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

Carbon nanotubes

[j00r0m4nc3r]

Is there anything they CAN'T do?

Re:Carbon nanotubes

[Knuckles]

Just a few things, but those are covered by Lithium, apparently.

Re:Carbon nanotubes

[ObsessiveMathsFreak]

Become affordable?

Re:Carbon nanotubes

[zenaida_valdez]

Between carbon nanotubes and Viagra, everything's covered!

Re:Carbon nanotubes

[cbreaker]

He didn't say CARBON, he said Carbon NANOTUBES. Last I checked, life on earth isn't based on Carbon Nanotubes.

Get a life.

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.

Re:I'm sorry

[cosinezero]

This is insightful?? What about the issue pointed out in the article?!? Satellites? Hey, let's recall Voyager just to replace it's batteries, then send it out for another 30 years.

Why is it...

[narrowhouse]

that all these neat technologies depend on exotic materials? Just once I would like some really cool technology to be dependent on something cheaper and easy to obtain, while being ten times more efficient that the gold/lithium irradiated crystals it replaces.

Today's news: hobo sweat and nail clippings mixed with Diet Coke and mentos == cold fusion.

Re:Why is it...

[Anonymous Coward]

You think hobo sweat and nail clippings are easy to obtain? Trust me, chasing them and holding them down while you get the supplies is a lot more work than you expect. Unless we set up some sort of hobo farm, I don't see your plan being feasible.

Re:Why is it...

[pla]

Why is it ... that all these neat technologies depend on exotic materials?

Because most of our existing technology comes from adapting what we've observed occurring more-or-less naturally in the world around us, and we've already plucked all the low-hanging fruit.

If you want to understand how to extract energy from hydrogen sulfide, you can study deep sea vent bacteria. If you want to understand how to directly convert radiation to electricity... Well, we don't know of anything that already does that, so if such a phenomenon exists (which seems reasonable), it makes sense to start with some of the most exotic substances we know of.

Re:Why is it...

[wattrlz]

Sure you would. What do you think we'd do with them after they'd been harvested? Heck, you could have them fight over a grate and some sluices and collect the sweat that way...

Re:I'm sorry

[Osurak]

If you think of the sun as a power source, it's not exactly user-replaceable either, but I'll be damned if its battery life isn't unbelievable.

Re:I'm sorry

[mo^]

Devices based on the material could be small enough to power anything from interplanetary probes to aircraft and land vehicles, he adds.

I think once we get to the level of space probes, "User Serviceable" is not particularly essential. Christ, I wont even change my car battery (due to laziness as much as anything).

Were you envisaging using these in your remote or something?

Re:I'm sorry

[Darkfred]

Idiot,
Some isotopes proposed for this use have lifetimes longer than yours, making the battery and device containing it effectively permanent.
In fact half the problem is finding ones that have a half-life short enough to give good power for say 10 years yet don't decompose into poisons or release gamma rays. Which isn't really a problem on interstellar space probes, but makes it difficult to develop consumer devices.

Re:no obvious tags please

[Anonymous Coward]

1. Complain about recycled humor on slashdot
2. ....
3. Profit!

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...?

[BlueParrot]

However, it's useless because it's no longer fissile and hence can't be used in a nuclear power plant.

Not true, spent fuel is discharged not because it is depleted of fissile material but because other elements generated in it absorb neutrons. If you remove those elements chemically the fuel can be re-used, and with some fast reactor designs you can even ensure that they produce the same amount of fissile material as they consume ( by converting U-238 into plutonium ). The end result is about 100 times better uranium utilization and nuclear waste which decays to uranium levels of radioactivity within 300 years or so.

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.

Re:no obvious tags please

[Applekid]

"Scientific developments that could cause serious problems if done wrong or misused." So, in other words, every scientific development ever? That makes it less of a tag and more of a blanket IMO.

Shielding?

[Bombula]

Would this material make good radiation shileding? Seems like manned spaceflight could make use of a material that did double-duty as radiation shields and solar panels.

Re:I'm sorry

[TooMuchToDo]

Technically, all batteries "generate" power through a chemical reaction, but I don't want to split "potential" hairs with you ;)

Probably much less efficent than steam

[erice]

The article didn't discuss any absolute efficiency numbers. It only said the new tech was much more efficient than thermoelectric generators, whose efficiency is abysmal. There is no mention of having efficiency better or even comparable to a steam turbine.

Steam turbines are mechanically complicated and smell of old tech but they are actually rather efficient. Large steam turbines have thermodynamic efficiency in the 90% range. I rather doubt this new nuclear photocell is anywhere close.

Re:Probably much less efficent than steam

[asuffield]

Large steam turbines have thermodynamic efficiency in the 90% range.

That's the loss in the turbine itself - the number most favourable to the turbine manufacturer's marketing department. The main loss in a steam turbine system is in the required cooling/condensing apparatus that must accompany the turbine to close the cycle.

Actual thermal efficiency for nuclear plants tends to be in the 5-30% range. The 40-year-old designs that comprise most plants in the US and western Europe are appalling; current designs manage about 30% at their optimal power level, but nobody's building new plants these days so there aren't many of them around.

Hirsch-Meeks fusor?

[OglinTatas]

Might this material make the Hirsch-Meeks fusor energy positive?
Or are the unnamed "radioactive particles that slam into the gold" not neutrons?
Is the energy recovery from this material, even 20 times better than thermoelectric materials, not nearly good enough to extract enough energy from the fusor?

Betavoltaics

[denominateur]

I'm pretty sure the article is reffering to technology very similar to betavoltaic cells but with the twist of using gold as an electron source and some more strongly radioactive isotope as the energy source rather than using beta-decaying tritium directly. http://en.wikipedia.org/wiki/Betavoltaics