The Chernobyl nuclear power plant disaster of 1986 is the greatest tragedy of nuclear power generation in history. The power plant, located just 10 miles from Chernobyl consisted of 4 reactors: each of which capable of producing 1000 megawatts of electrical energy.
Situation and location
The Chernobyl nuclear power plant is located 81 miles away from the north of the Ukrainian capital- Kyiv, according to the World Nuclear Association. This power plant is made up of 4 reactors which were designed and built during the 1970s and 1980s. The plant had a reservoir which provided cooling water for the reactor that was supplied by the Pripyat river. The city of Pripiyat was the closest city to this plant, which was just under 2 miles away and housed nearly 50 000 residents as of 1986. A smaller older town, Chernobyl, was about 9 miles away and housed around 12 000 residents. The remainder of this region was primarily farms and woodland.
Mechanisms of the power plant
The plant used 4 soviet designed RBMK-1000 nuclear reactors, which at this time we understand had many issues. RBMK models used a pressure tube design and used enriched Uranium-235 uranium dioxide as a fuel to heat the water, creating steam that helped to move the turbines of the nuclear reactor and generated electricity in that form, according to the World Nuclear Association. In most nuclear reactors water can also be used as a coolant and to moderate the activity of the nuclear core by removing heat and steam which is of excess. The problem with the RMBK 1000 was that it used graphite as a moderator of the core’s activity but also allowed the continuous nuclear reaction to occur.
As the core heated and produced more and more steam bubbles the core became more reactive, allowing the positive feedback loop to occur where the cycle keeps repeating itself without further action. In engineering this term can be referred to as the positive-void coefficient.
How do nuclear reactors work:
- The reaction is first triggered. Neutrons are fired at uranium atoms, causing them to split and release more neutrons. This chain reaction is what allows the generation of a high amount of energy.
- Water is heated. The temperature rises to around 300 degrees celsius, which needs to be in the liquid form at the power station, so the pressure inside is 155 times greater than atmospheric pressure. This prevents boiling and evaporating.
- Hot water is circulated
- Steam is created, This hot and pressurised water flows through the thousands of looped popes while a second stream of water flows around the border (outside) of the pipes. This water is under much less pressure, so heat from the pipes boil it back into the bloodstream
- Steam energy is converted into electric energy. The mechanism of action involves a series of turbines that activate and run. A “shaft” contains heat energy which spins at around 3000 revs per minute. The generator is electromagnetic.
What were the ions involved?
Most of the radiation released from the failed nuclear reactor included iodine-131, caesium-134 and caesium-137. Iodine-131 has a short half life of about 8 days. It tends to localise within the thyroid gland of an individual. Caesium isotopes tend to have longer half lives of years, where caesium-137 has a half life of around 30 years. These are more dangerous as it means years after the explosion active radioactive matter still remains within the environment.
So…. What went wrong?
The explosion occurred in April 1986, during a routine maintenance check. Operators wanted to test the electrical systems, however they reportedly failed to follow safety regulations as stated by the UNSCEAR. As a result the plant reactor reached dangerously unstable and low power levels. Reactor 4 had been shut down for the day in order to perform the maintenance and safety checks during potential power outages, There is actually some dispute between how the explosion really occurred. Some believe that it was caused by an excess amount of steam, others say it was influenced by contact with hydrogen. During the checks steam may have accumulated within the cooling pipes (positive void coefficient), causing an enormous rise up in operators that was uncontrollably hard to shut down. Reactor 4 was destroyed after an explosion, which then initiated a large fire. Radioactive material poured down the air onto buildings, industries and houses nearby. Toxic fumes and dust was also being blown through the wind to surrounding areas, bringing fission products and noble gas with it and spreading it across a wide area too. Unfortunately the explosion had killed 2 of the plant workers immediately. For the next few days a lot of effort was put into trying to contain the fires and the leaks, however the death toll still climbed dramatically through death due to acute radiation sickness.
The initial fire was stifled by around 4 hours, but the surrounding granite fuelled fire took around 10 days and at least 250 firefighters to extinguish. Toxic emissions continued to be released into the atmosphere for 20 days post-calamity.
Evacuations within Pripyat had commenced on April the 27, 36 hours after the incident had occurred. By that time several residents were experiencing symptoms of vomiting, headaches and other signs of radiation sickness. Officials closed off an area around the plant as reported on May 14, evacuating 116 000 residents. Within the next few years 220 000 residents were advised to move to less contaminated areas, reported by the world nuclear association.
