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NASA completes full-power tests of small, portable nuclear reactor
- rbanffy 8y agoI wonder if it can operate in zero g...
- zaroth 8y agoThat is in fact precisely what it is designed for.
- linuxguy2 8y agoIsn't it actually designed for working on Mars? Convection in the sodium heat pipes wouldn't work in zero G. > generate heat that is carried to the Stirling converters via passive sodium heat pipes. https://en.wikipedia.org/wiki/Kilopower https://en.wikipedia.org/wiki/Kilopower
- asteli 8y agoThe wiki page you linked specifically mentions deep space applications as a design goal. I'm not sure about the sodium heat pipes but the alcohol vapor heat pipes you see in electronics typically use an internal wick to return the working fluid.
- rbanffy 8y agoWorst case scenario is you put the reactor next to the toilet, in the rotating part of the spacecraft, to solve the problem with convection... These two things are enormously simplified when there is gravity.
- mcguire 8y ago"Worst case scenario is you put the reactor next to the toilet..." Please don't give any ideas to our collective employers.
- jfrankamp 8y agoWould you mind backing up the assertion about convection being the mechanism of sodium transport? e.g. on earth are you saying the sterling part wouldn't work if the hot fluid had to traverse say down (a gravity gradient) instead of up?
- rbanffy 8y agoThe Stirling converters will need a heatsink which can connect to an actively circulated coolant even in zero g. Thanks for the article.
- InclinedPlane 8y agoConvection still works in zero g, it's just driven by pressure gradients instead of density gradients.
- ianai 8y agoOn resiliency “cutting off the system's cooling or ramping it up to its maximum level both resulted in a core temperature change of just 15 degrees or less”
- netzone 8y agoWhat would the effects be of releasing nuclear waste in space? Could we sent up all of our nuclear waste, put a rocket on it and just let it disappear into the distance?
- HappyRobot 8y agoI think the drawback for space disposal is the risk of rocket failure. If a rocket explodes with nuclear waste on board, the waste would spread over a large area. It's safer at the moment to consolidate nuclear waste in small areas away from civilization.
- lightbyte 8y ago>If a rocket explodes with nuclear waste on board, the waste would spread over a large area. Space is very big. Is it actually likely that said waste spreading would even be noticeable?
- monocasa 8y agoWhen a rocket explodes, it's normally in the atmosphere right over an ocean.
- lightbyte 8y agoI misunderstood what you were saying than, I thought you meant the rocket was exploding when it was already far into space away from Earth.
- noir_lord 8y agoIf it blows up 500m above the launch pad you aren't in space.
- diggan 8y agoThink what the argument against it is that the rocket explodes during launch, before actually leaving earth behind. Then it would most probably be noticeable.
- syntaxing 8y agoFor those curious, this uses a nuclear reactor to power a Stirling engine.Stirling engines are a good choice because there is no mass transfer to create the work (i.e. no fuel needed, just heat). It only needs a temperature differential and sealed gas/liquid to work. I highly recommend to read more about Stirling engines since they are of one the most efficient form of work generation with just a temperature differential.
- cathhhhji 8y agoStirling engines are not efficient. Using that heat to make steam to turn a turbine is much more efficient. But it would be harder to make that portable.
- telchar 8y agoYes they are. An ideal stirling engine has the Carnot level efficiency, i.e. maximum theoretical efficiency for a heat engine. https://blog.mide.com/thermodynamic-theory-of-the-ideal-stirling-engine https://blog.mide.com/thermodynamic-theory-of-the-ideal-stir...
- coryrc 8y agoExcept the ideal one doesn't exist and multistage stream turbines are more efficient in practice.
- Sir_Substance 8y agoConspicuously not mentioned: what kind of design the reactor uses. Thanks engadget, 10/10 reporting. Based on the wikipedia article, it looks like a passive decay heater attached to a bunch of sterling engines. Pretty much a souped up RTG that trades more energy output for having moving parts. Neat.
- dukoid 8y agoWouldn't "passive decay" mean it's not based on fission -- but the article and video both mention fission...?
- Sir_Substance 8y agoPassive decay is still fission, it's just not artificially sped up fission :) it's probably more complex than that. Is high speed natural decay of an artificially created or enriched heavy element natural or artificial? I'm not sure how that gets classified.
- dukoid 8y agoMy bad, I had assumed fission was splitting atoms by adding neutrons, but actually fission is just the "splitting" part, so both cases are indeed fission....
