Question

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

Answer 1

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