The reactor was a pistol with the hammer cocked. All that remained was for someone to pull the trigger. A few seconds later, Metlenko gave the command.
“Oscilloscope on!”
Over on the turbine desk, Senior Turbine Control Operator Igor Kershenbaum closed the turbine steam relief valves. Six seconds later, an engineer pressed the design-basis accident button. Alexander Akimov watched as the needle on the tachometer measuring the speed of Turbine Number Eight dropped, and the four main circulation pumps began to coast down. The control room was calm and quiet; it would soon all be over. Inside the reactor, the cooling water passing through the fuel channels slowed and grew hotter. Deep in the lower part of the core, the amount of coolant turning to steam increased. The steam absorbed fewer neutrons, and reactivity increased further, releasing more heat. Still more of the water turned to steam, absorbing even fewer neutrons and adding more reactivity, more heat. The positive void effect took hold. A deadly feedback loop had begun.
Yet still the instruments on Leonid Toptunov’s control panel revealed nothing unusual. For another twenty seconds, the readings from the reactor remained within their normal limits. Akimov and Toptunov talked quietly. Over on the pump desk, Boris Stolyarchuk, absorbed in his tasks, heard no commotion. Behind them all, Deputy Chief Engineer Dyatlov remained silent and impassive. Turbine Generator Number Eight slowed to 2,300 revolutions per minute. It was time to end the test.
“SIUR—shut down the reactor!” Akimov said in a level voice. He waved his hand in the air. “AZ-5!”
Akimov lifted a transparent plastic cover on the control panel. Toptunov pushed his finger through the paper seal and pressed the circular red button beneath. After exactly thirty-six seconds, the test was over.
“The reactor has been shut down!” Toptunov said. High above them in the reactor hall, the rods’ electric servomotors whirred. The glowing displays of the 211 Selsyn monitors on the wall showed their slow descent into the reactor. One meter. Two meters—
Inside the core, what happened next took place so fast that it outstripped the recording capacity of the reactor instrumentation.
For one scant second, as the boron carbide–filled upper sections of the rods entered the top of the reactor, overall reactivity fell, just as it was supposed to. But then the graphite tips began to displace the water in the lower part of the core, adding to the positive void effect, generating steam and more reactivity. A local critical mass formed in the bottom of the reactor. After two seconds, the chain reaction began to increase at an unstoppable speed, blooming upward and outward through the core.
In the control room, just as the staff was expecting to relax, the SIUR’s annunciator panel suddenly lit up with a frightening succession of alarms. The warning lamps for “power excursion rate emergency increase” and “emergency power protection system” flashed red. Electric buzzers squawked angrily. Toptunov shouted out a warning: Power surge!
“Shut down the reactor!” Akimov repeated—yelling, this time.
Standing at the turbine desk twenty meters away, Yuri Tregub heard what he thought was the sound of Turbine Number Eight continuing to decelerate, like a Volga driving at full speed and then beginning to slow down: wooo-woo-woo-woo. But then it grew to a roar, and the building started to vibrate ominously around him. He thought it was a side effect of the test. But the reactor was destroying itself. Within three seconds, thermal power leapt to more than a hundred times maximum. In the lower southeast quadrant of the core, a handful of fuel channels overheated rapidly, and the fuel pellets approached melting point. As the temperature climbed toward 3,000 degrees centigrade, the zirconium alloy casing of the assemblies softened, ruptured, and then exploded, dispersing small pieces of metal and uranium dioxide into the surrounding channels, where they instantly evaporated the surrounding water into steam. Then the channels themselves broke apart. The AZ-5 rods jammed at their halfway point. All eight emergency steam release valves of the reactor’s protection system snapped open, but the mechanisms were quickly overwhelmed, and disintegrated.
Out on a gantry at mark +50, high above the floor of the central hall, Reactor Shop Shift Foreman Valery Perevozchenko watched in amazement as the eighty-kilogram fuel channel caps in the circular pyatachok began bouncing up and down like toy boats on a storm-tossed pond. At Toptunov’s control panel, the alarm sounded for povyshenie davleniya v RP—“pressure increase in reactor space.” The walls of the control room had begun to shake, the oscillations slow but growing in force. At his post on the pump desk, Boris Stolyarchuk heard a rising moan, the protest of a giant beast in anguish. There was a loud bang.
