Thorium MSR 釷熔鹽反應器

Thorium-based Molten Salt Reactor (TMSR)  釷基熔鹽反應器
China Discovers 60,000-Year Supply of Thorium(Th)

Last week, the media reported that China had discovered 1 million tons of thorium – enough of the nuclear fuel to power the country for 60,000 years. How big is this news really? 

China is actively developing thorium-based molten salt reactors (TMSRs) to enhance energy security and reduce reliance on uranium. A 2 MW experimental TMSR was completed in 2021 and successfully reached criticality, using a molten salt mixture and operating at high temperatures. 

Based on its success, China plans to build a larger 60 MW thermal (10 MW electric) demonstration reactor in the Gobi Desert by 2030. The technology offers safety and sustainability benefits but faces challenges such as uranium-233 proliferation risks and molten salt system complexities. China’s advancements place it at the forefront of thorium nuclear research.

The nuclear reaction in a thorium molten salt reactor (TMSR) primarily involves the conversion of thorium-232 (232Th^{232}Th) into uranium-233 (233U^{233}U), which undergoes fission to produce energy.

Key Nuclear Reactions

  1. Thorium Absorption and Conversion into Uranium-233:
    Thorium-232 captures a neutron and undergoes two beta decays to become uranium-233:

    232Th+1n233Th(β decay, half-life: 22 min)233Pa(β decay, half-life: 27 days)233U
  2. Fission of Uranium-233:
    The uranium-233 isotope then undergoes fission upon absorbing a thermal neutron, releasing energy, neutrons, and fission products:

    233U+1nFission Products+2.5 (average) 1n+Energy (about 200 MeV)

    The released neutrons sustain the chain reaction, with some continuing the cycle by converting more thorium-232 into uranium-233.

Fission Products Example

The fission of uranium-233 can produce various fission fragments, such as:

233U+1n144Ba+89Kr+21n+Energy^{233}U + {}^1n \rightarrow {}^{144}Ba + {}^{89}Kr + 2 {}^1n + \text{Energy}
233U+1n140Xe+94Sr+21n+Energy^{233}U + {}^1n \rightarrow {}^{140}Xe + {}^{94}Sr + 2 {}^1n + \text{Energy}

Summary

  • Fuel Cycle: 232Th^{232}Th → 233U^{233}UFission

  • Output: Energy (~200 MeV per fission), neutrons (to sustain the reaction), and fission products.

  • Advantage: Almost all thorium-232 can be converted into fuel, making the process highly efficient.

This cycle enables a self-sustaining, cleaner nuclear reaction with high fuel efficiency and lower long-lived radioactive waste.

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