The beginning of the 21st century is the explosion at the Fukushima 1 nuclear power plant, which occurred in March 2011. On the scale of nuclear events, this radiation accident belongs to the highest level - the seventh level. The nuclear power plant was closed at the end of 2013, and to this day work continues there to eliminate the consequences of the accident, which will take at least 40 years.
Causes of the Fukushima accident
According to the official version, the main cause of the accident is an earthquake that caused a tsunami. As a result of this, power supply devices failed, which led to disruption of the operation of absolutely all cooling systems, including emergency ones, and melting of the reactor cores of operating power units (1, 2 and 3) occurred.
As soon as the backup systems failed, the owner of the nuclear power plant informed the Japanese government about the incident, so mobile units were immediately sent to replace the failed systems. Steam began to form and pressure increased, and heat was released into the atmosphere. The first explosion occurred at one of the station’s power units, concrete structures collapsed, and the level of radiation increased in the atmosphere in a matter of minutes.
One of the reasons for the tragedy is considered to be poor placement of the station. It was extremely unwise to build a nuclear power plant near water. As for the construction of the structure itself, the engineers had to take into account that tsunamis and earthquakes occur in this area, which could lead to disaster. Also, some say that the reason is the unscrupulous work of the management and workers of Fukushima, which is that the emergency generators were in poor condition, so they failed.
Consequences of the disaster
The explosion in Fukushima is a global environmental tragedy for the whole world. The main consequences of the accident at the nuclear power plant are as follows:
the number of casualties is more than 1.6 thousand, the number of missing people is about 20 thousand;
More than 300 thousand people left their homes due to radiation exposure and destruction of houses;
environmental pollution, death of flora and fauna in the area of the nuclear power plant;
financial damage – over 46 billion dollars, but over the years the amount will only increase;
The political situation in Japan worsened.
Due to the accident in Fukushima, many people lost not only a roof over their heads and their property, but also lost their loved ones, their destinies were crippled. They have nothing to lose, so they take part in eliminating the consequences of the disaster.
Protests
Mass protests occurred in many countries, especially in Japan. People demanded to stop using nuclear power. Active renewal of outdated reactors and the creation of new ones began. Now Fukushima is called the second Chernobyl. Perhaps this disaster will teach people something. We need to protect nature and human lives, they are more important than profits from the operation of nuclear power plants.
/Corr. ITAR-TASS Yaroslav Makarov/.
JAPAN-FUKUSHIMA-CONSEQUENCES
The accident at the Fukushima-1 nuclear power plant can, without exaggeration, be called the largest man-made disaster in the history of Japan, after which this country will never be the same. Five months after the March events, which the whole world watched with bated breath, one can only roughly estimate the impact they had on the future of Japan.
The economic damage from the Fukushima-1 accident, according to the most preliminary estimates, exceeds 11 trillion yen (over 142 billion dollars). This is about a third of the total damage that Japan suffered from the powerful earthquake and tsunami wave on March 11. And yet, the wounds inflicted by the elements will heal much faster than those caused by the nuclear crisis. Many years will be spent on emergency work at the station itself: in all three emergency power units, a meltdown of nuclear fuel has been confirmed, the extraction of which will begin no earlier than 2020. The labor-intensive process of decontaminating vast areas of radioactive contamination will take even longer, and this will inevitably change the appearance of the Tohoku region of northeastern Japan.
Traditionally important areas for this part of the country - agriculture and fishing - are under threat. Farmers from Fukushima, Iwate, Miyagi, Tochigi and Ibaraki prefectures are suffering huge losses after numerous cases of radioactive substances being detected in vegetables, milk and meat. In July, radioactive cesium was discovered in Fukushima beef, which was distributed to store shelves throughout almost all of Japan. Subsequently, excess radiation standards were detected in meat from other neighboring prefectures, and the government introduced a temporary ban on the export of meat products outside their borders.
There have not yet been any cases of excess background radiation in fish products, but their sales have already dropped noticeably. After the incident, consumer confidence in the products offered predictably fell. The situation should not be expected to improve in the near future, because the “ghost” of radioactive contamination will haunt Tohoku for many years to come. At the moment, the only thing left for farmers and fishermen is to demand compensation from the operator of the damaged nuclear power plant, Tokyo Electric Power (TEPCO). It is obvious that these compensations alone will not make up for the losses in the agricultural and fishing sectors, and the government of the country will have to actively support them. This, in particular, may suspend Japan's integration into some international organizations, which, as a rule, require the abandonment of benefits for national producers.