How could this be happening?
As the fuel channels failed, water circulation through the core ceased entirely. The check valves on the massive main circulation pumps closed, and all the remaining water trapped in the core flashed into steam. A neutron pulse surged through the dying reactor, and thermal power peaked at more than 12 billion watts. Steam pressure inside the sealed reactor space rose exponentially—eight atmospheres in a second—heaving Elena, the two-thousand-tonne concrete-and-steel upper biological shield, clear of its mountings and shearing the remaining pressure tubes at their welds. The temperature inside the reactor rose to 4,650 degrees centigrade—not quite as hot as the surface of the sun.
On the wall of Control Room Number Four, the lights of the Selsyn dials flared. The needles had stopped dead at a reading of three meters. In desperation, Akimov threw the switch releasing the AZ-5 rods from their clutches, so they could fall under their own weight into the reactor. But the needles remained frozen. It was too late.
At 1:24 a.m., there was a tremendous roar, probably caused as a mixture of hydrogen and oxygen that had formed inside the reactor space suddenly ignited. The entire building shuddered as Reactor Number Four was torn apart by a catastrophic explosion, equivalent to as much as sixty tonnes of TNT. The blast caromed off the walls of the reactor vessel, tore open the hundreds of pipes of the steam and water circuit, and tossed the upper biological shield into the air like a flipped coin; it swatted away the 350-tonne refueling machine, wrenched the high-bay bridge crane from its overhead rails, demolished the upper walls of the reactor hall, and smashed open the concrete roof, revealing the night sky beyond.
In that moment, the core of the reactor was completely destroyed. Almost seven tonnes of uranium fuel, together with pieces of control rods, zirconium channels, and graphite blocks, were pulverized into tiny fragments and sucked high into the atmosphere, forming a mixture of gases and aerosols carrying radioisotopes, including iodine 131, neptunium 239, cesium 137, strontium 90, and plutonium 239—among the most dangerous substances known to man. A further 25 to 30 tonnes of uranium and highly radioactive graphite were launched out of the core and scattered around Unit Four, starting small blazes where they fell. Exposed to the air, 1,300 tonnes of incandescent graphite rubble that remained in the reactor core caught fire immediately.
Inside his workspace on mark +12.5, a few dozen meters away from the control room, Alexander Yuvchenko was talking to a colleague who had come in to collect a can of paint. Yuvchenko heard a thud, and the floor shook beneath his feet. It felt as if something heavy—the refueling crane, perhaps—had fallen to the floor of the reactor hall. Then he heard the explosion. Yuvchenko saw the thick concrete columns and walls of the room buckle like rubber, and the door, blown in by a shock wave carrying a wet, roiling cloud of steam and dust, was torn from its hinges. Debris rained from the ceiling. The lights went out. Yuvchenko’s first impulse was to find a safe place to hide. Finally, he thought, the war with the Americans has begun.
Over in the turbine hall, turbine engineer Yuri Korneyev gazed up in horror as the corrugated steel ceiling panels above Turbine Generator Number Eight began to collapse toward him, tumbling down one after another like a series of massive playing cards, crashing onto the equipment below.
Looking out toward the central hall, former nuclear submariner Anatoly Kurguz saw a dense curta
in of steam rolling out toward him. As he was overwhelmed by the searing cloud of radioactive vapor, Kurguz struggled to swing shut the pressurized airlock door, sealing off the hall and saving his colleagues in the reactor shop. It was the last thing he did before losing consciousness.
At his post in the shadow of the main circulation pumps, Valery Khodemchuk was the first to die, vaporized instantly by the explosion or crushed beneath the mass of collapsing concrete and machinery.
Inside Control Room Number Four, tiles and masonry dust fell from the ceiling. Akimov, Toptunov, and Deputy Chief Engineer Dyatlov looked about them in confusion. A gray fog bloomed from the air-conditioning vents, and the lights winked out. When they came back on, Boris Stolyarchuk noticed a sharp, mechanical smell, unlike any he had ever encountered before. On the wall behind them, the indicator lamps monitoring levels of radiation in the room abruptly turned from green to red.
