As the airborne attack went on, the levels of radionuclides issuing from the reactor continued their downward trajectory: from 6 million curies of radiation on Sunday to 5 million on Monday, 4 million on Tuesday, and 3 million on Wednesday. By the end of the day, the incandescent spot the airmen had been targeting seemed to have been extinguished. On the evening of the next day, Thursday, May 1, General Antoshkin reported to Boris Scherbina that his pilots had bombarded Reactor Number Four with more than 1,200 tonnes of lead, sand, and other materials. Some members of the government commission got to their feet and applauded. Scherbina graced the general with a rare smile. Then he set a new target for the following day: 1,500 tonnes.
But by the next evening, Valery Legasov and the team of scientists analyzing the latest data from Unit Four had made a horrifying and apparently inexplicable discovery. Instead of continuing to fall, the radioactive releases from the reactor had now suddenly begun to increase again, doubling from 3 million to 6 million curies overnight. The temperature of the burning core, too, was rising rapidly. By Thursday night, Legasov’s estimates suggested that it was already approaching 1,700 degrees centigrade.
The academicians now feared that the uranium dioxide fuel and zirconium cladding remaining inside the vault of Reactor Number Four had become so hot that they had started to fuse into a mass of radioactive lava in what amounted to a total core meltdown. Worse still, the 4,600 tonnes of sand, lead, and dolomite that had been flung into the damaged building from two hundred meters in the air, combined with the impact of the initial explosions a week before, might have fatally compromised the foundations of the reactor. If the temperature of the molten fuel reached 2,800 degrees centigrade, they suspected it could begin burning through the reinforced concrete floor of the reactor vault. Pressed down from above, it could eat its way through the bottom of the vault, into the basement of the building, and deep into the earth below. This was the doomsday scenario of reactor accidents: the China Syndrome.
Although first envisioned by US nuclear engineers, the China Syndrome had been made infamous as the title of the hit Hollywood movie released less than a month before the accident at Three Mile Island. It starred Jane Fonda as an intrepid TV reporter, aghast to discover how a mass of melted uranium fuel might burn through the base of a faulty reactor in California and continue, inexorably, until it reached the other side of the world, in China. And while this hypothetical nightmare defied the laws of physics, geology, and geography, if a core meltdown had begun in Chernobyl, the China Syndrome posed two real threats. The first and most obvious was to the local environment. The power station sat just a few meters above the water table of the Pripyat River, and if the melted fuel penetrated that far, the consequences would be catastrophic. A whole range of toxic radionuclides would poison the drinking water not only supplied to Kiev but also that of everyone in Ukraine who drew from the waters of the Dnieper River basin—some thirty million people in all—and, beyond that, flow into the Black Sea itself.
But the second threat was even more immediate and frightening to contemplate than the poisoning of the water table. The molten fuel would reach the Pripyat and the Dnieper only if it escaped the foundations of the building. Before that happened, it would have to pass through the steam suppression pools, the flooded safety compartments beneath Reactor Number Four. And some of the scientists feared that if the white-hot fuel made contact with the thousands of cubic meters of water held in the sealed compartments there, it would bring about a new steam explosion orders of magnitude larger than the first. This blast could destroy not only what remained of Unit Four but also the other three reactors, which had survived the accident intact.
Amounting to a gargantuan dirty bomb formed of more than five thousand tonnes of intensely radioactive graphite and five hundred tonnes of nuclear fuel, such an explosion could exterminate whatever remained alive inside the Special Zone—and hurl enough fallout into the atmosphere to render a large swath of Europe uninhabitable for a hundred years.
* * *
On Friday, May 2, the new team ordered to replace Boris Scherbina and the members of his government commission, led by Ivan Silayev and including Legasov’s old rival Evgeny Velikhov, arrived in Chernobyl from Moscow.
