[femto]

What's lithium hydroxide used for in fusion reactors?

Edit: A bit more searching turned up an answer. It's a neutron absorber. So it's used as a shield to stop the neutrons leaving the reactor?

[ncmncm]

The lithium + neutrons would breed the tritium you need for fuel to burn tomorrow.

Extracting parts-per-billion of tritium distributed throughout thousands of tons of hot, brittle, radioactive, super-flammable LiH would be no picnic. Melting it probably would not make that easier.

Fortunately, no one will need to.