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Chinese pebble-bed nuclear reactor passes "meltdown" test
- thebeardisred 2y ago20+ years later - https://www.wired.com/2004/09/china-5/ https://www.wired.com/2004/09/china-5/
- dbcooper 2y agoI remember that article. An older friend had worked on fluidised-bed reactors at Tsinghua in the 1990s, and I sent it to him. Using helium indicates a problem with kinematic viscosity of cooling gases? Nitrogen would be non-reactive enough, I assume?
- deleted 2y ago[deleted]
- semi-extrinsic 2y agoHelium has excellent heat transfer properties (low Prandtl number) and does not undergo nuclear reactions when subjected to a neutron flux. Nitrogen will undergo an (n-p) reaction to produce carbon-14 which has a half-life of 5700 years.
- cyberax 2y agoYup. That's why regular PWRs take care not to nitrogen to pressurize or flush the primary coolant loop after maintenance.
- pfdietz 2y agoAnd why reactors that use nitride fuels use fuel made with the isotope nitrogen-15. The front runner steel for use in fusion reactors, EUROFER-97, contains a necessary small amount of nitrogen. This is enough under some nations' rules to render it into intermediate level radioactive waste after use, due to the carbon-14 content.
- cyberax 2y agoOh yeah. I have a friend who was working on researching fusion-safe steels. Solving it fully is going to be a real engineering challenge. Apparently, even a small natural niobium contamination would make it a low-grade waste.
- pfdietz 2y agoYes, niobium is the other problem. I think steel makers are used to adding alloying elements, but not set up for excluding them to ppm levels. I saw someone bemoaning that the steel alone for DEMO would cost 3 billion euros (or dollars?), and I've wondered if this is the reason. https://scipub.euro-fusion.org/wp-content/uploads/eurofusion/WPPMICPR18_19392_submitted-4.pdf https://scipub.euro-fusion.org/wp-content/uploads/eurofusion... "[...] in the first layer, nearest the plasma, the rate of production of 94Nb – via neutron capture (n,γ) reactions on the stable 93Nb of niobium – is so high that Eurofer in this region is predicted to exceed the France-LLW limit within the first year of operation, and consequently would not be disposable as LLW under French regulations for more than 1000 years." It's not just the steel. Beryllium typically contains about 100 ppm U, and an estimate of the cost of purifying it enough to avoid excessive fission products was another billion.
- chasil 2y agoIt will likely be necessary to start with steel made before atmospheric nuclear tests began. There are many uses for such steel already. https://en.m.wikipedia.org/wiki/Low-background_steel https://en.m.wikipedia.org/wiki/Low-background_steel
- pfdietz 2y agoI don't think that would make any difference. The problem isn't traces of radioisotopes in the initial steel, the problem is vastly larger amounts of radioisotopes created in the steel under intense neutron bombardment due to absorption in certain stable impurity elements.
- HPsquared 2y agoNitrogen is a big neutron absorber in gas-cooled reactors. It's actually used as a secondary shutdown mechanism in the UK's AGR reactors. So if it was to leak out (lose pressure) you'd see an increase in power at the same time as a loss of cooling... Not a great idea!
- kordlessagain 2y agoInteresting they are now posed to take advantage of this power for applying AI: https://www.washingtonpost.com/opinions/2024/09/24/ai-power-grid-china-competition/ https://www.washingtonpost.com/opinions/2024/09/24/ai-power-...
- pineaux 2y agoCan someone explain to me how this reactor is meltdown proof?
- DennisL123 2y agoIt’s meltdown proof in principle since the process goes into an equilibrium rather than into a runaway process.
- cosmotic 2y agoWikipedia has an explanation: https://en.wikipedia.org/wiki/Pebble-bed_reactor#Safety https://en.wikipedia.org/wiki/Pebble-bed_reactor#Safety Summary: As the temperature rises, neutron absorption increases, reducing fission and thus temperature.
- chickenbig 2y ago> As the temperature rises, neutron absorption increases, reducing fission and thus temperature. Negative fuel temperature coefficient is not an unusual feature. The real question is whether the heat removal system of the reactor as a whole is sufficient to remove the decay heat to keep the fuel within the limits.