By now, Scherbina and his group were exhausted, and—after five days of often reckless disdain for the intangible dangers surrounding them—thoroughly irradiated. The commission members had not been given iodine tablets or dosimeters until they had already been in the accident zone for twenty-four hours, and not everyone had bothered to use them. Now their eyes and throats were red and raw from exposure to radioactive dust; some noticed their voices becoming high and squeaky—a strange side effect of alpha contamination. Others felt sick, their heads swam, and they became so agitated they could barely concentrate. On Sunday, May 4, when they eventually returned to Moscow, Scherbina and the others were hospitalized and examined for symptoms of radiation sickness. They surrendered their clothes and expensive foreign-made watches, too contaminated to be saved, for burial. One of Scherbina’s assistants was showered eighteen times in an attempt to remove the radioactive particles from his skin. Nurses shaved the heads of everyone, except for Scherbina, who declared that such treatment was beneath the dignity of a member of the Council of Ministers of the USSR and assented only to a short trim.
Yet despite his mounting radiation dose and the departure of his colleagues, Valery Legasov chose to stay behind in Chernobyl. By the end of Sunday, emissions from the reactor had reached 7 million curies, even higher than the day the helicopter operation had first begun. And now Legasov found himself at odds with Evgeny Velikhov over how to respond.
Like Legasov, Velikhov had no direct experience with nuclear power reactors and arrived at the scene planning to learn on the job. His manner didn’t impress the generals, who preferred the athletic and decisive Legasov—an avowed Socialist, a Soviet leader in the traditional mold—to the portly academic with his Western friends and loud check shirts. But Velikhov could count on his long-standing relationship with Gorbachev to guarantee a direct line to the general secretary—who had already taken a personal dislike to Legasov, begun to suspect he wasn’t being told the whole truth about the accident, and needed someone in Chernobyl he could trust.
Now, in addition to their different personalities, the two scientists were divided by their approach to the threat of meltdown in Unit Four. Velikhov had recently seen The China Syndrome—screened to a restricted audience in the Physics Department of Moscow State University just over a year before—and feared the worst. However, Legasov and other nuclear specialists at the scene were unswayed by the Hollywood version of events. They believed the chances of a full meltdown were insignificantly small.
The scientists still had little real idea what might be happening deep in the bowels of Unit Four. They had no reliable data from inside the burning reactor, and even their measurements of radionuclides escaping into the atmosphere had a 50 percent margin of error. They knew nothing about the state of the graphite and lacked a full inventory of the fission products being released by the fuel; they couldn’t be certain if the zirconium was burning, or how any of these elements might be interacting with the thousands of tonnes of different materials dropped from the helicopters. They did not know how hot nuclear fuel might react with an enclosed body of water. Nor did they have any hypothetical models to help them.
In the West, scientists had been simulating the worst-case scenarios of reactor meltdowns for fifteen years, in ongoing research that had only intensified after the disaster in Three Mile Island. But Soviet physicists had been so confident of the safety of their own reactors that they had never bothered indulging in the heretical theorizing of beyond design-basis accidents. And appealing directly to Western specialists for help at this stage seemed unthinkable. Despite the growing atmosphere of alarm among the physicists at the burning reactor, the government commission and the Politburo remained determined to conceal the news of a possible meltdown from th
e world beyond the thirty-kilometer zone.
Velikhov contacted the head of his research lab on the outskirts of Moscow and summoned his team to work over the May Day holiday weekend. The dozen scientists weren’t given any details over the phone, and even when they reached the lab were told about the accident only in the most general terms. They were required to find out all they could about the potential speed of a reactor core meltdown—but they were all theoretical physicists, experts in the study of esoteric phenomena related to the interaction of lasers and solids, plasma physics, and inertial fusion. None of them knew anything about nuclear reactors, and the first thing they had to do was learn all they could about the RBMK-1000. They plundered the library for reference books on the properties of different radioisotopes, decay heat, and thermal conductivity and commandeered the lab’s suite of Soviet-built mainframe computers to begin making calculations.
