Alexie Ananenko, Valeri Bezpalov, and Boris Baranov volunteered to dive into the extremely radioactive water, knowing full well that it was far, far more radioactivity than what was known to be the lethal limit. They were able to find the manual release valve, and drain the basement of water. They died of radiation poisoning 2 weeks later. The corium did eventually melt through the concrete and reach the basement, as feared, but now dry. These 3 men saved millions of lives, and half a continent from being exposed to radiation.
News report from later that week: