The accident
In August 1986, in a report submitted to the International Atomic Energy Agency , explaining the causes of the accident at the Chernobyl plant. This revealed that the team that operated in central Saturday April 26 of 1986 proposed test with the intention to increase reactor safety. To this should continue to find out how long the turbine power generating steam once cut the flow of steam. The emergency cooling pumps, in case of failure, requiring a minimum of power to start (until torn diesel generators) and plant technicians did not know whether, once cut the flow of steam turbine inertia could keep the pumps running.
To perform this experiment, the technicians did not want to stop the chain reaction in the reactor to avoid a phenomenon known as xenon poisoning . Among the products of fission that occur within the reactor, is the Xenon (Xe), a gas very absorbent neutrons. While the reactor is operating normally, there are so many neutrons that the absorption is minimal, but when the power is too low or the reactor is stopped, the amount of 135Xe increases and prevents the chain reaction for a few days. When the 135Xe decay is when the reactor can be restarted.
operators control rods inserted to reduce the reactor power and this dropped to 30 MW . With such a low level, automatic systems would stop the reactor and therefore the operators disconnected the system power regulation, system emergency core cooling and other systems of protection. These actions, as well as the line drawn from the central computer that prevented the prohibited operations, were serious and multiple violations of the Nuclear Security Regulations of the Soviet Union. 30 MW
begins with xenon poisoning and to avoid increasing the reactor power up the control rods, but with the reactor about to go out, operators manually removed too many control rods. Of the 170 bars boron steel having the core safety rules have always required that a minimum of 30 bars decreases and this time let alone 8. With emergency systems disconnected, the reactor underwent an extremely rapid rise in power that operators do not detect in time. At 1:23, four hours after starting the experiment, some in the control room began to realize something was wrong.
wanted to come down again when the control rods by pressing the SCRAM emergency (AZ-5 button "Rapid Emergency Defense 5"), these did not respond because they were already possibly deformed by heat and disconnected to allow them to fall by gravity . We heard loud noises and then there was an explosion caused by the formation of a cloud of hydrogen within the nucleus, that blew the roof of 100 t reactor causing a fire in the and a giant plant emissions of fission products into the atmosphere.
To perform this experiment, the technicians did not want to stop the chain reaction in the reactor to avoid a phenomenon known as xenon poisoning . Among the products of fission that occur within the reactor, is the Xenon (Xe), a gas very absorbent neutrons. While the reactor is operating normally, there are so many neutrons that the absorption is minimal, but when the power is too low or the reactor is stopped, the amount of 135Xe increases and prevents the chain reaction for a few days. When the 135Xe decay is when the reactor can be restarted.
operators control rods inserted to reduce the reactor power and this dropped to 30 MW . With such a low level, automatic systems would stop the reactor and therefore the operators disconnected the system power regulation, system emergency core cooling and other systems of protection. These actions, as well as the line drawn from the central computer that prevented the prohibited operations, were serious and multiple violations of the Nuclear Security Regulations of the Soviet Union. 30 MW
begins with xenon poisoning and to avoid increasing the reactor power up the control rods, but with the reactor about to go out, operators manually removed too many control rods. Of the 170 bars boron steel having the core safety rules have always required that a minimum of 30 bars decreases and this time let alone 8. With emergency systems disconnected, the reactor underwent an extremely rapid rise in power that operators do not detect in time. At 1:23, four hours after starting the experiment, some in the control room began to realize something was wrong.
wanted to come down again when the control rods by pressing the SCRAM emergency (AZ-5 button "Rapid Emergency Defense 5"), these did not respond because they were already possibly deformed by heat and disconnected to allow them to fall by gravity . We heard loud noises and then there was an explosion caused by the formation of a cloud of hydrogen within the nucleus, that blew the roof of 100 t reactor causing a fire in the and a giant plant emissions of fission products into the atmosphere.
immediate reactions:
Minutes after the accident, all firefighters assigned to the central military were already underway and preparations to control the disaster. The flames affecting several floors of the reactor 4 and came dangerously close to the building where the reactor 3. The heroics of firefighters during the first three hours of the accident prevented the fire spreading to the rest of the plant. Still, sought help from firefighters in Kiev because of the magnitude of the disaster. The plant operators put the other three reactors in emergency cooling. Two days later, there were 18 serious injuries and 156 wounded with serious injuries caused by radiation . There was still no death toll figure, but a nuclear accident increases every day the list of victims, even after many years later. The first approach
helicopter showed the magnitude of what happened. At the core, exposed to the atmosphere, the graphite the same burning red hot, while the fuel material and other metals had become an incandescent liquid mass. The temperature reached 2,500 ° C and a chimney effect, radioactive smoke drove to a considerable height.