The social damage from the nuclear power plant accident was no less widespread. The government of the country completely evacuated the population of the zone within a radius of 20 kilometers around the plant and recommended residents of areas 30 kilometers from Fukushima-1 to leave their homes. Subsequently, some other settlements located further than 20 kilometers from the station were added to the mandatory evacuation zone due to an increase in background radiation, in particular the village of Iitate is located 40 kilometers to the northwest. As a result, more than 80 thousand people were evacuated from dangerous areas. After some time, the authorities allowed refugees to make short trips home. Nevertheless, all these people still do not know when they will be able to return to their homes and whether they will be able to do so at all. The country's Prime Minister Naoto Kan said that this issue could only be considered no earlier than the beginning of 2012.
Meanwhile, residents of the evacuation zone have to get used to the fact that they are not just refugees, but those who fled from “radioactive Fukushima.” There have been repeated reports of blatant cases of discrimination against Fukushima residents. Thus, in schools in Chiba and Gunma prefectures, students transferred from Fukushima were teased as “radioactive” and “contagious”, and pressure was exerted on them not only by classmates, but also by teachers. There have also been cases where cars with license plates registered in Fukushima Prefecture were refused service at some gas stations. Justice Minister Satsuki Eda called these incidents a “violation of human rights” and initiated an investigation into them, but the possibility of discrimination in traditional Japanese society cannot be completely ruled out. Unfortunately, refugees from Fukushima in many ways repeat the fate of survivors of the atomic bombings of Hiroshima and Nagasaki, who also, despite all they experienced, often faced discrimination.
And yet, one cannot help but say that the Japanese public for the most part warmly supports its fellow citizens who survived the tragedy. Suffice it to say that several songs in support of the residents of Fukushima, which were recorded by both popular pop and rock groups and amateur musicians, became hits on the Japanese Internet. The authorities of Fukushima itself are also trying to ease the burden on their own residents, who, of course, are also concerned about the image of their prefecture. Thus, a special 30-year program was adopted to study the consequences of the nuclear power plant accident and their impact on the health of residents of the region. This study will be the largest ever conducted in the world. In addition, the authorities began distributing personal dosimeters to all children under 14 years of age and pregnant women living in the prefecture. In total, it is planned to issue 300 thousand devices. Ten stationary dosimeters are planned to be installed on the territory of each of the 500 schools in the prefecture. Plans are being drawn up to clean up the soil from radioactive materials deposited on it. In particular, in the capital of the prefecture it is planned to completely remove the top layer of soil and clean all buildings using water cannons. Fukushima authorities are also negotiating with the central government about removing waste, including radioactive waste, outside the prefecture. Undoubtedly, the nuclear crisis at the same time became a stimulus for the development of the region, as was the case with Hiroshima and Nagasaki.
Finally, the accident at the Fukushima-1 nuclear power plant had a strong impact on the energy strategy of Japan, which, after the March events, realized its excessive dependence on nuclear energy. The surge in anti-nuclear sentiment in Japanese society was supported by the authorities. Prime Minister Kan said the incident would require a complete overhaul of energy policy. The Ministry of Economy, Trade and Industry is already developing a new energy development program, which is designed for 30 years. Its main objectives are to reduce the role of peaceful nuclear energy, increase the level of use of renewable energy sources and introduce new technologies in this area. In addition, structural changes have taken place in the government apparatus, which reflect the attitude of the new Japan towards nuclear energy. The National Agency for Nuclear and Industrial Safety has been removed from the Ministry of Economy and is expected to be transferred over time to the control of the Ministry of Environment.
The transition to a new energy policy will not be easy. The gradual abandonment of nuclear power plants will inevitably lead to greater load on thermal power plants and will increase Japan's fuel needs for them, while this country is already one of the largest fuel importers in the world and, in particular, the largest purchaser of liquefied natural gas (LNG). An additional complication is the expected resistance from business circles, which form a kind of nuclear lobby in Japan. Most likely, the formation of a new national energy sector will become one of the main tasks of several future governments of the country.
Many experts are inclined to believe that the accident at the Fukushima-1 nuclear power plant was caused not only by an earthquake as the only cause; the facts show that the station itself withstood seismic tremors quite successfully. However, the problem was that there was an overlap of two natural disasters, which led to such a large-scale disaster. Although the official investigation into the cause of the accident has not yet been completed - its findings will not be ready until the end of the year - preliminary findings indicate that the earthquake was responsible for the loss of external power supply. After this, as expected, the diesel generators were started, but their work was disrupted by the arriving tsunami.
