China has multi-billion projects developing liquid and solid fuel molten salt reactors

China has $3.3 billion funding two large molten salt fission reactor projects. There are 400 SINAP (Shanghai Institute of Applied Physics) scientists that are working on molten salt reactors at a complex of three new building. There are 200 other researchers working on the same subject but at different institutions.

China already generates 60% more electricity than the USA in 2018. China plans to double this by 2030. China wants to increase from 3-4% nuclear power for electricity to 10%. This will mean 300 GW of electricity in 2030. This would be about triple the US generation of nuclear electricity.

Starting in 2010, China is now working on two very different thorium based molten salt reactor programs. One is based on liquid fuel, the other on molten salt cooled solid fuel. Both are designed for specific application areas.

The solid fuel MSR (ThMSR-SF) is a high-temperature reactor, intended for industrial heat, hydrogen-production and electricity production. The ThMSR-SF uses fuel pebbles similar to the ones we know from the gas-cooled High-Temperature Reactors. The difference is that in the ThMSR-SF the fuel pebbles are cooled by molten salt. One area of research is the optimization of the fuel elements. The pebbles are graphite spheres that contain solid fuel kernels, of which several compositions are tested, including thorium kernels.

The liquid fuel MSR (ThMSR-LF) is optimized for the use of thorium. Key to realizing a closed fuel cycle, thus unlocking the full thorium potential, requires mastering the salt chemistry. Adequate salt cleaning is even a prerequisite for the establishment of a closed thorium fuel cycle.

The Chinese development plan for the chemistry of the salt cleaning processes has three distinctive phases.

Phase 1

The deployment of an online batch process. The fuel cycle starts with fuel loading based on low enriched uranium and thorium. There will be online refueling and removal of gaseous fission products, and after several years of operation, the whole core fuel salt will be discharged. Uranium and thorium will be extracted and reloaded to the reactor core. Fission products and minor actinides will be temporarily stored.

Phase 2

The online removal of gaseous fission products will be continued, added will be online extraction and reloading of uranium to enhance the fuel utilization ratio. Fission products and minor actinides will still be stored temporarily.

Phase 3 – closed fuel cycle with virtually no waste

A fully closed fuel cycle will be created. The researchers foresee offline extraction of transuranics, that will be reloaded to the reactor. This may evolve into a full recycling mode in which all heavy elements are recycled until they fission. Once this is realized, geologic disposal will be limited to fission products and small amounts of uranium and minor actinides, basically limited to losses in the reprocessing.

They will use of fluorination for uranium recovery, combined with frozen-wall technique to mitigate corrosion, due to free fluorine (F2) during the fluorination process. The frozen wall technique basically means having some salt freeze on the reactor or piping walls, thus protecting the walls from free fluorine during periods of fluorination. Another area of interest is the demonstration of salt distillation, intended for carrier salt purification.

They will develop electrochemical separation technology for uranium recovery. Electro-deposition of uranium metal from the FLiBe-melt can yield a separation ratio of more than 99%.

Developing and testing new graphite materials

SINAP is testing and creating new nuclear graphites materials in ASME, and is setting new ASTM standards, for instance for testing impregnation of nuclear graphite by molten salt. ASME and ASTM are the worldwide reference standards describing materials properties for engineering applications. The Chinese are now adding new entries to the chapter on nuclear materials. This shows how the center of gravity in nuclear development is shifting from the West to non-Western countries.