Meanwhile, as Velikhov and Legasov disagreed about the risks of a meltdown, the graphite blazed on, and the temperature inside Reactor Number Four continued to rise. Velikhov called Gorbachev in Moscow. What was happening in Chernobyl was so secret he wouldn’t be allowed to call his wife for six weeks. But when he needed to talk to the general secretary, he could reach him on the car phone in his limousine right away. “Should we evacuate Kiev?” Gorbachev asked.
Velikhov admitted that he just couldn’t be sure.
The new leader of the government commission, Ivan Silayev, a Hero of Socialist Labor and holder of two Orders of Lenin, a long-serving technocrat with a direct manner and a steep crest of silver hair swooping back from his forehead, was less volatile than Boris Scherbina. But he faced an even more dire situation than his predecessor had: the fire, the escaping radiation, the core meltdown, and now the possible explosion. He began demanding updates from the scene every thirty minutes. The members of the commission started work at 8:00 a.m. and finished at 1:00 a.m. Many slept for only two or three hours a night.
In his headquarters in Chernobyl town, Silayev adopted a typically Soviet approach to the crisis: rather than choose a single course of action to halt the possible meltdown, he gave orders for dynamic action and patriotic sacrifice on all fronts at once. He issued instructions to the plant staff to find a way of piping nitrogen gas into the reactor vault to blanket the melting core and starve the graphite fire of oxygen. He summoned subway construction engineers from Kiev to begin drilling into the ground below Unit Four to freeze the sandy soil with liquid nitrogen or ammonia and protect the water table from the melting fuel. And he sent out word to find men brave enough to enter the darkened basement rooms directly beneath the reactor itself, open the valves of the steam suppression pool, and pump out the five thousand cubic meters of highly radioactive water they would find there.
In the meantime, General Antoshkin’s helicopter assault on Reactor Number Four continued.
* * *
At 1:00 a.m. on Saturday, May 3, Captain Piotr Zborovsky of the 427th Red Banner Mechanized Regiment of the civil defense had just finished washing in the field bathhouse, in his camp thirty kilometers south of the plant. He was toweling himself dry when he got word that someone was looking for him. A colonel and a major general approached. He had never seen either of them before.
“Get ready,” the general said. “The head of the government commission wants to see you.”
Zborovsky, at thirty-six, was a sixteen-year veteran of disaster remediation, nicknamed Los—“Moose”—on account of his physical strength. He had so far spent three days with his men in clouds of whipping dust and downdraft, heaving sacks of sand and clay into the parachutes beneath Antoshkin’s helicopters. He hadn’t eaten since breakfast the previous morning and was looking forward to a medicinal dose of 100 grams of vodka.
“I’m not going anywhere until I have dinner,” Zborovsky said.
“We’ll wait,” the general replied.
* * *
The steam suppression pools lay deep in the warren of claustrophobic spaces beneath Reactor Number Four. They were contained in a single, massive concrete tank with a volume of seven thousand cubic meters, split into two stories, cluttered with a forest of thick pipework, partitioned into corridors and compartments, and half filled with water. The pools had been part of the main reactor safety system intended to prevent a steam explosion in the event of a pressure channel rupture inside the core. In an emergency, the escaping steam was supposed to be released through safety valves and directed down into the pools, where it would bubble up through the water, condensing harmlessly into liquid as it did so.
But on April 26, the condensation system had been quickly overwhelmed and failed during the final destruction of Reactor Number Four. Now neither the station staff nor the scientists knew how much water the tanks contained, or even if they remained intact. Technicians from the plant had opened one valve connected to the system and heard only the whistling of air rushing in. But the scientists nevertheless suspected there was still water in the tanks. An order went out to find a good spot for blasting a hole through the wall—almost two meters thick and sheathed in stainless steel—using explosives. When this command reached a shift foreman at Unit Three, he suggested that there might be a less potentially catastrophic method of accomplishing the task. Examining the plant blueprints, he identified a pair of valves intended to drain the tanks for maintenance—located deep in the subterranean maze beneath the reactor—and scouted the route with a flashlight and a DP-5 military dosimeter.
