See "Corrosion of materials in fused hydroxides" - http://moltensalt.org/references/static/downloads/pdf/ORNL-2048.pdf

Nickel seems to be a good bet, but you may need to use it under a hydrogen-containing atmosphere (the original paper recommends 1 atm of hydrogen but this is too risky so you could try forming gas which is 4-5% hydrogen in nitrogen). You may need to run a baseline to see how much (if any) hydrogen the nickel crucible picks up during heating.

Alumina will definitely be attacked.

Thanks for the prompt reply, Emanuel Cooper.