Vintage: Chernobyl 32 years later
The Chernobyl disaster, also referred to as the Chernobyl accident, was a catastrophic nuclear accident that occurred on 25–26 April 1986 in the No 4 nuclear reactor of the Chernobyl Nuclear Power Plant, near the now-abandoned town of Pripyat, in northern Soviet Ukraine.
The accident occurred during a late-night safety test which simulated a station blackout power-failure, in the course of which both emergency safety and power-regulating systems were intentionally turned off. A combination of inherent reactor design flaws and the reactor operators arranging the core in a manner contrary to the checklist for the test, eventually resulted in uncontrolled reaction conditions. Water flashed into steam generating a destructive steam explosion and a subsequent open-air graphite fire. This fire produced considerable updrafts for about nine days and was finally contained on 4 May 1986. The lofted plumes of fission products released into the atmosphere by the fire precipitated onto eastern Europe and parts of the western USSR. The estimated radioactive inventory that was released during this very hot fire phase approximately equalled in magnitude the airborne fission products released in the initial destructive explosion.
During the accident, steam-blast effects caused two deaths within the facility: one immediately after the explosion and the other compounded by a lethal dose of radiation. Over the coming days and weeks, 134 servicemen were hospitalised with acute radiation syndrome (ARS), of which 28 firemen and employees died in the days-to-months afterward. Additionally, approximately fourteen radiation induced cancer deaths among this group of 134 hospitalised survivors were to follow within the next ten years, until 1996. Among the wider population, an excess of 15 childhood thyroid cancer deaths were documented as of 2011. It will take further time and investigation to definitively determine the elevated relative risk of cancer among the surviving employees, those that were initially hospitalised with ARS and the population at large.
The Chernobyl accident is considered the most disastrous nuclear power plant accident in history, both in terms of cost and casualties. It is one of only two nuclear energy accidents classified as a level 7 event (the maximum classification) on the International Nuclear Event Scale, the other being the Fukushima disaster in Japan in 2011. The struggle to safeguard against scenarios that were perceived as having the potential for greater catastrophe, together with later decontamination efforts of the surroundings, ultimately involved over 500,000 workers (called liquidators) and cost an estimated 18 billion roubles.
The remains of the No 4 reactor building were enclosed in a large cover which was named the "Object Shelter", often known as "sarcophagus." The purpose of the structure was to reduce the spread of the remaining radioactive dust and debris from the wreckage, thus limiting radioactive contamination and the protection of the site from further weathering. The sarcophagus was finished in December 1986, at a time when what was left of the reactor was entering the cold shutdown phase. The enclosure was not intended to be used as a radiation shield but was built quickly as occupational safety for the crews of the other undamaged reactors at the power station, with No 3 continuing to produce electricity up into 2000.
The accident motivated safety upgrades on all remaining Soviet-designed RBMK reactors, the same type as Chernobyl No 4, of which ten continue to power electric grids as of 2019.
The disaster began during a systems test on 26 April 1986 at reactor 4 of the Chernobyl plant near Pripyat and in proximity to the administrative border with Belarus and the Dnieper River. There was a sudden and unexpected power surge. When operators attempted an emergency shutdown, a much larger spike in power output occurred. This second spike led to a reactor vessel rupture and a series of steam explosions. These events exposed the graphite moderator of the reactor to air, causing it to ignite. For the next week, the resulting fire sent long plumes of highly radioactive fallout into the atmosphere over an extensive geographical area, including Pripyat. The plumes drifted over large parts of the western Soviet Union and Europe. According to official post-Soviet data, about 60 percent of the fallout landed in Belarus.
36 hours after the accident, Soviet officials enacted a 10-kilometre exclusion zone, which resulted in the rapid evacuation of 49 000 people primarily from Pripyat, the nearest large population centre. Although not communicated at the time, an immediate evacuation of the town following the accident was not advisable as the road leading out of the town had heavy nuclear fallout hotspots deposited on it. Initially, the town itself was comparatively safe due to the favourable wind direction. Until the winds began to change direction, shelter in place was considered the best safety measure for the town.
During the accident the wind changed direction; the fact that the different plumes from the reactor had different ratios of radioisotopes in them indicates that the relative release rates of different elements from the accident site was changing.
