Russian nuclear leak (belonging to the Chernobyl accident):
The Chernobyl nuclear accident (Ukrainian: Чорнобильська катастрофа), or simply the "Chernobyl Incident", was a nuclear reactor accident that took place in the former Soviet Union in Ukraine. Chernobyl accident", or simply "Chernobyl incident", was a nuclear reactor accident that occurred at the Chernobyl nuclear power plant in Ukraine under the former Soviet Union. It is considered to be the worst nuclear power accident in history, and the first major accident to be classified as a Level 7 event on the International Nuclear Event Scale (the second so far was the Fukushima Daiichi nuclear power plant accident on March 11, 2011 in Fukushima Prefecture, Japan).
At 1:23 a.m. (UTC+3) on April 26, 1986, an explosion occurred in Reactor No. 4 at the Chernobyl nuclear power plant near Pripyat, Ukraine. The successive explosions triggered fires and emitted large quantities of high-energy radioactive material into the atmosphere, and this radioactive dust covered a large area. The disaster released more than 400 times the dose of radiation as the atomic bomb that exploded in Hiroshima during World War II.
Economically, the total **** loss of the disaster was about 200 billion dollars (adjusted for inflation), making it the most "expensive" catastrophic event in modern history. The Chernobyl accident has been called the worst nuclear power accident in history. The city of Chernobyl was abandoned as a result.
The United Press International (UPI) reported on Nov. 29 that British TV producer Danny Cooke recently used a drone to take aerial photographs of the site of the Chernobyl nuclear accident in Ukraine, and the footage showed the deserted Chernobyl as a ghost town.
Second, the cause of the analysis:
On the cause of the accident, there are two conflicting official explanations. The first, released in August 1986, completely blamed the nuclear power plant operators for the accident. The second, released in 1991, attributed the accident to design flaws in the Pressure Tube Graphite Moderated Boiling Water Reactor (RBMK), particularly the design of the control rods. Both sides of the inquiry were lobbied on multiple fronts, including reactor designers, Chernobyl staff and the government.
Another important factor contributing to the accident was the fact that staff did not receive reports of problems with the reactor. According to Anatoli Dyatlov, one of the employees, the designers knew that the reactor would be dangerous under certain circumstances, but deliberately concealed it. This situation was caused by the fact that the plant supervisors were basically composed of employees who did not have RBMK qualifications: the plant director, V.P. Bryukhanov, who had only training and work experience in coal-fired power plants, was basically the supervisor in charge of political warfare and was not present at the time of the drill in the middle of the night of the incident, but the deputy director of the plant, who was leading the drill, was a nuclear energy professional. His chief engineer, Nikolai Fomin, was also from a conventional energy plant, and Anatoli Dyatlov, deputy chief engineer for reactors 3 and 4, had only "some experience with small reactors."
The second "flawed design explanation", published by Valeri Legasov in 1991, blamed the accident on flaws in the design of the RBMK reactors, particularly due to defective control rods.
The reactor had a dangerous void coefficient. The void coefficient is a measure of how safe a reactor is and is used to measure the effect on the reactor of the formation and increase of vapor bubbles in the water coolant. Most reactor designs will produce less energy as the water temperature rises. This is because if the coolant contains vapor bubbles, the number of neutrons that can be slowed down will decrease. Fast neutrons are generally less likely to cause fission of uranium atoms, so the reactor will produce less energy.
However, the RBMK reactor at Chernobyl used solid graphite as a neutron moderator to slow down neutrons and light water that absorbed neutrons to cool the core. So despite the steam bubbles in the water, a large number of neutrons were still being slowed down. In addition, because steam does not absorb neutrons as readily as water, increasing the temperature of the RBMK reactor results in more neutrons being able to fission uranium atoms, increasing the energy output of the reactor. This design causes the RBMK to be very unstable at low power and there is a tendency for the output energy to reach dangerous levels in a short period of time when the temperature rises. This was difficult for the staff to understand and anticipate.
A more significant flaw in this system was the design of the control rods. When controlling the reactor, the manipulator reduces the reaction rate by inserting the control rods into the reactor. In the design of the RBMK reactor, the end of the rod is made of graphite, and the extension (the part of the rod that extends beyond the end in the tail area, which is about a meter or three feet in length) is hollow and filled with water; the rest of the rod is made of boron carbide, which is the part that has the real ability to absorb neutrons. Because of this design, when the rods are first inserted into the reactor, the graphite end replaces the coolant, which in turn greatly increases the reaction rate of nuclear fission, since graphite can absorb fewer neutrons than boiling light water. Thus the first few seconds after the control rods are inserted at the beginning, the power output of the reactor will instead increase, instead of the expected decrease in power. This feature was also unknown and unforeseen by the reactor manipulators.
Water is piped vertically through the core, and as the water temperature increases the water level rises, creating a temperature gradient effect in the core. The effect is exacerbated if the top section has been completely turned to vapor. This is because the top section cannot be cooled sufficiently at this point, and the reaction is significantly increased (in contrast, the CANDU reactor design has water piped horizontally through the core, with neighboring piping flowing in the opposite direction, so that there is less change in the temperature of the water in the core).
