Fukushima Round Table Discussion 2

The cores on all three reactors melted down.These are the events that caused these reactors to melt down:

1. The water in the containment vessel evaporated because the pumps that keep the coolant water flowing were disabled by the flooding waters of the Tsunami;
2. The Nuclear fuel became uncovered and heated up to a temperature of 2,300 degrees Celsius.
3. The nuclear fuel melted and mixed with the materials in containment vessel;
4. This melted core formed a magma called Corium which flowed down to the bottom of the reactor vessel.
5. The corium pierced the containment vessel and fell on the concrete containment ;

Currently, we don’t know what quantity of corium has fallen? How deep did the corium pierced the concrete containment vessel?