[cyberax]

> It boils off a 1 mile deep water column?

Yes?

> And you don't need a core catcher when you are already 1 mile deep in bedrock.

Yes, you do. Because if the shaft explodes or gets blocked near the top, the fission products can travel up the water column.

[consensus1]

So this thing is just boiling off water from the mile deep water column, and nobody things "hey maybe we could add some more water"? How does a shaft "explode"? What is generating the explosive force?