The nuclear accident took place on April 26, 1986, in reactor No. 4 of the Chernobyl Nuclear Power Plant of the Soviet Union, which today is located on the territory of Ukraine. The accident was in the category of the maximum predicted accident on the International Nuclear Event Scale, seriously disrupted the economic and social conditions prevailing in the surrounding areas and had significant environmental and health effects. Two of the station’s workers died on the spot from the accident. Within four months, 28 firefighters who rushed to the scene died from radiation and heat burns, and 19 additional deaths were recorded up to 2004. In addition, it is estimated that the health of hundreds of thousands of people was affected due to environmental radiation exposure. . Percentage increases in cancers were over 15% in exposed populations, with thousands of cancer and leukemia deaths linked to the accident.
The Chernobyl Nuclear Power Plant is located in the now abandoned town of Pripyat, Ukraine and was commissioned for the Soviet Union in 1977 as a model nuclear power plant. At the Chernobyl nuclear power plant it was planned to perform a test of the ability of turbine generator number 8 to provide power during a decelerating self-rotation after its power supply was cut off. The test was designed by the plant’s chief design engineer and its purpose was to test whether this method could provide enough power to force water into the reactor cooling system. The concept of this forced feed during the downswing of the turbine was anticipated and included as a possible feature in the design of the RBMK-1000 reactors used by Chernobyl. Corresponding checks had been made in 1982 on reactor No. 3 of the nuclear plant and it had been found that it was not possible to supply power for a long time. This resulted in new tests with a more modern turbine design in 1984 and 1985. The main idea behind the 1986 program was to test in conditions as close to real life as possible. Once again reviewed, the audit was scheduled to begin on April 25, 1986.
The accident occurred at 01:26 Moscow time, in the early hours of Saturday, April 26, 1986. At that time, there were approximately 200 workers at the plant whose occupations were related to the smooth operation of nuclear reactors 1, 2 and 3, as well as the control program that was taking place in reactor 4 where the explosion occurred. A kilometer away were other workers working the night shift to build reactors 5 and 6 that were to be operational in the fall of the same year. Two explosions occurred in the No. 4 reactor building. Their result was a hole in the roof of the building and the ejection of graphite, concrete and debris. As a result of these, the reactor core was in contact with the external environment. Much of the uranium used as fuel was blown into the air along with super-elements and fission products from the reactor core, drifting in a plume of smoke that reached a kilometer high. A fire broke out in the roof above the reactor turbine. There were also flames inside the building along with fumes and dust. The graphite acting as the reactor’s moderator was ignited by the heat and explosion. A plant worker who was directly above the reactor at the time of the explosion was killed instantly and his body could not be recovered, and a second worker was injured by falling debris and suffered severe burns. He was released immediately but succumbed a few hours later.
The Chernobyl accident generally resulted from a series of events that included, among other things, unintended handling and errors, which combined with the design of the RBMK-1000 reactor used by the plant, led to the accident. The scale of the disaster was enhanced by the lack of training and equipment of the factory staff, which led to serious errors in assessing the real situation. Radioactivity levels in the most contaminated areas of the plant have been estimated to be as high as 5.6 roentgens per second (P/d), which is equivalent to 20,000 roentgens per hour (P/h). As the lethal dose is 500 roentgens in 5 hours, unprotected workers received fatal doses in just a few minutes. However, at the time of the disaster, the workers did not know the true levels of radioactivity.
Because of the incorrect measurements, the reactor’s chief of staff, Alexander Akimov, assumed that the reactor was intact. Akimov stayed with his men in the reactor building until morning, trying to pump water into the reactor. None of them wore protective suits, and most, including Akimov, died of radiation exposure within three weeks. As a result of the accident 237 people suffered from acute radiation contamination, of which 31 died within the first three months. Most were firefighters and rescue workers, who were not fully aware of the dangers they faced. 135,000 people evacuated the area, 50,000 of them residents of Pripyat. The total number of deaths in the region is difficult to determine precisely due to the secrecy of the regime at the time, which led to incomplete recording of relevant statistics.
The Chernobyl accident affected most countries in Europe, with western, eastern and northern Europe receiving the largest percentage of radioactive isotopes. The area contaminated with more than 4,000 Bq/m2 covers 40% of Europe’s surface, while 2.3% received more than 40,000 Bq/m2. It is estimated that of the total dose of radioactivity received by the earth’s population due to the accident, 36% corresponds to the inhabitants of Russia, Ukraine and Belarus and 53% to the rest of the Europeans.