* * *
Outside the plant, on the concrete bank of the cooling pond, two off-duty workers had spent the night fishing and still had their lines in the warm outfall from the station’s reactors when they heard the first explosion. Turning toward the sound, they glanced back at the plant in time to hear a second report—a thunderous boom, like a plane breaking the sound barrier. The ground trembled, and then both men were struck by a shock wave. Black smoke curled above Unit Four, and sparks and hot debris arced upward into the night. As the smoke dispersed, they could see that the entire height of the 150-meter ventilation stack was now lit from below by a strange, cold glow.
In room 29, on the seventh floor of the Second Administration Building, Alexander Tumanov, an engineer, was working late. From his office window, he had a clear view of the northern side of the plant. At around 1:25 a.m., he heard a roar and felt the building shudder. This was followed by a cracking sound and two heavy thumps. Through the window, he saw a cascade of sparks flying out of Unit Four and what looked to him like fragments of molten metal or burning rags shooting from the unit in all directions. As he watched, larger pieces of blazing debris crashed onto the roofs of Unit Three and the auxiliary reactor equipment building, where they began to burn steadily.
Three kilometers away, the citizens of Pripyat slept on. Inside Viktor Brukhanov’s apartment on Lenina Prospekt, the telephone began to ring.
6
* * *
Saturday, April 26, 1:28 a.m., Paramilitary Fire Station Number Two
Just after 1:25 a.m., as a purple cone of iridescent flame leapt 150 meters into the air around Chernobyl’s candy-cane-striped ventilation stack, the alarm bell sounded at Paramilitary Fire Station Number Two. In the telephone dispatcher’s room, the master status board, with its hundreds of red warning bulbs—one for every room in the entire Chernobyl complex—suddenly lit up from top to bottom.
Many of the fourteen men of the third watch had been dozing on their beds in the ready room when a loud thud rattled the station windows and shook the floor, jolting them awake. They were already pulling on their boots as the emergency siren sounded, and ran out onto the concrete apron in front of the station, where the unit’s three trucks stood at the ready, keys in the ignition. They heard the dispatcher shout that there was a fire at the nuclear plant and looked over just in time to see a giant mushroom-shaped cloud blossoming into the sky above Units Three and Four, less than five hundred meters away—two minutes by road.
Lieutenant Pravik gave the order to go, and, one by one, the big red-and-white ZIL fire engines bounced off the apron and pulled away. Sergeant Alexander Petrovsky, at twenty-four the second-youngest member of the watch, didn’t have time to find his helmet and seized Pravik’s service cap instead. It was 1:28 a.m. Behind the wheel of the lead truck was Anatoly Zakharov, a thickset, gregarious thirty-three-year-old who served as the fire station’s Party secretary and who worked a second job as a lifeguard in Pripyat, where he had a pair of binoculars and a motorboat to help him pull drunken bathers from the river. Zakharov swung right and followed the plant perimeter fence, heading toward the gate of the plant at top speed. A sharp left, then through the gateway and into the grounds of the plant, flashing past the long, squat shape of the diesel generator station. The radio crackled with questions and instructions: What had happened? What was the damage? Two extra tanker trucks were already coming right behind them; the Pripyat city brigade was also on its way. Lieutenant Pravik called in a number three alarm, the highest-level emergency alert, summoning every available fire brigade in the Kiev region.
Now the giant superstructure of the plant filled the view through Zakharov’s windshield. He took the access road to the right, drove between the concrete stilts of an elevated causeway, and sped toward the northern wall of the third reactor. And there, just thirty meters away, he saw what remained of Unit Four.
* * *
Up in the Unit Four control room, everyone was talking at once, as Deputy Chief Engineer Anatoly Dyatlov struggled to understand what the instruments were saying. A constellation of warning lamps flashed red and yellow across the consoles of the turbine, reactor, and pump desks, and electric alarm buzzers honked incessantly. The news seemed grave. At Senior Unit Control Engineer Boris Stolyarchuk’s desk, the readings showed all eight main safety valves were open, and yet no water remained in the separators. This scenario was the maximum design-basis accident and an atomshchik’s worst nightmare: an active zone starved of thousands of gallons of vital coolant, raising the threat of a core meltdown.
