The Japanese nuclear power plant "Fukushima-1" was built in 1960-1970. and worked smoothly before the accident that occurred at the station on March 11, 2011. It was caused by natural disasters: earthquake and tsunami. If only one of them happened, and the nuclear power plant could resist, but nature has its own plans, and after the most powerful earthquake in the history of Japan, a tsunami struck.
Earthquake
In the middle of the day, seismic sensors at the nuclear power plant reacted and showed the first evidence of an earthquake. The safety system kicked in and began to slide control rods into the reactors to reduce the number of radioactive decays and the resulting neurons. Within 3 minutes, the power of the reactors dropped to 10%, after 6 minutes - to 1%, and finally, after 10 minutes, all three reactors stopped producing energy.
The process of decay of one uranium or plutonium nucleus into two other nuclei is accompanied by the release of a huge amount of energy. Its amount per unit mass of nuclear fuel is a million times greater than that from the combustion of fossil fuels. The products of nuclear decay are very radioactive and produce a large amount of heat in the first hours after the shutdown of the reactor. This process cannot be stopped by turning off the reactors; it must end naturally. That is why control over the heat of radioactive decay is the most important aspect of the safety of nuclear power plants. Modern reactors are equipped with a variety of cooling systems, the purpose of which is to remove heat from nuclear fuel.
Tsunami
Everything could have been bypassed, but while the Fukushima 1 reactors were cooling down, the tsunami struck. It destroyed and disabled spare diesel generators. As a result, the power to the pumps, which forced the coolant to circulate through the reactor, was cut off. The circulation stopped, the cooling systems stopped working, as a result, the temperature in the reactors began to rise. Under such conditions, naturally, the water began to turn into steam, and the pressure began to rise.
The creators of the reactors for Fukushima-1 foresaw the possibility of such a situation. In this case, the pumps had to pump hot liquid into the condenser. But the point is that this whole process was impossible without the work of diesel generators and a whole system of additional pumps, and they were destroyed by the tsunami.
Under the influence of radiation, the water in the reactor began to decompose into oxygen and hydrogen, which began to accumulate and seep under the dome of the reactor. In the end, the concentration of hydrogen reached a critical value and it detonated. First, in the first, then in the third and, finally, in the second block, powerful explosions took place, tearing off the domes of buildings.
The situation at the Fukushima-1 NPP was stabilized only in December, when all three reactors were brought to a cold shutdown state. Now the Japanese specialists are faced with the most difficult task - the extraction of the molten nuclear fuel. But its solution is impossible earlier than 10 years later.
As a result of explosions at power units, there was a large release of radioactive substances (iodine, cesium and plutonium). The amount of radionuclides released into the atmosphere and the ocean amounted to 20% of the emissions after the accident at the Chernobyl nuclear power plant. Leaks of radioactive substances, the sources of which are unknown, continue to this day.
