This April 26, 1986 marks thirty-five years since the worst nuclear accident in human history unfolded at the Chernobyl Nuclear Power Plant, in the then USSR, now located in Northern Ukraine. The accident led to several devastating immediate and long-term impacts and cost around US$ 235 Billion in damages.
The Chernobyl Nuclear Power Plant was officially known as the Vladimir Ilyich Lenin Nuclear Power plant. It is located near the border of Ukraine and Belarus in northern Ukraine near the city of Pripyat. The plant consisted of four RBMK-1000 type nuclear reactors. The first reactor was made operational in 1977. Subsequent reactors went into operation in 1978, 1981, and 1983, respectively. With its four reactors, the plant produced about 10% of Ukraine’s electricity.
What Led To The Chernobyl Disaster?
The chain of events that led to the accident began on April 25, 1986, when a fourth attempt at the safety test was scheduled. The first three tests had failed to provide a proper solution. The test aimed at forming a safety procedure for maintaining reactor cooling water circulation until the backup electrical generators could provide power in the case of an electrical power outage.
The test was to be conducted during the day shift of April 25, 1986, and preparations for it began at 1:00 AM. The test was scheduled to begin at 2:15 PM. Preparations were carried out, and the emergency core cooling system was disabled. However, the test did not begin as scheduled because a regional power station went offline unexpectedly, and additional electricity output was requested from the Chernobyl plant, postponing the test.
The evening shift replaced the day shift. Meanwhile, the emergency core cooling system was left disabled- which goes on to show there was a general lack of regard for safety at the plant. Finally, at 11:04 PM, the test proceeded, and the evening shift initiated the process. The delay meant that the test, supposed to end during the day shift on April 25, was now extended well into the night shift of April 26. The evening shift left at midnight, leaving the test to be carried out by the night shift. The night shift was never equipped for the test; it was only supposed to maintain the plant’s decay heat cooling systems that were to be shut down.
At 1:23:04 AM, the test began, and at 1:23:40 AM, the emergency shutdown, also known as scram, was initiated. As the scram continued, the reactor output jumped to 10 times its average operational value. This led to a steam explosion, caused by the damaged fuel rods, which blew the upper biological shield through the roof of the reactor building. The entire reactor assembly was attached to the upper biological shield. A second more powerful explosion happened immediately within two to three seconds, and it dispersed the already damaged core. It ejected hot lumps of graphite moderator. The ejected graphite and the demolished graphite channels in the damaged reactor caught fire on exposure to air. This significantly contributed to the nuclear fallout from the disaster.
The disaster was caused by a combination of violation of safety protocols and design flaws in the plant, which were kept hidden from the plant operators.
Attempt To Hide It From The World
Initially, there were attempts to hide the disaster from the world. After Swedish authorities detected a higher than average radiation level in Forsmark Nuclear Power Plant in Sweden and determined that the radiation was coming from the USSR, the announcement was made. The Soviet authorities tried to deny any accidents in the country and relented only after the Swedish threatened to file an official alert with the International Atomic Energy Agency. An official announcement was made on the evening of April 28, 1986.
How Was It Contained?
The roof of the reactors was constructed using a combustible material called bitumen which violated safety protocols. The hot ejected graphite led to fires on the roof of the neighboring reactor no. 3, which was still operating and wasn’t shut until 5 AM. Firefighters began arriving at the site at 1:45 AM but were not aware of how harmful the radiation was. The fires were brought under control by 5:00 AM, but the fire inside the reactor kept burning till May 10, 1986. The fire inside the core was attempted to be put out by dumping a mixture of sand, lead, clay, and boron from helicopters. It took around 600 pilots to carry out the operation. It is now known that virtually none of this mixture reached the core.
There were also two floors of blubber pools beneath the reactor, which were used stored water for the emergency cooling pumps. After the disaster, the basement flooded with firefighting water, and there were severe chances of another steam explosion happening, which would have released more radioactive material into the atmosphere. Thus it was essential to drain the blubber pool. The task was carried out manually by three engineers. The risk of a steam explosion decreased after the pools drained. There were still possibilities of this if the molten core reached the natural water table. It was decided to make a graphite-concrete cooling system below the reactor by excavating a tunnel.
Almost 100 tonnes of radioactive debris on the roof had to be removed to construct a containment structure, later called the sarcophagus, safely. Humans primarily achieved this task on protective roofs.
Construction on a containment structure could begin after they removed the debris. This was essential to prevent the spread of contamination by natural elements like wildlife, rain, and wind. It was decided to enclose the reactor with a substantial composite concrete and steel structure. Its construction began in June and was finished in November.
Chernobyl Exclusion Zone
Initially, an area of 30km in radius was to be the exclusion zone. It was officially called the “zone of alienation”. The area is now largely covered by forests and abundant wildlife and was later expanded to 4,143 sq km to include more contaminated areas. While Ukraine state authorities say the area will become habitable in 300 years, some nuclear experts say it might be 20,000 years before the area becomes habitable.
Human And Environmental Impact
The evacuation of the people living in the nearby city of Pripyat did not commence immediately after the disaster. Residents reported various illnesses and metallic tastes in their mouths. The evacuation order came 36 hours after the initial blast and the process began at 2 PM on April 27, 1986. Between 1986 to 2000, approximately 350,000 people were evacuated and permanently resettled from the region.
In the disaster, 28 people died due to the accident, and more than 100 were injured. Since the accident, many reports have claimed thousands of people exposed to radiation suffered from cancer. The reports are, however, highly debated, and their claims are disputed.
The impact of the disaster on the environment is also highly researched. Immediately after the disaster, the surrounding forest turned reddish-brown and died, which earned it the name ‘red forest’. In Belarus, 23% of its land was contaminated, and a fifth of its agricultural land became untenable.
The Chernobyl exclusion zone is now lush with wildlife which is thriving due to a lack of human intervention. However, there have been higher levels of cataract and albinism in animals. There is also a lack of beneficial bacteria in the region. As a result of the disaster, many animals died or suffered from stunted growth. There were also cases of animals born with deformities such as missing limbs.
Over the years, the Chernobyl disaster has fascinated people around the world. It has inspired fiction worldwide and was the subject of the hit HBO TV series “Chernobyl”. Today, the exclusion zone is open to tourists who want to explore the area and know its history.
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