As plumes and subsequent fallout continued to be generated, the evacuation zone was increased from 10 to 30km about one week after the accident. A further 68 000 persons were evacuated, including from the town of Chernobyl itself. The surveying and detection of isolated fallout hotspots outside this zone over the following year eventually resulted in 135 000 long-term evacuees in total agreeing to be moved. The near tripling in the total number of permanently resettled persons between 1986 and 2000 from the most severely contaminated areas to approximately 350 000 is regarded as largely political in nature, with the majority of the rest evacuated in an effort to redeem loss in trust in the government. Many thousands of these evacuees would have been "better off staying home." Risk analysis in 2007, supported by DNA biomarkers, has determined that the "people still living unofficially in the abandoned lands around Chernobyl" have a lower risk of dying as a result of the elevated doses of radiation in the rural areas than "if they were exposed to the air pollution health risk in a large city such as nearby Kiev," around 100 km away.
In 2017 Philip Thomas, Professor of Risk Management at the University of Bristol, used the years of potential life lost metric to conclude that "Relocation was unjustified for 75 percent of the 335 000 people relocated after Chernobyl", finding that just 900 people among the 220 000 relocated during the second evacuation would have lost three months of life expectancy by staying home and that "none should have been asked to leave". For comparison, Thomas found that the average resident of London, a city of ~8 million, loses 4,5 months of life due to air pollution.
Russia, Ukraine and Belarus have been burdened with the continuing and substantial decontamination and monthly compensation costs of the Chernobyl accident. Although certain initiatives are legitimate, as Kalman Mizsei, the director of the UN Development Program, noted, "an industry has been built on this unfortunate event," with a "vast interest in creating a false picture."
The number of nuclear power plant constructions started each year worldwide, from 1954 to 2013. The rate of new construction builds for civilian fission-electric reactors dropped in the late 1980s, with the effects of accidents having a chilling effect. The World Association of Nuclear Operators was formed as a direct result of the accident, with the aim of creating a greater exchange of information on safety and on techniques to increase the capacity factor of operational reactors.
The accident raised the already heightened concerns about fission reactors worldwide and while most concern was focused on those of the same unusual design, hundreds of disparate nuclear reactor proposals, including those under construction at Chernobyl, reactor No 5 and 6, were eventually cancelled. With the worldwide issue generally being due to the ballooning in costs for new nuclear reactor safety system standards and the legal costs in dealing with the increasingly hostile/anxious public opinion, there was a precipitous drop in the rate of new startups after 1986.
The accident also raised concerns about the cavalier safety culture in the Soviet nuclear power industry, slowing industry growth and forcing the Soviet government to become less secretive about its procedures. The government cover-up of the Chernobyl disaster was a catalyst for glasnost, which "paved the way for reforms leading to the Soviet collapse".
Shortly after the accident, fire fighters arrived to try to extinguish the fires. First on the scene was a Chernobyl Power Station fire fighter brigade under the command of Lieutenant Volodymyr Pravik, who died on 9 May 1986 of acute radiation sickness. They were not told how dangerously radioactive the smoke and the debris were and may not even have known that the accident was anything more than a regular electrical fire, "We didn't know it was the reactor. No one had told us."
Grigorii Khmel, the driver of one of the fire engines, later described what happened, “We arrived there at 10 or 15 minutes to two in the morning.... We saw graphite scattered about. Misha asked, "Is that graphite?" I kicked it away. But one of the fighters on the other truck picked it up. "It's hot," he said. The pieces of graphite were of different sizes, some big, some small, enough to pick them up... We didn't know much about radiation. Even those who worked there had no idea. There was no water left in the trucks. Misha filled a cistern and we aimed the water at the top. Then those boys who died went up to the roof – Vashchik, Kolya and others and Volodya Pravik.... They went up the ladder ... and I never saw them again.”
Anatoli Zakharov, a fireman stationed in Chernobyl since 1980, offers a different description in 2008, “I remember joking to the others, "There must be an incredible amount of radiation here. We'll be lucky if we're all still alive in the morning." He also said, “Of course we knew! If we'd followed regulations, we would never have gone near the reactor. But it was a moral obligation, our duty. We were like kamikaze.”