- darken 8y agoThe fission process releases neutrons, so you effectively "add neutrons" by concentrating self-fissioning material in a small space. To put another way: If you increase the size of a sphere of fissionable material, its rate of "natural" decay stays the same, but more of these decays lead to neutrons triggering additional fission reactions. So doubling the size of the sphere leads to >>2x fission events due to neutrons having more fissile material to hit on the way out. A large fission reactor is just a scaled up version of this with control rods to adsorb extra neutrons to control secondary "induced" fission.
- 8y ago
- JTbane 8y agoPretty amazing that the simple Stirling engine can be the best choice for generating kilowatts of power in a hostile environment.
- esmi 8y agoIt’s simplicity is probably what makes it the best choice.
- jjoonathan 8y agoThe magic comes from the nuclear half, not the Stirling half.
- dgoodell 8y agoThe free piston stirling engines required also operate via magic and few people understand them well enough to make one suitable for this purpose. The engines required for a reactor like this haven’t been designed yet and it would take years of effort before They would be designed and approved for flight use. For this test they used a couple of undersized (<100W) stirling engines and the rest were just thermal simulators.
- jjoonathan 8y agoStirling Engines exceed their competition by percentage points. Nuclear energy exceeds its competition by orders of magnitude. I stand by my statement that the magic comes from the nuclear half of this relationship -- so long as we accept a definition of magic related to, you know, energy production, rather than effort or hipster points.
- mkoryak 8y agoI wonder how safe these are. Could I get one in my basement and stop paying nstar for the rest of my life? Would my neighbors complain much?
- jabl 8y agoThe black helicopter people might arrive and have a nice chat with you when they discover you ordered a bunch of HEU from aliexpress.
- fragmede 8y agoYou misspelled http://www.unitednuclear.com http://www.unitednuclear.com ;)
- reaperducer 8y agoFunny you should use the phrase "black helicopter." During the Cold War, the military used tiny nuclear reactors to power automated remote sensing stations in the Arctic. We called them "Power Pigs" and they were delivered by helicopter to very remote places. They were fascinating little devices, and because of where they were placed, used the outside air/ice/snow/rocks for cooling. Don't know if they are still being used, or what happened to the old ones, but they were very clever technology.
- godelski 8y agoI am guessing that you are talking about betavoltaics [1]. They were used to power pacemakers and are very useful for remote devices. They can't power much, but they are smaller than PV and don't have to be exposed to the sun (reflective). Though there are larger devices that were used too. [1] https://en.wikipedia.org/wiki/Betavoltaic_device https://en.wikipedia.org/wiki/Betavoltaic_device
- jarvist 8y agoI guess these are the Strontium-90 RTGs made by the Soviets. There's about 1000 out there still - some have been vandalised, some washed out to sea, some sitting rusting in a lighthouse outhouse etc. http://bellona.org/news/nuclear-issues/radioactive-waste-and-spent-nuclear-fuel/2003-11-two-strontium-powered-lighthouses-vandalised-on-the-kola-peninsula http://bellona.org/news/nuclear-issues/radioactive-waste-and...
- Thorazul 8y agoThey should team up with Tesla to develop storage batteries for the reactors in case a reactor fails you would still have some temporary emergency power.
- rmah 8y agoTesla doesn't make the batteries, Panasonic, Samsung and Hitachi does. IIRC, Panasonic is the firm building batteries at Tesla's new gigafactory facility. Tesla simply slaps their name on the battery packs.
- sigstoat 8y agoplenty of companies already make batteries for space applications. and the environment is demanding enough, the budget large enough, and the production volume low enough that more exotic battery chemistries are used. https://en.wikipedia.org/wiki/Batteries_in_space https://en.wikipedia.org/wiki/Batteries_in_space
- forkandwait 8y agoSo... Are plans available anywhere?
- GCU-Empiricist 8y agoUmm. . . it probably wouldn't be cost effective for you: the NRC is pretty brutal in it's regulations. I'm very gun-ho on nuclear power, but that is one bureaucracy I don't mind charging ~$4-500/hr for people to review submitted designs for approval and then painfully inspecting operating plants.
- forkandwait 8y agoI would still like to look at the plans (though it's charming you thought I might try to build it...)