Because of the huge size of the reactors, the plants were built without any containment built around the reactors as a barrier to keep costs down. This allowed radioactive contaminants to go directly into the environment after a steam explosion caused the reactor to break down.
The reactors had been operating continuously for more than a year, storing byproducts of nuclear fission. These byproducts enhanced the uncontrolled reaction and made the accident more difficult to control.
When the reactor got too hot, design flaws deformed, twisted and ruptured the reactor vessel, making the insertion of more control rods impossible.
One notable point is that manipulators have blocked the safety protection systems of many reactors - something that is prohibited by technical specifications unless the safety protection system fails.
The report of the government's Commission of Inquiry, published in August 1986, noted that the manipulators withdrew at least 205 control rods from the reactor core (211 are required for this type of reactor***), leaving six behind, whereas the technical specifications forbid the use of fewer than 15 control rods in the core area during operation of RBMK-1000.
The report also noted that the manipulators had removed a number of control rods from the reactor core.
Three National Impacts:
Radiation dust leaking from the meltdown of the atomic furnace drifted over Russia, Belarus and Ukraine, as well as over parts of Europe such as Turkey, Greece, Moldova, Romania, Lithuania, Finland, Denmark, Norway, Sweden, Austria, Hungary, Czech Republic, Slovakia, Slovenia, Poland, Switzerland, Germany, Italy, Ireland, France (including Corsica) and the UK.
In the earliest days of the accident, it was thought that the nuclear leak at Chernobyl had come from Sweden rather than Russia, when on April 27, 1986, workers at Sweden's Forsmark nuclear power plant, which is about 1,100 kilometers away from Chernobyl, found unusual particles of radiation clinging to their clothes. According to Swedish research, it was found that the radiation did not come from the local nuclear power plant, and they suspected that there was a problem with the Russian nuclear power plant. At that time, Sweden had asked the Soviet Union through diplomatic channels, but it was not confirmed. In addition, the French government claimed that the fallout only reached the borders of Germany and Italy. In Italy, some crops, such as mushrooms, were forbidden to be eaten because of the fallout. The French government did not make similar measurements to avoid arousing fear among the public.
The Chernobyl disaster not only contaminated the surrounding towns, but it was also aided by air currents, which allowed it to spread out in an erratic manner. According to reports by Russian and Western scientists, 60 percent of the radioactive dust that fell in Russia is in Belarus. According to TORCH 2006, half of the volatile particles fell in Ukraine, Belarus, and outside Russia. A large area of the southern part of Bryansk in the Russian Federation and parts of the northern part of Ukraine are contaminated with radioactive material.
Soviet authorities began evacuating people living around the Chernobyl reactor 36 hours after the incident. In May 1986, a month after the incident, some 116,000 people living within a 30-kilometer (18-mile) radius of the plant were evacuated to other areas. For this reason, this area is often referred to as the Zone of alienation. However, the effects of radiation can be spread farther than a 30-kilometer radius.
The long-term effects of the nuclear plant explosion on Chernobyl's inhabitants have been debated, with more than 300,000 people removed from the threat of the disaster, but millions more continuing to live in the contaminated zone. However, those who had been exposed to low doses of radiation showed few symptoms of increased mortality, cancer or birth defects. But it is still not possible to determine the cause in connection with the radioactive contamination. At the same time, the authorities of the former Soviet Union had placed obstacles in the way of the disaster: scientific research had been limited, perhaps because of a lack of democratic thoroughness. In Belarus, an officially challenged scientist, Yuri Bandazhevsky, was detained by the State Control Organization for incorrectly assessing the horsepower of the Chernobyl plant (1000 Bq/kg).
Food RestrictionsIn April 1986, a number of European countries (except France) had already imposed food restrictions, particularly on mushrooms and milk. Twenty years after the disaster, food contamination from radioactive fallout from Chernobyl during manufacturing, transportation, and consumption, and in particular the control of cesium-137 indicators, were mainly restricted to prevent them from entering the human food chain. In parts of Sweden and Finland, some meat products are monitored, including antelope, which live in natural and near-natural environments.
In some areas of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland, levels of cesium-137 in game [including wild boar and deer], wild mushrooms, berries and predatory fish from lakes reached several thousand becquerels per kilogram. Some wild mushrooms in Germany even contain 40,000 Bq/kg of Cesium-137. According to the 2006 TORCH report, the average level in these areas is about 6,800 Bq/kg, which is more than 10 times the EU limit of 600 Bq/kg. As a result, the European Commission has said that "restrictions on certain food imports from these member states will have to be maintained for many years to come."
In the UK, the movement and sale of sheep with a radioactivity index of more than 1,000 Bq/kg has been restricted since 1986 under the Food and Environment Protection Act (FEPA), which has been in force since 1985. This safety measure was based on the recommendations of the 31st report of the Group of Experts of the European Commission. Since 1986, however, the restricted area has been reduced by 96%: from almost 9,000 farms and 4 million sheep at the beginning of the restriction, by 2006 it had been reduced to 374 farms and about 750 square kilometers and about 200,000 sheep. Only some areas in Cumbria, North Wales and south-west Scotland remain restricted.
In Norway, the Sami have been affected by contaminated food, and some reindeer have been contaminated by eating lichen, which absorbs radioactive particles as it takes nutrients from the air.