US Navy did research into nuclear jet fuel

The price was higher than what I figured, unfortunately.

However, it should be pointed out that they were probably using electricity, not thermal.  That would make some difference, but probably not enough.

It seems that I've made a mistake.

The problem is the necessity to make hydrogen.  It is very energy intensive.  You could use a high temperature electrolysis, but it still takes electricity.  Heat alone would require 2500 degrees Centigrade in order to break the chemical bonds.