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upstart writes:

China may have achieved a "Sputnik moment" in the clean energy technology race by successfully reloading a nuclear reactor that runs on thorium:

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.

Original Submission