Reply #44: 'Net' as in net/gross (and a breeder reactor essay :b ) [View All]

[Celefin]

Not as in 'network'or 'grid'.
It takes 7-10 years for a state of the art atomic power plant to produce the energy equivalent consumed in building it, fueling it over its lifetime and decommissioning it. Only after that time does the energy balance turn positive, or to say it like in my previous post, produce a net energy surplus. Hope that clears up the misunderstanding.

You don't hear much of breeder reactors, regrettably, though the concept is great.
So are the technical and economic challenges.
If it was straightforward, the west would surely be powered by fast breeder reactors like the French 'Superphenix' by now, which has never produced the energy equivalent consumed during construction. India is experimenting with a water cooled thorium reactor as far as I know but a long way from developing anything truly functional.

1 - reprocessing is highly complex due to the nature of plutonium. Ask the French (or actually, ask their neighbours) about La Hague.
2 - reprocessing almost eliminates high level radioactive waste but creates large amounts of low to medium level waste that still needs to be disposed of safely.
3 - reprocessing of spent FBR fuel is an unsolved technical problem due to high burnup rates and buildup of trans-uranium elements
4 - reprocessing requires road or rail transport of waste and fuel, increasing the risk of accidents involving highly hazardous material

4 - cooling in existing designs cannot rely on water as water makes the reaction inefficient
5 - cooling by means of generally very corrosive molten metal like lithium or sodium (the latter being the best coolant but reacting violently when coming into contact with air or water) is an enormous technical challenge as you cannot observe the core through the coolant, cannot shut the reactor down cold with the coolant inside as it would solidify and ruin the reactor, cannot properly decontaminate the coolant in the case of a fuel element failure etc. etc.
6 - cooling by gas (Helium, CO2, N2) is less dangerous but not very efficient for heat transfer and poses its own challenges revolving around containing superheated gas

7 - upscaling much beyond 1GW (like the Superphenix) invalidates the breeders main selling point, as the breeding ratio plummets when the breeding blanket around the core gets to thick because neutrons increasingly fail to reach the outer layers. Breeders are also much more expensive to build due to the technical challenges. These two factors combine to make them uncompetitive to light water reactors that produce 4-5 times the energy at half the cost.

If you have more recent information on workarounds to these problems, please fill me in.
I'm not opposed to the concept as such.

In the meantime until/if such power stations come online (meantime being the next 3-4 decades) i think we're stuck with reducing our energy demands and using available technologies. Which means reducing consumption and going for renewables. If the golden age of limitless thorium-generated energy should become reality, great! But don't hold your breath. It would be far easier, cheaper and more peaceful to drop the illusion of a sustainable consumer society which creates the need for unlimited energy in the first place.

Kind regards,
Cel