DARPA Wants To Bypass the Thermal Middleman In Nuclear Power Systems (ans.org) 45
The Defense Advanced Research Projects Agency (DARPA) is exploring the possibility of directly converting radiation from nuclear reactors into electricity using radiovoltaics, a technology that could potentially revolutionize nuclear power generation by moving beyond traditional steam turbine methods. The agency is requesting information and suggestions on this topic in an RFI released on August 1st. Nuclear News reports: There's got to be a better way": Methods to convert the energy of nuclear fission reactions and the decay of radioisotopes into electricity have not evolved since the invention of radioisotope power systems and fission reactors over 70 years ago and remain unoptimized," the RFI says. They rely on thermal heat transfer, and "in each step of this indirect conversion method neutrons, heat, and energy are lost to the shielding material, working fluid, and other system materials." Advanced reactor designs that use alternative coolants, including helium, sodium, and salts, would still use what DARPA calls "heritage nuclear power conversion technology" with water and steam as the working fluids, as would the fusion power plants being planned today.
Why now? Tabitha Dodson, the program manager for DARPA DSO, which is launching the RFI, told Nuclear News that "two big things" are driving the interest. "One is the extreme surge of investment in small and advanced nuclear technologies, such as in fusion and space reactors, which do not have a concurrent pairing of advanced power generation methods that doesn't involve liquid-based heat transfer," she said. "Next, there has been an order of magnitude improvement in radiation tolerance and efficiency for voltaics in recent years with encouraging performance that indicates radiovoltaics could scale up as an array usable in nuclear reactors." [...]
What is the ask?: The RFI asks: "Is it possible to achieve [a] direct energy conversion nuclear power system, ranging in power from 10s of watts electric (We) to 100s of kWe?" DARPA wants information "on the potential to improve specific power greater than 1 We/kg conversion from watts-thermal per radiation emission product," and information on the potential to improve damage tolerance of the voltaic to nuclear radiation to reach an operating lifetime comparable to the life of its nuclear source, on the scale of decades. "We will learn what our boundary conditions are when respondents tell us what technologies in the field of voltaics are possible, and we'll use that to see if there is sufficient scientific rationale make a case to present for further DARPA investment," Dodson said. "I also hope people are going to start thinking about nuclear systems that use electromagnetic versus thermal-kinetic methods to harvest nuclear energetic reactions."
Why now? Tabitha Dodson, the program manager for DARPA DSO, which is launching the RFI, told Nuclear News that "two big things" are driving the interest. "One is the extreme surge of investment in small and advanced nuclear technologies, such as in fusion and space reactors, which do not have a concurrent pairing of advanced power generation methods that doesn't involve liquid-based heat transfer," she said. "Next, there has been an order of magnitude improvement in radiation tolerance and efficiency for voltaics in recent years with encouraging performance that indicates radiovoltaics could scale up as an array usable in nuclear reactors." [...]
What is the ask?: The RFI asks: "Is it possible to achieve [a] direct energy conversion nuclear power system, ranging in power from 10s of watts electric (We) to 100s of kWe?" DARPA wants information "on the potential to improve specific power greater than 1 We/kg conversion from watts-thermal per radiation emission product," and information on the potential to improve damage tolerance of the voltaic to nuclear radiation to reach an operating lifetime comparable to the life of its nuclear source, on the scale of decades. "We will learn what our boundary conditions are when respondents tell us what technologies in the field of voltaics are possible, and we'll use that to see if there is sufficient scientific rationale make a case to present for further DARPA investment," Dodson said. "I also hope people are going to start thinking about nuclear systems that use electromagnetic versus thermal-kinetic methods to harvest nuclear energetic reactions."
A reverse Peltier system? (Score:4, Interesting)
This would be interesting to see, not just because it gets rid of three energy conversions (heat to steam, steam to spinning a generator shaft, generator to electricity), but if work is done that can help separate the hot and cold ends for better efficiency, this can mean great leaps in refrigeration and cooling, which also have to deal with energy conversions (electricity to spinning a compressor, compressor phase changes the gas to a liquid, the liquid evaporates on the other side to cool that side down.) Having a solid cooling system, as well as one that can use thermal differences for electricity directly can go a long way.
