The Chinese Ministry of Ecology and Environment has last month approved the commissioning of a prototype thorium-fuelled molten-salt reactor (MSR) built by the Shanghai Institute of Applied Physics (SINAP), the construction of which started in September 2018.
The SINAP, which is part of the Chinese Academy of Sciences, unveiled the design for the experimental molten salt reactor and performed the first tests in September last year, paving the way for building the first commercial 100 MW MSR that is scheduled for completion by 2030.
The SINAP project will be the world’s first molten-salt reactor since the failed experiment with such a reactor at the Oak Ridge National Laboratory in the US led to its abandonment in 1969.
The molten salt nuclear reactor does not require water, which means these will be able to operate in desert areas, and China’s first commercial MSR will be located in the desert city of Wuwei. China plans to build more such small reactors across its remote desert regions and plains in the western part of the country.
The Thorium Molten Salt Reactor (TMSR) project, started in 2011, has been underway in Wuwei city in China’s Gansu province in the northwest. The new reactor is a part of the nation’s drive to make China carbon-neutral by 2060, according to the team at the Shanghai Institute of Applied Physics that developed the prototype.
According to an article by Professor Yan Rui of the SINAP, “a molten salt reactor has the advantage of being multipurpose, small in size and highly flexible. In recent years, the potential of small-scale molten salt reactors has caught international attention.”
“Small-scale reactors have significant advantages in terms of efficiency, flexibility and economy. They can play a key role in the future transition to clean energy. It is expected that small-scale reactors will be widely deployed in the next few years”, Yan said.
The molten-salt nuclear reactor runs on liquid thorium rather than uranium, and is expected to be safer than traditional reactors because the molten salt cools and solidifies quickly when exposed to the air, insulating the thorium. Thus, any potential leak from MSRs would spill much less radiation into the atmosphere than traditional reactors, in case of an accident.
Besides, thorium is much cheaper and more abundantly available as compared to uranium. Nearly all mined thorium is thorium-232, the isotope used in nuclear reactions. Instead, only 0.72 percent of total mined uranium is the fissile uranium-235 used in traditional nuclear reactors. Moreover, the main byproducts of a thorium nuclear reaction are uranium-233, which can be recycled in other reactions.
According to the World Nuclear Association (WNA), China leads global MSR research, which includes work in this area by countries such as France, India, Japan, Norway, and the US.
The development holds considerable interest for India as its three-stage nuclear power production program has been conceived with the ultimate objective of utilising the country’s vast reserves of thorium-232. India has the world’s third largest reserves of thorium. The first stage envisages the use of pressurised heavy water reactors (PHWRs) to produce energy from natural uranium. Besides energy, PHWRs also produce fissile plutonium (Pu-239).
The second stage involves using the indigenous fast breeder reactor (FBR) technology fuelled by Pu-239 to produce energy, as well as more Pu-239. By the end of the second stage of the cycle, the reactor would have produced, or “bred” more fissile material than it would have consumed. The FBR being developed in Kalpakkam in Tamil Nadu state will use a mixed oxide of Pu-239 – derived from reprocessed spent fuel from the thermal PHWRs – and uranium-238 as fuel to generate energy. This nuclear reaction will also produce more Pu-239 by converting both U-238 in the fuel mix, as well as a blanket of depleted uranium surrounding the core, into plutonium. This plutonium will then be processed and used as nuclear fuel in a chain of commercial FBRs in the second stage of the nuclear programme.
The final stage of the cycle would involve the use of Pu-239 recovered from the second stage, in combination with thorium-232, to produce energy and uranium (U)-233 using “thermal breeders”. This production of U-233 from thorium-232 would complete the cycle, while the U-233 would then be used as fuel for the remaining part of the fuel cycle.