Introduction
The Chernobyl Nuclear Power Plant is a power plant with 4 nuclear reactors located 130 km from the city of Kyiv, Ukraine. Units 1 and 2 at the power plant were built in 1970 and 1977, and units 3 and 4 were completed in 1983 [1]. During the time of the accident, 2 more units are under construction. 49,000 people live in the city of Pripyat, which is 3 km from the power plant, and 12,500 people live in the city of Chernobyl, which is 15 km from the power plant [2]. The estimated total population in the 30 km radius of the power plant at the time of the accident was between 115,000 and 135,000 [1]. The Soviet-designed Power Plants are a boiling light water reactor with a pressure tube system using graphite as the moderator and lightly enriched Uranium as fuel.
Details of the Accident
On April 25, the operators of Chernobyl prepared to conduct an experiment. The experiment is to determine how long the turbines will power the main pumps when the main power source is lost [3]. The same experiment was carried out at the Chernobyl power plant a year ago and it was observed that the power from the turbine drops very quickly. In this experiment, the new voltage regulator will be tested. In the early hours of April 26, the experiment was initiated by the operators. When the operator takes action to shut down the reactor, the reactor is unstable and there is a power increase when the control rods enter the reactor due to the different design of the control rods. Contact of the hot fuel rods with the cooling water caused the fuel rods to break apart and the pressure to rise as a result of excessive steam production. As a result of the design features of the reactor, significant damage to 3 or 4 fuel bundles causes the destruction of the reactor. As a result of the excessive increase in pressure, the 1000-tonne top cover of the reactor was separated and damaged the fuel channels. Excessive steam production covered the entire core and caused a steam explosion that caused the fission products to scatter into the atmosphere. After 2-3 seconds, a second explosion caused the fuel channels and hot graphite to be dispersed into the environment. Although it is not known exactly what caused the second explosion, it is thought that the Hydrogen gas, which emerged as a result of the Zirconium-steam interactions, caused the explosion. As a result of these explosions, 2 workers lost their lives. As a result of fires caused by graphite and fuel particles, a significant amount of radiation has been released to the environment. The reactor was supplied with 200-300 tons of water per hour, but this process was not continued after half a day, as the 1st and 2nd units were in danger of flooding. From the second to the tenth day, 5000 tons of boron, dolomite, sand, clay and lead were thrown onto the burning core by helicopters in order to extinguish the fire and prevent the release of radioactive particles into the reactor [1].
What happened after the accident
An accident is a nuclear accident in which the largest recorded amount of radioactive material was released into the environment in the history of civil use of nuclear energy. A large amount of radioactive material was released into the air for 10 days after the accident [1]. It has caused the public to ingest significant amounts of harmful substances. Most materials released into the environment were collected on the debris, but lighter materials were carried by wind to Ukraine, Belarus, Russia and parts of Scandinavia and Europe [4]. Radiation exposure in contaminated areas is largely emitted by Iodine-131 and later Cesium-137, which has a short half-life. An estimated 1.8 EBq of Iodine-131, 0.085 EBq of Cesium-137 was released. The activity in the region of Belarus, Russia and Ukraine, where approximately 5 million people live, was 37 kBq/m2 Cesium-137 in the soil, and 555 kBq/m2 Cesium-137 in the region where 400,000 people lived. The city of Pripyat was evacuated on 27 April, and the 30-km diameter area with 116,000 inhabitants began to be evacuated on 14 May. Most people living in the evacuated area received doses below 50 mSv, but a few people received doses of 100 mSv or more [1].
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This disaster is actually a nuclear disaster that teaches a lesson to everyone in the world with the collapse of the soviets. It is an indication that power plants that cannot be kept under control can have a real impact on the world. Similar nuclear disasters have occurred, such as the Three Mile Island disaster. In my opinion, Chernobyl is actually a message with its importance, although it is the most effective and least damaging energy generation technique, if it cannot be controlled, it causes a disaster, and its effect still continues today. Unfortunately, these effects will continue for a long time.
Works Cited
https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/chernobyl-accident.aspx
https://www.daily-bangladesh.com/english/Chernobyl-Worlds-greatest-nuclear-disaster/28233
https://stories-ebrd.com/chernobyl/
https://books.google.com.tr/books?id=sFQbDQAAQBAJ&pg=PA25&lpg=PA25&dq=debris+lighter+materials+carried+wind+ukraine+belarus+russia+parts+scandinavia+europe&source=bl&ots=SgJ8QUYH1n&sig=ACfU3U0JDv7kEJ-ZvDItDGCYjswhQsCYmg&hl=en&redir_esc=y#v=onepage&q=debris%20lighter%20materials%20carried%20wind%20ukraine%20belarus%20russia%20parts%20scandinavia%20europe&f=false