Thorium vs Uranium: A Game-Changer in Nuclear Energy?

Nuclear energy has been a central topic of global debate for decades, primarily due to its potential to meet the increasing global energy demands while offering low greenhouse gas emissions. Uranium-based fuels like uranium-235 and plutonium-239 provide around 20-40% of the energy needs for many countries. However, there are issues and concern regarding these uranium-based fuels:

1. Resource Limitations: Uranium reserves are depleting, with estimates suggesting that at the current consumption rates, conventional uranium resources could last only 75 years. This looming shortage has led many to seek alternatives to ensure long-term energy security.
2. Waste and Safety Issues: The issue of nuclear waste disposal remains largely unresolved. The withdrawal of repository projects like Yucca Mountain has further complicated matters. Additionally, high-profile accidents such as Three Mile Island, Chernobyl, and Fukushima have heightened public distrust in uranium-based reactors.
3. Proliferation Risks: The production of weapon-grade plutonium and transuranic isotopes in uranium reactors poses significant security risks, further complicating the role of uranium-based reactors in future energy systems.

Despite these challenges, uranium-based reactors, particularly pressurized water reactors (PWRs), still dominate global nuclear energy production due to the well-established nature of the technology. However, in recent years, a renewed interest in thorium as a potential alternative nuclear fuel has garnered significant attention.

Global Developments in Thorium Energy

Thorium, a silvery, slightly radioactive metal, presents several advantages over uranium-based nuclear fuels:

1. Abundance: Thorium is 3–4 times more abundant than uranium and is widely available in countries such as India, China, Brazil, the USA, and Australia. It is primarily found in the mineral monazite, which contains 6–7% thorium.
2. Sustainability: Given its abundance and ease of extraction, thorium is seen as a promising candidate for large-scale energy production. As demand for uranium-based energy grows, thorium could serve as a sustainable alternative.
3. Safety: Thorium-232, the most common isotope of thorium, is proliferation-resistant. When irradiated, thorium-232 transmutes into uranium-233, a fissile material that can be used as nuclear fuel. However, uranium-233 is contaminated with uranium-232, which emits high-energy gamma radiation, making it difficult to misuse for weapons production.
4. Neutron Economy: Thorium-based reactors, particularly those using uranium-233, offer higher neutron yields and greater efficiency, making them suitable for thermal reactors. This improved neutron economy allows thorium to potentially produce more fissile material than it consumes, a property known as “breeding.”

However, the economic and technical challenges of thorium-based nuclear power are significant. Thorium extraction remains costly, and the lack of infrastructure for thorium reactors means that significant investment in research and development is necessary.

Thorium-based nuclear fuel has been explored since the 1950s. Early experimental reactors in the 1960s showed the potential of thorium as a nuclear fuel, but interest waned with uranium’s dominance in both military and civilian applications. However, in recent decades, there has been a resurgence of interest, particularly driven by countries with significant thorium reserves or nuclear ambitions:

• India: With vast thorium reserves and limited uranium supplies, India has invested heavily in thorium-based nuclear reactors for commercial energy production. The country’s three-stage nuclear program aims to exploit thorium’s potential to generate a significant portion of its energy.
• China: In August 2021, China completed its first experimental thorium-based nuclear reactor in the Gobi Desert. The reactor will undergo extensive testing, and if successful, Beijing plans to construct additional reactors, potentially capable of supplying power to over 100,000 homes. This marks a significant milestone in thorium research.
• Global Efforts: Countries like the USA and China are collaborating on thorium utilization through molten salt reactor (MSR) designs as part of Generation IV nuclear reactors. These reactors are expected to become operational around 2030, with thorium serving as a core component.

Other than that, countries across the world are exploring the use of thorium in various reactor designs. The International Atomic Energy Agency (IAEA) has been closely studying the potential of thorium as part of its coordinated research efforts. A 2021 IAEA report titled “Near-Term and Promising Long-Term Options for the Deployment of Thorium-Based Nuclear Energy” summarizes the challenges and benefits of using thorium as a fuel in different types of reactors, including water-cooled reactors and molten-salt reactors.

Notable Thorium-Fueled Projects

Several experimental reactors have successfully demonstrated the use of thorium-based fuels:

1. Thorium High-Temperature Reactor (THTR), Germany (1983–1989): A 300 MWe reactor that used thorium-HEU fuel pebbles. Although it was shut down due to technical issues, it demonstrated the potential of thorium for power generation.
2. Peach Bottom HTR, USA (1967–1974): A 40 MWe demonstration reactor that used thorium-HEU fuel. It achieved a 74% capacity factor and generated a significant amount of electricity over its operation.
3. Shippingport Light Water Breeder Reactor, USA (1977–1982): This reactor used U-233 as the fissile driver in movable fuel assemblies and successfully demonstrated breeding with a ratio of 1.01, producing over 2 billion kWh.
4. India’s PHWRs: Indian reactors have used thorium-bearing fuel bundles for power flattening and reactivity control.

These projects highlight thorium’s potential, but they also underscore the technical and operational challenges that need to be addressed for thorium to become a mainstream energy source.

Conclusion: The Future of Thorium

Thorium presents an intriguing alternative to uranium-based nuclear power. With its abundance, safety advantages, and potential for reduced nuclear waste, thorium could play a crucial role in the future of global energy production. However, the economic challenges related to its extraction, fuel fabrication, and reactor design must be overcome before thorium can be deployed at scale. Ongoing research, particularly in molten-salt reactors and high-temperature designs, will be key to unlocking thorium’s potential. With countries like India, China, and the USA leading the charge, thorium could eventually become a cornerstone of the nuclear energy landscape, contributing to a more sustainable and secure energy future.

Source:

Humphrey, Uguru Edwin; Khandaker, Mayeen Uddin . (2018). Viability of thorium-based nuclear fuel cycle for the next generation nuclear reactor: Issues and prospects. Renewable and Sustainable Energy Reviews, 97(), 259–275. doi:10.1016/j.rser.2018.08.019

Thorium – World Nuclear Association. (2024, May). World Nuclear Association. https://world-nuclear.org/information-library/current-and-future-generation/thorium

Thorium’s Long-Term Potential in nuclear energy: new IAEA analysis. (2023, March). IAEA. https://www.iaea.org/newscenter/news/thoriums-long-term-potential-in-nuclear-energy-new-iaea-analysis