MELTDOWN

The V.I. Lenin Nuclear Power Station at Chernobyl, with its four RBMK nuclear reactors, was the pride of the Soviet Union, generating electricity for 30 million homes and businesses.

It was an operating system the West had rejected because of concerns about design flaws and its safety, but the Soviets were confident it was secure. In an interview in Feb ruary 1986, Vitali Sklyarov, the Minister of Power and electrification of the Ukraine, said: ‘The odds of a meltdown are one in 10,000 years.’

As a major drama series, Chernobyl, sheds new light on the impact of one of the world’s worst nuclear incidents — ranked equal with Fukushima in Japan, in 2011 — JONAThAN MAYO reveals, in gripping detail, how the catastrophe unfolded minute by minute...

11pm

IT hAS been an unseasonably warm day at Chernobyl, in northern Soviet Ukraine, and the cherry trees are already in bloom. In the shadow of the power station, scores of fishermen are settling on the edge of a large artificial pond — its waters are used to cool the plant’s four giant reactors. Power station bosses boast that the water is so safe they are breeding fish there. Angling is prohibited but the fishermen know that at this time of night no one will bother them.

Anatoly Dyatlov, Chernobyl’s 55-year-old deputy chief engineer, arrives at work. Tonight he will be overseeing a test authorised by the Soviet energy Authority to assess the plant’s ability to keep its latest reactor, No 4, cool in the event of a power cut.

The test should have been carried out before the reactor became operational in 1984, so it is two years overdue.

The son of a Siberian peasant, Dyatlov has risen to become the leading nuclear expert at Chernobyl. he is an intolerant manager and keeps a notebook to write down the names of those who cross him.

11.45

eNgINeeR Sasha Yuvchenko, 24, clocks on for the night shift. The tall young man is one of 176 workers at the power station tonight. he changes into regulation white overalls and cap and makes his way to his office, between Reactors No 3 and No 4, to be briefed by the engineer he is taking over from.

A former champion rower, he has just said goodbye to his wife Natasha and their two year- old son Kirill in the nearby city of Pripyat, built from scratch in 1970 to house the thousands of workers at the plant. It now has a population of just under 50,000.

The nuclear industry is prestigious and Pripyat’s supermarkets are better stocked than most in the Soviet Union. It has good schools and sports facilities.

SATURDAY, APRIL 26, 1986 00.20

The large control room of Reactor No 4 is harshly lit by fluorescent lights and full of cigarette smoke. The atmosphere is tense. No one has done a shutdown test like this before.

Anatoly Dyatlov is arguing with the shift foreman, Alexander Akimov, about the level of power produced by the reactor at which it is safe to begin the test. The lower the power, the more danger there is of an accidental shutdown.

The rule book, which Akimov has in his hands, stipulates that it should be no less than 700 megawatts, otherwise the reactor will become unstable. Dyatlov insists that 200 megawatts is safe. Akimov is outranked by Dyatlov, so he reluctantly agrees to allow the test to continue.

00.28

The reactor control engineer, 26year- old Leonid Toptunov, who has only been in his job a few months, switches the system from manual to automatic. But he misses a vital step, failing to select a megawatt level at which the control room computer would then operate.

The computer defaults to the last level that had been inputted — near zero. Power in Reactor No 4 falls almost to zero megawatts. The reactor is now unstable and has the potential to explode.

Alarms begin to sound. Alexander Akimov says that the rulebook states the test should now be aborted. But Dyatlov wants it completed and insists they continue. That the reactor might explode is unthinkable to him.

In the reactor’s core are more than 1,600 radioactive uranium235 metal fuel rods. Uranium-235 is unstable, its atoms constantly breaking down to release subatomic particles called neutrons — which hit more uranium atoms, so triggering a chain reaction that generates enormous heat and energy.

In a controlled chain reaction, this heat can be used to turn water into steam that powers a turbine to generate electricity.

Control of the reaction depends on 211 boron control rods spread throughout the reactor’s core. They can absorb neutrons and so slow the chain reaction.

If the rods are raised, the chain reaction accelerates. If they are taken out altogether, the engineers lose their ability to stop the reactor overheating.

