Thorium Molten Salt Reactors Could Create a Cleaner Safer Nuclear Future

The Chinese government revealed plans to build up to 30 thorium molten salt reactors (MSRs). China will test its first 2 MW prototype in September 2021 and plans to build a commercial reactor by 2030. China may include thorium MSRs in its Belt and Road initiative. 

Engineers and scientists have theorized about and attempted to build thorium MSRs since the 1940s. They ran into early problems with corrosion and sustaining fission since thorium has weak reactivity. Functional thorium MSRs could provide cleaner and safer nuclear energy compared to uranium-fueled, liquid-based reactors. No large-scale projects have yet been successful; however, in the past decade or so, thorium MSRs have received a new wave of attention and funding. Though thorium has been used as a nuclear fuel in other types of reactors, MSRs could provide opportunities for large-scale commercialization.

Benefits of Thorium MSRs

Thorium has numerous advantages over uranium, which is currently the standard nuclear energy fuel. Thorium is 3-4 times as naturally abundant and cheaper to mine than uranium. Thorium is also much safer than uranium, both in terms of nuclear proliferation risk and environmental harm. In an MSR, U-232 is a byproduct of thorium use. U-232 is highly radioactive and therefore discourages potential proliferation efforts. Environmentally, thorium is only reactive for 500 years, compared to Uranium’s half-life of 10,000 years. This significantly shorter timeline vastly lowers waste leakage risk and would make nuclear waste engineering and legislative feats much more doable.  

Finally, MSRs have advantages since they do not require water. If exposed to air, an MSR would quickly solidify and encapsulate the thorium-uranium substance, lowering the likelihood that nuclear material is released. Additionally, since MSRs use molten salt rather than fuel rods, the reactor does not require water and can operate in arid and desert climates. 

What Would It Take for Thorium to Become Widespread?

The future of thorium MSRs relies on the success of pilots, such as the Chinese government’s, and the first full-scale reactors. However, as with any new energy technology, thorium MSRs will face significant regulatory barriers. Though recent legislative action could help support MSRs and other advanced reactors, there remains a focus on uranium and liquid reactors. Nuclear regulations are often built upon existing reactors, such as light-water reactors. MSRs operate much differently than classic reactors, and though safety features may be more easily designed in an MSR, adapted regulation and significant testing will be required for licensing. Regulation will also have to be adapted to accommodate thorium mining and end-product waste control. These regulations will have to be informed by rigorous testing and will vary from country to country. 

The other significant challenge thorium MSRs face is public acceptance as a clean and safe energy source. Countries have historically had varying positions on nuclear energy because of the risks of proliferation and meltdowns. Though scientifically, thorium MSRs rise to this challenge, public perception of the technology could make or break implementation. If the first commercial reactors do not meet energy or safety standards, the technology may not be accepted. 

Thorium MSRs are currently a promising alternative nuclear pathway; however, many barriers remain to reaching commercialization and widespread adoption. The next few years will be telling of the technology’s viability and how resilient it will be when facing government regulations and public pushback.