[xyzzyz]

I seriously doubt that. What would you make the reactor of, so that it withstands temperatures that melt steel? How are you going to move that coolant around? There are hard physical limits here. In reality, nobody would bother, because you can just make electricity and use it to melt steel instead.

[m4rtink]

Nuclear lightbulb engine - but for process heat!

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

Like it was not crazy dangerous enough. ;-)