Previous accidents, dog hunts, military plutonium, lunar rovers, 40-second shifts, suicides and the engineer who after Chernobyl went to work at another power station. Among the folds of the event that shook the world's energy history, there are still many things to discover — things that make you think.
The Chernobyl plant consisted of four reactors of 1,000 MW each, producing one tenth of all Ukrainian electricity. The first reactor was commissioned in 1977, the second in 1978, the third in 1981, and the fourth (the one involved in the accident) in 1983. These were RBMK-1000 reactors (РБМК – Реактор Большой Мощности Канальный, or Reaktor Bolshoi Moshchnosty Kanalny, meaning 'high-power channel reactor'), produced only in the Soviet Union. The plant had been designed to generate electricity but also plutonium. It used ordinary water for cooling and graphite as a moderator: this made it possible to use natural uranium as fuel, significantly lowering construction and operating costs. That is why the electricity was cheaper. The problem is that a plant of this kind is inherently unstable, because in the absence of water, rather than shutting down (as many Western reactors do), it surges in power to extreme consequences. The disaster served as a lesson to the world, not only to communist countries: from that point on, a sweeping rethink of national energy policies began.
On 9 September 1982, an accident occurred in reactor no. 1 at the Chernobyl nuclear power plant, accompanied by the release of radioactive substances into the environment. The accident was caused by the rupture of the reactor's fuel channel, which led to a release of a high peak of radioactivity. High levels of iodine and caesium-137 were detected outside the plant. The reactor remained shut down for months, was then repaired and restarted.
In the hours immediately following the explosion, decisions were taken in sequence to pump water into the reactor crater to cool it, then to inject liquid nitrogen into the ground, and then to attempt to bury it under loads of sand and boron dropped from above by 1,800 helicopters. The liquid nitrogen injected into the ground worked. The water did not — on the contrary, it reacted with the graphite and the incandescent metal of the pipes, producing hydrogen, short circuits and further explosions — nor did the sand dropped by the helicopters, most of which dispersed and missed the target, but which above all increased the heating of the core by preventing heat exchange with the atmosphere. On 9 May 1986, the 5,000 tonnes of boron, dolomite, clay and boron carbide discharged onto the reactor in the first days in an attempt to smother the graphite fire and stem the release of radiation weighed on the already cracked structures and collapsed further into the chasm. This new collapse released an additional, weaker column of radioactive smoke over a radius of 35 kilometres (already evacuated) around the plant.
According to experts, there was a good chance that the still-incandescent and highly active core could sink further, coming into contact with groundwater and thereby causing new steam explosions. Miners were called in and worked with their bare hands beneath the reactor, digging a tunnel to insert cooling systems into the lower levels of the plant.
The decision to allow the production of weapons-grade plutonium in a civil reactor proved particularly ill-fated. It required the installation of large cranes above the reactor core to allow fuel to be moved without shutting the reactor down. This meant constructing very tall buildings — over 70 metres — which it was impossible to build with the structural robustness and containment properties required for nuclear safety. The containment building, in fact, had the characteristics only of an ordinary civil construction. Military plutonium production also required running the plant at temperatures far too high by safety standards: at operating level, the graphite temperature was 600 °C, with peaks of 700 °C, close to thresholds for extremely dangerous reactions between the materials.
The picture painted of the evening after the accident is haunting — when, incredibly, the evacuation of the city of 47,000 inhabitants had still not been ordered. Certainly, the graphite fire rising with multicoloured flames and rainbow lights above the blanket of smoke must have been spectacular in the evening. Enough to attract everyone's curiosity. Indeed, 24 hours after the explosion, the residents of Pripyat were all still there. So they decided to go, with their families or friends, to watch the spectacle from the most panoramic vantage point: the railway bridge, from which the view was perfect. What they did not know, and what nobody had told them, was that the gentle evening breeze was carrying 500 roentgens per hour of radioactivity. They all died shortly afterwards.