At the same time, the leaders of the region began to prepare for the evacuation of the city of Pripyat and a radius of 10 km around the plant. This first evacuation began the day after a massive and it was concluded 36 h later. The evacuation of Chernobyl and a radius of 36 km was not carried out until six days after the accident. By then I had more than 1,000 affected by acute injury caused by radiation.
concrete structure called "sarcophagus" designed to contain radioactive material from the reactor core and was designed to last 30 years.
Saturday morning, several army helicopters were preparing to throw on the core mix material consisting of sand , clay, lead , dolomite and boron absorbing neutrons . Boron neutron absorbing prevent there being a chain reaction. The lead was intended to contain gamma radiation and other materials remained united and homogeneous mixture. When May 13 ended emissions had been thrown into a core 5,000 tons of materials.
then began building a tunnel under the reactor accident with the initial objective of implementing a cooling system to cool the reactor. This tunnel, as well as much of the cleanup of highly radioactive material, was developed by the Russian army reservists, young people between 20 and 30. Finally, never implemented the cooling system and the tunnel was filled with concrete to strengthen the ground and prevent the heart from sinking under the weight of material dumped. In a month and 4 days the tunnel was completed and began the uprising of a structure called a sarcophagus, which would involve isolating the reactor from outside. The construction lasted 206 days.
helicopter showed the magnitude of what happened. At the core, exposed to the atmosphere, the graphite the same burning red hot, while the fuel material and other metals had become an incandescent liquid mass. The temperature reached 2,500 ° C and a chimney effect, radioactive smoke drove to a considerable height.
At the same time, the leaders of the region began to prepare for the evacuation of the city of Pripyat and a radius of 10 km around the plant. This first evacuation began the day after a massive and it was concluded 36 h later. The evacuation of Chernobyl and a radius of 36 km was not carried out until six days after the accident. By then I had more than 1,000 affected by acute injury caused by radiation.
concrete structure called "sarcophagus" designed to contain radioactive material from the reactor core and was designed to last 30 years.
Saturday morning, several army helicopters were preparing to throw on the core mix material consisting of sand , clay, lead , dolomite and boron absorbing neutrons . Boron neutron absorbing prevent there being a chain reaction. The lead was intended to contain gamma radiation and other materials remained united and homogeneous mixture. When May 13 ended emissions had been thrown into a core 5,000 tons of materials.
then began building a tunnel under the reactor accident with the initial objective of implementing a cooling system to cool the reactor. This tunnel, as well as much of the cleanup of highly radioactive material, was developed by the Russian army reservists, young people between 20 and 30. Finally, never implemented the cooling system and the tunnel was filled with concrete to strengthen the ground and prevent the heart from sinking under the weight of material dumped. In a month and 4 days the tunnel was completed and began the uprising of a structure called a sarcophagus, which would involve isolating the reactor from outside. The construction lasted 206 days.
The effects of the disaster
The explosion caused the greatest catastrophe in the history of civil exploitation of nuclear energy. 31 people died at the time of the accident, about 135,000 people were evacuated immediately from the 155,000 km ² affected large areas remain uninhabited for many years to be subsequently relocating from other 215,000 people. Radiation spread to most of Europe, the levels of radioactivity remaining in areas close to dangerous levels for several days. The estimate of radionuclides were released into the atmosphere is about 3.5% of material from spent fuel (about 6 tons of fuel fragmented) and 100% of all noble gases in the reactor contents. Most representative of radioisotopes, the estimate of the spill is 85 peta becquerels of 137 Cs and between 50 and 60% of the total inventory of 131 I , ie between 1600 and 1920 petabecquerel. These two are the most important radioisotopes from the radiological point of view, although the spill included other on a smaller scale, such as 90 Sr or 239 Pu .
