5 ms·
On the other hand, basically every complicated bit of engineering on the PWR is due to the fact that it does have such a high volumetric power density. A PWR is
by Mvandenbergh 4y ago
On the other hand, basically every complicated bit of engineering on the PWR is due to the fact that it does have such a high volumetric power density. A PWR is basically a fancy (very fancy) pressure vessel which is cheap (in relative terms) and then parallel redundant cooling systems and containment buildings because dealing with such high power density is hard. Right after shutdown, the power density from decay heat is still 1.3MW/m3 and dealing with that decay heat in all currently conceived circumstances is where all the money goes.
- pfdietz 4y agoSo, why do fission reactors go with high volumetric power density, then? Because they'd be even more expensive if they didn't.
- tlb 4y agoThe uranium has to be in a small volume for the chain reaction to work.
- pfdietz 4y agoThat doesn't mean the power density has to be high.
- tlb 4y agoIt has to be high within the core. I suppose you could add some empty space nearby
- pfdietz 4y agoNo, it does not have to be high within the core. A reactor can be operated at a low power level. This is not like a fire that goes out if the flame is too weak.
- tlb 4y agoThe problem with that is that cores are very expensive. They require 100s of kgs of enriched uranium. If you run them at half power, you need twice as many and your cost goes up dramatically.
- pfdietz 4y agoThe uranium lasts twice as long, though. So aside from interest costs it's a wash, at least for fuel costs. You are right that the reactor structure costs more. Which is the point I've been trying to make.
- Mvandenbergh 4y agoEssentially. The CO2 cooled AGR has much lower power density and was thought by its designers to be a much superior design to water cooling for safety and cost reasons. It turns out, definitely not on cost grounds and the AGRs are all reaching technical end of life a few years after their original rated lives whereas light water reactors are getting life extensions basically everywhere for decades beyond that. Light water thermal reactors are the worst kind of nuclear reactor except for all the other ones which have been built.