Causes of the accident
Thus, the superposition of two catastrophic events further aggravated the already difficult situation at the nuclear power plant. The station did not withstand the elements due to the fact that it was built back in 1970. Her design was, from a modern point of view, already outdated, and she had no means of managing accidents outside the scope of the design. The result of the station’s unavailability was that the result of the superposition of two emergency situations – the loss of external supply and the failure of diesel generators – resulted in a meltdown of the reactor core. This generated radioactive steam, which personnel were forced to release into the atmosphere. And the explosion of hydrogen released showed that the station did not have means of controlling and suppressing it, or there were not enough of them.
All three power units operating before the accident were left without sufficient cooling, which resulted in a decrease in the coolant level, and the pressure created by the resulting steam began to increase sharply. The catastrophic development of events began to develop from power unit No. 1. The personnel, in order to avoid damage to the reactor by high pressure, began to release steam first into the containment, and this led to the fact that the pressure in it more than doubled. Now, in order to preserve the containment, steam began to be released into the atmosphere, while the responsible organizations stated that radionuclides would be filtered out of the released steam. Thus, it was possible to relieve the pressure in the containment. But at the same time, hydrogen, formed due to the exposure of fuel and oxidation of the shell of fuel elements made of zirconium, penetrated into the reactor compartment. The high temperature and concentration of steam led to a subsequent hydrogen explosion in the first power unit of the nuclear power plant. This event occurred the day after the earthquake, March 12 in the morning at 6:36 UTC. The consequence of the explosion was the destruction of part of the concrete structures, while the reactor vessel was not damaged, only the outer reinforced concrete shell was damaged.
Developments
Immediately after the explosion, there was a strong increase in radiation levels, reaching more than 1000 μSv/hour, but a few hours later, the radiation level dropped to 70.5 μSv/hour. Mobile laboratories that took samples on the territory of the nuclear power plant showed the presence of cesium, which could indicate a violation of the tightness of the shells of the fuel elements. The Japanese government confirmed at noon on the same day that there had indeed been a radiation leak, but the scale was not reported. Subsequently, officials from both the government and TEPCO, which operates the plant, said that seawater mixed with boric acid would be pumped into the reactor's containment to cool it, and according to some reports, water would also be pumped into the reactor's containment. into the reactor itself. According to the official version, hydrogen leaked into the space between the steel shell and the concrete wall, where it mixed with air and exploded.
The next day, at the Fukushima-1 nuclear power plant, problems began with unit No. 3. It turned out to have a damaged emergency cooling system, which was supposed to be connected when the coolant level dropped below a predetermined level. Also, preliminary data indicated that the fuel elements were partially exposed, so again there was a threat of a hydrogen explosion. A controlled release of steam from the containment began to reduce pressure. Since it was not possible to cool the reactor of block No. 3, they also began pumping sea water into it.
However, the measures taken did not help to avoid an explosion at the third power unit. On the morning of March 14, an explosion similar to the explosion at the first power unit occurred at this unit. In this case, both the reactor vessel and the containment were not damaged. Personnel began to restore emergency power supply to units 1 and 2, and sea water was pumped to units 1 and 3. Subsequently, on that day, the emergency cooling system also failed at the second power unit. TEPCO said the same measures are being taken at this unit as at Units 1 and 3. While pumping seawater into block 2, the safety valve for releasing steam failed, the pressure increased, and pumping water became impossible. Due to the temporary complete exposure of the core, some of the fuel elements were damaged, but subsequently it was possible to restore the function of the valve and resume the supply of sea water.
The troubles of the nuclear power plant did not end there. The next morning, an explosion occurred at the second power unit, which resulted in the failure of the unit for condensing steam coming out of the reactor during accidents. The containment may also have been damaged. At the same time, an explosion occurred in the spent nuclear fuel storage facility at unit No. 4, but the fire was extinguished in 2 hours. The personnel from the station, due to the increased level of radiation, had to be evacuated, leaving only 50 engineers.
On the morning of March 17, the release of sea water from helicopters into the pools of power units 3 and 4 began to eliminate possible damage to spent fuel. Two helicopters made 4 flights each and tried to fill the pools with water. In the future, due to the scale of damage and the wide scope of work, the emergency response headquarters faces the difficult task of choosing priority work. Sea water needs to be pumped into the first four power units, while basic personnel are needed at units 5 and 6 to maintain them in normal condition. All this was complicated by very high levels of radiation, especially during the release of steam, during which people had to take shelter. Therefore, it was decided to increase the number of personnel at the industrial site to 130 people, including soldiers. It was possible to restore the diesel power plant of unit 6, and it began to be used to supply water to power unit 5 as well.