Fauna and flora:
After the disaster, an area of \u200b\u200b4 square miles of pine trees in the vicinity of the reactor acquired a golden brown and died, acquiring the name "Red Forest" . Some animals in the hardest hit areas also died or stopped reproducing. A herd of horses stranded in an island 6 km from the nuclear plant went out to disintegrate their thyroid glands.
In the years following the disaster in the exclusion zone abandoned by humans wildlife has flourished. Belarus has already declared a nature reserve , and in Ukraine there is a similar proposal. Several species of wild animals and birds that had not been seen in the area before the disaster, are now in abundance, due to the absence of humans in the area.
In a 1992-1993 study of game species in the area, in a kilo of beef and venison is measuring up to about 300,000 becquerels of cesium-137. This action was taken during a period of highly radioactive anomaly possibly caused by falling pine needles contaminated. The concentrations of radioactive elements have been declining since then to an average value of 30,000 Bq in 1997 and 7,400 in 2000, levels that remain dangerous. In Belarus, the maximum allowable limit radiocaesium in a kg of game meat is 500 Bq. In Ukraine is 200 Bq for any type of meat.
After the disaster, an area of \u200b\u200b4 square miles of pine trees in the vicinity of the reactor acquired a golden brown and died, acquiring the name "Red Forest" . Some animals in the hardest hit areas also died or stopped reproducing. A herd of horses stranded in an island 6 km from the nuclear plant went out to disintegrate their thyroid glands.
In the years following the disaster in the exclusion zone abandoned by humans wildlife has flourished. Belarus has already declared a nature reserve , and in Ukraine there is a similar proposal. Several species of wild animals and birds that had not been seen in the area before the disaster, are now in abundance, due to the absence of humans in the area.
In a 1992-1993 study of game species in the area, in a kilo of beef and venison is measuring up to about 300,000 becquerels of cesium-137. This action was taken during a period of highly radioactive anomaly possibly caused by falling pine needles contaminated. The concentrations of radioactive elements have been declining since then to an average value of 30,000 Bq in 1997 and 7,400 in 2000, levels that remain dangerous. In Belarus, the maximum allowable limit radiocaesium in a kg of game meat is 500 Bq. In Ukraine is 200 Bq for any type of meat.
Controversy on the estimates of victims:
is expected that most premature deaths from the Chernobyl accident are the result of cancer and other diseases induced by radiation for several decades after the event. A large population (some studies consider the entire population of Europe) was subjected to relatively low radiation dose, increasing the risk of cancer in the population (according to linear no-threshold model ). It is impossible to attribute deaths specific accident, and many estimates indicate that the number of excess deaths will be too small to be statistically detectable (for example, if one out of every 5,000 people died due to accident, in a population of 400 million would be 80,000 deaths due to accident statistically undetectable). Moreover, interpretations of current health status of exposed populations are variable, so that estimates of casualties are always based on numerical models of the effects of radiation on health. On the other hand the effects of low level radiation on human health is still not well understood, so that no model is completely used reliable (even several authors claiming that the effect of hormesis , which is found in the action of other toxic elements, should also apply to radiation).
Given these factors, different studies on the effects of Chernobyl on health have yielded very different conclusions, and are subject to political and scientific controversy. Here are some of the major studios.
Immediate
Chernobyl contamination did not spread evenly throughout the adjacent regions, but is unevenly distributed depending on the weather. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. The TORCH report 2006 states that half of the airborne particles were deposited outside Ukraine , Belarus and Russia . A large area of \u200b\u200bthe Russian Federation south of Bryansk was also contaminated, as well as parts of northwestern Ukraine.
In Western Europe taken various measures in this regard, including restrictions on imports of certain foods. The statements of senior officials from France in the sense that the Chernobyl accident had no significant impact on his country were ridiculed on the grounds that the radioactive cloud would have stopped at the borders German and Italian.
Two hundred people were hospitalized immediately, of whom 31 died (28 of them due to direct exposure to radiation). Most were firefighters and rescue personnel involved in the work to control the accident. An estimated 135,000 people were evacuated from the area, including 50,000 residents Pripyat (Ukraine). For more information on the number of people affected, see the following sections.
