[philipkglass]

That's part of some newer reactor designs: https://en.wikipedia.org/wiki/Core_catcher

[petre]

Expensive. The concrete can also crack in the event of an earthquake.

[Cthulhu_]

Not as expensive as having to clean up three reactors worth of nuclear meltdown and a few exploded reactors.

I'm sure they can prevent the concrete from cracking in an earthquake.

[petre]

Cheaper solutions exist, such as the one with borosilicate sand on the bottom of the reactor. Building passive cooling pools with those resources is orders of magnitude more useful because it prevents a meltdown rather than attempting to catch the molten core. The ESBWR uses such a passive cooling design.

https://en.m.wikipedia.org/wiki/Economic_Simplified_Boiling_...