If they’re released during a nuclear accident, the same neutrons that ping around inside the nuclear reactor breaking apart uranium atoms can careen through a worker’s body. Radiation might knock out a piece of the cell’s DNA, change the structure of the cell wall, or alter the thickness of the fluid in the cell. In the end, the effect is the same: a damaged cell cannot function properly. When enough cells are damaged, the body begins to break down.
The course of radiation sickness, also called acute radiation syndrome, varies widely depending on what kind of radiation was absorbed and where in the body it causes the most damage. But some effects are universal. In high enough doses, radiation sickness almost always causes nausea, headaches, and a general feeling of illness that can last anywhere from a few hours to two days. After that, the symptoms disappear for a time. With milder poisoning, this period of normalcy can last up to two weeks; in severe cases, it ends in as little as five days. Then the real impact of the radiation strikes, with grisly symptoms that range from hair loss and extreme fatigue to the destruction of bone marrow and internal bleeding.
Naturally occurring radiation can be found everywhere—even at low levels in many of the foods we eat regularly. It is only at higher levels of exposure that it poses a threat. The base unit in this chart is the sievert (Sv): “µSv” stands for “microsievert,” which is one millionth of a sievert, and “mSv” stands for “millisievert,” which is one thousandth of a sievert.
The Japanese Nuclear Regulation Authority measures radiation exposure in sieverts, a unit of measure that takes into account the strength and type of radiation and indicates the likely impact a given amount of radiation will have on the human body. (In the United States, a similar unit of measure called a rem is often used.) A person exposed to 1 sievert (Sv) of radiation suffers light radiation poisoning and has a 90 percent chance of survival. Around 4 Sv, the odds of survival drop to 50 percent. At 10 Sv, exposure is always fatal.
It sounds terrifying, but the odds of the average person encountering that kind of radiation are minuscule. It can only be found in environments where nuclear fission is occurring—in nuclear weapons and nuclear power plants.
The heart of a nuclear reactor seethes with deadly radioactivity. In the 1950s and ’60s, the U.S. Air Force ran a series of experiments in a secluded stretch of woods 50 miles from Atlanta, Georgia. The Georgia Nuclear Aircraft Laboratory ran a 10-million-watt nuclear reactor completely unshielded. Everything within 1,000 feet of the reactor died. And that really means everything, from trees and birds to single-celled organisms and viruses.
On a normal day at a nuclear plant, workers are completely shielded from the radiation inside the reactor by the vessel’s thick steel casing, by the water that covers the fuel rods, and by the thick concrete of the containment chamber. The average worker’s radiation exposure is measured in millisieverts (mSv)—thousandths of sieverts. In Japan, a law set the maximum exposure allowed for a nuclear power plant worker under normal conditions at 50 mSv a year, or 100 mSv over five years. Nuclear workers carry dosimeters, badges that keep track of how much radiation they have encountered over time.
Nuclear plant workers know that if they need to enter an area where they may be exposed to radiation, there are three factors that can reduce their exposure: time, distance, and shielding.
If you’ve ever had a dental X-ray, you’ve seen these principles in action. Before starting the X-ray machine, the dentist always leaves the room, putting distance between herself and the radiation source. That’s because radiation spreads out as it travels, making it less likely to strike you the farther away you are.
Leaving the room also reduces the amount of time that the dentist is exposed to X-rays. The short burst pointed at your teeth is no problem for you, since that happens only once every year or so, but if dentists stood right next to every patient they took X-rays of, they’d be getting exposed—at close range—many times a day. The same is true for nuclear power plant workers. Since the reactor is continually producing radiation, shortening their time near it reduces the amount of radiation workers are likely to absorb.
You probably also remember that the dentist placed a heavy lead bib over you before running the machine. The lead acted as a shield, blocking almost all of the X-rays from reaching your body.
