Nuclear!! What happends to the reactor if the aircraft crashes or gets shoot down? It does not sound safe to me.
I agree with Raptor on the hydrogen part, the spaceshuttle is a good example of the amount it takes just to get the thing off the ground, and still it needs help with solid rockerboosters. Ok, i know its much larger then a fighter, but you do want to be able to travel some distance before you run out of fuel. Maybe its time to build a X-wing or a TIE-fighter and move on into space (Antigravity propulsion).
Anyway, the military fuel used today is cleaner then the ones used by civilian airliners. Problem is that its really expensive. After these fourt generation fighters its really time to think about alternative fuel or powerplants for the next generation, or there wont be any future at all for dogfighting.