On the eighth day, after the devastating earthquake, a special fire unit was deployed at the nuclear power plant, which had powerful vehicles in its arsenal. With their help, water is poured into the spent fuel pool of power unit 3. At the same time, small holes were drilled on the roofs of blocks 5 and 6 to prevent hydrogen accumulation. The next day, March 20, according to plan, it was planned to restore power supply to Unit 2 of the nuclear power plant.
Liquidation
At the end of March, it became necessary to pump water out of the flooded turbine rooms of blocks 1, 2 and 3. If this is not done, then restoring power supply will be impossible, and standard systems will not be able to function. Considering the size of the flooded premises, the liquidators found it difficult to talk about the timing of this work; at the same time, the turbine condensers where it was planned to pump this water were full, which means that the water had to be pumped out somewhere first. Water activity in the turbine compartments indicated that the containments of the first three blocks were leaking radioactive water. There is a high level of radiation in the turbine rooms, which significantly slows down emergency work.
The condition of all reactors remains relatively stable; fresh water is supplied to them using an electric pump. The pressure in the containment shells of blocks 1, 2 and 3 is gradually returning to normal. TEPCO decided to build a sewage treatment plant next to the emergency units to solve the problem of flooded premises. Preparatory work is underway to pump water from the condensers into special tanks for storing condensate, and from them into other containers.
The beginning of April was marked by the fact that liquidators discovered highly active water in a concrete channel for laying electrical cables, located at a depth of 2 meters. In addition, a 20 cm wide crack was found in the wall of the cable channel. Several attempts to fill the crack with concrete were unsuccessful, since the water did not allow the concrete to harden. After this, they tried to seal the crack with a special polymer composition, but this attempt also turned out to be unsuccessful. In order not to waste time on this work, the employees decided to make sure that it was through this crack that radioactive water entered the sea, but the study refuted this assumption. Attempts to seal the crack continued anyway, and if they failed, it was decided to strengthen the ground in the area of the leak with chemicals.
On April 2, temporary electric pumps supplying water to the containment shells of the first three blocks were switched from mobile units to external power supply. From the condenser of block 2, water began to be pumped into storage tanks, for subsequent pumping of water into the condenser from the basement of the power unit. TEPCO stated that it was forced to dump 10 thousand tons of low-level radioactive water into the sea in order to free up the standard storage facility for pumping high-level radioactive water from blocks 1, 2 and 3. The Japanese government allowed such measures to be taken, especially since, as reported, this discharge does not threaten the health of people living near the nuclear power plant.
We managed to seal the leak from the electrical cable duct. Nitrogen was pumped into the containment of the first block to displace hydrogen, in order to avoid the occurrence of an explosive concentration. As before, the issue of pumping water into storage facilities is acute; their volumes are clearly not enough, therefore, at the request of TEPCO, a technical “island” “Mega-Float”, which is designed for 10,000 tons of water, was sent to the accident area. Upon arrival at its destination, it was converted to accommodate radioactive water storage. In addition, the company plans to build temporary storage facilities for radioactive water in the area of the station.
In mid-April, powerful aftershocks and a magnitude 7 earthquake did not interfere with the progress of emergency work, however, some operations had to be postponed. Pumping of water began from the structures of block 2. The temperature in the cooling pool of block 4 rose, and it was decided to pump 195 tons of water into it to cool it. The level of contamination of seawater with iodine-131 has decreased, but within a radius of 30 km from the station, the level of radiation in seawater is still significantly higher than permissible and the closer to the station, the higher it is. TEPCO, to prevent repeated water leakage, decided to build steel slabs that completely fenced off the process water intakes from the sea.
In mid-April, TEPCO announced that a new response plan had been approved. According to this plan, the company intends to build a closed system consisting of pumps to pump water out of the premises, followed by its filtration and purification, and its further cooling. Subsequently, the purified water can be used to cool the reactors. Thanks to this, there will be no need to discharge water into storage facilities, and its volume will not increase. The installation of this system will take about 3 months, and within six months the liquidation of the accident should be completed.
In parallel with these works, the station area is being cleaned using remotely controlled equipment. On April 20, full-scale spraying of chemicals began over the industrial site to settle dust. These reagents bind dust into larger particles, and it settles near the accident site without being carried away by the wind. At the end of April, TEPCO began preparations for a new phase of reactor cooling.
Consequences of the accident
As a result of all these incidents, a radiation leak occurred at the Fukushima-1 nuclear power plant, both through air and water, so the authorities had to evacuate the population from an area with a radius of 20 km from the plant. In addition, people were prohibited from staying in the exclusion zone, and people living within a 30 km radius from the station were strongly recommended to agree to evacuate. A little later, information appeared that radioactive elements of cesium and iodine isotopes had been discovered in some areas of Japan. Two weeks after the accident, radioactive iodine 130 was detected in the drinking water of some prefectures, but its concentration was below the permissible level. During the same period, radioactive iodine - 131 and cesium - 137 were discovered in milk and some products, and although their concentrations were not hazardous to health, their use was temporarily banned.