In an attempt to lift the power level, Dyatlov orders the control rods to be raised. Alarmed by the likely loss of control, Toptunov refuses to do so.

1am

ThReATeNeD with the sack by Dyatlov, Toptunov finally agrees to raise the control rods and the reactor is powered up to what is regarded as a safer 200 megawatts. But it is increasingly unstable.

1.23

The control room computer is demanding that the reactor be shut down, but the test is scheduled to begin. Alexander Akimov hesitates over the controls. ‘What are you waiting for?’ Dyatlov says impatiently.

1.23 and 40 seconds

The temperature in the reactor is now 4,650c — almost as hot as the surface of the Sun. Akimov presses the button to start the test, inadvertently starting a catastrophic chain reaction that generates enormous amounts of steam.

Suddenly, Valeri Perevozchenko, an engineer who had been on a catwalk high above the reactor, bursts into the control room in a panic, shouting that he has seen the 350kg (772lb) caps on the fuel rods jumping up and down in their sockets. Then the control room walls start shaking and the men hear a sound like a long, low human moan — followed by a huge explosion as a build-up of steam blasts the 200- ton concrete shield above the reactor into the air.

In the control room, Akimov shouts: ‘Shut down the reactor!’ But it is too late.

1.23 and 45 seconds

TheRe is a second, much louder blast as 50 tons of radioactive uranium fuel from the reactor core — ten times the amount at hiroshima — vaporises and is blasted into the atmosphere. Uranium-235 has a half-life (the time it takes for the radioactivity to fall to half its original value) of 700 million years.

A further 70 tons of uranium and 900 tons of radioactive graphite is scattered around the surrounding area, including on Reactor No 3.

In No 4’s reactor core, 800 tons of graphite start to burn, sending more lethal radioactive material 3,000 ft into the night sky. The men fishing by the cooling pond are illuminated by the flames.

In the control room, dust and debris are falling from the ceiling and the terrified technicians think they are in the middle of an earthquake. No one imagines it could possibly be the reactor.

More alarms sound, the fluorescent lights go off and the emergency generators kick in.

Sasha Yuvchenko is in the senior engineer room, talking to a colleague who has come to collect a tin of paint, when a shockwave hits the room. ‘ The metre-thick concrete walls were bent like rubber. I thought war with the Americans had begun,’ he later said.

everywhere there is an ominous hissing noise. Yuvchenko runs from the room and, behind a pile of rubble, finds a badly scalded and bloody pump operator, who tells him he must rescue their colleague Valery Khodemchuk, who is in the main circulating pump room close to the explosion. ‘he’s still trapped in there!’

Outside Paramilitary Fire Station Number Two, 500 yards away, firemen enjoying the cool night air watch in horror as a giant mushroom cloud of smoke rises from the power station. In their operations room, hundreds of red lights are flashing — one for every room in the power plant.

The crews run to their trucks. In charge is youthful but respected 23-year- old Lieutenant Vladimir Pravik. On his radio, he summons every fire crew in the region.

1.25

AT hIS home in Pripyat, Viktor Bryukhanov, the director of the Chernobyl plant, is woken by a phone call. his wife watches as the colour drains from his face. Bryukhanov gets dressed and leaves without saying a word.

Sasha Yuvchenko is still searching for Valery Khodemchuk in the reactor building. he looks up and sees stars — the ceiling has disappeared.

Sparks are showering from severed power cables and a bluewhite beam of radiation from the core is shooting upwards.

‘ I remember thinking how beautiful it was,’ Yuvchenko said afterwards. There is no sign of Khodemchuk.

The control room of Reactor No 4 is filled with dust. A shocked Dyatlov is trying to understand what has happened. Unaware that the reactor is a blazing volcano, he hopes water might save it from damage and orders Akimov to activate the emergency cooling pumps. ‘We’ve got to get water into the reactor!’

1.35

ON A ledge more than 100ft up in the remains of the main reactor hall, three technicians are looking down into the blazing reactor. A few yards away, Sasha Yuvchenko is straining to hold the steel and concrete reactor hall door open. It has come off its hinges. If it closes, his three colleagues will be trapped inside.

