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According to Chinese state media, a group of scientists recently managed to refuel a working thorium molten salt reactor without causing a shutdown — a feat never achieved before. The success was announced by the project's chief scientist Xu Hongjie during a closed-door meeting at the Chinese Academy of Sciences on April 8, Chinese news outlet Guangming Daily reported last week.
Such a breakthrough could be transformative to the global energy landscape, as thorium has long been hailed as a far safer and cheaper alternative to uranium in nuclear reactors. While also a radioactive element, thorium produces less waste, and the silver-colored metal, mostly found in monazite, is much more common in the Earth's crust.
According to the International Atomic Energy Agency (IAEA), thorium is three times more abundant in nature than uranium, but historically has found little use in power generation due to the significant economic and technical hurdles.
[...] Compared to uranium, thorium can generate a significantly higher amount of energy via nuclear fission. A Stanford University research estimates that thorium's power generation could be 35 times higher. Thorium molten-salt reactors (TMSRs) are also compact, do not require water cooling, cannot experience a meltdown and produce very little long-lived radioactive waste, according to the IAEA.
When announcing the breakthrough, Xu acknowledged that its project was based on previous research by US researchers who pioneered molten salt reactor technology in the 1950s, but abandoned shortly after to pursue uranium-fueled ones.
Xu — who was tasked with the thorium reactor project in 2009 — told Chinese media that his team spent years dissecting declassified American documents, replicating experiments and innovating beyond them.
China's TMSR-LF1 Molten Salt Thorium Reactor Begins Live Refueling Operations:
Although uranium-235 is the typical fuel for commercial fission reactors on account of it being fissile, it's relatively rare relative to the fertile U-238 and thorium (Th-232). Using either of these fertile isotopes to breed new fuel from is thus an attractive proposition. Despite this, only India and China have a strong focus on using Th-232 for reactors, the former using breeders (Th-232 to U-233) to create fertile uranium fuel. China has demonstrated its approach — including refueling a live reactor — using a fourth-generation molten salt reactor.
The original research comes from US scientists in the 1960s. While there were tests in the MSRE reactor, no follow-up studies were funded. The concept languished until recently, with Terrestrial Energy's Integral MSR and construction on China's 2 MW TMSR-LF1 experimental reactor commencing in 2018 before first criticality in 2023. One major advantage of an MSR with liquid fuel (the -LF part in the name) is that it can filter out contaminants and add fresh fuel while the reactor is running. With this successful demonstration, along with the breeding of uranium fuel from thorium last year, a larger, 10 MW design can now be tested.
Since TMSR doesn't need cooling water, it is perfect for use in arid areas. In addition, China is working on using a TMSR-derived design in nuclear-powered container vessels. With enough thorium around for tens of thousands of years, these low-maintenance MSR designs could soon power much of modern society, along with high-temperature pebble bed reactors, which is another concept that China has recently managed to make work with the HTR-PM design.
(Score: 3, Touché) by gnuman on Tuesday May 06, @08:36AM (3 children)
There is nothing special about Thorium for power generation. It's basically like Uranium. You can very similar short term issues with Thorium as you do with Uranium reactors. You can melt them down (depending on reactor design, of course, *not* fuel dependent here), you can create radioactive crap lasting many many generations. It's just a different fuel. So if you have lots of Thorium around and not much Uranium, then you probably want to have Thorium reactors.
One difference between thorium and uranium is that ALL thorium require some uranium to get going, then you *want* to refuel them online and keep only using thorium input as it breeds uranium in the reactor. Basically, you can already use CANDU reactors to burn Thorium -- you don't need fancy designs here.
https://www.sciencedirect.com/science/article/abs/pii/S0196890405002670 [sciencedirect.com]
As for molten salt reactors, well, those are "meltdown reactors" by definition. The fuel is liquid and quite warm. If you get any leaks, you end up with a massive mess on your hands. That's the main reason no one is using MSRs -- they are a nightmare to cleanup. And if primary vessel needs major maintenance --- yeah, good luck!! There are some theoretical calculations how these reactors can run for 200 years or so, but then who maintains that? The current reactors are much much easier to cleanup and it's already difficult enough. I would say, MSRs are great in theory, terrible in practice.
FTFA (I can't resist):
Which is same for Chernobyl, hahaha. It also "cooled down" when "exposed to air". It's the other issues that happen when your core is "exposed to air" that is the problem.
(Score: 2) by turgid on Tuesday May 06, @11:30AM (2 children)
The Chernobyl problem was quite different. When you have a uranium rector, over time, the U-238 captures neutrons and decays to plutonium-239, which is fissile. This leads to the positive temperature coefficient of reactivity. Because the Pu-239 is fissile (fast neutrons), the hotter the reactor, the more fission it undergoes and the more heat it produces. It's positive feedback.
You can get into a situation in an emergency that if you have shut your reactor down and it over-heats, it comes back to life (goes critical) all on its own due to the high temperature. Uranium reactors are designed very carefully to prevent this. They have "hold down" rods as well as control rods. There are other features such as boron balls, boron dust, nitrogen injection and boric acid (in water cooled reactors).
If you get into the terrible situation where the core is disturbed and the fuel melts, if there is enough of it and if it gets hot enough, you might get a re-crtiticality. That won't last long. It'll blow itself apart. It will be quite unpleasant. I believe PWRs are designed to contain melted fuel. This is what saved the day at Three Mile Island.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 2) by gnuman on Tuesday May 06, @12:34PM (1 child)
I think you meant *positive void coefficient* ... it's a property of reactor *design*, not the fuel.
You can have this with thorium just as you can have this with plain uranium.
Thorium is not better or worse than Uranium or even Plutonium as fuel. It's just a fuel. The difference is like using methane to power your car or gasoline or diesel. They all burn. They all produce CO2. They all can cause same engine problems. etc. etc. Nuclear fuels are exactly the same --- they burn similarly but have slight different characteristics. The arguments is like arguing has methane is sooo much safer than gasoline or diesel. In the end, it doesn't matter -- you can die by accident with any of these fuels.
(Score: 2) by turgid on Tuesday May 06, @01:24PM
I think you meant *positive void coefficient* ... it's a property of reactor *design*, not the fuel.
No, that's something else. It is related, however.
you can die by accident with any of these fuels
True, but the probability of an accident is greater or lesser depending on the fuel and the uses, and so are the consequences of that accident.
I worked in Reactor Physics at a nuclear power station for a few years. I had a bit of training. We looked at certain famous accidents.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].