During the same period, in samples of sea water taken within the 30-kilometer zone of the station, an increased content of iodine was found - 131, and a slight presence of cesium - 137. However, later, due to leakage from radioactive water reactors, the concentration of these substances in sea water increased greatly and at times reached concentrations several thousand times higher than the permissible limit. In addition, at the end of March, an insignificant concentration of plutonium was found in soil samples taken at the industrial site. At the same time, in many regions of the planet, including Western Europe and the USA, the presence of radioactive substances uncharacteristic for these areas was noted. Many countries have temporarily banned the import of products from certain prefectures in Japan.
In financial terms, the accident at Fukushima-1 also has dire consequences, especially for Japan and, in particular, for the owner of the nuclear power plant, TEPCO. The nuclear industry also suffered significant damage, for example, after the accident, quotes of uranium mining companies sharply decreased and spot prices for raw materials for nuclear power plants fell. According to experts, the construction of new nuclear power plants, after the accident in Japan, will increase by 20–30%. TEPCO, at the request of the Japanese government, is obliged to pay compensation for 80 thousand people affected by the consequences of the accident, the amount of payments could reach $130 billion. The company itself, the owner of the nuclear power plant, lost $32 billion of its market value due to a decrease in the price of its shares. And although the nuclear power plant was insured for several million dollars, this case, according to the contract, does not fall under the “insurance” category.
State of the problem today
The latest information on the state of the reactor of the first power unit, published by TEPCO, shows that, most likely, a significant part of the core melted and, having fallen to the bottom of the reactor, burned through it, then fell into the pressurized shell, damaging it, and therefore a leak occurred into the underground structures of the unit . Work is currently underway to find the location of the leak in the containment. Today, the construction of a protective shelter for the first power unit is underway to eliminate further radiation from entering the atmosphere. The area near the block has been cleared, making it possible to install a large crane there. The entire block, according to the plan, will be covered with a steel frame structure covered with polyester fabric.
On May 24, TEPCO said it accepted the meltdown of reactor cores 2 and 3, which occurred in the early days of the accident, and that it was necessary. So, according to the company, the efforts that were made in the first days, in all likelihood, were not enough to cool the reactor. Since the water flow was very large and, as a result, the active zone remained completely open. Therefore, most of the fuel elements of block 3, and a little earlier, block 2 melted and accumulated on the bottom of the reactors. But the company hopes that a significant portion of the fuel cells has survived, as instruments show that water levels are now sufficient to prevent a complete meltdown of the core. Today, the condition of blocks 2 and 3 is stable and does not pose any danger.
On May 26, the company announced that it had detected a leak of radioactive water in the treatment facilities of Unit 3, so pumping water from Units 2 and 3 was temporarily suspended. At the same time, work is being carried out on power supply lines. Although the company says the water will stop leaking soon, it will have to take steps to fix the problem, which is made difficult by the high levels of radiation emanating from the contaminated water. On the last day of May, an explosion occurred at power unit 4. It is believed that a gas cylinder exploded in a pile of dismantled rubble, which was hit by remotely controlled equipment.
Although TEPCO said in a statement in mid-April that it would be able to clean up the accident by the end of the year, it is now clear that this deadline will not be met. Both experts and representatives of the company themselves talk about this. The schedule will not be able to be met due to the apparent meltdown of fuel in the first three reactors of the nuclear power plant. Therefore, the problem of fuel melting will have to be solved first, and this will negatively affect the entire work schedule, which will be far behind the planned one. Company representatives did not provide any new deadlines for completing the work.
Nuclear energy is a virtually inexhaustible source of inexpensive electricity, which has been saving the world from energy hunger since the middle of the last century. But nuclear power plants are not only rivers of cheap electricity, but also the most terrible radiation disasters that can destroy an entire country. Such a catastrophe was avoided at the Three Mile Island nuclear power plant, irreparable damage was caused by Chernobyl, and in 2011 a blow was unexpectedly struck by the Japanese Fukushima-1 plant, which still keeps the world in suspense.
Accident at the Fukushima-1 nuclear power plant
An object: Fukushima-1 Nuclear Power Plant, Okuma City, Fukushima Prefecture, Japan.
