7 ms·
Here's a fun and almost forgotten fact. In the early 1960s, the US government built a prototype nuclear reactor that was cooled with liquid metal sodium but had
by acidburnNSA 5y ago
Here's a fun and almost forgotten fact. In the early 1960s, the US government built a prototype nuclear reactor that was cooled with liquid metal sodium but had graphite moderators to slow the neutrons down. This reactor could start up with very low enriched uranium (as opposed to sodium cooled fast-neutron reactors which need quite high enrichments to start up) and make superheated steam at the exact same conditions as a coal plant.
Well the local utility just SW of Lincoln Nebraska needed the power one way or the other, and didn't know if the new type of reactor was going to work or not. So they decided to build an equivalent power coal plant on the other side of the turbo-generator building! The idea was that when the nuclear reactor was in an outage, the coal plant could spin the turbine. Two plants, one turbine-generator! Wild.
So anyway the nuclear plant did have a few troubles. The vendor, Atomics International, had them figured out and was planning to fix, but the utility declined it's option to purchase the plant in the end. Today, a grassy outline of a nuclear reactor can be seen right next to the still-operating coal plant down in Hallam, NE.
Honestly it was an awesome reactor concept and I want to see it brought back. I visited this site a few months ago and got a little tour. Very fun.
https://whatisnuclear.com/reactor_history.html#the-hallam-sodium-graphite-reactor-in-nebraska https://whatisnuclear.com/reactor_history.html#the-hallam-so...
https://en.wikipedia.org/wiki/Hallam_Nuclear_Power_Facility https://en.wikipedia.org/wiki/Hallam_Nuclear_Power_Facility
Google maps view of the outline: https://www.google.com/maps/place/Hallam,+NE+68368/@40.5586409,-96.785054,297m/data=!3m1!1e3!4m5!3m4!1s0x8796f30cb6f05711:0x3abdf7c827f6b224!8m2!3d40.5376381!4d-96.7868565?hl=en https://www.google.com/maps/place/Hallam,+NE+68368/@40.55864...
- cardy31 5y agoBill Gates’ nuclear play uses liquid sodium
- acidburnNSA 5y agoYes. That is the more traditional fast neutron version. We have 450 reactor years of experience w those.
- formerkrogemp 5y agoHow do you measure those years? Experience of designers and engineering? Or years of reactors in operation?
- ch4s3 5y agoyears of reactors in operation
- formerkrogemp 5y agoThanks for the explanation.
- polski-g 5y agoCANDU reactors (Canadian) use non-enriched/naturally occurring uranium (0.72% u-235) by using heavy water as a moderator. Not sure why you'd use anything but them if you were starting a nuclear program from scratch.
- Manuel_D 5y agoHeavy water reactors have their drawbacks. Heavy water is expensive, which offsets the cost of uranium enrichment. The lower energy density of un-enriched uranium means more frequent refueling. They also produce more waste.
- deleted 5y ago[deleted]
- yohannparis 5y agoAnd this is why it was made in Canada, cheap electricity and uranium all around to make heavy water and fuel those reactors.
- hcknwscommenter 5y agoare industrial quantities of heavy water "made" or just extracted/isolated?
- yabones 5y agoYou still create the waste either way, either as depleted uranium or as spent fuel.
- coredog64 5y agoDepleted uranium means “uranium that is even less radioactive than naturally occurring uranium”. You don’t want to eat it, or atomize it and blast it out into the environment, but it’s actually a useful material. It’s sometimes used as a radiation shield for X-ray equipment.
- vermilingua 5y agoThis is entirely off topic, but scrolling around the map you linked, it looks like massive portions of Nebraska and surrounds are gridded by roads. Is this true? I'm an Australian, never been to the US, but is that common? I can't imagine that kind of project here. EDIT: Massive portions of the US! I find this mindblowing.
- michael1999 5y agoThere's a slow-rolling crisis as many local governments find they can't afford to maintain (much less rebuild) so many roads. Many are being downgraded to gravel.
- sanderjd 5y agoI find this fascinating! Do you mind if I ask what you found surprising, exactly? Is it more that those fairly sparsely populated areas have so many roads, or is it more that the inland areas are populated at all? For what it's worth, quite a few people live in the plains states in the US. Not many relative to the real population centers in the country, but I think perhaps significantly more than the inland areas of Australia.
- vermilingua 5y agoPrimarily the sheer number and scale of roads, yes. I’ve done a lot of driving inland in Aus, and even where there is a lot of arable land it is not nearly so neatly or densely carved up, generally just hectares of paddocks/farmland with fire and access trails and fences. I’m utterly awed at the scale of infrastructure that must’ve been involved in building those thousands of kilometres of roads, let alone maintaining them (I imagine they aren’t particularly “maintained”, but all the same).
- sidewndr46 5y agoAs an American who has traveled abroad, I can assure the vast majority of our roads are "maintained" only in the sense that they are passable roads. There really are no standards that are adhered to. It's common where I live to find potholes that would destroy the front suspension of any car attempting to traverse them.
