A new page in the history of nuclear energy may be written in September, in the middle of the Gobi Desert.
China announced at the end of August that it had completed the construction of its first thorium-fueled molten salt nuclear reactor.
It intends to start the first tests of this alternative technology to current nuclear reactors in the next fifteen days.
The prototype, erected not far from the city of Wuwei, is of modest power since it is supposed to be able to produce energy for less than 1,000 homes, specifies the scientific journal Nature.
But if the upcoming tests satisfy the Chinese authorities, they will start a program to build a reactor capable of generating electricity for more than 100,000 homes.
This would allow Beijing to become an exporter of reactor technology that has been the subject of much ink for more than 40 years, recalls Les Échos.
Lower accident risks
China is in fact taking up the torch from the United States, which had built, then abandoned, a similar nuclear reactor at the end of the 1960s. The main difference with current reactors is that "almost all of them use uranium. as fuel and water, instead of molten salt and thorium ", recalls Jean-Claude Garnier, program manager at the energy department of the French Atomic Energy and Alternative Energies Commission (CEA), contacted by France 24.
Two "new" ingredients that were not chosen by chance by Beijing.
Molten salt reactors are among the most promising technologies identified by the Generation IV forum - an American initiative to promote international cooperation in the field of civil nuclear power - for the power plants of the future.
The principle is that "it is the salt itself which becomes the fuel", underlines Sylvain David, research director at the CNRS and specialist in nuclear reactors, contacted by France 24. The crystals are mixed with nuclear material - uranium or thorium - then heated to over 500 ° C to become liquid and transport the heat and energy produced.
A process which, on paper, would offer greater safety for the installations.
"Certain accident risks are theoretically eliminated because liquid combustion makes it possible to avoid situations where the nuclear reaction can get carried away and damage the structures of the reactor", underlines Jean-Claude Garnier.
Another advantage for China: this type of reactor does not need to be built near water because it is the molten salt "which serves as coolant, unlike conventional uranium power plants which need enormous quantities of water to cool their reactors, "writes the newspaper Les Echos.
As a result, reactors can be installed in isolated and desert regions, such as the Gobi Desert.
Thorium in abundance
Beijing has also opted to add thorium rather than uranium to its new molten salt reactor.
Again, this is an idea that has been floating around for a long time.
The main advantage, "is that there is much more thorium than uranium in nature", underlines Francesco D'Auria, specialist in nuclear reactor technologies at the University of Pisa, contacted by France 24.
Best of all, thorium belongs to the famous family of rare earths which are much more abundant in China than elsewhere.
Beijing could thus increase its energy independence from major uranium-exporting countries such as Canada or Australia, two countries with which China does not maintain the best diplomatic relations.
It is also a bet on the longer term.
"For the moment, there is enough uranium to supply all the reactors in service. But if their number increases, we could end up with a situation where the supply would no longer follow, and the use of thorium makes it possible to drastically reduce uranium needs, which makes it a potentially more sustainable sector, ”explains Sylvain David.
Proponents of thorium add that it is also a "cleaner" solution because its combustion does not create plutonium - a very toxic chemical element -, unlike the uranium currently used in nuclear power plants, underlines the Nature journal.
On paper, the marriage of molten salt reactor and thorium therefore seems to have everything good.
If it was not used earlier, "it is essentially because uranium 235 was the natural candidate for nuclear reactors and the market did not look much further", assures Francesco D'Auria .
Radiation and corrosion
It is true that of the three candidates for a nuclear reaction - uranium 235, uranium 238 and thorium - the first is "the only natural fissile isotope", recalls Sylvain David.
That is to say that the others must be bombarded by neutrons to obtain fissile material that can be used by a nuclear reactor.
A feasible but more complex process.
This is how thorium yields uranium 233, which is the fissile material necessary for the production of nuclear energy.
And that's another problem with thorium: "The radiation emitted by uranium 233 is stronger than that of other isotopes, so you have to be more careful," says Francesco D'Auria.
The feasibility of molten salt reactors is also questionable.
The technical headache stems from the fact "that at very high temperatures, the salt becomes corrosive for the reactor structures and we must find a way to protect them", explains Jean-Claude Garnier.
This is why the tests carried out by China on their new reactor will be followed very closely to find out how the engineers overcame this obstacle. But even if the Chinese claim victory, we must not rejoice too quickly, assures Francesco D'Auria. "The problem with corrosive products is that you only realize it after five to ten years", notes this researcher.
And then, in his opinion, there is no reason to cut the champagne for a reactor which, in addition to energy, produces uranium 233. "It is an isotope that does not exist in its natural state and which can be used to build an atomic bomb ", emphasizes Francesco D'Auria.
Clearly, the Chinese will perhaps revolutionize the nuclear industry, but they will also add an additional concern to all those who are worried about nuclear proliferation.
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