Meltdown: Earthquake, Tsunami, and Nuclear Disaster in Fukushima

by Deirdre Langeland

  Yet the workers were determined. “We knew that we would not be replaced,” Yoshizawa remembered. “No one was forced to stay, but those of us who remained knew that we would be there until the end. We knew that we were the only people capable of saving the plant.”

  * * *

  The explosion in unit 4 had caused the top two floors of the building to collapse and sent workers who had been out on the grounds cleaning up the radioactive debris left by the first two explosions scurrying for safety. Dressed in full radiation suits, they headed for the emergency response center. It was not an easy trip. The roads between the reactor and the seismic isolated building were choked with debris from the explosions. The workers’ protective suits restricted their movement, and it was almost two hours before they reached the emergency response center. Until then, Superintendent Yoshida had no idea that the explosion they had heard that morning had actually come from unit 4.

  The explosion in the unit 4 building collapsed its top floors and destroyed equipment on other levels.

  He received the news with dismay. Because the reactor at unit 4 had been shut down when the tsunami swept in, it seemed likely that the explosion had come from a spent fuel pool. And that was a nuclear disaster of a whole different kind.

  * * *

  The fuel pellets that drive the chain reaction in a nuclear reactor are not particularly radioactive. About 95 percent of each pellet is uranium 238, an isotope with a half-life of 4.5 billion years. The rest is uranium 235, which has a half-life of 704 million years. That means that the atoms in the fuel are much, much, much slower to decay than, say, the atoms in iodine 131, which has a half-life of eight days. The pellets of uranium will be as old as Earth is now before half of the uranium 238 atoms have emitted radiation. To put it simply: They are safe enough to be handled with bare hands.

  Once uranium atoms have been struck by neutrons and fissioned, however, it is a completely different matter. In a reactor, many of the uranium 235 nuclei split apart, transforming into radioactive isotopes such as iodine 131 and cesium 137. Some of the uranium 238 atoms will absorb a stray neutron and undergo a series of transformations to become plutonium 239.

  As the uranium 235 atoms in the fuel are split, their numbers begin to dwindle. It becomes less likely that a neutron will strike a uranium 235 nucleus, and the fuel can no longer sustain a chain reaction. At that point, the fuel is considered spent. The rods must be removed from the reactor and stored. But they are still highly radioactive, loaded with radioactive isotopes, the by-products of fission.

  Each of the reactor buildings at Fukushima Daiichi included a massive spent fuel pool on the fifth floor. The smallest pool, in unit 1, held 261,000 gallons of water. The largest, in unit 6, held more than 385,000—a little more than half the volume of an Olympic-sized pool.

  When it was time to store the fuel from one of the reactors at Fukushima Daiichi, operators would bring the reactor to cold shutdown. They would flood the entire fifth floor of the building with water. A crane could then carry the spent fuel through the water to the storage pool, keeping the fuel rods submerged the whole time. The excess water would later be drained off.

  The fuel pools were designed to provide maximum shielding: Each was made of 5-foot-thick concrete with a steel liner. Although the top of the pool was open, the rods were covered by at least 23 feet of water at all times.

  Just like the water that cooled the reactor, the water in the spent fuel pools did double duty. It provided a shield, preventing radiation from escaping, and it also cooled the rods. Although mostly spent, the rods could still produce decay heat. A cooling system kept the water surrounding the fuel rods in the storage pools below 95°F.

  In order to move spent fuel, nuclear operators must first bring the reactor to cold shutdown. Then the reactor core and spent fuel storage are flooded with enough water to submerge the area to a depth of about 30 feet. Rods remain submerged in the coolant and radiation shield of the water while they are being moved.

  Before the tsunami, units 4, 5, and 6 had been shut down for maintenance. Units 5 and 6 still had fuel in their reactors, but they were in cold shutdown. They also still had power, so the water level and temperature inside each reactor could be monitored. In unit 4, however, the fuel from the reactor had already been transferred to the storage pool. That meant the pool had more spent fuel than the others. And since it had only recently been removed from the reactor, the fuel was hotter, too.

  When the plant lost power, operators had known that the spent fuel pools were in peril, but they also knew that they had some time to solve the problem. The shaking from the earthquakes and explosions had sloshed about 3 feet of water from each, but that still left hundreds of thousands of gallons in the pools. In unit 4, the entire fifth floor was still flooded from the fuel-removal process. By the emergency team’s calculations, they had at least a week before enough water would be lost to cause trouble, so they had focused on more pressing problems.

  But all that changed when the unit 4 operators arrived at the command center with news of its explosion. Radiation levels near the building had soared to 400 mSv an hour—a dose high enough to be deadly after several hours’ exposure. They knew a fire was burning inside the unit, but no one could get close enough to see where it was. Everything pointed to the possibility that the fuel in the spent pool was no longer underwater, and that the zirconium cladding that encased the fuel rods had ignited.