Before the accident, opening the valves would have been a simple task: walk down a staircase to level -3, three meters below ground level, to corridor 001, a long concrete passageway connecting Units Three and Four; find the valve compartment; and turn the wheels on valve numbers 4GT-21 and 4GT-22. But now radioactive water flooded corridor 001. In the valve compartment, it was one and a half meters deep. When he reached that point, the shift foreman’s DP-5 ran off the scale, and there was no telling how much radiation lay inside. The valves could not be opened until the corridor had been cleared.
* * *
It was still the small hours of the morning when Moose Zborovsky was shown in to the meeting room on the second floor of the government commission headquarters in Chernobyl. Deputy Minister Silayev came out from behind his desk and stood to attention, his thumbs on the seams of his pants.
“Comrade Captain, you have an order from the government: to pump water out from under Unit Four.”
Zborovsky didn’t have a chance to think. “Yes, sir!”
“You’ll be given details by military headquarters,” Silayev said. “Be ready at 0900.”
Only on his way back down the stairs did the captain consider the latest conditions reported near Unit Four: 2,800 roentgen an hour beside the outer wall of the reactor. He had been taught in military technical school that 700 rem was a lethal dose. At the wall, he’d get that in fifteen minutes. How much radiation would there be beneath the core itself?
Zborovsky drove the 120 kilometers back to the civil defense base in Kiev to gather men and equipment, stopping at home on the way. Knowing that his clothes were highly contaminated, he stripped in the hallway before going inside his apartment. He kissed his sleeping twelve-year-old son and said good-bye to his wife; he didn’t tell her where he was going.
Reporting back to Silayev at nine o’clock on Saturday morning, the captain learned that the operation had to be planned from scratch. Even the elementary questions of how to get into the basement of Unit Four to get the water out, and where it could go once removed, had not been considered. At the meeting of the government commission that morning, the experts couldn’t agree on a safe location for the storage of five thousand cubic meters—enough to fill two Olympic swimming pools—of highly radioactive effluent. While he waited for a decision, Zborovsky scouted the site in an armored personnel carrier and found a place to break through the wall into the basement service tunnel. Once again fearing the consequences of using explosives so close to the damaged reactor, Zborovsky asked f
or volunteers from his company to go in with a sledgehammer. Five men stepped forward. The radiation was high; the captain estimated each of them could work for a maximum of twelve minutes. When they finally broke through, Zborovsky went into the basement with a rope tied around his waist, like a deep-sea diver. He walked on through the blackness until his footsteps began to squelch. Gradually, the water level rose to a depth of more than four meters. It felt warm—45 degrees centigrade, hot as bathwater—and reeked of hydrogen sulfide.
Back in Moscow, Evgeny Velikhov’s team of theoreticians began conducting experiments to investigate the behavior of melting nuclear fuel. In the absence of real data from the plant, Velikhov had arranged for boxes of papers on the phenomenon to be flown over from his contacts in the West, but the scientists were in too much of a hurry to read and synthesize the mountain of material. They decided it was quicker to do the research themselves. They worked around the clock and slept on the chairs in the office. In the lab, they heated metal cylinders and uranium fuel pellets with carbon dioxide lasers, laid them on pieces of concrete, and recorded the results. They sent samples to Kiev, where a specialist examined the interaction between uranium dioxide, molten heavy concrete, and sand. They quickly confirmed Velikhov’s worst fears: a mass of fuel weighing only ten kilograms could generate enough heat to melt right through the reinforced concrete floor of the reactor vessel and then keep going, traveling downward as quickly as 2.5 meters a day. But they also found that the incandescent uranium could fuse with and absorb pieces of debris, metal, and sand to form entirely new substances—highly radioactive and possessed of as yet unknown characteristics.
Midnight in Chernobyl Page 23