- Gibbon1 2y agoI remember talking to an engineer at the old GE nuclear research facility in San Jose. He said you can design reactors to be cooled by natural convection.
- pfdietz 2y agoIt just makes them larger. And it makes the building containing them larger. And this makes them more expensive. NuScale's reactor was originally motivated by the desire to make it safer by using natural convection. But it ends up requiring 1/3rd more labor hours to build a NPP using their reactors than it does to build a conventional large reactor power plant.
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- muditmudit 2y agoTangentially related: https://youtu.be/0gskQJE6lxU?si=nztv5C0Et7pBJeMj https://youtu.be/0gskQJE6lxU?si=nztv5C0Et7pBJeMj This video explores an incident with a reactor of a similar design, and very rudimentarily explains the way pebbles and the helium gas is used.
- petre 2y agoThey should also test with cracked pebbles.
- cyberax 2y agoPebble bed reactors are a bad idea in general. They will be HUMONGOUS because they need a large surface to radiate away the heat for the passive safety, so they can't be easily put into a containment building. A core of a PWR plant is _tiny_ for the amount of power it produces (around 3GWt!), just around 5 meters in diameter and 15 meters in height. The pebble bed reactor in the article (HTR-PM) is around the same size, but it produces a mere 0.25 GWt. Pebbles themselves are also problematic, they tend to swell, crack, and they can't be reprocessed using the current technologies. They MASSIVELY increase the amount of waste.
- Grosvenor 2y agoSeems like that would be fine for places where you have < 0.25GWt energy needs, and need a safe power source. Like remote installations/towns. Antarctic research stations, etc.
- cyberax 2y agoPebble bed reactors are indeed researched as a source for process heat (e.g. for steel or concrete production). But I really dislike that. If you just need 250MW of power, then just use electricity sourced from a regular PWR for heating. It'll be cheaper.
- Retric 2y agoThe maximum temperature from nuclear reactors is far below what you need for steel production because otherwise you’d melt the steel used to construct them. Waste heat can be useful for district heating systems because houses don’t need to reach high temperatures, but few designs give you access to even 300C and nothing currently hits 1,000+C.
- cyberax 2y agoSorry, you're right. Pebble bed reactors can provide helium at around 600C (reasonably up to 700C, but that's at the limits of material science).
- Animats 2y agoBut is it jam-proof? [1][2] [1] https://en.wikipedia.org/wiki/AVR_reactor https://en.wikipedia.org/wiki/AVR_reactor [2] https://en.wikipedia.org/wiki/THTR-300 https://en.wikipedia.org/wiki/THTR-300
- consumer451 2y agoThanks for sharing those links. That was a very interesting read.
- cynicalsecurity 2y agoThe obsession with "green" energy wouldn't do us any good, would it.
- yk 2y ago> Other pebble beds: The pebble bed technology and design has previously been used in prototype reactors in China and Germany, but not a larger-scale plant like Shidaowan. That's wrong, Hamm-Uentrop was a full scale commercial reactor. It did run in total for a week or so between 1985 and 1989 and was then shut down. The fundamental problem is, that the pebbles grind against each other, and being of the same material as pebbles they can grind each other down. (Now if you wonder why this wasn't discovered at the experimental reactor in Juellich, those guys just never mentioned that they lost fuel.)
- bargainbot3k 2y ago> New testing done at China’s Shidaowan nuclear power plant has confirmed its ability to be naturally cooled down, an industry-first milestone for achieving commercial-scale inherent safety, according to researchers. Amazing. Well done! How far this country has come in the last few decades is nothing short of breathtaking.
