Does 68% of the electrical energy in the united states produced by nuclear fuel

No, although it has increased in recent years as new, more efficient power stations have been built.  

In 2014 only 19.5% of all power generated in the USA came from nuclear power.

Figures for 2010 showed that nuclear power provided even less, with the split being as follows:

25% petroleum
22% coal
22% natural gas
8.4% nuclear
8% renewable energy