Soviet scientists reported that the reactor 4 containing between 180 and 190 tons of uranium dioxide and fission products. estimates released in the exhaust material ranging from 5% to 30%, but some receivers who were inside the sarcophagus and the reactor containment (eg Usatenko and dr. Karpan claim is not within more than 5 or 10% of the fuel. Due to the intense heat caused by fire, the radioactive isotopes released from nuclear fuel in the atmosphere rose by dispersing it.
The "liquidators " received large doses radiation. According to Soviet estimates, between 300,000 and 600,000 liquidators worked on cleaning up the evacuation zone of 30 km around reactor, but some of them entered the zone two years after the accident.
Chernobyl contamination did not spread evenly throughout the adjacent regions, but is unevenly distributed depending on the weather. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. The TORCH report 2006 states that half of the airborne particles were deposited outside Ukraine , Belarus and Russia . A large area of \u200b\u200bthe Russian Federation south of Bryansk was also contaminated, as well as parts of northwestern Ukraine.
In Western Europe taken various measures in this regard, including restrictions on imports of certain foods. The statements of senior officials from France in the sense that the Chernobyl accident had no significant impact on his country were ridiculed on the grounds that the radioactive cloud would have stopped at the borders German and Italian.
Two hundred people were hospitalized immediately, of whom 31 died (28 of them due to direct exposure to radiation). Most were firefighters and rescue personnel involved in the work to control the accident. An estimated 135,000 people were evacuated from the area, including 50,000 residents Pripyat (Ukraine). For more information on the number of people affected, see the following sections.
Soviet scientists reported that the reactor 4 containing between 180 and 190 tons of uranium dioxide and fission products. estimates released in the exhaust material ranging from 5% to 30%, but some receivers who were inside the sarcophagus and the reactor containment (eg Usatenko and dr. Karpan claim is not within more than 5 or 10% of the fuel. Due to the intense heat caused by fire, the radioactive isotopes released from nuclear fuel in the atmosphere rose by dispersing it.
The "liquidators " received large doses radiation. According to Soviet estimates, between 300,000 and 600,000 liquidators worked on cleaning up the evacuation zone of 30 km around reactor, but some of them entered the zone two years after the accident.
Effect on long-term health
Immediately after the accident, the greatest concern focused on the radioactive iodine a half-life eight days. Today (2008) concerns are focused on soil contamination strontium-90 and Cesium-137 , with half-lives of about 30 years. The highest levels of cesium-137 found in the surface layers of soil are absorbed by plants, insects and fungi, entering the food chain.
According to the report of the Nuclear Energy Agency of OECD Chernobyl were released the following proportions of the core inventory. 133Xe
100% 131 50-60% 20-40% 134Cs, 137Cs 20-40%, 25-60% 132Te, 4-6% 89Sr, 90Sr 4-6%, 4-6% 140Ba, 95Zr 3, 5%, 99 Mo> 3.5%, 103Ru> 3.5%, 106Ru> 3.5%, 3.5% 141Ce, 144Ce 3.5% 239Np 3.5%, 3.5% 238Pu, 239Pu 3.5%, 3.5% 240Pu, 241Pu 3.5%, 3.5% 242Cm
physical and chemical forms including exhaust gases, aerosols and finally , solid fuel fragmented. Pollution and its distribution within many of these parts scattered by the explosion of the core there is public reporting.
Some people in contaminated areas were exposed to large doses of radiation (up to 50 Gy ) in thyroid , due to absorption of iodine-131, which focuses on the gland. Radioactive iodine come from milk locally produced contaminated and would have been particularly in children. Several studies show that incidence of thyroid cancer in Belarus, Ukraine and Russia has risen greatly. However, some scientists believe that most of the detected increase is due to increase in controls. So far not detected a significant increase in leukemia in the general population. Some scientists fear that the radioactivity will affect local populations for generations.
Soviet authorities began evacuating people in the cer
Canio in the Chernobyl nuclear power plant 36 hours after the accident. In May 1986, approximately one month after the accident, all the inhabitants who had lived within a radius of 30 km around the plant had been displaced. However, the radiation affected a much larger area than the area evacuated. 
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