- dongobongo 2y agoThis actually happened in August and September of 2023 and it’s great validation for High Temperature Gas-cooled Reactor (HTGR) at larger scales. I hope they have the guts to also do a full loss of coolant test. I’ve also heard the these two reactors have been turned off for quite a while due to issues with the primary heat exchangers, temperature fluctuations, and uneven cooling - characteristically disadvantages of pebble beds. There’s of course 2 flavors of HTGR (prismatic and pebble bed), and people choose the pebble version for continuous refueling despite all the drawbacks [1]. But there’s a lot of reasons to do prismatic. Can’t wait to see China’s prismatic HTGR. [1] https://lvenneri.com/blog/pebble-bed-nukegumball https://lvenneri.com/blog/pebble-bed-nukegumball
- 8bitsrule 2y agoHmmm. The Titanic had sixteen watertight compartments. Did the pebble-bed reactor's "commercial-scale inherent safety" also pass a test with an compromised container, which would admit air that would cause the graphite to burn?
- JumpCrisscross 2y ago> which would admit air that would cause the graphite to burn? Rats, then it would cause about as many deaths per GWh as the coal it's replacing.
- natmaka 2y agoThe real underlying subject isn't "coal or nuclear" but "nuclear or renewables", and a potential nuclear plant not inducing any risk of major nuclear accident (nor any annoying waste? nor any dependency towards any fuel?...) would induce quite new way to consider it.
- JumpCrisscross 2y ago> real underlying subject isn't "coal or nuclear" but "nuclear or renewables" Not in the real world. We're deploying solar and wind as quickly as we can because they're the cheapest sources of power. The bottlenecks are production and permitting, and there is no indication either of those are seeing a step change in the next decade. There is a reason America and Europe, where anti-nuclear sentiment runs ripe, are building gas power plants and infrastructure at the fastest clip in history. In the West, the choice is gas or nukes. In the China and India, it's coal or nukes.
- natmaka 2y agoNuclear is plateauing, and renewables are booming: https://ourworldindata.org/grapher/renewable-nuclear-direct-substitution https://ourworldindata.org/grapher/renewable-nuclear-direct-... World: Energy: https://ourworldindata.org/grapher/primary-energy-share-nuclear-renewables https://ourworldindata.org/grapher/primary-energy-share-nucl... Electricity: https://ourworldindata.org/grapher/electricity-fossil-renewables-nuclear-line?time=2001..latest https://ourworldindata.org/grapher/electricity-fossil-renewa... China, while being the most efficient nation at deploying nuclear, illustrates it perfectly: https://ourworldindata.org/grapher/primary-energy-share-nuclear-renewables?country=~CHN https://ourworldindata.org/grapher/primary-energy-share-nucl... https://ourworldindata.org/grapher/electricity-fossil-renewables-nuclear-line?time=2001..latest&country=~CHN https://ourworldindata.org/grapher/electricity-fossil-renewa... India: https://ourworldindata.org/grapher/primary-energy-share-nuclear-renewables?country=~IND https://ourworldindata.org/grapher/primary-energy-share-nucl... https://ourworldindata.org/grapher/electricity-fossil-renewables-nuclear-line?time=2001..latest&country=~IND https://ourworldindata.org/grapher/electricity-fossil-renewa... Europe: https://ourworldindata.org/grapher/primary-energy-share-nuclear-renewables?country=~OWID_EU27 https://ourworldindata.org/grapher/primary-energy-share-nucl... https://ourworldindata.org/grapher/electricity-fossil-renewables-nuclear-line?time=2001..latest&country=~OWID_EU27 https://ourworldindata.org/grapher/electricity-fossil-renewa...
- m3kw9 2y agoThe automatic mechanism could fail right?
- paranoidrobot 2y agoThe safety of the system comes from it's design. It doesn't rely on anyone, or any mechanical process cooling it. > The pebble-bed reactor is designed so that this effect is relatively strong, inherent to the design, and does not depend on moving parts. This negative feedback creates passive control of the reaction process. From the Wikipedia article on the PBR that was linked in a neighbouring comment. It should, at least if built correctly, be impossible for it to get into a run-away state. Even if it lost all power, and everyone walked away, it should not melt down. [1] https://en.wikipedia.org/wiki/Pebble-bed_reactor#Safety https://en.wikipedia.org/wiki/Pebble-bed_reactor#Safety
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