russ_watters
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Yes.zoobyshoe said:O.K. So what you're saying is that, in the switch from current power generation to all nuclear/electric, we would have to consume more than 15 TW to get the same 7.2 TW output. Consumption would be more like 22TW.
We're still a very long way from getting to that issue, given all the other related problems in the paper. For example, can I keep the Hoover Dam or do we have to replace that with nuclear power too?But uranium is non-renewable, so it is important.
In any case, you still aren't hearing me on why the thermal energy input itsn't important to the discussion. It will become more apparent at the end of this post.**
Output, right. So anyway, after I put numbers to it, he over-estimated - using his logic - by a factor of 2, not 3. But so much of the rest of the logic is bad that I still wouldn't consider 7.2 TW as a good starting point for the discussion. However, since we are on it, here's a source for the calculation of longevity, using his logic:This goes to his claim that, were we to be generating the current output exclusively by nuclear we'd use up all the viable uranium in 5 years. That was my original question: how long will supplies of nuclear fuels last? If he's overestimated consumption by a factor of 3, as you say, that means we actually would have 15 years of an all nuclear/electric world before the viable uranium got used up. Not better enough to be worth correcting him, IMO. "The world," as you put it, "doesn't care about" ten more years. The world is looking for the longest lasting possible energy source. Should we invest so much in something that's just going to be fossil fuels all over again?
http://www.scientificamerican.com/article/how-long-will-global-uranium-deposits-last/According to the NEA, identified uranium resources total 5.5 million metric tons, and an additional 10.5 million metric tons remain undiscovered—a roughly 230-year supply at today's consumption rate in total.
Currently, we have about 440 reactors. If we needed 7200, that's 440/7200*230= 14 years under current usage patterns. So that's roughly where his math comes from.
But:
So combining those two yields an additional factor of 4: now we're at 56 years.Further exploration and improvements in extraction technology are likely to at least double this estimate over time.
Using more enrichment work could reduce the uranium needs of LWRs by as much as 30 percent per metric ton of LEU. And separating plutonium and uranium from spent LEU and using them to make fresh fuel could reduce requirements by another 30 percent. Taking both steps would cut the uranium requirements of an LWR in half.
An additional factor of 100: now we're at 5,600 years and we haven't even brought seawater into the discussion yet.Second, fuel-recycling fast-breeder reactors, which generate more fuel than they consume, would use less than 1 percent of the uranium needed for current LWRs.
**Notice that nowhere in the post did I reference the thermal input energy of the nuclear fuel. It's very much like discussing a car's fuel efficiency in terms of miles per gallon: the usage is given in units of volume (mass for uranium) per output, so we can skip the step of calculating (by efficiency or heat capacity per gallon/ton) the input heat.
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