Before Chernobyl: the secrets that paved the way for disaster

Officially, neither the town nor the Mayak plant even existed. They were so secret that their names had never appeared on any maps; they were nodes on a network of so-called closed cities known only by numbers and operated by the Ministry of Medium Machine-Building, the clandestine agency that oversaw the Soviet atom weapons programme and much of the civilian nuclear industry. Scientists and technicians who worked there had access to privileges and facilities out of the reach of most Soviet citizens; in exchange, they were forbidden from communicating with friends and relatives in the ‘big world’ – essentially, anywhere beyond the perimeter wire.

The blast was so powerful that it hurled the tank’s 160-tonne lid into the air and sent a pillar of smoke and dust soaring high in the sky

Waste Tank #14 was an underground silo filled with highly radioactive slurry, an intensely toxic by-product of plutonium processing for atomic weapons. When internal cooling and temperature-monitoring systems failed, the tank boiled dry. The resulting blast was so powerful that it hurled the tank’s 160-tonne lid 20 metres into the air, blew out the windows of the convicts’ barracks, and sent a pillar of dust and smoke soaring over half a mile into the sky.

Grey radioactive ash blanketed the nearby industrial zone. Soldiers labouring there were soon admitted to hospital, suffering bleeding and vomiting. By the time the senior management of the Mayak plant became aware of the catastrophic accident, 74 million gigabecquerels of radioactive contamination had begun to drift over the surrounding Chelyabinsk Oblast (province) and east across the Urals in a deadly swathe nearly four miles wide and 30 miles long.

The next day, as light rain and thick black snow fell on the peasant settlements beyond the wire, military ‘liquidation’ of the accident began. Soldiers used shovels to toss pieces of the shattered storage tank into a nearby swamp. Eventually, more than 10,000 people were evacuated from the surrounding countryside – but only after they had been instructed to harvest their crops and bury them. Troops herded cattle into open pits and shot them. Entire villages were ploughed into the ground, and as many as half a million men, women and children were exposed to dangerous levels of radioactivity.

• Read more: Chernobyl: the story of a tragedy

Rumours of a nuclear accident in the Urals eventually reached the west, but the Soviet government refused to acknowledge that the Mayak Production Association even existed, let alone that anything might have happened there. Trying to uncover the details, the CIA later sent high-altitude U-2 spy aircraft on missions over the area to photograph the site; it was on the second of these reconnaissance flights, in 1960, that US pilot Francis Gary Powers was shot down by the Soviets, in what became one of the defining incidents of the Cold War.

The truth about the explosion in Waste Tank #14 would not emerge for decades. Yet the Mayak disaster was, at the time, the worst nuclear accident in history – a dubious honour it would hold until the devastating events at Chernobyl in April 1986, nearly three decades later.

As one of the 12 original signatories to the charter of the International Atomic Energy Agency (IAEA) that came into effect in July 1957, the government of the USSR had agreed to report any nuclear accidents within its borders. The Soviet Union came to the table as a global leader in the field of civilian nuclear power, having only recently made public the completion of the world’s first commercial nuclear power plant, in the city of Obninsk outside Moscow. In the decades following the establishment of the IAEA, a succession of embarrassing and dangerous setbacks plagued the developing nuclear industries in Britain and the United States. Most notable were the devastating fire at Windscale in Cumbria, north-west England in October 1957, and the reactor meltdown at Three Mile Island, Pennsylvania in March 1979.

By contrast, during that period the Soviet government failed to register with the IAEA a single incident at a nuclear power plant or reprocessing facility, helping to foster the illusion that the USSR was operating the safest atomic industry in the world. Officially, the explosion that tore apart Reactor Number Four of the Chernobyl nuclear power plant in northern Ukraine on 26 April 1986 was an unprecedented tragedy – a stain on the otherwise spotless record of the Soviet Union’s most advanced and prestigious technology.

The truth was very different. The foundations of the road to Chernobyl had in fact been laid decades before that fatal explosion in 1986. The disaster had its origins in the pattern of secrecy and ruthless expedience that characterised almost every aspect of Soviet government, and was particularly pervasive in the shadowy Ministry of Medium Machine-Building and among the architects of the civilian nuclear programme at Moscow’s Kurchatov Institute of Atomic Energy.

The roots of the disaster can be traced back to the choice of reactor type selected for Chernobyl. By the late 1960s, the pace of development in the USSR’s civilian nuclear industry had fallen behind those in the west. In a bid to catch up, Soviet leaders launched an accelerated programme of power-plant construction. Pressed for time, and hobbled by backward Soviet tooling and manufacturing that made the mass production of western-style reactors impossible, the model adopted was the RBMK (Reaktor Bolshoy Moshchnosti Kanalnyy; High Power Channel-type Reactor). A gigantic cylinder of graphite blocks housing tonnes of uranium fuel pellets cooled by water, the RBMK was based on the same principles as those built at Mayak to make plutonium for nuclear weapons, scaled up to titanic proportions and modified to generate electricity. It was trumpeted as the Soviet ‘national’ reactor, unique to the USSR and far larger than those in the United States.

• Eyewitness account: the aftermath of the 1986 Chernobyl disaster

However, almost all graphite-water reactors suffered from the same fundamental drawback that made them susceptible to a loss of operator control of the nuclear fission process in the reactor core, leading to a meltdown or explosion. Before the initial designs of the RBMK had even left the drawing board, whistle-blowers within the Soviet atomic energy establishment warned their superiors that this reactor was too dangerous to enter civilian use. Their concerns were ignored, though, and it was rushed into production.

