Stinger, it is not so much that the Hydrogen has to be released [Yes it does] but that Hydrogen was "burned" when it combined with the oxygen to become water. Its energy was released in that process.
Hydrogen from natural gas is a matter of seperating the hydrogen from the carbon. The hydrogen in natural gas still has it's energy. The problems with this method of aquiring hydrogen is that it (1) requires natural gas. (2) Unless the carbon is sequestered some how, there is no benifit to the environment over burning the natural gas.
That same 600 million tons of pipe would have gone into power plants [with the same total output] if they were fired with natural gas, oil, coal, or even solar. As You know a nuclear plant is huge, with a tremendous output. You can get electricity by sticking a penny and a dime in a lemon, but it doesn't compair to a nuke plant.
I read somewhere it was around a year of the output for those plants. However; The cost of producing the plant from A-Z was factored into it before it was built. Since most of them have been profitable for the companies that own them, I'd say it took less energy to make and run them Than they are putting out, as the energy sources used (nuclear fuel) yield more combined energy over time than it took to make them.
If you want to go back to the start of things, and calc out how much it actually took to make that plant, you'd have to look at the raw materials, the associated equipment and cost of making the tools to mine the same, then the associated material created by those tools, and on down the line until you have a completed plant. Start adding that up, and I'd say it probably goes upwards of 5 years of that plants output. To me, it doesn't make any sense to chase it that far.
No matter what anyone's opinion is, I don't see hordes of people lining up at the power utility demanding them to cut off their power. Nor do I see hordes of people wholesale ditching their TV's, their cars, nor anything else associated with a modern society. Without electricity, the world as you know it will come to a grinding halt. No more anything, not even toilet paper. So it's kinda pointless to worry about how much energy went into making a nuclear plant, especially when they are the only viable source of energy that with enough plants and restructuring of our infrastructure, could leave us energy independent.
While it's true the energy potential in long chained hydrocarbons is higher, there is a finite amount of that commodity and any other hydrocarbon in the world. Sooner or later, the country and the world will have to bit the energy bullet and drop the hydrocarbons cold preferably before we run out of them, and find ourselves digging through the woods for a piece of flint and stone.