[PCRit]

The melting temp for NaCl is 800.8C (or 1473.4F), that’s a LOT of heat to store for using in a steam generator!

[RSmithOpt]

One thing's for sure....they'd better be using inner insulating material much like space shuttle tiles to 'hold' the heat with pure silica backing that up.

The thermal radiation will dissipate regardless of the insulation used for the storage tank.