Yuvchenko doesn’t realise that radiation from the door is already attacking his skin. Although the three men on the ledge are only there for a minute, the radiation will kill them in less than two weeks. Sasha Yuvchenko will die of leukaemia in 2008.

1.38

The fire crews from Paramilitary Fire Station Number Two arrive at the power station. They are stunned to see that the roof of Reactor No 4 is missing.

Lieutenant Pravik says to his colleague Leonid Shavrey: ‘We’ll really have our work cut out here.’ Shavrey knows they are heading into danger. ‘My hair stood on end,’ he later said.

There is a strange vapour in the air.

IT HINGED ON THE PRESS OF A BUTTON AND PETTY SQUABBLING. IT LED TO A NUCLEAR DISASTER THAT COULD HAVE WIPED OUT LIFE ON EARTH. ON THE EVE OF A CHILLING TV DRAMA, A MINUTE BY MINUTE ACCOUNT OF THE CHERNOBYL CATASTROPHE

1.50

VIKTOR Bryukhanov, the director of the plant, drives through the gates and sees the devastation for the first time. He knows his career is over. ‘I’m going to prison,’ he thinks. He had overseen the building of the power station and, like many Soviet officials, had cut corners, signed off tests that were never conducted and hit targets by reducing the time spent in making urgent repairs.

Bryukhanov orders that the power station’s underground bunker — built as a command post in case of nuclear war — be opened, then tells his managers to assess the situation in their departments and report back to him. Soon the bunker is filled with 40 men, all frantically making telephone calls.

In the rubble of the kilometrelong turbine hall that links all four reactors, a team of engineers armed with a single torch are searching desperately for their colleague Vladimir Shashenok. They find him barely alive, badly burned and with bloody foam coming out of his mouth. They pick him up and carry him to safety.

Above them on the burning turbine hall roof, firemen Leonid Shavrey and Vladimir Pryshchepa are trying to extinguish the flames. Reluctant to use water because of the danger from exposed electricity cables, they are throwing sand on the fires and beating them out with their canvas hoses.

Contrary to fire regulations, the roof is covered with highly flammable bitumen. Shavrey later recalled: ‘ With the slightest increase in temperature, the bitumen immediately caught fire. If you stepped on it, you couldn’t put one foot in front of the other — it tore off your boots.’

The men have no training in putting out fires such as this, and are kicking away burning debris with their boots, not realising that it is radioactive.

1.55

DR VALENTYN Belokon, 28, arrives from Pripyat Hospital armed only with painkillers to treat burns. But there are no burns victims yet. A young worker from Reactor No 3 is brought to him suffering from nausea and a violent headache. Belokon assumes the man was drinking the night before.

2am

THE young fire chief, Lieutenant Pravik, is concerned that the roof of Reactor No 3 (built close to Reactor No 4 to save money) is now on fire. A westerly wind could spread the flames farther, to Reactors 1 and 2, which are both still operating.

Even though Pravik’s walkietalkie isn’t working and they have no anti-radiation equipment, he bravely leads his men up a fire ladder to the roof of Reactor No 3.

On the roof of the turbine hall, fireman Leonid Shavrey is getting so hot he removes his helmet. The fishermen, still by the cooling pond, see this and cheer what they think is bravado. ‘He’s taken his helmet off!’ says one. ‘He’s a real hero!’

In Reactor No 4’s control room, Anatoly Dyatlov, the dogmatic deputy chief engineer, is told by a technician that the reactor has blown up. Dyatlov refuses to believe it and heads outside to see for himself. He is stunned by the apocalyptic scene before him.

2.05

THE local fire brigade chief, Lieutenant- colonel Leonid Teliatnikov, has assembled a team of 28 men to put out the reactor fires. Thoughts of his family flash through his mind, but his main worry is that his men won’t have the strength to keep going until reinforcements arrive.

2.10

THE condition of the young man Dr Belokon thinks is hung over worsens. He is very pale and continually muttering ‘The horror of it! The horror of it!’ Belokon gives him a sedative. More men appear with similar symptoms.

Leonid Shavrey’s younger brother Petr, who is also a fireman, arrives at the power station not wearing

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