By the time the first reactor came online in Chernobyl in 1977, the first of what would prove to be a succession of faults with the RBMK had already become apparent to its designers. As well as being inherently unstable, the reactor was so huge that it proved hard to control, and its instrumentation was so rudimentary that operators could sometimes only guess at what was going on inside it. The complex plumbing was plagued with leaks, and staff had to work the control panel so hard that the buttons wore out and had to be repeatedly replaced.

Most worrying of all, in 1983 engineers testing the RBMK reactor at a new nuclear plant in Ignalina, Lithuania discovered that the reactor’s emergency control rods – designed to regulate and, if necessary, halt the fission process inside the reactor core – had a potentially catastrophic flaw. For the first fraction of a second after they were inserted, instead of reducing power, in some circumstances they might momentarily increase it. In such a key safety system, this was a chilling potential inversion – as if the brakes and accelerator of a car had been wired in reverse. Nuclear engineering experts in Moscow warned their bosses that accidents were not merely possible but likely in the normal course of operation. Once again, their warnings went largely unheeded.

True, the authorities eventually ordered some modifications to RBMK reactors that were already online at plants around the USSR; however, the work was complex and expensive, so was scheduled to be conducted piecemeal, one reactor at a time. The fourth reactor at the Chernobyl station – the newest and most advanced of the line – was slated to be fixed only after its first scheduled maintenance shutdown at the end of April 1986.

In the meantime, the litany of accidents at civilian nuclear plants around the Soviet Union continued to be hushed up, their details kept secret even from those who worked elsewhere in the industry. In October 1982, a generator exploded at the Metsamor nuclear plant in Armenia. The turbine hall burned down, and an emergency team was airlifted in from more than 3,000 miles away in the Arctic Circle to save the core. Less than three years later, during the start-up of a new reactor at Balakovo in the Russian Republic, a relief valve burst, releasing superheated steam into the annular compartments surrounding the reactor well; 14 men were poached alive. Such incidents were shrouded in secrecy, and word reached nuclear operators elsewhere only through rumours and hints in the official Communist Party newspaper Pravda. Because of this, opportunities to learn valuable lessons from mistakes and accidents were missed.

Incidents were shrouded in secrecy, meaning that chances to learn lessons from mistakes and accidents were lost

The Chernobyl plant – ostensibly among the best-performing nuclear power stations in the USSR, and a prized posting for atomic workers from across the Soviet Union – was certainly not immune from problems. After years dogged by faults and accidental shutdowns, on 9 September 1982 the plant suffered a major incident: a partial meltdown in the core of Reactor Number 1.

That evening, Nikolai Steinberg, the 35-yearold head of turbine units 3 and 4 at the plant, was sitting in his office. Gazing from his window as the end of the working day approached, he saw steam rising from the chimney stack that towered over the reactor building. He knew that it meant trouble, and was alert to the possibility of a radiation leak, but when he phoned the reactor control room to warn them, the shift supervisor brushed him off. Steinberg mustered his men to wait for an emergency call, but no summons came.

Afterwards, the director of the plant and his chief engineer insisted that no radioactive material had been released into the atmosphere as a result of the meltdown, and the KGB took measures to “prevent the spread of panic-mongering, provocative rumours and other negative manifestations”. In fact, radioactive contamination – including highly toxic iodine-131, hot particles containing zinc-65 and zirconium-niobium-95, and fragments of uranium fuel from the core of Reactor Number 1 – had been carried on the wind and deposited in rain over the nearby city of Pripyat and other locations over eight miles from the plant.

A team of experts from the state atomic energy authority insisted that there was nothing to be concerned about; contaminated areas around the plant were simply sluiced down with water and covered with soil and leaves. Trucks were deployed to wash the streets of Pripyat with decontaminant, and the main thoroughfare into town was discreetly repaved with asphalt. The cover-up was successful and the town’s citizens, numbering tens of thousands, remained none the wiser. It would be years before Steinberg uncovered the truth.

By the time the next accident shook Chernobyl on 26 April 1986, less than four years later, Steinberg had moved on, disillusioned by the moral collapse within the workforce at the plant. He was hundreds of miles away at a new nuclear station in Russia when a pair of explosions tore apart the core of Chernobyl’s Reactor Number 4, obliterating the roof and the upper reaches of the reactor building, setting fire to the graphite in the core and creating a blaze that almost proved impossible to extinguish. The plume of radionuclides released by the blast was snatched away by high-altitude winds, and rainclouds soon deposited fallout on Scandinavia, Wales and Scotland.

Days passed before Steinberg, still sealed within the clandestine bubble of the nuclear state, received word of what had happened. But by then the invisible clouds of radioactive contamination had begun to encircle the northern hemisphere, beyond the reach of even the Medium Machine Building, beginning a process that would not merely reveal the deepest secrets of the RBMK reactor and the Soviet nuclear industry, but would help unravel the fabric of the USSR itself.

Adam Higginbotham is a journalist and author of Midnight in Chernobyl: The Untold Story of the World’s Greatest Nuclear Disaster (Bantam, 2019)

This content first appeared in issue 16 of BBC World Histories magazine