On April 26, 1986, an accident occurred at the Chernobyl nuclear power plant, which became the largest disaster in the Soviet nuclear power industry as a result of the unprofessionalism of managers and administrative and technical workers, the result of the desire to achieve results at any cost.
The Chernobyl disaster took place at 1 hour 23 minutes on April 26: a reactor explosion occurred at the 4th power unit with a partial collapse of the power unit building. A strong fire started in the premises and on the roof. A mixture of the remains of the reactor core, molten metal, sand, concrete and nuclear fuel spread over the premises of the power unit. The explosion released a huge amount of radioactive elements into the atmosphere.
Causes of the accident
A day earlier, on April 25, Unit 4 was shut down for preventive maintenance. During this repair, the turbine generator was tested on a freewheel. The fact is that if you stop supplying superheated steam to this generator, it will be able to generate energy for a long time before it stops. This energy could be used in case of emergencies at nuclear power plants.
These were not the first tests. The previous 3 test programs were unsuccessful: the turbine generator gave less energy than calculated. Great hopes were pinned on the results of the fourth tests. Omitting details, reactor activity is driven by the insertion and withdrawal of absorption rods. At the Chernobyl nuclear power plant, these rods had an unsuccessful design, due to which, when they were abruptly removed, a "end effect" arose - the reactor power, instead of falling, sharply increased.
Unfortunately, such features of the rods were studied in detail only after the Chernobyl disaster, but the operating personnel should be aware of the "end effect". The personnel did not know about this, and during the simulation of an emergency shutdown, that very sharp increase in the activity of the reactor occurred, which led to the explosion.
The power of the explosion is evidenced by the fact that the 3,000-ton concrete lid of the reactor came off, broke through the roof of the power unit, carrying a loading and unloading machine along the way.
Consequences of the accident
As a result of the Chernobyl disaster, 2 employees of the nuclear power plant were killed. 28 people later died from radiation sickness. Of the 600 thousand liquidators who took part in the work at the destroyed station, 10% died from radiation sickness and its consequences, 165 thousand became disabled.
A huge amount of equipment used in the liquidation had to be written off and left in cemeteries, right in the contaminated area. Subsequently, the technique slowly began to go into scrap metal and remelting.
Huge areas were contaminated with radioactive substances. An exclusion zone was created within a radius of 30 km from the nuclear power plant: 270 thousand were relocated to other regions.
The territory of the station was deactivated. A protective sarcophagus was built over the destroyed power unit. The station was closed, but due to a lack of electricity, it was reopened in 1987. In 2000, under pressure from Europe, the station was finally closed, although it still performs distribution functions. The protective sarcophagus fell into disrepair, but there are no funds for the construction of a new one.