Material Converts Radiation Into Electricity

holy_calamity writes "Nuclear powered space probes like Pioneer have 'nuclear batteries' that (very inefficiently) convert heat from decaying isotopes into electricity. US researchers think a new material that converts radiation directly into power instead could make nuclear batteries 20 times more efficient. (Unfortunately they will likely not be user-replaceable.) The material consists of gold, carbon nanotubes, and lithium hydride."

Comments

There could be a serious benefit

[Samalie]

If this works, imagine being able to generate electricity not just from nuclear power plants themselves, but from the nuclear waste storage facility?

I would think, assuming of course this proved as pratical in pratice vs theory, that this could dramatically reduce our dependance on fossil fuels. Assuming of course you could use the "pure" radiation of the waste into electricity.

Re:There could be a serious benefit

[asuffield]

If this works, imagine being able to generate electricity not just from nuclear power plants themselves, but from the nuclear waste storage facility?

To heck with that, and with batteries - imagine being able to generate electricity from nuclear power plants themselves, rather than using them to heat water, shove it through an inefficient turbine, and then let most of the energy evaporate off in a cooling tower. The steam turbine system is horrendously inefficient. Cutting all of that out of the loop would make nuclear power so hilariously efficient that nobody would care about the waste storage (we wouldn't need much of it anyway). It would also be far safer: a lot of the stuff in a current nuclear plant goes into managing the water moving through the reactor, which is all expensive, fragile equipment that gets mildly contaminated. Replacing all that junk with some electrical cabling would be a major breakthrough.

Re:There could be a serious benefit

[Thelasko]

The steam turbine system is horrendously inefficient.

Compared to what? I have news for you. Steam Turbines are one of the most efficient engines we have. That's why we use them!

The second law of thermodynamics says that no engine can be 100% efficient. The reason is, a 100% efficient engine would require an infinitely hot source of energy and infinitely cold surroundings, assuming there is no friction. Carnot, says that the best we can hope for is more like 60-70% efficiency, and Rankine, suggests that a more realistic number is somewhere between 40-50%. That "inefficient turbine" you speak of is 40% efficient in reality. That's pretty good considering the best we can hope for is 60-70%.

I am not a nuclear physicist, but the laws of thermodynamics still apply. We can still only hope for 60-70% efficiency, but for various reasons we still won't be able to archive this. Now, instead of letting "most of the energy evaporate off the cooling tower" we will be radiating it to the surroundings instead. Fine for spacecraft, not fine here on Earth. Even though this technology sidesteps the creation of thermal energy it still must obey the laws of thermodynamics.

Re:There could be a serious benefit

[asuffield]

Compared to what?

Compared to the amount of energy wasted. Most of it is lost in the cooling towers that are needed to keep the cycle closed, the rest is lost in transfer from the core.

Steam Turbines are one of the most efficient engines we have. That's why we use them!

Yes. And guess what? The most efficient system we have is not very efficient at all. Also note that the main problem is not the turbine itself, but the system as a whole used to transfer energy from the nuclear core to the grid output.

Carnot, says that the best we can hope for is more like 60-70% efficiency, and Rankine, suggests that a more realistic number is somewhere between 40-50%.

Which is precisely why a system based on a new material like this, which does not involve the Carnot (or Rankine) cycle at all, would be hugely more efficient. The whole point is that heat transfer systems are not a good way to extract energy from a nuclear power plant, because of those intrinsic inefficiencies.

Waste...?

[Half-pint HAL]

Cutting all of that out of the loop would make nuclear power so hilariously efficient that nobody would care about the waste storage (we wouldn't need much of it anyway).

Actually, you've missed an important point about nuclear waste. Nuclear waste is dangerous because it's still radioactive. However, it's useless because it's no longer fissile and hence can't be used in a nuclear power plant.

This technology should be just as efficient with nuclear waste as with fissile materials. However, the problem with this technology is time. Fission releases a lot of energy very quickly, but most most common radioisotopes have very long half-lifes, releasing their radiation over thousands of years. (Anything with a short half-life will have "died" millenia ago.) The applications for this will be relatively low-power, long-term projects.

HAL.

Re:Waste...?

[SatanicPuppy]

BlueParrot is 100% correct; if we reprocessed our nuclear waste it would virtually eliminate our waste storage problems. The final product would be much less radioactive, and degrade much more quickly.

The only reason it's not done is that re-enrichment produces large amounts of bomb-grade material, which could theoretically be stolen and used to make a nuke, as opposed to our normal waste which is pretty much useless.

This is getting to be a poorer and poorer excuse as time goes on, as more and more unstable countries learn to do the bomb thing for themselves. All we're really doing is saddling ourselves with a nasty radioactive waste problem.

Re:Waste...?

[BlueParrot]

No, but if I were to try I would use low-burnup thermal reactors on PUREX reprocessing rather than ultra high burnup fast breeders with full actinide recovery heavily spiked with transuranics that have high rates of spontaneous fission. Alternatively I'd go for highly enriched uranium.

Seriously thou, modifying the reprocessing cycle for a fast breeder and then use the very low grade plutonium to produce a nuclear weapon would be so unpractical that it would probably be easier to just start a uranium based weapons program from scratch. Simply separating the plutonium from traces of very troublesome elements with high spontaneous fission rates ( think californium, einsteinium ... ) would require a reprocessing plant unlike anything ever constructed or proposed. Building a nuclear device out of the recovered plutonium ( which would have a much less suitable isotopic composition than traditional reactors ) would require groundbreaking research into nuclear weapon design, and probably a number of tests.

At the end of the day the effort involved would likely surpass that needed to build a more traditional graphite moderated reactor and extract the plutonium from that. I.e, even if somebody was to give you the reprocessing plant for a fast breeder with actinide recycling, as well as the spent fuel, you would probably have an easier time trying to do it the old fashion way. In addition it is hardly as if a rogue nation with the necessary economics would not be capable of building a nuclear weapon anyway. The technology is more than 6 decades old.