Corium lava in basement of Chernobyl which is covered by a gigantic and deteriorating sarcophagus

The Chernobyl sarcophagus is 2307kg x 400,000 meter cubed [~ one billion pounds] of cement surrounding 7300 tons [fifteen million pounds] of metal framework. That is how dangerous this small amount of corium is [compared to the amount generated in Fukushima].