China set to begin first trials of molten salt nuclear reactor using thorium instead of uranium
Scientists in China are about to turn on for the first time an experimental reactor that’s believed by some to be the Holy Grail of nuclear energy — safer, cheaper and with less potential for weaponisation.
Construction on the thorium-based molten salt reactor was expected to be finished this month with the first tests to begin as early as September, according to a statement from the Gansu provincial government.
Thorium is a metallic element with radioactive properties, close to uranium on the periodic table, which was considered as an alternative fuel source when the US was first developing nuclear energy technology in the 1940s.
The Americans even developed an experimental thorium-based molten salt nuclear reactor at the Oak Ridge National Laboratory in Tennessee, but the US shut it down and abandoned thorium in favour of uranium in the early 1970s.
The new reactor, built at Wuwei on the edge of the Gobi Desert in northern China, is an experimental prototype designed to have an output of just 2 megawatts.
According to a paper published in the Chinese scientific journal Nuclear Techniques by the Shanghai Institute of Applied Physics, the longer-term plan is to develop a series of small molten salt reactors each producing 100 megawatts of energy, enough for about 100,000 people.
Molten salt plants don’t use water for cooling like traditional nuclear power plants and so can be built in desert areas, the paper says, such as China’s sparsely populated western regions.
The first commercial plants using the new technology are reportedly planned to come online in 2030.
President Xi Jinping has pledged to make China carbon neutral by 2060.
Nigel Marks, an associate professor of physics at Curtin University, said China pushing ahead with thorium as a nuclear fuel was an exciting development.
“They’ve effectively reactivated a research program that the US mothballed back in the 60s,” Dr Marks said.
“Who knows, maybe in a different climate with some different economics they could make it work.”
Thorium — named after Thor, the Norse god of thunder — has a few key advantages over uranium.
The radioactive waste from thorium only needs to be stored for about 500 years, compared to several thousand for uranium.
It’s also much more difficult and time consuming to make weapons-grade uranium out of thorium.
Some thorium advocates have even speculated that the US only went with uranium rather than thorium because it was more useful to make nuclear weapons.
However, Dr Marks said this was “all bollocks”.
“The main reason that uranium has been used since the first reactor back in the early 40s is just because everything works so easily for uranium,” he said.
“There’s only one element that can naturally produce a fission reaction out of the box, and that’s uranium.
“Thorium, in principle, you can release the energy but it’s nowhere near as easy as it is with uranium.”
For example, thorium is fertile rather than fissile, which means it needs another nuclear technology, typically a uranium reactor, to kick start the thorium chain, he said.
“Chemically it’s a very different element,” he said.
“So things that just happen to be simple for uranium, just happen to be complicated for thorium.”
India, which was unable to access uranium for nuclear power plants until 2008, had been trying for decades to develop thorium power but never got it to work, he said.
He said the main thing holding back thorium as a potential fuel source was the expense and risk of developing a new technology that may not ultimately work or be cost-effective.
Dr Marks said the same molten salt technology could just as easily be used with uranium as thorium.
Using molten salt instead of water means a reactor can’t melt down in the same way as traditional water-cooled reactors.
Molten salt reactors are also potentially cheaper because they don’t need to be pressurised to keep the coolant water from turning into steam.
Dr Marks said China’s approach was not to “keep all their eggs in one basket”.
“They’ve got a couple of different technologies, and there’s loads of different reactor designs they’re pursuing across their whole nuclear sector,” he said.
“So they’re giving it a good shot, and I’m really interested to see what happens.”