The accident at Fukushima-1 was caused by an earthquake and the tsunami that followed. The station itself had a margin of safety and would withstand one of the spontaneous actions.
The catastrophe led to the fact that two natural disasters hit the nuclear power plant at once . Due to the earthquake, the power supply to the station turned off, immediately after that 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The Fukushima-1 NPP was built in the 70s of the last century and at the time of the accident was simply outdated. The nuclear power plant project did not imply the availability of accident management tools that were outside the scope of the project.
And if the station survived the earthquake, then the tsunami, as mentioned above, left the nuclear power plant without power supply.
Before the accident, three power units worked, and they remained without cooling, as a result - the coolant level decreased, but the pressure that began to be generated by the steam, 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, it was decided to dump the steam into the pressure chamber. But her pressure too quickly increased.
Now, in order to preserve it, steam began to be dumped directly into the atmosphere. The containment was managed to be preserved, but the hydrogen that 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 happened the day after the March 12 earthquake . Concrete structures partially collapsed from the explosion, but the reactor vessel was not damaged.
Development of events
After the explosion at the power unit, the level of radiation increased significantly, but after a few hours fell. Samples were taken at the Fukushima-1 nuclear power plant, and studies showed cesium. This meant that the tightness of the reactor was broken.
To cool the reactor, seawater was pumped. The next day, it turned out that the emergency cooling system was damaged in the third block. And there was a suspicion that the fuel elements were partially exposed, and again a hydrogen explosion could occur.
They began to dump steam from the containment and pump sea water. But this did not help, and the explosion occurred on March 14. However, the reactor vessel was not damaged.
Continue work to restore electricity on the first and second blocks. Also continued to pump water to the first and third blocks.
On the same day, the emergency cooling system also failed at the second power unit. They started to pump sea water for cooling. But suddenly the valve for steam discharge 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 still happened in the morning of March 15. The nuclear fuel storage facility at the fourth power unit exploded immediately. The fire was extinguished only after two hours.
On March 17, in the morning, they began to dump sea water from helicopters into the pools of blocks 3 and 4. After it was possible to restore the diesel station at the sixth block, it became possible to pump water using pumps.
Liquidation of an accident
For regular systems to start functioning, it was necessary to restore power supply. And for its restoration 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 out this water. To do this, they decided to build treatment facilities.
The company, which owns Fukushima-1, said that it would have to dump 10 thousand tons of water with low radiation into the sea in order to free the tanks for highly radioactive water from the first three units of the nuclear power plant.
According to the plan, the full elimination of the consequences will take about forty years. The reactors of the nuclear power plants were stopped, and the extraction of spent nuclear fuel from the pools began. Later, complete dismantling of the Fukushima-1 reactors is expected.
Accident consequences
As a result of all the events, a radiation leak has occurred. The government had to evacuate the population from the 20-kilometer zone around the plant. It was strongly recommended that those who lived 30 kilometers from the Fukushima-1 nuclear power plant be evacuated.
Japan, Fukushima-1 and its environs are contaminated with radioactive elements. They were also found in drinking water, milk and some other products. The norm was below the permissible, but for reinsurance their use was temporarily banned.
Radiation was detected in sea water and soil. In some regions of the planet, the background radiation has increased .
In addition to environmental pollution, there are financial losses. TERSO is obliged to pay compensation to the victims of the accident.
Fukushima-1 today
Today, liquidation work is continuing at the nuclear power plant. In May 2015, there was a leak of radioactive water. The purification of the water that was removed from the blocks also continues.
This is one of the main problems. There is a lot of highly radioactive water, and in the process of cooling the reactors it becomes even more. It is pumped into special underground storage, gradually clearing.