25 Jul What happened at Chernobyl in 1986?
On 26 April 1986, one of the most damaging nuclear disasters in history occurred in Ukraine. The Chernobyl nuclear disaster, despite having happened 33 years ago, continues to affect our environment dramatically. What began as a simple safety test of the plant would escalate into a nuclear event that would shape the global landscape for a generation. With enormous scientific, legislative and cultural impact, the Chernobyl nuclear disaster is one of the most prominent events in modern history. Upon closer inspection, one can investigate the not only scientific, but historical and political forces at play during and following the disaster, involving an estimated 600,000 people at the time.
The day of the disaster began as any other would in Pripyat, the town established specifically to house plant workers and their families. The safety test was designed to depower the plant with an emergency shutdown in order to test how well the backup generators could supply water to Reactor No. 4. It is important to note that this test was not reliable, went against safety guidelines. All tests such as the one performed had to be approved by the lead designer of the RMBK reactor used at Chernobyl. Needless to say, this approval was not granted. Additionally, the test was only approved by the director of the plant, and nobody else, which was also against safety guidelines. It had never been proven that the plant could function for long with the diesel backup generators alone, meaning that the plant ran the risk of being unable to adequately cool the incredibly hot uranium core.
The test began at 1:23:04 AM. With the steam that lead to the water supply being shut off, the backup generators were supposed to be able to supply enough power to the water pumps within 39 seconds. However, the main turbines for the water supply could not maintain the flow of water into the reactor in this interim period. As a result, steam began to form in the reactor core. Due to the design of the reactor, this formation of steam caused a positive feedback loop. This in turn raised the rate of fission in the core, increasing the temperature and supplying more steam, which further increased the rate of reaction.
This was supposed to be moderated by the reactor’s control rods, 12 of which were lowered by the computer system. The rest of the rods, however, had been manually retracted. At this point, a button was pressed in the control system that forcibly lowered all the control rods, even those that had been retracted earlier. While it is unknown why exactly this button was pressed, it can be inferred that it was in reaction to the huge increase in the core’s temperature. The result of the rods lowering was a displacement of water within the reactor, due to the unorthodox and unsafe design of the control rods. This caused a spike in power from the reactor, which was a known issue of the RMBK control rods.
The resulting power increase caused the core to overheat rapidly, causing fractures in the control rods. These fractures stopped the control rods from fully inserting, limiting their ability to slow the rate of reaction in the core. The end result of this cascade was a dangerous increase in power in the core. Steam buildup due to the temperature within the core then caused the reinforced cladding to rupture, allowing the fuel elements to enter the coolant directly. The last power reading was 30,000MW of power, ten times the normal power capacity, however it is unknown if the real value was actually higher, as data was stopped by the following explosion.
This explosion explosion followed by a second, more powerful one. This ruptured the containment of the core and scattered hot graphite from the control rods across the surrounding environment. After this, a fire was started that began to spread highly radioactive particles into the air, drifting towards the sleeping town of Pripyat.
Bitumen on the roof of the plant caught fire in multiple places, at which point firefighters were on their way. They did not know about the now enormous levels of radioactive material in the area. This was because the staff of the power plant did not fully know the severity of the situation either. The instruments used to measure the initial intensity of radioactivity near the explosion site were unfit to represent such high levels, and so the readings were off the scale of most of the dosimeters used. The staff was a group of stressed and overworked individuals, in a culture where safety was not one of the main concerns.
After this, the material still left inside the reactor began to burn through the floor of the reactor, creating a hugely radioactive material known as corium, a mixture of cement, water and radioactive material. Before this melted through into the water below, causing a huge explosion of radioactive steam, the pool of water had to be drained. Three operators volunteered: Alexei Ananenko, Valeri Bezpalov and Boris Baranov. These men entered deadly radioactive water equipped with wetsuits and dosimeters and managed to empty the pool by opening the valves that allowed the water to flow out. These men obviously died but were posthumously awarded the Order For Courage by the Ukrainian President in 2018.
Initially there were efforts to stop the fire with water, since the firefighters were not informed of the incredibly dangerous radioactive smoke that followed the fighting of the fire. In fact, the firefighters assumed that they were fighting a normal electrical fire. Before long, men began dropping dead due to deadly doses of radiation.
It was decided that the town of Pripyat should be evacuated, but even this decision took time. Townspeople began to fall ill, vomiting and coughing in fits. A committee was formed wherein they gathered the evidence that the reactor had most definitely been destroyed and began to fully realise the severity of the situation. Before this, due to the staff’s poor condition, inadequate equipment and censorship for the sake of posterity. The day following the explosion, the evacuation effort started, a poor start considering the dozens that had already been straining the local hospitals. Planning of a three day evacuation, initially townsfolk were told to only bring bare necessities. This caused further quality of life problem once the evacuation was made permanent.
The USSR refused to publicly acknowledge the incident for some time, despite the evacuation taking place soon after the accident. It was only after international pressure from the Atomic Energy Agency that the Soviet government conceded that an accident had happened, but they assured the accident was very minor. However before long the global media began to gain momentum with the severity of the accident and it could not long be denied that the Chernobyl disaster was a worldwide issue.
Long term efforts to reduce the risk of the disaster include removal of graphite shrapnel, the decommissioning of now radioactive vehicles and other clean up of contaminated areas surrounding the plant.
After seven months of effort, the immediacy of the threat posed by the disaster was lessened. The international community condemned the lack of oversight and so many more strict safety measures were forced upon the USSR for the short time it would still continue to function. The exclusion zone of radioactivity still stands to this day, with large parts of the abandoned town remaining off-limits. A large metal dome has been erected over Reactor No. 4, and the general public have very restricted permissions to exclusion zone. The worldwide atomic climate still shows the effects of the Chernobyl disaster, as well as the disaster at Fukushima Daiichi Nuclear Plant. Countries across Europe continue to exhibit abnormally high levels of radiation, spreading even to the highlands of Scotland due to weather conditions following the accident.
It is unlikely the world will ever be so thoroughly affected and damaged by a single event ever again, and so measures are continually developed to ensure that a disaster such as this does not happen ever again.