Oh bother! The gas emmision is a one time thing. The plant runs for decades.
Besides, ever hear of electric furnaces?
Try building a nuclear plant without emitting carbon. Manufacturing steel requires lots of coal. Cement also requires lots of heat, most of it is supplied by natural gas. Could you be any dumber? Of course it requires energy to build one, but that is a one time expenditure of energy, once it is built it is producing cheap non-carbon energy, and if enough of them were built they could replace even the coal used to make steel. Use your head for more than a hat rack, it helps to actually engage the brain before talking.
What you are getting at has a name in engineering. It is called Life-Cycle Emissions. You take into account the energy use at each point in a system, accounting for extraction of raw materials, fabrication of components, site clearing and preparation, construction of facilities, operations and maintenance, and waste disposal. People have done this analysis for various energy sources. Here is a result which might be surprising:
Source: "Life-Cycle Assessment of Electricity Generation Systems and Applications for Climate Change Policy Analysis," Paul J. Meier, University of Wisconsin-Madison, August, 2002.
You can see they have shown the amount of greenhouse gas-equivalent released to the biosphere normalized to unit energy output for the various sources.
As you can see, the "footprint" for nuclear is about the same as for so-called "clean" or "green" or "renewable" energy sources. Nuclear is actually "greener", by this measure, than that darling of the environmental movement, solar PV, and also biomass, so I guess Sheryl Crow will have to park that biodiesel bus in favor of a nuclear-electric one (wouldn't that be sweet revenge?). And this isn't even getting into the meatier issues such as reliability, capacity factor, availability, etc. On those counts, nuclear clobbers all the others.