The immediate priority was to extinguish fires on the roof of the station and the area around the building containing Reactor No 4 to protect No 3 and keep its core cooling systems intact. The fires were extinguished by 5h00 but many fire fighters received high doses of radiation. The fire inside reactor 4 continued to burn until 10 May 1986; it is possible that well over half of the graphite burned out.
The fire was extinguished by a combined effort of helicopters dropping over 5 000 metric tons of sand, lead, clay and neutron-absorbing boron onto the burning reactor and injection of liquid nitrogen. It is now known that virtually none of the neutron absorbers reached the core.
From eyewitness accounts of the fire fighters involved before they died (as reported on the CBC television series Witness), one described his experience of the radiation as "tasting like metal" and feeling a sensation similar to that of pins and needles all over his face. (This is similar to the description given by Louis Slotin, a Manhattan Project physicist who died days after a fatal radiation overdose from a criticality accident.)
The explosion and fire threw hot particles of the nuclear fuel and also far more dangerous fission products, radioactive isotopes such as caesium-137, iodine-131, strontium-90 and other radionuclides, into the air: the residents of the surrounding area observed the radioactive cloud on the night of the explosion.
Equipment assembled included remote-controlled bulldozers and robot-carts that could detect radioactivity and carry hot debris. Valery Legasov (first deputy director of the Kurchatov Institute of Atomic Energy in Moscow) said, in 1987, "But we learned that robots are not the great remedy for everything. Where there was very high radiation, the robot ceased to be a robot, the electronics quit working."
1h26:03 – fire alarm activated
1h28 – arrival of local fire fighters, Pravik's guard
1h35 – arrival of fire fighters from Pripyat, Kibenok's guard
1h40 – arrival of Telyatnikov
2h10 – turbine hall roof fire extinguished
2h30 – main reactor hall roof fires suppressed
3h30 – arrival of Kiev fire fighters
4h50 – fires mostly localised
6h35 – all fires extinguished‡
‡With the exception of the "fire" contained inside Reactor 4, which continued to burn for many days.
The nearby city of Pripyat was not immediately evacuated. The townspeople, in the early hours of the morning, at 1h23 local time, went about their usual business, completely oblivious to what had just happened. However, within a few hours of the explosion, dozens of people fell ill. Later, they reported severe headaches and metallic tastes in their mouths, along with uncontrollable fits of coughing and vomiting.
As the plant was run by authorities in Moscow, the government of Ukraine did not receive prompt information on the accident.
Valentyna Shevchenko, then Chairman of the Presidium of Verkhovna Rada Supreme Soviet of the Ukrainian SSR, recalls that Ukraine's acting Minister of Internal Affairs Vasyl Durdynets phoned her at work at 9h00 to report current affairs; only at the end of the conversation did he add that there had been a fire at the Chernobyl nuclear power plant but it was extinguished and everything was fine. When Shevchenko asked "How are the people?", he replied that there was nothing to be concerned about, "Some are celebrating a wedding, others are gardening and others are fishing in the Pripyat River". Shevchenko then spoke over the phone to Volodymyr Shcherbytsky, Head of the Central Committee of the CPU and de facto head of state, who said he anticipated a delegation of the state commission headed by the deputy chairman of the Council of Ministers of USSR.
A commission was set up the same day (26 April 1986) to investigate the accident. It was headed by Valery Legasov, First Deputy Director of the Kurchatov Institute of Atomic Energy and included leading nuclear specialist Evgeny Velikhov, hydro-meteorologist Yuri Izrael, radiologist Leonid Ilyin and others. They flew to Boryspil International Airport and arrived at the power plant in the evening of 26 April. By that time two people had already died and 52 were hospitalised. The delegation soon had ample evidence that the reactor was destroyed and extremely high levels of radiation had caused a number of cases of radiation exposure. In the early daylight hours of 27 April, approximately 36 hours after the initial blast, they ordered the evacuation of Pripyat. Initially it was decided to evacuate the population for three days; later this was made permanent.
