Chinese Government to invest billions on Molten Salt Reactor technology

Last month, China Academy of Sciences and the government of Gansu Province signed a co-operation agreement to work together on China’s Thorium Molten Salt Reactor (TMSR) project and to have a demonstration or research reactor built inin Gansu Province by 2020.

The total investment was planed to be 22 billion CNY (3 billion USD) and build up a TMSR demonstration project in Wuwei, a city in Gansu. China is regarded as the worldwide leader in the field of molten salt reactor research, with a budget estimated at 500 million USD.

China is becoming the testing ground for a new breed of nuclear power stations designed to be safer and cheaper, as scientists from the U.S. and other Western nations find it difficult to raise enough money to build experimental plants at home.

Update on the Chinese molten salt reactor project

The Chinese central government selected molten salt reactor as one of its R&D focus of the nuclear GEN IV technology. The China Academy of Sciences in January 2011 launched an R&D program on LFTRs, known there as the Thorium-Breeding Molten Salt Reactor (Th-MSR or TMSR), hoping to obtain full intellectual property rights on the technology. This was called as China’s Strategic Priority Research Program. Since then the project was undertaking by Shanghai Institute of Applied Physics (SINAP) which is a sub-institute of China Academy of Sciences.

SINAP has two streams of TMSR development – solid fuel with once-through fuel cycle, and liquid fuel with reprocessing and recycle.

The TMSR-SF stream has only partial utilization of thorium, relying on some breeding as with U-238, and needing fissile uranium input as well. It is optimized for high-temperature based hybrid nuclear energy applications. Besides, SINAP has also signed a cooperation agreement with Oak Ridge National Laboratory on developing the advanced technology using lithium-beryllium-fluoride salts for cooling.

The TMSR-LF stream claims full closed Th-U fuel cycle with breeding of U-233 and much better sustainability with thorium but greater technical difficulty. It is optimized for utilization of thorium with electrometallurgical pyroprocessing.

In 2014, China Academy of Sciences set up the TMSR Center which takes the responsibility of developing the China TMSR technology. Following that, China National Nuclear Corporation (CNNC) also signed a co-working agreement on the design of 10MW TMSR-SF.

This year in November, China Academy of Science has signed the strategic cooperation agreement with government of Gansu Province, with the total investment of 22 billion (CNY) and build up a TMSR demonstration project in Wuwei, a city in Gansu.

What is the concept of Molten Salt Reactor?

The key difference between molten salt reactor and other fission reactor types are the coolant or sometimes the fuel itself is liquid instead of solid rods as the molten salt mixture. With this feature, molten salt reactors can be operated with lower vapor pressure but with higher thermodynamic efficiency.

Unlike other conventional reactors, the rate of fission in a molten salt reactor is inherently stable. The molten salt reactor cannot melt down unlike conventional reactors, because they are molten by their design. If an MSR were to overheat, the heat would melt a freeze-plug at the bottom of the reactor vessel and the liquid fuel salts would drain into the emergency cooling tanks where it would cool and solidify.

A general design type of molten salt reactor

The first concept of molten salt reactor has been put up for over 60 years. It was used for the US Aircraft Reactor Experiment with a prototype of thorium fuel cycle breeder nuclear power plant, where all today’s molten salt reactor designs were from. There are few different types of molten salt reactor developed by different companies or countries today.

Fluoride High-Temperature Reactor (FHR) is a typical molten-salt cooled reactor which is different with molten-salt fueling reactors. FHR uses a low-pressure coolant that does not boil off, and a robust ceramic fuel form that can withstand very high temperatures without leaking, they greatly reduce the risk of accidents and on-site releases of radioactivity.

Liquid Fluoride Thorium Reactor (LFTR) is a basic type of the molten salt reactor. It uses the thorium fuel cycle with a fluoride-based, molten, liquid salt for fuel. The LFTR concept was designed by Oak Ridge National Laboratory in 1960s. As the reactor contains molten thorium salt, it has the possibility to the abundant thorium fuel cycle which uses an isotope of thorium, Th232, as the fertile material.

Stable Salts Reactor (SSR) is developed by Moltex Energy. There is no pumps only small impellers in the secondary salt bath, and this reactor relies on convection from static vertical fuel tubes in the core to convey heat to the steam generators. Core temperature is 500-600°C, at atmospheric pressure. Decay heat is removed by natural air convection.

Integral MSR is developed by the Canadian company Terrestrial Energy. This simplified MSR integrates the primary reactor components, including primary heat exchangers to secondary clean salt circuit, in a sealed and replaceable core vessel that has a projected life of seven years. The IMSR will operate at 600-700°C, which can support many industrial process heat applications. Recently, Terrestrial Energy’s Molten Salt Reactors completed phase 1 of the vendor design review – the first advanced reactor to do so, which is a landmark achievement.

There are also some other types of MSR such as Flibe LFTR and Molten Chloride Salt Fast Breeder Reactor (MCSFR).

What is the advantages of molten salt reactor to the business content?

Compared to the light water reactor, one of the greatest difference is that molten salt reactor uses very little water if it is cooled by the molten salt. It means that the molten salt reactor has more various suitability to different geographic conditions. Conventional reactors always need to build near the water or with a huge water-container. But for the molten salt reactor, it can be built in the dry place such as Gansu where water shortage is always restricting the economic development.

A phantom image of the TMSR project in Gansu dessert

Another good advantage of the molten salt reactor is its safety. Unlike steam, fluoride salts dissolve poorly in water, and do not form burnable hydrogen. Unlike steel and solid uranium oxide, molten salts are not damaged by the core's neutron bombardment. Light water reactor (and most other solid-fuel reactors) have no fundamental "off switch", but once the initial criticality is overcome, an MSR is comparatively easy and fast to turn off by letting the freeze plug melt. It also added the extra safety feature to the molten salt reactor especially the liquid fuel type.

Molten salt reactors are always operated under lower pressure, and it doesn’t require fuel rods for the operation. In other words, the supply chain of the molten salt reactor will also be simpler than a conventional reactor.

The thorium fuel cycle has several potential advantages over a uranium fuel cycle as well, including thorium's greater abundance, superior physical and nuclear properties, reduced plutonium and actinide production.

As one of the GEN IV nuclear technology which just went off the laboratory, we still need time to practice on the actual feasibility of the molten salt reactor. But with the advantages above-mentioned, I believe the future molten salt reactors will definitely play a bigger role in the global nuclear industry. And it might become the key to opening up the new emerging market of the industry.

Molten salt reactors and other advanced nuclear reactors have received increased attention over the last few years as the world is looking for alternative technologies for energy production.

Dr. Chen Kun, Professor & Director, Reactor System Engineering, Shanghai Institute of Applied Physics, Chinese Academy of Sciences is an Advisory Board member for the 6th edition of Asia Nuclear Business Platform (ANBP). He is working on the development of the Chinese TMSR project.

Nuclear Innovations including molten salt reactors will be an area of focus during the Asia Nuclear Business Platform which will take place 9-10 May 2018 in Shanghai, China.