For every type of radiation, there is some material that it is unable to travel through. In a nuclear power plant, water serves as a shield, slowing down and capturing neutrons, as do the steel walls of the reactor vessels and the thick concrete of the primary containment chamber. On a normal day, those shields prevent radiation from reaching workers and any other people nearby. But March 13, 2011, wasn’t a normal day—the water in the reactor was gone, corium had melted through the reactor vessel, and the primary containment had been breached.
Three hours after the explosion at unit 1, the Japanese government had doubled the evacuation zone around the plant to 12.4 miles. But for those at the plant, evacuation wasn’t possible.
* * *
The unthinkable had already happened—a nuclear reactor had melted down. But operators still needed to find a way to get water into the reactor at unit 1. Unless they could cool the mass of corium, the chain reaction would continue unchecked, growing hotter and hotter until the corium ate through the concrete of the secondary containment. And they had five other reactors to keep an eye on, too. Workers had been sleeping at the plant, cycling in and out of the control rooms and repair teams in shifts. Many feared they were putting themselves in mortal danger to save the power plant, but they were determined to protect their families and all the people living in the surrounding towns. They went about their work with the grim resolve of soldiers in battle.
One worker later described taking off his wedding ring before his shift because he feared it would be contaminated with radiation and have to be left behind. But then he thought better of it—he knew that if something happened to him, his body could be identified by the ring. So he put it back on. Another worker remembered calling his father before his shift and asking him to take care of his wife and daughter if he died.
Operators wore radiation suits for protection. The suit’s function is to prevent radioactive dust from hitching a ride on the wearer’s body—in their hair or clothes, on their skin, or in their lungs. But the fabric of a radiation suit cannot block the kind of radiation that comes from a reactor. Even with protective gear, the workers were exposed.
To make matters worse, the plant’s store of alarm pocket dosimeters, which let out a high-pitched two-tone alarm if the radiation level climbs too quickly, was largely wiped out by the tsunami. Usually, anyone working near radiation would be required to carry this potentially lifesaving device. Instead, only the leader of each operational team was given one.
Following the explosion in unit 1, operators in the control room next to it didn’t have a lot of options to reduce their radiation exposure. There was no shield between the control room and the radiation that had escaped containment. They simply didn’t have the option to leave the control room and reduce the length of their exposure. The best they could manage was to move to the unit 2 side of the building when they didn’t need to be at the instruments and crouch down—adding a little distance between themselves and the radiation source and reducing their height so they presented less surface area to be hit by radiation.
Despite the explosion, operators for unit 1 needed to press forward with their efforts to cool the reactor. No one could be sure what, exactly, was going on inside it. They only knew that they needed to get water into the reactor core to prevent the chain reaction from spiraling out of control. A fire engine had already managed to pump more than 20,000 gallons of water into the reactor at unit 1. But by 2:53 that afternoon, less than an hour before the explosion, they had run out of fresh water to inject. Desperate to replace the cooling water in the reactor, Yoshida decided it was time to try his last resort: seawater.
Normally, nuclear reactors use purified water,
which runs through a closed system to ensure that none of the water from the reactor can get out—and that no impurities can get in. That’s because minerals in unpurified water can attach to the metal surfaces and fuel rods in the reactor core, interfering with the carefully maintained reaction occurring inside. The salt in seawater also corrodes metal and destroys electrical connectors. (That was why the plant’s backup generators had failed after they were flooded by the tsunami.) Everyone knew the injection of seawater would damage the reactor beyond repair. But they had no choice—nothing was more important than getting water around the overheating fuel rods.
In order to span the distance from the seawater holding tank, three fire trucks needed to be connected by a series of hoses to form a chain. In the hours before the explosion, workers had laid out fire hoses in preparation for the seawater injection, but those had been damaged by the blast. They needed to be repaired or replaced. Workers scrambled to get the pumping system back online, patching the hoses that could be salvaged and cobbling together any new hoses they could find to replace the ones that could not. It was past 7:00 P.M. before they started pumping seawater into the reactor. But in the meantime, Prime Minister Naoto Kan had balked at the idea. Not fully versed on the workings of the reactor, he was concerned that the seawater could lead to another explosion. The drastic measure would also send a clear message to the outside world that TEPCO had given up on the idea that unit 1 could be saved.