And at Senior Reactor Control Engineer Toptunov’s control panel, the needles on the dials of the Selsyn gauges were stuck at the four-meter mark, showing the control rods had stopped dead not even halfway through their descent. Toptunov had released the rods from their electromagnetic clutches to let gravity take them all the way to their stops, but somehow they had halted before bringing the reactor to shutdown. The gray LED numbers on the reactimeter—showing activity in the core—fluttered up and down. Something was still going on in there, but Dyatlov and the technicians around him no longer had any means of controlling it.
In desperation, Dyatlov turned to the two trainee reactor control engineers who had come to work that night to observe the test, Viktor Proskuryakov and Alexander Kudryavtsev, and gave them instructions to complete the scram manually. Head up to the reactor hall, he told them, and force the control rods into the core by hand.
The two men obeyed, but almost as soon as they had left the room, Dyatlov realized his mistake: if the rods wouldn’t fall under their own weight, they would also be impossible to move manually. He ran into the corridor to call back the trainees, but they had disappeared, swallowed by the clouds of smoke and steam that had filled the halls and stairwells of Unit Four.
Returning to the control room, Dyatlov took command. He gave orders to Shift Foreman Alexander Akimov to dismiss all nonessential personnel still at their posts, including Senior Reactor Control Engineer Leonid Toptunov, who had pressed the AZ-5 scram button. Then he told Akimov to activate the emergency cooling pumps and smoke exhaust fans, and gave instructions to open the gates of the coolant pipe valves. “Lads,” he said, “we’ve got to get water into the reactor.”
* * *
Upstairs, inside the windowless senior engineers’ room on level +12.5, Alexander Yuvchenko was engulfed in dust, steam, and darkness. From beyond the shattered doorway came a terrible hissing sound. He groped along his desk for the telephone connecting him with Control Room Four, but the line was dead. Then someone from Control Room Three rang through with a command: Bring stretchers immediately.
Yuvchenko gathered a stretcher and ran downstairs toward mark +10, but before he could reach the control room, he was stopped by a dazed figure, his clothes blackened, his face bloody and unrecognizable. Only when he spoke did Yuvchenko realize it was his friend, the coolant pump operator, Viktor Degtyarenko. He said he had come from near his station, and there were others still there who needed help. Probing the humid blackness with a flashlight, Yuvchenko came upon a second operator on the ot
her side of a pile of wreckage: still able to stand but filthy, wet, and grotesquely scalded by escaping steam. He was quivering with shock but waved Yuvchenko away. “I’m all right,” he said. “Help Khodemchuk. He’s in the pump room.”
Then Yuvchenko saw his colleague Yuri Tregub emerging from the gloom. Tregub had been sent from Control Room Number Four to manually turn on the taps of the emergency high-pressure coolant system and flood the reactor core with water. Knowing this task would require at least two men, Yuvchenko told the injured pump operator where to go to get help and accompanied Tregub toward the coolant tanks. Finding the nearest entrance blocked by rubble, they went down two flights of stairs and immediately found themselves knee-deep in water. The door to the hall was jammed shut, but through a narrow gap, the two men glimpsed inside.
Everything was in ruins. The gigantic steel water tanks had been torn apart like wet cardboard, and above the wreckage, where the walls and ceiling of the hall should have been, they could see only stars. They were staring into empty space; the bowels of the benighted station were lit by moonlight.
The two men turned into the ground-level transport corridor and reeled outside into the night. Standing no more than fifty meters away from the reactor, Tregub and Yuvchenko were among the first to comprehend what had happened to Unit Four. It was a terrifying, apocalyptic sight: the roof of the reactor hall was gone, and the right-hand wall had been almost completely demolished by the force of the explosion. Half of the cooling circuit had simply disappeared: on the left, the water tanks and pipework that had once fed the main circulation pumps dangled in midair. Yuvchenko knew at that moment that Valery Khodemchuk was certainly dead: the spot where he had been standing lay beneath a steaming pile of rubble, lit by flashes from the severed ends of 6,000-volt cables as thick as a man’s arm, swaying and shorting on everything they touched, showering the wreckage with sparks.
Midnight in Chernobyl Page 11