radioactive material. “Please remain calm,” Edano told viewers. It was advice the government repeated often.

  Absent from this briefing was Koichiro Nakamura, deputy director general at NISA, who had been handling regular updates for the media. Nakamura’s candor at press conferences earlier that day apparently had gotten him in hot water with Kan’s office. In a morning session with reporters, Nakamura, who had a degree in nuclear engineering, was asked if the fuel had started to melt. He replied: “We cannot deny the possibility.” Four hours later, at another briefing, Nakamura said: “It looks like a core meltdown is occurring.” A short time later, NISA was notified that the prime minister’s office had to clear all statements about the situation, and that NISA also needed to obtain permission from Kan’s office before holding further briefings. Nakamura asked to be replaced.

  When reporters gathered for another briefing shortly after 9:00 p.m., a new NISA spokesman was in charge. Asked about media accounts of a meltdown, the spokesman backpedaled, saying: “The condition of the core has not been clearly identified yet.” The word meltdown was not mentioned. The next morning, another NISA briefer was asked about the likelihood of a meltdown. The answer: “The likelihood cannot be denied because such a material [cesium] has already been detected and we must keep that in mind.”

  In short, if reporters were looking for definitive answers from the government’s nuclear safety officials, NISA wasn’t providing them. In its steadfast effort to avoid the word meltdown, NISA ultimately came up with its own terminology: fuel pellet melt. (TEPCO also eschewed meltdown, preferring core damage.) Although NISA’s classification made technical sense, the agency had little basis to avoid concluding that a full-scale meltdown had occurred. In the minds of many listeners, its careful parsing of words was a distinction without a difference.

  During the afternoon of March 12, after the explosion in Unit 1, Kan was meeting in his office with Madarame and several others when the discussion turned to the question of injecting seawater into the Unit 1 reactor as a last-ditch attempt to cool the damaged core.

  TEPCO officials, realizing that the injection of seawater offered perhaps the last hope of cooling the reactor, had already given the go-ahead. That information was passed along to members of the Emergency Operations Team working in the basement of the prime minister’s office building. But the news never made it upstairs to Kan’s office.

  The decision to use seawater is the death knell for a reactor, and in this case it would send an unequivocal signal that Unit 1 had now been written off by its owners as a piece of radioactive scrap. Seawater is highly corrosive to the internal parts of a nuclear reactor; even the freshwater used in a reactor is filtered to protect components from impurities. The Pacific might cool the core, but it would finish the job of destroying the reactor.

  Kan asked Madarame about the possibility that the seawater could trigger recriticality—an uncontrolled chain reaction—in the damaged fuel.2 Madarame reassur
ed the prime minister that this was unlikely. Participating in the conversation was TEPCO’s liaison, Ichiro Takekuro, who interpreted the discussion to mean that the government might not approve of injecting seawater.

  Shortly after 7:00 p.m., Takekuro called plant superintendent Yoshida to tell him about the conversation. Yoshida said that the seawater injection had already begun. Takekuro told him to stop it because the prime minister’s office was still weighing that option. An angry Yoshida called TEPCO headquarters and was told he had no choice but to suspend the injection pending a decision by Kan.

  Yoshida knew that if he stopped the injection, he might not get the jury-rigged pumping system to work again. And he knew that continuing to get water into the core was the highest priority, regardless of the government’s apparent dithering. In a moment of bare-knuckled defiance, Yoshida summoned the person in charge of the injection work and whispered instructions: “I’m going to direct you to stop the seawater injection, but do not stop it.” Then, in a loud voice, heard in the plant’s emergency response center—and, via video feed, in Tokyo—Yoshida ordered that the pumping be halted. Finally, at 8:20 p.m., Takekuro delivered word that the prime minister had given the okay and the injection could resume. By then, however, Yoshida had a new spate of emergencies.

  On Saturday morning, March 12, NRC chairman Gregory Jaczko was en route to an 11:00 a.m. meeting at the White House to discuss the situation in Japan when he received an update. Information was still in short supply at the NRC, with most coming via media outlets. The NRC wasn’t alone; the Departments of State, Defense, and Energy, the U.S. Agency for International Development, and especially the U.S. Embassy in Tokyo were also laboring to learn more.