Until mid-April 1986, Chernobyl was a small city in the erstwhile Soviet Union that lay some 93 km north of the Ukrainian capital Kyiv and about 350 km from the Belarusian capital Minsk. But on the intervening night of April 25-26, 1986, the name entered global infamy with what would be remembered as the worst disaster in the history of nuclear power generation. So, what happened in Chernobyl on April 26, 1986, and why does it count as the costliest man-made disaster of all time? We explain. Situated in present-day Ukraine, the so-called Chernobyl nuclear power station was located 16 km northwest at Pripyat, an industrial town that housed close to 50,000 residents — including most of the workers at the power station (Chernobyl itself had 12,500 residents). Operational since 1977-83, the station had four reactors, each of which could produce 1,000 megawatts of electricity.…