China’s Molten Salt Nuclear Reactors

China is completing a 2 megawatt molten salt reactor this month (August) and will start tests next month. Professor Yan Rui of the Shanghai Institute of Applied Physics, was a lead researcher on the TMSR (molten salt reactor). He wrote in a paper published in the Chinese journal Nuclear Techniques. The commercial reactor (100 MW due to be started in 2030) designed by Yan and his colleagues would be only 3 meters tall and 2.5 meters wide, but could produce enough electricity to power town of 100,000 inhabitants.

Weilong ZHOU,Rui YAN,Bo ZHOU. Radioactive product analysis of a small molten-salt reactor in primary loop[J].Nuclear Techniques, 2021, 44(7): 76-82

Based on the research of molten salt reactor (MSR), a conceptual design of small MSR core with thermal power of 100 MWt is proposed to meet the power supply demand of small area. By adjusting the initial fuel load of the reactor core, the reactor can operate at full power for 1 250 days without refueling, and then batch process fuel at the end of its life.

This study aims to analyze the yield and source of radionuclides in the main loop during such a small MSR operation by providing the constitutions, main components, and parameters according to the burnup characteristics and fuel salt characteristics of the long refueling cycle.

The calculation software KENOVI for three-dimensional Monte Carlo transportation program and burnup analysis module Origen-S were employed to analyze the fuel consumption analysis module, the storage of radioactive products in the main loop and the neutron energy spectrum and other neutron parameters.

The computation results show that the radioactivity at the end-of-life this small MSR is about 7.36×10^18 Bq, and the radioactivity of fission products in the end-of-life primary loop is about 5.89×1018 Bq, of which the inert gases, iodine isotopes and the volatile fission metal account for 7.35×10^17 Bq, 9.56×10^17 Bq, 8.17×1017 Bq respectively. The total radioactivity of actinide nuclides is about 1.47×10^18 Bq, of which the 239Np accounts for 98%.

This study provides a reference for radiation protection design and fuel reprocessing scheme of molten salt reactor.

Nextbigfuture had coverage last month on global molten salt and thorium reactor work.

SINAP aims for a 2 MWt pilot plant (TMSR-LF1) initially, then a 10 MWt experimental reactor (TMSR-LF2) by 2025, and a 100 MWt demonstration plant (TMSR-LF3) with full electrometallurgical reprocessing by about 2035, followed by 1 a GW demonstration plant. The TMSR-LF timeline is about ten years behind the SF one.

A TMSFR-LF fast reactor optimized for burning minor actinides is to follow.

The TMSR-SF0 is one-third scale and has a 370 kW electric heat source with FLiNaK primary coolant at 650°C and FLiNaK secondary coolant.

The 10 MWt TMSR-SF1 has 17% enriched TRISO fuel in 60mm pebbles, similar to HTR-PM fuel, and coolant at 630°C and low pressure. Primary coolant is FLiBe (with 99.99% Li-7) and secondary coolant is FLiNaK. Core height is 3 m, diameter 2.85 m, in a 7.8 m high and 3 m diameter pressure vessel. Residual heat removal is passive, by cavity cooling. A 20-year operating life was envisaged but the project is discontinued.

The 2 MWt TMSR-LF1 is under construction at Wu Wei in Gansu in a $3.3 billion program. It will use fuel enriched to under 20% U-235, have a thorium inventory of about 50 kg and a conversion ratio of about 0.1. FLiBe with 99.95% Li-7 would be used, and fuel as UF4. The project would start on a batch basis with some online refueling and removal of gaseous fission products, but discharging all fuel salt after 5-8 years for reprocessing and separation of fission products and minor actinides for storage. It would proceed to a continuous process of recycling salt, uranium and thorium, with online separation of fission products and minor actinides. It would work up from about 20% thorium fission to about 80%.

Beyond these, a 373 MWt/168 MWe liquid-fuel MSR small modular reactor is planned, with supercritical CO2 cycle in a tertiary loop at 23 MPa using Brayton cycle, after a radioactive isolation secondary loop. Various applications, as well as electricity generation, are envisaged. It would be loaded with 15.7 tonnes of thorium and 2.1 tonnes of uranium (19.75% enriched), with one kilogram of uranium added daily, and have 330 GWd/t burn-up with 30% of energy from thorium. Online refueling would enable eight years of operation before shutdown, with the graphite moderator needing attention.

There was a 2019 presentation on the SINAP molten salt project and the long-term plans through 2050 for China’s molten salt reactors. They would be six times more efficient with nuclear fuel, would need no water cooling and would be able to desalinate seawater.