- larkeith 8y agoLink [pdf] to NASA's Kilopower Project media slides, which includes the design (not full plans, but close enough) [1]. [1] https://www.nasa.gov/sites/default/files/atoms/files/kilopower-media-event-charts-final-011618.pdf https://www.nasa.gov/sites/default/files/atoms/files/kilopow...
- forapurpose 8y agoWhat are the other uses for this? Civilian power? Military applications?
- philipkglass 8y agoSome background on this: NASA deep space missions have historically used radioisotope thermal generators powered by the decay of the exotic plutonium isotope Pu-238. This isotope has a good balance of lifetime (87.7 year half life) and specific energy (0.5 watts/gram). It is non-fissile -- no risk of criticality. It also decays solely by alpha emission, so there are no problems with shielding the rest of the systems from e.g. gamma or neutron radiation. American plutonium 238 was formerly produced using Savannah River Site reactors that primarily produced materials for nuclear weapons. With the retirement of those reactors in 1988, and the American nuclear weapons program going to maintenance mode, NASA lost the side-benefit of Pu-238 production using the weapons infrastructure. Deep space missions requiring RTGs had to subsist off of historical Pu-238 stockpiles and additional material purchased from Russia. But the Russian supply has run out too now -- apparently they aren't producing more of it either. American plutonium 238 production efforts resumed in 2013: http://www.spacesafetymagazine.com/aerospace-engineering/nuclear-propulsion/nasa-pay-entire-pu-238-production/ http://www.spacesafetymagazine.com/aerospace-engineering/nuc... With NASA now paying the full cost, including fixed startup costs, Pu-238 is extraordinarily expensive: NASA and DOE have estimated the rebooting will cost between $75 million and $90 million over five years. According to NASA officials, the agency expects to have 1.5 to 2 kilograms produced per year, starting 2018. The high cost and limited supplies of Pu-238 have spurred the search for alternatives to Pu-238 RTGs. A few years ago I remember reading that the European Space Agency was going to try to design its own RTGs using the less powerful but more abundant americium 241 instead of plutonium 238. But a quick search just now doesn't show any concrete development effort. This Kilopower reactor is an alternative to RTGs for some mission profiles -- in fact offers more power than RTGs and uses cheaper nuclear materials. (Highly enriched U-235 isn't cheap in an absolute sense, but it's far less expensive than Pu-238. And the security of supply is effectively backstopped by its use in reactors for the US Navy.) It can offer ample power for very deep space missions at a cost significantly less than using years' worth of Pu-238 production. Improved photovoltaic cells have also enabled missions further from the Sun than they could have supported in 1988. The Juno mission, which entered Jupiter orbit in 2016, relies on PV instead of RTGs. It seems plausible that further evolution will eventually push PV's reach out to Saturn missions. But PV is not currently plausible for missions beyond Jupiter, and it is reliant on slowly-evolving battery technology for surface missions on Mars. Martian missions using PV also face significant problems from cell-obscuring dust. This reactor seems too large to be conveniently integrated in a Martian rover, but enabling non-surface missions to avoid Pu-238 use may mean more can be reserved for future rovers akin to the RTG-powered Curiosity.
- ajuc 8y ago> For example, cutting off the system's cooling or ramping it up to its maximum level both resulted in a core temperature change of just 15 degrees or less. Why use cooling at all then?
- Symmetry 8y agoYou can't extract energy from a heat engine without cooling. Useful work is done in the process of moving thermal energy from a high temperature location to a low temperature location.
- godelski 8y agoStirling engines drive because of a temperature differential. If you don't cool then those two temperatures will tend to equalize, becoming less efficient as the entire device warms up.
- stcredzero 8y agoI think someone should develop a 2 module design for this, where the Stirling engine is separated from the fission reactor with insulated pipes. Why? Weight savings. Insulated pipes can be made very efficient and relatively light. Radiation shielding can't easily be made light. By separating the modules into two sections, martian soil can be more easily used to provide the radiation shielding. It could even be built out of bricks, which we already know can be made out of martian soil.
- simcop2387 8y agoThat might be a good second phase setup for a larger base, but this current one would be good for initial setup since it could be ready without having to produce anything on planet. That makes it good for rovers or other unmanned setups.
- baybal2 8y agoI wonder, can you make a stirling with plutonium pentafluoride working fluid? Eg, cold chamber with neutron poison, hot chamber out of a neutron moderator material?
