What Caused the 1986 Chernobyl Disaster?

The deadly Chernobyl Disaster, which killed 31 people, was caused by operators running reactor four at a dangerously low power level during a test of the turbine cooling pumps.

In the aftermath of the explosion, the radioactive fallout spread across the entire northern hemisphere, including 150,000 square kilometers contaminated throughout Ukraine, Belarus, and Russia.

Meanwhile, in Europe, severe shifting winds carried the radioactive cloud over 40% of the continent, reaching Sweden, the United Kingdom, and France.

After the disaster, cities and towns were evacuated.

For example, Pripyat, a town of 50,000 residents located three kilometers from the Chernobyl Nuclear Power Plant, was evacuated 36 hours after reactor four exploded; the town of Chernobyl with 12,000 residents was evacuated during the expansion of the 30-kilometer exclusion zone; and Poliske was evacuated in 1993 due to lingering contamination levels.

Today, the Chernobyl Exclusion Zone has expanded to 2,600 kilometers in Ukraine, heavily guarded by the military, while Pripyat, Ukraine was completely abandoned.

Overall, the disaster at the Chernobyl Nuclear Power Plant shaped nuclear policy and public perception of nuclear energy around the world. 

Frequently Asked Questions:

1) How many immediate fatalities occurred after the explosion?

Two workers died during the initial explosion, along with 28 emergency workers and firefighters within the first four months from acute radiation sickness.

Source: https://www.iaea.org/topics/chornobyl/faqs

2) How large is the exclusion zone today?

2,600 square kilometers.

Source: https://ua.boell.org/en/2020/05/08/avariya-na-chornobilskiy-aes-vidpovidi-na-poshireni-zapitannya-faq

3) How many nuclear reactors were at the Chernobyl Nuclear Power Plant?

Four completed nuclear reactors were at the Chernobyl Nuclear Power Plant, while reactors five and six were under construction when the disaster happened.

Source: https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/chernobyl-accident