If carbon emissions are an imminent threat to our planet, why isn't nuclear being aggressively pursued,?

Considering the fact that nuclear power does not generate carbon emissions in the large quantities that coal, oil or natural gas does; why hasn't the global warming alarmists demanded more nuclear power plants for our energy mix, or portfolio if you will. If you threw in there the fact that spent nuclear fuel pins can be reproccessed to extract useful uranium and plutonium to be burned again (as the French have been doing for years, successfully), nuclear seems to me the way to go.