- ChuckMcM 8y agoThey nailed all their milestones. This is tremendously important work with regards to a future outpost anywhere and possible outposts on Earth. (Imagine how much fuel you wouldn't have to ferry down to Antartica each year to prepare for winter operations, for example). Now to ruggedize the heck out of it and make it easily transportable.
- jabl 8y agoNot Antarctica but pretty close to the other end, this thing is being towed up there at the moment: https://en.wikipedia.org/wiki/Akademik_Lomonosov https://en.wikipedia.org/wiki/Akademik_Lomonosov (it's a fairly traditional PWR, though, so nothing new technology-wise per se)
- ausjke 8y agocan this be used for car/boat/etc-fuel somehow one day, then all gas-station will be run out of business and middle-east-plus-texas-oil-field all file for chapter-11? not sure how to prevent radiation though.
- TangoTrotFox 8y agoSomething that's often left out in the discussion of nuclear because it's not an issue yet, is that nuclear fissile materials are also rare. If nuclear became the standard for energy production, the rarity of these materials would, in the longrun, end up creating more stupid games similar to what we play with fossil fuels today. 'Time do bring democracy to Australia!' 'Wait guys... what?? We are a democracy!!' 'Sorry, can't hear you over the sounds of FREEDOM coming your way!'
- jabl 8y agoIt's usually left out of the discussion because it really is a non-issue long term as well. With breeder reactors (technology which already exists), Th in addition to U, U/Th extraction from seawater, we have enough fission fuel to power the entire planet at current levels for tens of thousands of years, if not indefinitely.
- MertsA 8y agoThat's vastly understating the amount of Uranium and Thorium we can access. Without a breeder reactor it might only be tens of thousands but with a breeder reactor the amount of material we could use goes up by several orders of magnitude.
- TangoTrotFox 8y agoYou can't just handwave away the economics or practical issues here. Seawater extraction is incredibly expensive. Breeder reactors are also expensive, ignoring the countless other technical and practical issues that they come with. For instance the output level for optimal efficiency with breeder reactors is quite low. You'd have literally thousands of breeder reactors spread around (with a proportional number of fuel reprocessing plants) when you run into the practical problem that, while failure rates are low, with the number of facilities scaled up by orders of magnitude they are currently intolerable due to the consequence of failure. But back to cost your argument is like saying that "Bah, there's no concern about a lack of freshwater. We can just desalinate the sea!" You sure can, but that's completely irrelevant as the costs make it an unreasonable solution. Using conventionally obtained and utilized material, we only have enough nuclear material for about 200 years of consumption. [1] And in looking at the longrun it's obviously quite myopic to take as an assumption that humanity has reached the highest energy usage it will ever have. [1] - https://www.scientificamerican.com/article/how-long-will-global-uranium-deposits-last/ https://www.scientificamerican.com/article/how-long-will-glo...
- DuskStar 8y agoFor those interested in learning more, I've found the Beyond NERVA blog to have really good articles! Their most recent post (and the 3rd in a series on Kilopower) [0] is on this set of tests, but there's also posts on more modern Nuclear Thermal Rocket designs [1] as you may have guessed from the blog's name. [0] https://beyondnerva.wordpress.com/2018/05/02/krusty-we-have-fission-kilopower-part-iii/ https://beyondnerva.wordpress.com/2018/05/02/krusty-we-have-... [1] https://beyondnerva.wordpress.com/2018/01/19/leu-ntp-part-two-cermet-fuel-nasas-path-to-nuclear-thermal-propulsion/ https://beyondnerva.wordpress.com/2018/01/19/leu-ntp-part-tw...
- api_or_ipa 8y ago> Lower power Kilopower systems, like the one kilowatt version, can power a basic toaster, Toaster is a bad example, a laptop uses around 30 watts so the 1kw version can power several dozen laptops.
- chiph 8y agoHow do they manage to not have the reciprocating mass (the piston) throw off a space vehicle's trajectory? IIRC the Space Shuttle used magnetic tape because a hard drive would have acted as a gyroscope.
- Doxin 8y agoKeep in mind that in the space shuttle era hard drives were a good deal more massive than today. Presumably a modern hard drive wouldn't present much of a problem. In any case a rotating mass isn't too big of a problem, it's changes in rotational speed that'll mess with your heading -- not your trajectory though. The piston itself shouldn't be too much of a problem either because any motion it makes one way it shortly after makes the other way balancing out the forces over time.
- BrownArch3310 8y agoLot's of insights just by reading the comments! haha