Fire trucks, photographed on March 16 among tsunami and explosion debris on the Fukushima Daiichi grounds, were used to pump seawater into the reactors.
Kan pressured TEPCO to stop the seawater injection. But Yoshida worried that the odds of getting their ad hoc pumping system going again would be slim if they stopped. He also knew that injecting the seawater was their only hope of keeping the chain reaction in unit 1 from reaching a point of no return, and that every minute counted. So he hatched a plan to keep the seawater flowing. He took one of his workers aside and told him that, on a video conference call with TEPCO headquarters, he was going to order the workers to stop the seawater injection … but he wanted them to ignore the order.
It was a gutsy move. Yoshida was not only lying to his bosses at TEPCO, he was also defying an order from the prime minister of Japan. But he knew that nothing was more important than getting water into the melting core.
The call went as planned; the seawater injection continued.
* * *
Workers in the main control room for units 3 and 4 had noticed a sudden climb in radiation in their workspace after the hydrogen explosion in unit 1 the day before, but they didn’t have the luxury of evacuating. They had their own problems to deal with.
After the earthquake, reactor 3 had scrammed, triggering the RCIC system to keep cooling water flowing through the reactor. All had gone well until the morning after the tsunami, when the RCIC had shut down. An emergency injection system, or HPCI (pronounced “Hipsy”), had automatically kicked in when the RCIC shut down around noon on March 12. Because they had battery power, water injection had been a far easier task for the operators of unit 3 than it was for those of unit 1, but they were still improvising. The HPCI was meant to be used in the case of a sudden loss of water, like when a pipe ruptures. It delivered far more water than the RCIC system, and operators had to constantly monitor the flow.
Despite the demands it placed on the operators, the HPCI had kept the core cool. But in the early morning light of March 13, the HPCI also appeared to be failing. Operators decided they would have to try to use fire hoses to deliver water to the core. But this solution was short-lived. Not long after the fire hoses began pumping, the batteries powering unit 3 sputtered out.
In an echo of the events at unit 1, pressure in the unit 3 reactor began to climb as operators tried to open a safety release valve and vent steam. It was 8:41 A.M. before they were successful. And it was too little, too late: At around 9:00, the water in the reactor sank below the tops of the fuel rods.
By 10:40, the core was melting down.
* * *
It was two days after the earthquake, and the bad news kept coming. Both the Fukushima Daiichi and Fukushima Daini plants were out of commission following the tsunami, creating a shortage in the electricity supply. TEPCO announced a series of rolling blackouts throughout central Japan. Necessities of all kinds were also in short supply near the stricken coast. Fuel became scarce, and emergency supplies such as water and batteries had flown off store shelves. Ninety-six aftershocks shook the island on the 13th, causing more damage and anxiety.
Even worse, all along the northeastern coast of Japan, bodies began to wash up on shore. More than two thousand would be found by the morning of March 14.
But help began to trickle in, too: 100,000 troops from the Japan Civil Defense forces arrived in Tohoku, along with trucks carrying drinking water and food. Search-and-rescue teams combed the wreckage for survivors and bodies. And the first helicopters cut in from the ocean, carrying emergency supplies from a fleet of American ships offshore.
Two days after the tsunami, tens of thousands of people were still missing. Residents in Natori, a town in Miyagi Prefecture, posted notes hoping that family members would read them and be reunited.
DAY 4
radioactive cloud
Monday, March 14, 2011
Reactor Status
Reactor 1: Melted down/building destroyed
Reactor 2: Scrammed
Reactor 3: Melted down
Reactor 4: Shut down
Reactor 5: Shut down
Reactor 6: Shut down
Two hundred and seven miles away from Fukushima Daiichi, the USS Ronald Reagan was standing by in the North Pacific Ocean. A U.S. Navy aircraft carrier more than 1,092 feet long and carrying about 3,200 crew members, it had been on its way to South Korea to participate in naval maneuvers when the earthquake hit Japan. It received new orders to join a relief effort called Operation Tomodachi. (Tomodachi means “friendship.”)