In the months that followed, hunting parties were organised around the exclusion zone perimeter to shoot all the dogs abandoned by fleeing residents. A measure that appeared cruel, yet with some background to it. One aim was to prevent radioactivity from spreading further through the bodies of stray and dying animals on the run. Another was to prevent these packs of dogs, as they went feral, from attacking the workers assigned to decontamination. Finally, there was the question of euthanasia: a quick death was perhaps preferable to an agony of starvation, radiation sickness, or the birth of deformed litters. "During the hunts, the dogs were near their homes, waiting for their owners to return," recounts Viktor Verzhikovskiy, head of the local hunters' association in Khoyniki, in a harrowing testimony. "And they were happy to see us — they came running towards us. We shot them in their homes, or in their gardens. Then we had to load the carcasses onto trucks. It wasn't pleasant, not at all. They couldn't understand: why were we killing them? They were easy to kill — they were domestic animals, affectionate, afraid of neither people nor guns."
The level of radiation inside the building is such that it burns camera film in a matter of seconds and destroys even the remote-controlled vehicles sent by Germany, the USSR and Japan. It was absolutely necessary to clear the site of radioactive graphite debris, capable of delivering lethal doses of radiation to anyone who came into contact with it. Attempts were made using small remote-controlled bulldozers, treated like scale models, but they malfunctioned due to the radiation. There were even attempts to repurpose rovers designed for lunar exploration, fitting them with buckets and lead partitions — without success. In the end, recourse was made to liquidators, hundreds of thousands of specialist workers. Among the 600,000 liquidators were also those who worked on the construction of the outer sarcophagus. In the first two years, 1986–1987, more than 200,000 workers took turns, first clearing the site and then building the protective shield. The reactor needed to be contained as quickly as possible, along with the explosion debris, which included 180 tonnes of fuel and highly radioactive dust and 740,000 cubic metres of contaminated rubble. They were dressed in lead suits that became unusable after a single use. They would enter the zone in insulated vehicles, then collect and throw away graphite debris for 40 seconds before being forced to retreat immediately. Any longer, and they would have absorbed a lethal dose of radiation.
Valerij Legasov was one of Russia's most eminent scientists, a chemist by training. He rose with remarkable speed through Soviet circles — and the Communist Party — to become deputy director of the I. V. Kurchatov Institute for Atomic Energy: the very institute where the RBMK reactors, those used at Chernobyl, were designed. He also headed the emergency scientific commission sent to the site of the explosion just hours afterwards to manage the initial operations. In the months that followed, he took a position contrary to the version that placed all the blame on the plant's staff. His persistence, however, ruined his career. With his reputation in the balance, his proposal for reform of the Soviet scientific community rejected, his health deteriorating as a direct result of the radiation he had absorbed and, perhaps, the weight of the victims on his conscience, on 27 April 1988 — shortly after the second anniversary of the nuclear catastrophe — Legasov hanged himself.
The Politburo found six Chernobyl managers guilty — they had been charged as early as July 1986 — but admitted no design flaw in the RBMK reactor, as doing so would have undermined the credibility of Soviet superpower technology. One of them, chief engineer Nikolai Fomin, was declared of unsound mind during his imprisonment in 1990 and transferred to a psychiatric hospital. Incredibly, once his recovery was certified, he was permitted to return to work at the Kalinin nuclear power station, near Moscow.
For years, raids have been taking place in the now-uninhabited flats of Prypiat and the some twenty permanently evacuated villages. The Kiev court has repeatedly convicted those responsible for looting — an activity dangerous not only in legal terms, but also because stealing metals and materials that have absorbed such high doses of radiation, in order to melt them down and put them back into circulation, risks spreading nuclear contamination.
The temperature inside the sarcophagus still reaches 1,000 degrees centigrade in some places, near the core, to this day. First discovered by a Soviet scientific expedition into the reactor in December 1986, it is now known that something is still burning in that infernal chamber, generating semi-liquid lava so radioactive that five minutes of exposure would leave a person with two days to live.
Should the magma carve a path towards the ground or the water table, it could trigger another radioactive explosion or contaminate the entire water supply. Thirty years on, the heart of the plant is still bleeding, and will continue to do so for centuries — a permanent testament to the unresolved risks of nuclear energy.