The catastrophic nuclear disaster the world had long feared finally happened in 1986 at the Chernobyl plant in Ukraine. Reactor number four exploded early one morning in April, sending a vast plume of radioactive fallout into the atmosphere. This would contaminate large areas of the western Soviet Union and Europe, with nuclear rain being recorded as far away as Ireland.
The initial power excursion (nuclear chain reaction) was followed by further chemical and gas explosions, then fire. Unlike those in most Western plants, the reactor building was not a reinforced containment vessel designed to limit the effects of just such an accident. It was therefore destroyed, allowing disastrous quantities of radioactive material to escape. Yet this was an accident that could have been avoided.
Ironically, the catalyst was an experiment carried out to test reactor safety. Operators were worried that a power failure might result in the reactor core overheating, as vast quantities of cooling water were required and standby generators didn’t get the pumps back up to speed for over a minute. They therefore decided to test whether an emergency core-cooling procedure would work should such a situation arise. Had regulations been followed there would have been no problem, but safety features were disabled in order to complete the test. This decision proved fatal. After complex setup procedures were completed, the test commenced but within seconds the core went critical and a powerful explosion rocked the plant.
The aftermath was horrific, though Soviet authorities initially tried to conceal the scale of the disaster. The town of Prypiat was evacuated the following day and remains a deserted time capsule. The accident site was contained within a vast concrete sarcophagus at the center of the 30 km (19 mi) exclusion zone around Chernobyl that is in force to this day.
When: April 26 1986
Where: Prypiat, near Chernobyl, Ukraine
Death toll: Over 200 people suffered acute radiation sickness in the immediate aftermath of the explosion, of whom 31 died within three months. The total number of deaths directly attributable to the accident was 56, mostly irradiated rescue workers but including some children who died of thyroid cancer. The number of premature deaths to be expected from related diseases was estimated at 5,000.
You should know: The radioactive fallout from the disaster at Chernobyl was 400 times greater than the amount released by the atom bomb dropped on Hiroshima at the end of World War ll.