With supply routes on land severely damaged, the quickest route for bringing humanitarian supplies such as food, water, and first-aid equipment to devastated coastal towns was by sea, so the aircraft carrier headed for Japan, where it would serve as a fueling and supply station for disaster relief operations. The Reagan was moving fast, but as it neared Sendai, the sea became thick with wreckage from the tsunami. The ship slowed to a crawl. Lindsay Cooper, a petty officer third class on the aircraft carrier, later remembered, “You could hardly see the water. All you saw was wood, trees, and boats. The ship stopped moving because there was so much debris.” When the tsunami waves receded, they had dragged the rubble of the Japanese coastal communities they had devastated—buildings, telephone poles, cars, and even people—with them.
An aerial photo taken from a U.S. Navy helicopter on March 12 shows timber and rubble swept out to sea by the tsunami.
But tsunami debris wasn’t the only danger off the coast. The ship took a position at what was considered a safe distance from Fukushima Daiichi—100 miles. They soon discovered that they needed to be farther away.
A nuclear-powered ship, the Reagan was equipped with radiation sensors. On the morning of the 13th, sensors in the engine room had registered radiation levels on deck at more than twice normal. That same day, three helicopters that flew on a mission closer to the plant had returned to the ship covered in radioactive dust.
Seventeen crew members who had ridden in the helicopters had to be decontaminated, scrubbed from head to foot to remove any radioactive particles. Their clothes were sealed in plastic bags for disposal.
Sailors aboard the USS Ronald Reagan scrub down the ship’s decks to remove any radioactive particles that may have accumulated.
Sailors on the Reagan later reported that they had been caught in a radioactive cloud. A senior chief petty officer named Angel Torres remembered, “All of the sudden, this big cloud engulfs us. It wasn’t white smoke. It was like something I’d never seen before.”
Lindsay Cooper remembered not how the cloud looked, but how it felt. A gust of warm air blew across the ship’s deck, cutting through the falling snow. “Almost immediately, I felt like my nose was bleeding,” she said. It wasn’t, but the air smelled and tasted metallic, like blood.
The Reagan had run afoul of nuclear power’s thorniest problem: radioactive isotopes.
* * *
As sources of electricity go, nuclear fission is incredibly efficient. A single uranium pellet, just half an inch across, can produce the same amount of energy as 1 ton of coal or 149 barrels of oil. And while burning a ton of coal in a properly functioning coal-burning plant releases more than 2 tons of carbon dioxide (one of the gases that contributes to global climate change), a nuclear reactor releases none. But nuclear fission does create waste, in the form of radioactive isotopes.
When an atom of uranium splits, the pieces aren’t just smaller than the original atoms; they also have a different number of protons in their nuclei. That means that the new atoms are no longer uranium—they have become different elements. And they aren’t necessarily stable.
Elements are defined by the number of protons in their nucleus—all oxygen atoms have eight, and if an atom has six protons, it’s carbon—but the number of neutrons can vary. Atoms of the same element that have different numbers of neutrons are called isotopes of each other. If the number of neutrons creates an imbalance in the atom’s nucleus, that isotope is radioactive. Over time, it will shed neutrons, protons, or both until it reaches a more stable form. As the neutrons and protons fly the coop, they travel as radiation.
Exactly when any given atom will shed its loose particles is anyone’s guess. Scientists talk about the life of an isotope in terms of probability. Imagine that you’ve been put in charge of ten energetic kindergartners. You sit them all on a rug, crisscross applesauce, and tell them to stay seated. You can’t predict exactly when each kid will pop up from his or her seat. But you know that at some point, they all will. If you’ve done this before, you probably know that the wiggliest kid can only keep their butt on the carpet for about thirty seconds. The calmest one will make it to ten minutes. Based on that range, you can predict that about half of the kids will be up and running around in about five minutes.
Meltdown: Earthquake, Tsunami, and Nuclear Disaster in Fukushima Page 6