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Re:A reverse Peltier system? (Score:5, Informative)
Yeah, "Reverse Peltier devices" are common. In fact, most Peltier devices can be run backward by reversing the voltage. This is the Seeback effect.
But they are notoriously inefficient, usually about 5%. They are not a replacement for steam engines.
TFA is talk'n about something different: Generating electricity directly from the emission of charged particles (alpha particles and beta particles (electrons)).
Sandwich a radioactive emitter between two layers of insulators and then put conductors on the outside. Then a beta emitter, such as tritium, directly creates a voltage between the radioactive layer and the conductors.
Additional alternating layers of insulator and conductor can be added to harvest more energy from electrons emitted at higher energy or obtuse angles.
The end result is a low-maintenance generator with no moving parts that can be used in place of an RTG but is way more efficient.
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Yeah, "Reverse Peltier devices" are common. In fact, most Peltier devices can be run backward by reversing the voltage. This is the Seeback effect.
That is nonsense. Obviously, when you connect a Peltier element in reverse, it pumps heat in the the direction (usually at even worse efficiency), but that is not the scenario here. The scenario is applying a heat difference to a Peltier element and using the power it outputs. It is true that this incredibly inefficient, because the voltages are so small. One reason RTGs are not in common use.
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What (I think) DARPA is targeting here is capturing and converting the non-thermal radiation from the natural decay of various isotopes. Kinda like photo voltaics work for light, but for
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Just look at what they are asking for. 10s of watts, maybe scaling up to hundreds of kilowatts. And it will be DC, not AC, and the largest AC inverters we have are in the megawatt range.
Also if they made it much larger they would need to actively cool it anyway, and then you have all the downsides of such a cooling system anyway, and the potential for meltdown. RTGs avoid that by having output low enough that they just don't get hot enough to melt in the environments they operate in.
So this isn't a commerci
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Re:A reverse Peltier system? (Score:4, Interesting)
But water serves as more than an energy transport, it's also a neutron moderator and a cooling system. Even if they come up with some magic radiation-to-electricity conversion mechanism, how are they going to fill the other two roles?
That's easy. Mayonnaise [slashdot.org].
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Re:A reverse Peltier system? (Score:5, Interesting)
But water serves as more than an energy transport, it's also a neutron moderator and a cooling system.
The isotopes used in radiovoltaics don't emit neutrons.
Since they are more efficient than thermal reactors, there is less waste heat to deal with.
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It will all work by magic! Nuclear power is so great, there is no doubt it will!
That said, this is just an attempt to get some useful research out of the abysmally stupid SMR craze.
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The thermoelectric effect has been known for a long time, and if it were efficient, it would already been in wide use. Consider the reverse effect. You can find Peltier effect cooling in small/portable refrigerators, where small space and the lack of moving parts is important, but there's a reason most fridges use evaporation and condensation of a fluid. It's kind of interesting how the industrial revolution started with steam engines, and we're still using them, just with different heat sources.
The arti
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The reason is that in practical terms, steam-engies are abut 10x more efficient. Same for compressor coolers.
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I would say closer to a nuclear battery which the Russians invented and NASA has since used in various spacecraft. Basically a specific type of solar panel near a radiation source will provide energy like the sun does, but continuously. The designs from the 50s had the issue that solar panels of any sort were only 2% effective, modern ones you find commercially are ~20% effective, practically you could get up to 40% effectiveness or better with the radiation and silicon tuned to each other's frequencies wit
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No. That is still a variant of the thermal cycle -which is what they are specifically attempting to move away from.
This research is about finding a way to directly harness the stimulation of electrons via radioactive excitement - "radiovoltaics".
Small dyson sphere like (Score:1)
1) Build room in the shape of a Dyson sphere.
2) Put solar panel like captors around the sphere which will catch whichever particle we can easily catch that has solar light like energy.
3) Put reactor in the middle of sphere. Unshield it so it lets the particles we are interested into through. Who knows? maybe reactor could even run cooler and cheaper that way...
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1) Build room in the shape of a Dyson sphere.
A spherical swarm of satellites?
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There's a reason that most planetary systems (and a number of stellar systems) are concentrated on a plane pretty close to the fundamental plane of the system - that's the low energy configuration.
Particle decelerator (Score:3)
As a teenager I liked the idea of capturing the energy from alpha and beta particles by decelerating them electromagnetically. Problem is, with radioactive decay the particles shoot off in random directions, and I could never figure out a configuration of coils and magnets that worked.
