That's steam. You have to know all three melted down, and are China Syndrome. They had no power to cool them for the first few days after it all happened. It doesn't take a rocket scientist to figure that out.
3 mile island almost melted down in just a few HOURS. They barely contained it, by releasing some steam out, that gave about 1900 people downwind early cancer. That reactor has been shut down ever since.

You could see the reactor 3 at Fukushima blew it's top off an into a nearby building. Some called it a nuclear explosion but it wasn't. Just built up steam, and it popped it's top. Sent it flying.

Thanks for posting this video, keeps us updated as the Japs are too proud to admit their mistakes.