By 11h00 on 27 April, buses had arrived in Pripyat to start the evacuation. The evacuation began at 14h00. A translated excerpt of the evacuation announcement follows:
For the attention of the residents of Pripyat! The City Council informs you that due to the accident at Chernobyl Power Station in the city of Pripyat the radioactive conditions in the vicinity are deteriorating. The Communist Party, its officials and the armed forces are taking necessary steps to combat this. Nevertheless, with the view to keep people as safe and healthy as possible, the children being top priority, we need to temporarily evacuate the citizens in the nearest towns of Kiev region. For these reasons, starting from 27 April 1986 2pm each apartment block will be able to have a bus at its disposal, supervised by the police and the city officials. It is highly advisable to take your documents, some vital personal belongings and a certain amount of food, just in case, with you. The senior executives of public and industrial facilities of the city has decided on the list of employees needed to stay in Pripyat to maintain these facilities in a good working order. All the houses will be guarded by the police during the evacuation period. Comrades, leaving your residences temporarily please make sure you have turned off the lights, electrical equipment and water and shut the windows. Please keep calm and orderly in the process of this short-term evacuation.
— Evacuation announcement in Pripyat, 27 April 1986 (14h00)
To expedite the evacuation, residents were told to bring only what was necessary and that they would remain evacuated for approximately three days. As a result, most personal belongings were left behind and remain there today. By 15h00, 53 000 people were evacuated to various villages of the Kiev region. The next day, talks began for evacuating people from the 10km zone. Ten days after the accident, the evacuation area was expanded to 30km. This "exclusion zone" has remained ever since, although its shape has changed and its size has been expanded.
Evacuation began long before the accident was publicly acknowledged by the Soviet Union. In the morning of 28 April 1986, radiation levels set off alarms at the Forsmark Nuclear Power Plant in Sweden, over 1 000 kilometres from the Chernobyl Plant. Workers at Forsmark reported the case to the Swedish Radiation Safety Authority, which determined that the radiation had originated elsewhere. That day, the Swedish government contacted the Soviet government to inquire about whether there had been a nuclear accident in the Soviet Union. The Soviet government initially denied it and it was only after the Swedish government suggested they were about to file an official alert with the IAEA, that the Soviet government admitted an accident took place at Chernobyl. At first, the Soviets only conceded that a minor accident had occurred but once they began evacuating over 100 000 people, the full-scale of the situation was realised by the global community.
At 21h02 the evening of 28 April, a 20-second announcement was read in the TV news programme Vremya:
There has been an accident at the Chernobyl Nuclear Power Plant. One of the nuclear reactors was damaged. The effects of the accident are being remedied. Assistance has been provided for any affected people. An investigative commission has been set up.
— Vremya, 28 April 1986 (21h00)
This was the entirety of the announcement of the accident. The Telegraph Agency of the Soviet Union (TASS) then discussed Three Mile Island and other American nuclear accidents, an example of the common Soviet tactic of emphasising foreign disasters when one occurred in the Soviet Union. The mention of a commission, however, indicated to observers the seriousness of the incident and subsequent state radio broadcasts were replaced with classical music, which was a common method of preparing the public for an announcement of a tragedy. Around the same time, ABC News released its report about the disaster.
Shevchenko was the first of the Ukrainian state top officials to arrive at the disaster site early on 28 April. There she spoke with members of medical staff and people, who were calm and hopeful that they could soon return to their homes. Shevchenko returned home near midnight, stopping at a radiological checkpoint in Vilcha, one of the first that were set up soon after the accident.
There was a notification from Moscow that there was no reason to postpone the 1 May International Workers' Day celebrations in Kiev (including the annual parade) but on 30 April a meeting of the Political bureau of the Central Committee of CPU took place to discuss the plan for the upcoming celebration. Scientists were reporting that the radiological background in Kiev city was normal. At the meeting, which was finished at 18:00, it was decided to shorten celebrations from the regular 3,5–4 to under two hours.
Several buildings in Pripyat were officially kept open after the disaster to be used by workers still involved with the plant. These included the Jupiter Factory which closed in 1996 and the Azure Swimming Pool, used by the liquidators for recreation during the clean-up, which closed in 1998.
During the dry seasons, a perennial concern is forests that have been contaminated by radioactive material catching on fire. The dry conditions and build-up of debris make the forests a ripe breeding ground for wildfires. Depending on the prevailing atmospheric conditions, the fires could potentially spread the radioactive material further outwards from the exclusion zone in the smoke. In Belarus, the Bellesrad organisation is tasked with overseeing the food cultivation and forestry management in the area.