Fukushima-1 was one of the most powerful nuclear power plants in the world. It consists of 6 power units, which before the accident supplied up to 4.7 gigawatts of energy to the electrical network. At the time of the disaster, only reactors 1, 2 and 3 were in working order, reactors 4, 5 and 6 were shut down for scheduled repairs, and the fuel from the fourth reactor was completely unloaded and was in the cooling pool. Also, at the time of the disaster, in the cooling pools of each power unit there was a small supply of fresh fuel and a fairly large amount of spent fuel.
Victims: 2 died and 6 were injured at the time of the disaster, another 22 people were injured during the liquidation of the accident, 30 people received dangerous doses of radiation.
Causes of the disaster
The accident at the Fukushima-1 nuclear power plant is the only radiation disaster caused by a natural disaster. And it would seem that only nature can be blamed here, but, surprisingly, people are also to blame for the accident.
It is interesting that the notorious earthquake that occurred on March 11, 2011 cannot be considered the main cause of the Fukushima accident - after the first tremors, all reactors operating at the nuclear power plant were shut down by the emergency protection system. However, after about an hour, the station was covered by a tsunami wave almost 6 meters high, which led to fatal consequences - the normal and emergency reactor cooling systems were turned off, and then a chain of explosions and radiation emissions followed.
It's all to blame for the wave, which disabled all power sources for cooling systems and also flooded backup diesel power plants. The reactors, deprived of cooling, began to heat up, their core melted, and only the selfless actions of the plant personnel saved the world from a new Chernobyl. Although Fukushima could have become worse than Chernobyl - three reactors at the Japanese plant were in an emergency situation.
What is people's fault? Everything is very simple: when designing the station (and construction began back in 1966), the locations for the location of diesel power plants were chosen incorrectly and the supply of electricity to the standard reactor cooling systems was not thought out. It turned out that the reactors withstood colossal loads, but the auxiliary systems failed from the first blow of the elements. This can be compared to installing a new armored door with old wooden jambs - the door cannot be broken into, and the hinges are unlikely to hold out a burglar...
Chronicle of events
The elements struck the first blow in 14.46 local time. The reactors of the Fukushima-1 nuclear power plant (power units No. 1, 2 and 3) that were operating at that time were shut down by activated emergency protection systems. And everything would have worked out, but approximately 15.36 The dam protecting the station from the sea was overtaken by a tsunami wave 5.7 meters high.
The wave easily overflowed the dam, penetrated the territory of the nuclear power plant, causing various damages, began to flood buildings and premises, and 15.41 The water disabled the standard power supply systems of the reactor cooling systems and emergency diesel power plants. It is this moment that can be considered the zero point of the disaster.
As is known, reactors continue to emit large amounts of heat even after shutdown - this is mainly due to the ongoing decay of highly active fission products of nuclear fuel. And, despite the fact that the reactor is actually “turned off” (nuclear chain reactions are stopped), megawatts of thermal energy are released in it, capable of melting the core and leading to disaster.
This is exactly what happened at three reactors in Fukushima. Each of them released from 4 to 7 megawatts of energy, but due to the shutdown of the cooling systems, this heat was not removed anywhere. Therefore, in the first hours after the tsunami in the active zones of reactors 1, 2 and 3, the water level dropped significantly and at the same time the pressure increased (the water simply turned into steam), and, as experts suggest, some of the fuel assemblies with nuclear fuel melted.
Already on the evening of March 11 a significant increase in pressure was recorded in the containment of power unit No. 1, which was twice the permissible limit. And in 15.36 March 12 The first explosion occurred, as a result of which the power unit building was partially destroyed, but the reactor was not damaged. The cause of the explosion was the accumulation of hydrogen, which is released during the interaction of superheated steam and zirconium shells of fuel assemblies.
On the second day after the disaster - on the morning of March 12- it was decided to cool reactor No. 1 by supplying sea water. At first they wanted to abandon this measure, since sea water, saturated with salts, accelerates the corrosion process, but there was no other way out; there was simply nowhere to get many thousands of tons of fresh water.
On the morning of March 13 An increase in pressure was recorded inside reactor No. 3, and the supply of sea water to it also began. However at 11.01 am on March 14 an explosion occurred in the third power unit (as in the first power unit, hydrogen exploded), which did not lead to serious damage. In the evening of the same day, the supply of sea water inside reactor No. 2 began, but 6.20 am March 15 and an explosion occurred in its premises, which did not cause serious destruction. At the same time, an explosion occurred in power unit No. 4, supposedly in the nuclear waste storage facility. As a result, the structure of the fourth power unit received serious damage.
After a chain of these accidents and a significant increase in radiation on the territory of the station, a decision was made to evacuate the personnel. There were only 50 engineers left in Fukushima to solve current problems. However, employees of third-party companies were involved in eliminating the consequences of the accident, pumping water, laying electrical cables, etc.
