Thorium: Fueling the Future of Canada?

There is no denying the benefit nuclear power has had on reducing greenhouse gas emissions in Canada, especially Ontario where 60% of electricity is generated by nuclear. Canada has a long history of nuclear development, and continues to be a world leader in the nuclear industry. However, there is much debate on the role nuclear power would play in the long-term energy supply, after several of the biggest nuclear reactors in Canada would be decommissioned.

Advocates for nuclear energy argue that nuclear is the superior choice for baseload energy, due to its high capacity factor, high energy density per land use, low emissions, and high reliability. Meanwhile, critics of nuclear energy argue the need for investment in renewable sources instead, the risk of a nuclear accident, the high capital costs and time investment require for the deployment of new builds, availability of uranium supply in the long-term, and concerns on how waste management of radioactive spent fuel would be conducted.

So how can we take the advantages of nuclear power, while also addressing concerns? With increasing pressure on government, industry, and society as a whole to reduce carbon dioxide emissions and other pollution over the next few decades, emerging technologies must be considered in addition to energy systems already established. There are many developments being made, including Generation-IV reactors and fusion technology, as well as the development of small modular reactors. The use of thorium as fuel is also an option being considered, one with promise. Thorium-fueled reactors are still in the research and development stages, and will likely not be implemented until 2050, however, there is already an industry for thorium power development in Canada. Thorium is seen as a safer fuel due to the reduced risk of weapons proliferation with thorium, compared to uranium, as well as being potentially cheaper.

The exact amount of available thorium in the world is unclear, but it is generally assumed that thorium is approximately three times more abundant in nature than uranium is, especially in Canada, India, Turkey, Brazil, Australia, and the United States. With a greater abundance of thorium, comes lower costs. To further lower costs, is the advantage that thorium is easier to higher concentrations compared to uranium, making the mining of thorium much less easier.

In nature, thorium-232 has a half-life of 14.05 billion years. While uranium is a fissile element, thorium is a fertile element. A fissile material is capable of sustaining a fission chain reaction in a nuclear reactor. Because thorium is not fissile itself, neutrons must be provided by a fissile material. Fissile isotopes can be produced using the thorium, through neutron absorption, as shown in the equation below. After neutron capture, the thorium-232 becomes thorium-233, and undergoes beta decay as it becomes protactinium-232. The protactinoium-232 then undergoes beta decay to become uranium-233. The fission of the uranium-233 then is able to produce neutrons to repeat the cycle, as shown in the following diagram.

Liquid Fluorine Thorium Reactor is the prominent design option you might hear about advances in thorium power. However, because of Canada’s vast expertise in heavy water reactors, the its Advanced Fuel CANDU Reactor (AFCR) might be the most viable option for the implementation of thorium power into Canada’s integrated energy system, especially in Ontario where most electricity is generated from nuclear power.

SNC-Lavalin is currently working on incorporating the use of thorium fuel into CANDU reactors. The Advanced Fuel CANDU Reactor is a joint project with the China National Nuclear Corporation, to develop a reactor that can burn thorium, as well as recycled uranium.

In the AFCR, uranium 233 is produced through decay of thorium-233 and protactinium-233 would be trigged by neutron capture in thorium-232. It is important to note that the concentration of fissile uranium-233 is five times more than the concentration of plutonium-239 from spent uranium fuel. Another advantage is that ThO2 has a higher thermal conductivity than UO₂, with a melting temperature 340 degrees Celsius higher than UO2. Hence, lower fuel operating temperatures would be required, and processes such as diffusion of fission gas release from the fuel would be lower.

Features of the CANDU reactor that make it a suitable choice for the incorporation of thorium fuel include an excellent neutron economy, on-power refueling, and a simple fuel channel design. As with uranium, thorium would be out through a once-through cycle in the CANDU reactor, where unburned uranium-233 would be stored as spent fuel, potentially as recoverable fuel in the future.

Research is being done at Chalk River Laboratories on fuel-cycle studies, reactor physics measurements, fabrication and irradiation of thorium fuels, and waste management. There are many variations of a potential thorium-fueled reactor under consideration, thought the most optimal design would be one in which no uranium would be needed as a fissile topping material.

However, there are some rudimentary technological challenges that must be overcome, including the relatively long half-life of thorium, the loss of amount of available neutrons through leakage, and the fact that it takes a long time for breeding in a thermal neutron spectrum to occur.

Startups are also getting in on thorium-fueled technology, as Thorium Power Canada is a Toronto based startup company working to build and operate a scalable thorium reactor. Currently, it is seeking advisors to finance a 10 MW demonstration in Chile, with DBI Chile, as well as approval from the Chilean governmental to build the demonstration reactor. It would also be used to power a 2000 litre per day desalination plant.  The DBI reactor is Thorium Power Canada’s major focus.

This reactor has been under development for four decades, and is designed to breed uranium 233 from thorium, to burn the fuel that is bred, and to store unburned fuel. Through the use of thorium, it is estimated that the cost of electricity generated would be $0.04-0.07 per kilowatt-hour while reducing radioactive waste by more than 90%. The proposed design for the reactor that Thorium Power Canada is developing would be smaller and more modular, and would take 18-24 months to build, as opposed to at least 5 years for conventional reactors. In addition to the demonstration reactor in Chile, Thorium Power Canada is preparing a proposal for a 25 MW reactor in Indonesia, which will provide power to Indonesia’s electrical grid.

While there are many technological challenges to overcome with thorium-fueled reactors overall, there is a great deal of potential for thorium to provide cost-effective, clean energy for Canada. While Canada’s energy future will likely be mainly renewable energy sources, such as solar, wind, and hydroelectric, the integration of thorium-fueled reactors could also be a long-term possibility, especially with the decommission of Darlington Generation Station expected in 2050. With the technology still early in its research and development stages though, anything could happen. What do you think will be Canada’s energy future: thorium, fusion, the Generation IV SuperCritical Water-cooled Reactor, any of the other big developments in nuclear, or a much greater focus on renewables instead? Let me know in the comments below!