[Errant]

Uranium oxide melting is up close to 5000 deg. C.

I'm thinking that I read uranium oxide's boiling point was around that, but that the melting point was only about 2,800 C? No problem for a plasma torch though. :)

[chimera]

You're right, 2865 deg. C. according to Wiki. Must’ve switched vaporization point for melting point. So it is possible in the early stages of a LWR loss of coolant to approach that melting point. Probably not the later stages after decay has occurred and the initial heat load has dissipated. This is probably the design basis for the requirements of ECCS and core sprays.