How much of the power in the United States is generated by nuclear power plants?
The US government keeps track of this information. It updates it regularly. You might be surprised:
http://www.eia.gov/tools/faqs/faq.cfm?id=427&t=3
This list also reveals something else: coal power is here to stay. Just look at the numbers.
But it also tells us something else: so is nuclear, too. Its percentage of the total power generated is a trend that goes back at least 20 years:
http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_1_1