Re:Particle decelerator (Score:5, Funny)
Any word on when the NRC and EPA will release the empty land where the house used to be back to your parents?
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https://harpers.org/archive/19... [harpers.org]
Neutron windmills (Score:2)
Since most of the energy released by fission is in the form of highly kinetic neutrons, I wonder if there's some mechanical way to capture the energy. Lots of tiny windmills maybe?
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There are, in fact, MEMs-based micro-piezoelectric devices for harvesting energy from radiation that sort of work like that. They are very, very low voltage devices though.
If direct conversion works (Score:3)
Salt reactors look a lot better. Sodium is dangerous because of the risk of pipe fractures mixing sodium with water. No water, no hazard.
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Sodium is still dangerous without a water loop because it is corrosive.
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Everything nuclear is dangerous. Without the promise of the bomb, this tech would never have made it for electricity generation.
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Everything nuclear is dangerous. Without the promise of the bomb, this tech would never have made it for electricity generation.
Everyone here knows you think anything involving atoms is scary, but most countries with nuclear power don't have nuclear weapons. Your argument is so 1960s.
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The argument is actually completely current. For example Macron has said that just a couple of years ago in Le Monde. This does not mean all that went onboard because of this reason did make the last steps. But they did want the knowledge and nuclear material. Nuclear never made sense for power generation in a stationary scenario where it did need to compete. Hence the nuke-fans made sure it did not have to.
Incidentally, I never stated "scary", that is just you trying to be a manipulative asshole.
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Nuclear never made sense for power generation in a stationary scenario where it did need to compete.
Indeed, it had to compete with coal, the two of them being the defacto choice for the last four decades of the 20th century. So now we have 400 reactors and 8000 thermal coal plants and you complain about climate change. Rest assured much of that is on people like you. We certainly should not be taking any advice from you one what to do going forward, you have done quite enough damage already. You should crawl back under your rock and let the smart people sort it out.
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Trying to shift blame? How repulsive. No, that is _not_ on me. We should have scaled up renewables 50 years ago and if we had not wasted all that money on nuclear, we could have. That is on people like _you_. And today trying to waste tons of money on nuclear that will take too long to build and will be a lot less than renewables for the same money, that is on people like _you_.
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But whatever, have at it. You are going to fail, many of know this is obvious, but life is good here so I'm just going to sit back and watch you fail, content in the fact I am not participating or complicit in your failure.
Re: If direct conversion works (Score:2)
Nuclear was never cost competitive with anything. It has to be insured at the expense of The People and the decommissioning costs are always multiples of what is budgeted and we have to pay for that too. Even the solar panels of fifty years ago had lifespans of 20+ years (most of the panels installed then which were not replaced because better panels came out still work!) and even an old panel can do work like running an electric fence, while the parts of an old nuclear plant are low grade nuclear waste at
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We also have nuclear power, but no nuclear weapons, like most countries with nuclear power (though I also think that no country without nuclear weapons is ever really secure. Ukraine should have never given theirs up, and I can totally understand why places like Iran would want them).
While my province is blessed with lots of hydro power, the prov
Wow (Score:2)
This is amazing since I was thinking about this since at least 2008. Not original thought by any means, but converting X-rays to electron motion seems to run up against materials degrading under such a high-rad environment.
How -small- could this be? (Score:2)
Assuming you can solve the conversion problem, I wonder how small you could make the resulting generator system.
(I'm always interested in alternatives to the noisy and maintenance-intensive generators we had in my Army artillery unit. They were a great way to tell bad guys "There's a command and control facility here, just follow the heat & noise.")
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Finally (Score:2)
A use for all that low level radioactive waste we've got stored in pools.
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Granted, after several decades of storing high level waste, your typical concrete of a "pond wall" will have become low level waste by activation. But the activated nuclei are normally held in concrete, unlikely to move, and only last a few generations. So ... I know - use the old ponds to grow organic veg ! That'll cause all sorts of ups
A thin layer (Score:2)
Nukes are getting attention lately (Score:2)
"There's got to be a better way" (Score:2)
Really?
I'll agree it would be nice if there were a better way, but I know of no law of physics that says there must be a better way.