Twenty eight of the workers at Chernobyl died in the first few months following the incident, exposing workers who knew they were exposing themselves to toxic levels of radioactive substances within the environment they supported. The winds at the site of the explosion had commenced from the south and east side, hence a lot of the radioactive substance was blown towards the north of the power plant too, including Belarus. Soviet authorities were quite slow to release information of the disaster to the outside world. An increase of radiation levels were detected in Sweden which raised concerns, through which scientists could approximate the location of the nuclear disaster based on radioactive levels and wind speed and direction. This somewhat forced the soviet authorities then to reveal information with regards to the crisis.
Within 3 months of the disaster 31 people had died from the radioactive exposure. It was reported that between 1991 and 2015 a total of 20 000 cases of thyroid cancer were diagnosed in patients in 1986. Although there may have been more cases within the emergency workers, residents and evacuees, the overall rate of cancer deaths and other health effects directly associated with the disaster was actually less than what they had estimated. Recent research suggests that the available evidence doesn’t correlate the relationship between radiation induced areas and leukaemia or solid cancers other than thyroid cancer. Surprisingly, the fear of radiation poisoning actually leads to greater health suffering than the actual disaster itself. Doctors in Eastern Europe and the Soviet Union advised pregnant women to undergo abortion and stop bearing children to prevent birth defects or other disorders, although the level these women were exposed to were probably too low to cause any problems. In a report released in 2000 it was stated that there were a lot of unsubstantiated statements that were released at that time that had not supported scientific assessments.
Shortly after the explosion occurred, some of the trees within the woodland areas surrounding the plant were killed due to high levels of radiation. This region was then called the “Red Forest” as the dead trees ended up turning a bright ginger colour. The trees were removed and buried in trenches.
The now isolated forest was also known to have a large range of wildlife creatures such as wolves, deer, lynx, beaver, eagle, boar and bears. Nevertheless a handful of radiation effects such as stunted trees are still growing to this day in high radiation zones, so it won’t be abnormal to find animals living with cesium-137 in them.
The damaged reactor was sealed in a concrete sarcophagus, with the intention to contain the remaining radiation. There is still ongoing scientific debate as to how effective this isolation technique has been and will continue to be in the future. An enclosure named as the “New Safe Confinement” was constructed at the end of 2006 and ended in 2017. It was 257 metres wide, 531 metres long and 108 metres tall, and solely had the purpose to protect and enclose the reactor for the next 100 years.
The plant, the “ghost towns” Pripyat and Chernobyl, and the surrounding land made a 1000 miles squared exclusion zone, restricted for anyone’s access apart from government officials and scientists.
Despite the disaster and the operational risks, the power plant continued to serve electricity and meet the demand of Ukranian residents until the very last reactor was shut down in December 2000. Complete decommissioning of the site is expected to be completed by 2028. Despite the dangers of this area, many people had returned back to their homes shortly after the explosion and shared their stories with major news companies. The area has also become a place of tourism for those who want to see the after-effects of the disaster first-hand.
The area has recovered to some extent but can not be classed as normal. In the area just outside the exclusion zone, people are beginning to resettle. Tourists come to this site to visit, with visitation rates rising by 30-40% after a HBO show was released in 2019, based on this exact disaster.
The event had also resulted in a few significant changes in the nuclear industry too, concerns about reactor safety increased within eastern european countries as well as around the world. The remaining RBMK reactors were all modified to reduce the risk of another disaster. Many international funding programmes were also created after this event had taken place, such as the World Association of Nuclear Operators (WANO) and the International Atomic Energy Agency (IAEA).
Chernobyl plant and the Russian invasion
On this very day, Russia is advancing in its Ukrainian Invasion Mission. Just about a week ago Russian troops took over the Chernobyl Nuclear Power Plant. After heavy fighting of the Russians with the Ukrainians, a level of high radioactive matter has once again been detected within the area. Gamma radiation, a high energy electromagnetic radiation, increased by 20 times above typical levels. THis spike was because of the radioactive matter that was thrown into the air due to nearby disturbances from war equipment and the actual fighting.
Some say that the dose rates are not much greater than the rates in the area normally, which is around 100 times greater than areas where such disasters haven’t occurred. But even if it were, the risk of dying from this is much less likely than dying from war.
For a small explosion in a nuclear reactor, the consequences are that it isn’t safe for people to live there for the next 24 000 years. Nuclear reactors are useful yet come with dangerous consequences if radioactive leakage occurs. And recently, the biggest nuclear plant in the world was on fire due to the Russian and Ukrainian war. If one of these reactors burst, the damage will be indescribable.
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