- sandGorgon 5y agoMSR Thorium reactors are the holy grail clean fuel for India and China. Very interestingly, this is a 1974(!!) program plan to resume development of MSR from the US ORNL MSR team https://www.osti.gov/biblio/4227904 https://www.osti.gov/biblio/4227904
- sofixa 5y agoSimilar to sodium cooled reactors, there are also lead or lead-bismuth cooled reactors, which have had one real life deployment ( onboard the Soviet Alfa class submarines), with its own advantages and disadvantages, and there are proposals to develop new versions. There's so much interesting nuclear-related tech and concepts we haven't fully explored because of nuclear FUD ( much of which would be solved by the new tech).
- FlyMoreRockets 5y agoThanks, I had no idea lead-bismuth reactors existed. It seems the large number of unstable lead isotopes and their long decay chain would assure a long cooldown requirement before any maintenance could be done in the reactor compartment/primary coolant system. Not only that, but this stuff would present a huge disposal problem. https://en.wikipedia.org/wiki/Isotopes_of_lead https://en.wikipedia.org/wiki/Isotopes_of_lead It seems the Alfa class was decommissioned for scrapping, though one was refitted with a pressurized water reactor for a while. https://en.wikipedia.org/wiki/Alfa-class_submarine#Decommissioning https://en.wikipedia.org/wiki/Alfa-class_submarine#Decommiss... An interesting issue with this design is that if the Pb-Bi coolant ever solidified, the reactor control rods became frozen in place.
- api 5y ago> liquid metal sodium > graphite moderators Nope.
- kickout 5y agoLol, wild seeing Hallam, NE on a post on HN about nuclear reactors. Drive by this place often, will stop and look at it now. Thanks
- acidburnNSA 5y agoYeah the Sheldon station is right by that Monolith project. Fun to drive by for sure.
- Gravityloss 5y agoSodium cooled reactors with graphite moderator have not become common for some reasons. There are some issues like sodium burns in contact with air, as does hot graphite. Potential positive coefficient (unstable) states. But the pressure in the piping could be low, compared to water/steam, so maybe cost could be low and power density high. I think a lot of these plans to retrofit coal plants with nukes are quite overoptimistic. I'm ambivalent since they could be used as reasons to prop up coal plants longer. "See, we should invest in, and get some subsidy for a new steam turbine in our coal plant so it can be used with the graphite-sodium nuke that's going to replace the boiler in 15 years". But on the other hand, we need all potential, even unlikely solutions to replace coal burning.
- credit_guy 5y ago> sodium burns in contact with air Is that so? I think you are confusing air with water here. In contact with air, sodium oxidizes quickly, but it does not burn spontaneously.
- Trouble_007 5y agosearch: 'sodium leak at nuclear reactor' @DDG : <https://html.duckduckgo.com/html?q='sodium leak at nuclear reactor' https://html.duckduckgo.com/html?q='sodium leak at nuclear r...>
- Gravityloss 5y agoGood idea. "At 19:47 high temperature liquid sodium coolant at one of the three secondary heat exchangers started leaking through a broken thermometer sheath ... on the piping and it ignited on contact with air." https://onlineethics.org/cases/case-1-fire-sodium-coolant-leak-prototype-fast-breeder-reactor-monju https://onlineethics.org/cases/case-1-fire-sodium-coolant-le...
- credit_guy 5y agoThat's a good catch. For some reason I was thinking of room-temperature sodium, but of course the liquid sodium from sodium cooled nuclear reactors is hot, and apparently burns in contact with the air. If you read more closely though the article you linked to, you'll see that the complaint there was not the fire in particular (which caused some damage, but no radioactive leaks), but the claim of the plant operators that the plant was "absolutely safe", and the attempt of a cover-up. In other words, the safety of this plant was judged not in comparison with the safety of a conventional water-cooled reactor, but in comparison with an absurd goal of "absolute safety". When people hear the sodium can cause fire when in contact with the air, they immediately remember the spectacular explosions of sodium in contact with water. Then they assume a sodium cooled reactor is a beast that only a madman would contemplate. In reality, sodium cooled reactors are not any worse than water-cooled reactors. All reactors present various challenges, and some of the challenges faced by sodium cooled reactors will be higher, and some lower than those facing water-cooled reactors. But sodium cooled reactors have an absolutely tremendous advantage: most of the fissile material they use as fuel (be it Uranium or Plutonium) does undergo fission and creates fission products, as opposed to actinides. Bottom line: the nuclear waste from sodium cooled reactors (and all types of fast neutron reactors) is much, much more manageable than the nuclear waste of conventional nuclear reactors.
- cryptonector 5y agoConsidering our very recent understanding of sodium Coulombic explosions[0], using liquid sodium for... anything requires an enormous amount of care[1]. [0] https://www.youtube.com/watch?v=8PEVmflpUCo [1] https://www.youtube.com/watch?v=rAYW9n8i-C4
- Pinus 5y agoNot quite as wild, but there was a similar thing in Sweden 50 years ago, where an oil burner was retrofitted to the cancelled nuclear power plant at Marviken: https://en.wikipedia.org/wiki/R4_nuclear_reactor https://en.wikipedia.org/wiki/R4_nuclear_reactor . The reactor, which was more or less completed but never loaded with nuclear fuel, was used for various experiments related to reactor safety.
- thetinguy 5y agoYea and there’s a reason they stopped. It’s unmaintainable. How will you replace a section of cooling pipe with molten or solid sodium in it?