Due to the lack of electricity, the cooling pools in which the fuel assemblies of the fourth, fifth and sixth reactors were located also began to pose a threat. The water in the pools did not circulate, its level was falling, and on March 16, the operation to pump water into them began. The next day, the situation became extremely dangerous, and several tens of tons of water were sent from helicopters to the storage pools of blocks No. 3 and 4.
From the first day, work was carried out to connect power to the station from a power line located one and a half kilometers away. It must be said that the diesel power plant of the sixth power unit continued to operate, and it was periodically connected to other power units, but its power was not enough. And only by March 22, power supply to all six power units was established.
It was the injection of sea and then fresh water into the reactors that became the main strategy for stabilizing the situation. Water was supplied to the reactors until the end of May, when it was possible to restore the closed cooling system. Only on May 5, people entered power unit No. 1 for the first time after the accident - for only 10 minutes, since the level of radioactive contamination was very high.
It was only possible to completely shut down the reactors and put them into cold shutdown mode by mid-December 2011.
Consequences of the Fukushima accident
The accident at the Fukushima-1 nuclear power plant had the most disastrous consequences, which, surprisingly, arose due to the fault of people.
The most unpleasant thing in all radiation accidents is the contamination of air, water and land with highly active fission products of nuclear fuel. That is, radiation contamination of the area. A certain contribution to this contamination was made by explosions at power units that occurred from March 12 to 15, 2011 - the steam released from the reactor containments carried a certain amount of radionuclides that settled around the station.
However, the greatest pollution was caused by seawater, which was pumped into the reactors in the first week after the accident. After all, this water, passing through the reactor core, again ended up in the ocean. As a result, by March 31, 2011, the radioactivity of ocean water at a distance of 330 meters from the station exceeded the permissible limit by 4385 times! Currently, this figure has decreased significantly, but the radioactivity of the coast near the station is almost 100 times higher than all permissible standards.
Releases of radioactive substances forced the evacuation of people from a 2-kilometer zone around the station on March 11, and by March 24, the radius of the evacuation zone increased to 30 km. In total, according to various estimates, from 185 to 320 thousand people were evacuated, but this number also includes those evacuated from areas that suffered serious damage from the earthquake and tsunami.
As a result of water contamination, fishing has been prohibited in a number of areas, and a ban has been placed on the use of land in a 30-kilometer zone around Fukushima-1. Currently, active work is underway to decontaminate the soil in this area, however, due to high concentrations of radionuclides, the simplest solution was to remove the top layer of soil and its subsequent destruction. In this regard, local residents are prohibited from returning to their homes; it is unknown when this can be done.
As for the impact of the accident on human health, there are no particular concerns about this. It is believed that even residents of a 2-kilometer zone received minimal radiation doses that did not pose a danger - after all, the main contamination of the area occurred after the evacuation. However, according to experts, the true consequences of the disaster on human health will not be clear until 15 years from now.
The accident at the Fukushima-1 nuclear power plant had consequences of a completely different kind. Japan, due to the shutdown of all its nuclear power plants, was forced to significantly increase electricity production at traditional thermal power plants. But most importantly, the accident has caused fierce debate over the need for nuclear energy in Japan, and it is quite possible that the country will abandon the use of nuclear power plants altogether by the 2040s.
Now
The station is currently inactive, but work is underway to maintain the reactors and cooling pools in a stable condition. The fact is that heating of nuclear fuel is still occurring (in particular, the water temperature in the pools reaches 50 - 60 degrees), which requires constant heat removal both from the reactors and from the pools with fuel and nuclear waste.
This state will persist at least until 2021 - during this time the most active decay products of nuclear fuel will disintegrate, and it will be possible to begin the operation to remove the molten cores from the reactors (the removal of fuel and waste from the cooling pools will be carried out at the end of 2013). And by the 2050s, the Fukushima-1 nuclear power plant will be completely dismantled and cease to exist.
Interestingly, reactors No. 5 and 6 are still operational, but their normal cooling systems are damaged and therefore cannot be used to generate electricity.
Currently, the station is constructing a sarcophagus over power unit No. 4; similar measures are planned to be taken in relation to other damaged reactors.
Thus, at the moment, the emergency station does not pose a danger, but huge amounts of money have to be spent to maintain this situation. At the same time, various incidents periodically occur at the station that could lead to a new accident. For example, on March 19, 2013, a short circuit occurred, as a result of which the emergency reactors and cooling pools were again left without cooling, but by March 20 the situation was corrected. And the cause of this incident was an ordinary rat!
