Why did Chernobyl happen?

 Why did Chernobyl happen?

The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. The accident occurred during a systems test which simulated a power outage and resulted in a massive power surge that caused an explosion and fire at the reactor. This released a large amount of radioactive material into the atmosphere, which spread over a wide area and contaminated the surrounding environment.

The immediate cause of the accident was a violation of safety protocols at the plant, which allowed for a dangerous combination of events to occur. Specifically, the test that was being conducted at the time of the accident required the reactor to be operated at a low power level, but with a high level of cooling to the reactor core. This created a condition known as a "positive void coefficient," which means that as the reactor's power level drops, the coolant flow through the core increases, causing the reactivity of the core to increase. If the power drops too low, the coolant flow can cause the reactivity of the core to become unstable, which can lead to a rapid and dangerous increase in power.

During the test, operators at the plant made a series of mistakes that caused the reactor's power level to drop too low, triggering the positive void coefficient and leading to the explosion and fire at the reactor. Additionally, the design of the reactor itself had several safety deficiencies that contributed to the severity of the accident. The most significant of these was the lack of a containment structure around the reactor, which would have prevented the release of radioactive material into the environment.

Overall, it was a tragic combination of events of a system test that went wrong with lack of safety measures and lack of training of the operational staffs.