Kyshtym ans Sellafield (Windscale) disasters

[Axelrod]

In addition to the accident in Kyshtym (September 29, 1957), 2 weeks later a similar accident occurred in the UK, in the middle of the west coast

https://en.wikipedia.org/wiki/Sellafield

This accident in England had announced leak 10 times larger.

During the accident at the Windscale reactor on October 10, 1957, 750 TBq of radionuclides were released. Two graphite-moderated reactors, called "pile reactors" at the time, were built as part of the post-war British atomic bomb project.

Early on the morning of October 10, suspicions arose that something unusual was happening. It was expected that the temperature in the core would gradually fall as the release of Wigner energy ceased, but monitoring equipment showed something more ambiguous, and one thermocouple showed that the temperature of the core was instead rising. As this process continued, the temperature continued to rise and eventually reached 400 °C (750 °F).

To cool the pile, cooling fans increased speed and increased air flow. Radiation detectors in the chimney then indicated a release, and it was assumed that the cartridge had burst. This was not a fatal problem and has happened in the past. However, unbeknownst to the operators, the cartridge not only burst, but caught fire, and this was the source of the anomalous heating in channel 2053, and not the Wigner ejection.

Speeding up the fans increased the air flow in the duct, fanning the flames. The fire spread to the surrounding fuel ducts, and soon the radioactivity in the chimney began to rapidly increase. The foreman, arriving at work, noticed smoke coming from the chimney. The core temperature continued to rise, and operators began to suspect that the core was burning.

This accident is the largest in the history of the UK nuclear industry. The fire burned for three days and released radioactive fallout that spread across Britain and the rest of Europe.