  There was one major difference between the fuel in the spent storage pools and the fuel inside the reactors. The nuclear reactors were encased in containment vessels that kept most of the radiation from escaping in case of an accident. The storage pools, loaded with a total of almost 900 tons of spent fuel, had no containment structures. In the cases of units 3 and 4, there was no longer even a roof over them. If there really was a fire in one of the storage pools, there was nothing to hold in radioactive materials, which would be carried in the smoke. Even worse, the heat generated could create an updraft, carrying any radiation that was released high into the atmosphere, where it could travel for miles before coming back down.

  * * *

  Both TEPCO and the Japanese government were concerned about causing panic among the population. In public statements, they tried to walk a fine line between keeping people informed about radiation leaks that could affect them and holding back details so people wouldn’t experience unnecessary fear.

  But news agencies had been filming Fukushima Daiichi from the air almost continuously since the slow-motion accident had begun. Attempts to reassure people that things were under control were undermined by footage of units 1 and 3 belching smoke. Videos of the explosions ran continuously on television and online, and the efforts of the skeleton crew at the plant captured imaginations around the world. Although there were seventy workers, the media called them the Fukushima 50.

  Travelers in Seoul, South Korea, which is across the Sea of Japan and about 750 miles away from the plant, watch television news coverage of the Fukushima Disaster on March 16, 2011.

  The reduced crew at Fukushima Daiichi was scrambling to understand and control the situation. They had very little information to work with. But the government and news organizations outside the plant had even less.

  Around the world, experts tried to piece together the fragments of information they did have in order to form a picture of what was happening. It didn’t look good. The crisis was at its peak, with three reactors melting down and an additional building in flames.

  At about the same time as the explosion in unit 4, operators in the unit 2 control room had thought they heard another explosion coming from the torus beneath reactor 2. A malfunctioning gauge in the torus had shown a sudden drop in pressure. They assumed that the torus had ruptured—meaning that the containment vessel for the reactor had been breached.

  The possibility of a containment breach in unit 2 combined with a meltdown in the unit 4 fuel pool was a radiological nightmare. A senior reactor engineering specialist
at the Research Reactor Institute at Kyoto University, Hiroaki Koide, was interviewed by The New York Times that day. “We are on the brink,” he said. “We are now facing the worst-case scenario.”

  * * *

  Officials at the Nuclear Regulatory Commission in the United States had the same thought. They ran simulations and realized that a breach in the unit 2 torus combined with a meltdown in the unit 4 fuel pool would require everyone within a 50-mile radius of the plant—more than 2 million people—to evacuate. Privately, Prime Minister Naoto Kan worried that the fuel in all six of the fuel pools might melt. A meltdown of that size could require the evacuation of Tokyo—a city of more than 13 million. “If Tokyo needed to be evacuated,” he later said, “I feared the entire nation of Japan would be paralyzed by chaos for quite a long time.”

  Some residents of Tokyo decided not to wait. They packed their bags and headed out of town. Many people living outside the evacuation zone in Fukushima decided to err on the side of caution, too. The government had issued an order for people living beyond the evacuation zone of 12 miles but within 19 miles of the plant to remain inside with their windows and doors closed, and helicopters and airplanes were banned from flying over the site. Many people feared they might be trapped in their homes if conditions worsened, so they opted to leave instead. They may have had the right idea. That night, radiation fell from the clouds in a flurry of rain and snow, endangering the residents of towns that weren’t in the evacuation zone.

  Evacuees at a shelter about 40 miles from Fukushima Daiichi on March 18.

  Gasoline supplies petered out. Suppliers were reluctant to drive near the evacuation zones, so no more would be coming. Still, a stream of refugees made their way to Yamagata, the prefecture west of Fukushima, where they would sleep on floors in crowded gymnasiums and municipal buildings.

  * * *

  At the plant, all eyes turned to the steaming buildings of units 3 and 4. Operators needed to get water into the fuel pools, but the pools were five stories in the air, and there was no way to access them from below. A plan to have Special Defense Forces helicopters drop water on the reactors was scuttled when it became clear that radiation levels above the reactors were too high for helicopter pilots to safely do the job. As night fell, the picture looked grim.

  DAY 6

  turning point

  Wednesday, March 16, 2011

  Reactor Status

  Reactor 1: Melted down, building destroyed

  Reactor 2: Melted down

  Reactor 3: Melted down, building destroyed

  Reactor 4: Building destroyed

  Reactor 5: Shut down

  Reactor 6: Shut down

  On Wednesday, the U.S. ambassador to Japan, John V. Roos, issued a recommendation that all American citizens living within 50 miles of the plant evacuate. The announcement did little to settle the fears of Japanese citizens, who had been told to evacuate only up to 12 miles from Fukushima Daiichi. The governor of Fukushima, Yuhei Sato, said, “Anxiety and anger felt by people have reached boiling point.”

  It didn’t help that another fire had broken out at the unit 4 reactor, and attempts to reach the fuel pools by helicopter that morning were once again stymied by radiation. The copters did manage to drop some water onto the buildings, but they were forced to fly so high that very little made it to their targets.

  Despite their inability to add water to the pools, the helicopter flights marked a change in fortune for the workers at the plant. The night before, they had been sure that the spent fuel pools were on the brink of disaster. But as the light of a new day shone into the reactor buildings, they saw an entirely different picture. Although the helicopter had to stay high above the reactors, skirting the areas of extremely high radiation directly above them, operators on board saw a glimmer of something in the spent fuel pool for unit 4—a snippet of sky, reflected on the surface of the water.