The accident at the Fukushima-1 nuclear power plant attracted the attention of the whole world, causing fear and anxiety among people even on the far side of the globe. And now each of us can personally see what is happening at the station - several web cameras are installed around it, transmitting images from key facilities of Fukushima-1 around the clock.
And we can only hope that the station employees will not allow new accidents, and all Japanese and half the world can sleep peacefully.
Animation of the processes that took place at the Fukushima nuclear power plant after the tsunami:
One of the most shocking tsunami videos:
The accident at Fukushima-1 was caused by an earthquake and the subsequent tsunami. The station itself had a safety margin and would have withstood one of the natural disasters.
What led to the disaster was that two nuclear power plants were hit at once. Because of the earthquake, the power supply to the station was turned off, immediately after that the emergency generators turned on, but they also did not work for a long time due to the tsunami.
Causes of the accident
The Fukushima-1 nuclear power plant was built in the 70s of the last century and at the time of the accident was simply obsolete. The design did not assume the presence of accident management facilities that would be outside the scope of the design.
And if the station withstood the earthquake, then the tsunami, as mentioned above, left the nuclear power plant without power supply.
Before the accident, three power units were operating, and they were left without cooling; as a result, the coolant level decreased, but the pressure that the steam began to create, on the contrary, began to increase.
The development of the disaster began with the first power unit. To prevent the reactor from being damaged due to high pressure, they decided to dump the steam into a containment vessel. But the pressure in her also quickly increased.
Now, to preserve it, they began to dump steam directly into the atmosphere. The containment was preserved, but the hydrogen, which was formed due to the exposure of the fuel, leaked into the reactor compartment.
All this led to an explosion at the first power unit. It occurred the day after the earthquake. The explosion partially destroyed the concrete structures, but the reactor vessel was not damaged.
Developments
After the explosion, the radiation level at the power unit increased greatly, but dropped a few hours later. Samples were taken on the territory of the Fukushima-1 nuclear power plant, and studies showed the presence of cesium. This meant that the reactor's seal was broken.
Sea water was pumped in to cool the reactor. The next day it turned out that the emergency cooling system in the third unit was damaged. And a suspicion arose that the fuel elements were partially exposed, and a hydrogen explosion could occur again.
They began to release steam from the containment and pump in sea water. But this did not help, and on March 14th. However, the reactor vessel was not damaged.
Continue work to restore electricity to the first and second units. They also continued pumping water to the first and third blocks.
On the same day, the emergency cooling system at the second power unit also failed. They started pumping in seawater for cooling. But suddenly the steam release valve broke, and it became impossible to pump water.
But the troubles of Fukushima-1 did not end there. The explosion at the second power unit nevertheless happened on the morning of March 15. The nuclear fuel storage facility at the fourth power unit immediately exploded. The fire was extinguished only after two hours.
On the morning of March 17, sea water began to be dropped from helicopters into the pools of blocks 3 and 4. After the diesel station at the sixth block was restored, it became possible to pump water using pumps.
Elimination of the accident
In order for the standard systems to begin functioning, it was necessary to restore the power supply. And to restore it, it was necessary to pump out water from the flooded turbine compartments.
Everything was complicated by the fact that the level of radiation in the water was very high. The question arose: where to pump this water. For this purpose, they decided to build a wastewater treatment plant.
The company that owns Fukushima 1 said it would have to dump 10,000 tons of low-radiation water into the sea to free up highly radioactive water tanks from the plant's first three units.
According to the plan, complete elimination of the consequences will take about forty years. The nuclear power plant's reactors were shut down and the removal of waste from the pools began. Later, it is planned to completely dismantle the reactors of the Fukushima-1 nuclear power plant.
Consequences of the accident
As a result of all events, a radiation leak occurred. The government had to evacuate the population from a 20-kilometer zone around the nuclear power plant. Those who lived 30 kilometers from the Fukushima-1 nuclear power plant were strongly recommended to evacuate.
Japan, Fukushima-1 and its surroundings are contaminated with radioactive elements. They have also been found in drinking water, milk and some other products. The norm was below the permissible limit, but to be on the safe side, their use was temporarily banned.
Radiation was detected in sea water and soil. In some regions of the planet it has increased
In addition to environmental pollution, there are financial losses. The TERCO company is obliged to pay compensation to victims of the accident.
Fukushima-1 today
Today, liquidation work continues at the nuclear power plant. In May 2015, radioactive water leaked. The purification of water extracted from the blocks also continues.
This is one of the main problems. There is a lot of highly radioactive water, and as the reactors cool, it becomes even more abundant. It is pumped into special underground storage facilities, gradually purified.