"If the plants get decommissioned it will literally cut our energy production by 1/2"
According to the Department of Energy's Energy Information Administration, in August 2009 Nuclear power produced approximately 0.758 quadrillion BTUs of energy, out of a total of 6.266 quadrillion BTUs produced across all sources. That's approximately 12% of total output. Thus, decomissioning nuclear power plants would not cut our energy production by half, either literally or figuratively.
Extensive stats from EIA available here: http://www.eia.doe.gov/emeu/mer/overview.html