  A properly filled spent fuel pool at Fukushima Daiichi, photographed before the disaster.

  There was water in the pools. It was impossible to say how much was there, but the nightmare scenario, that the fuel was dry and burning, had not turned out to be true.

  The hydrogen explosion in unit 4 had had nothing to do with the spent fuel pool. The building shared a smokestack with unit 3. When hydrogen had built up in the unit 3 building, it had backed up into unit 4, too, and been sparked into an explosion in the air ducts on the building’s fourth floor. The fires, which had been caused by oil spilled on the floor, burned out on their own.

  Eventually, the plant operators realized that the worst-case scenario in unit 2—that the torus had exploded and was leaking—hadn’t happened, either. Much later, investigators would realize that faulty readings from the broken gauge accompanied by the sound of the explosion from unit 4 had led operators to the wrong conclusion.

  * * *

  Although the crisis would drag on for long weeks and months after March 16, the operators had reached a turning point. There would be no further explosions to undo their work. Seawater was being pumped into the reactors at units 1, 2, and 3, pulling them farther from the brink of destruction every day.

  Anxious to stabilize the spent fuel pools, operators ran four more helicopter flights on the evening of March 17, but radiation levels above the reactors were still too high. The helicopters had to fly too far above the reactor buildings, and the strong March winds carried most of the water they dropped—about 6,000 pounds in all—away from their targets.

  On the night of March 18, a team of elite firefighters from Tokyo arrived with fire trucks designed to put out fires in skyscrapers. Seasoned professionals who were trained to navigate towering fires in the skyscrapers of Tokyo, they were nevertheless visibly shaken by the challenge of working close to the open reactor pools. “The plan was to get water into unit 3 by any means necessary,” deputy fire chief Yukio Takayama later recounted. Their target was five stories over their heads and hidden from view, but they had to hit the pools dead-on. And they needed to do it quickly. “Two thoughts kept running through my mind,” Takayama remembered. “Please be over soon, and What will I do if this place explodes? I had never felt that kind of fear before. I thought, This is what it feels like to really be in trouble.”

  The firefighters did their jobs as quickly as possible and made a hasty retreat. The following morning, the radiation levels at the plant dropped sufficiently for reinforcements to join the Fukushima 50, bringing the total number of workers on-site to 580.

  “Little by little, in a small way, we started to have some hope,” Takeyuki Inagaki remembers. “Up until then, we were spiraling further down … Now we were dangling there. We weren’t falling anymore.”

  It might not sound like much, but after a week of ever-worsening conditions, they would take it.

  * * *

  On March 21, ten days after the earthquake and tsunami, power was restored to all six reactor buildings at Fukushima Daiichi. Although having electricity certainly made the work easier, the cooling systems that the operators had tried so desperately to keep working ten days earlier were no longer of any use. They were pumping thousands of tons of seawater a day into reactors 1, 2, and 3, where it flowed around the melted cores and pooled in a radioactive mess in the buildings’ basements. It would be almost nine months before all three reactors reached cold shutdown.

  Workers in radiation suits try to restore power to the units 3 and 4 reactors on March 18.

  The slow creep toward stability was difficult to see from outside the plant. In the first days following the earthquake and tsunami, refugees had been without power and access to outside news coverage. Even many of those who were forced to relocate when evacuation orders were issued were unaware of what was going on at Fukushima Daiichi during the crisis. But slowly, as power was restored in areas farther away from the plant, a steady stream of bad news came with it.

  While many of the dire predictions that had been made about the crisis at the plant in the early days of the disaster had
n’t come to pass, it quickly became clear that the three meltdowns had had a devastating impact on the surrounding region, and would continue to do so for years to come.

  On March 19, the Japanese health ministry reported that it had found radioactive iodine in cows’ milk from farms in Fukushima prefecture. Two days later, on March 21, it found radioactive iodine and cesium on spinach harvested at farms up to 90 miles away from the plant, resulting in bans on the shipment of milk and produce from four nearby prefectures.

  On March 24, Katsunobu Sakurai, the mayor of a town near the plant, recorded an impassioned plea for help and posted it on YouTube. Residents of the town, Minamisoma, had been in the 12- to 19-mile zone around the plant and had been told to stay indoors to avoid radiation. A full nine days after the order was issued, they were still trapped in their homes and evacuation centers, and they were running out of food. The order had forbidden people to travel into the area as well, so no deliveries would be coming. Sakurai feared they would starve.

  Closer to the plant, the town of Futaba was eerily silent, its buildings frozen as they had been in the moments following the earthquake. Bookbags still hung on hooks in classrooms; dishes and pictures littered the floors of houses; signposts pitched at angles across streets. Instead of cleaning up the mess, 1,415 of the town’s residents could be found more than 150 miles away, in a suburb of Tokyo. There, they had set up a town in exile at Saitama Kisai High School. Residents lived in classrooms or the school gym. Relief agencies served meals in the cafeteria. The school’s administrative offices functioned as a makeshift town hall.