Rare earth by-product thorium has the potential to trigger a nuclear renaissance as the mineral offers the opportunity to manage concerns surrounding waste management and proliferation in the provision of nuclear energy, North West University (NWU) Postgraduate School of Nuclear Science and Engineering director Professor Eben Mulder tells Mining Weekly.
He explains that the world and South Africa are starting to focus on the potential of thorium, which holds a number of advantages over uranium. “Fuel from thorium burns longer than uranium in a reactor, producing more energy in a unit mass,” he says.
Therefore, thorium was recognised as the primary alternative to uranium at the dawn of the nuclear energy age. “Despite the advan- tages of thorium, earlier generations preferred the use of uranium, as it allowed the pioneering nuclear nations to produce weapons-grade material,” adds Mulder.
Thorium provides solutions to industries’ most significant concerns regarding nuclear energy and sustainability criteria, which include economics, safety, emissions, waste management, proliferation risk, sustainability of fuel supply and the ability to provide reliable baseload power.
However, he explains that it is only in exceptional circumstances that an energy solution meets all seven of these sustainability criteria. In a world of trade-offs, a sound commercialisation strategy must also have two additional attributes – prioritising the sustainability criteria to enable improved investment decisions and defining an array of energy solutions.
Further, the nuclear energy industry has high expectations that the adoption of Generation IV (Gen-4) reactors and advanced fuel cycles will conclusively manage the safety, waste management and proliferation risk problems.
Uranium fuel predominantly comprises two forms of uranium, U-235 and U-238. During a nuclear reaction, the U-235 produces energy while the U-238 is converted into plutonium. However, only 67% of fissionable materials is used and plutonium is contained in the reactor as waste, which raises proliferation risks.
In contrast, in a thorium-232 fuel cycle, the thorium is converted into U-233 in the reactor. The reactor then uses the U-233 and up to 99% of any plutonium formed in the reactor during fission. The reactor waste, predominantly comprised of radioactive chemicals called actinides, is also benign owing to their smaller quantities. This not only makes the reactor proliferation resistant, but it also makes it a useful technology for processing the nuclear waste produced by conventional nuclear reactors, Mulder says.
Further, thorium reactors reinforce the traditional cost advantages of conventional nuclear energy. Although smaller than conventional nuclear reactors and providing fewer economies of scale, it compensates through a far shorter development phase, lower capital requirements owing to its modularity, and significantly lower life-cycle costs. The modularity of the reactor also makes it possible to locate it near load centres, making it possible to deploy it as a distributed generation solution. And, unlike fossil-fuelled energy solutions, the thorium reactors do not emit carbon dioxide, making it a viable environmental choice.
Meanwhile, the world’s second-largest economy, China, has committed itself to establishing a new nuclear energy programme, using thorium as a fuel, within 20 years. The liquid fluoride thorium reactor is a Gen-4 reactor that uses liquid salt as both fuel and coolant. Mulder comments that this is the only large-scale industrial programme to build thorium reactors and that the West, particularly the US, is ignoring the potential of what could become a transformational technology with the capability to affect important economic, political and social issues.
Mining companies are discovering more rare earth deposits around the world and threatening China’s dominance over this sector. Mulder says that even South Africa has good reserves of throium and that there is a relative abundance of thorium in the world, up to four times more than uranium, and the space for opportunity is growing.
He adds that there is great market opportunity for the resource owners of thorium, as nuclear reactors and high-temperature gas-cooled reactors with accompanying fuel design already exist. “In South Africa, the opportunity is affored for private industry to create a public–private partnership to beneficiate this mineral to its fullest. It is time for South African leadership to step up to the challenge and make this happen. Today, leadership of this calibre is noted in France, South Korea, China and the United Arab Emirates,” he says.
Mulder says that, although there is a significant need for rare earth minerals, it is believed that mining opportunities are scant as rare earths are difficult to extract and there are a number of regulatory hurdles, such as those related to processing and environmental management, in the Western mining world.
Mulder differs: “The cost of mining thorium and converting it to fuel is much cheaper than the mining and processing of uranium, in terms of less capital equipment requirements at start-up, as well as lower operating costs. Also, thorium is relatively abundant in most parts of the world, so, relative to uranium oxide mining and processing, the cost of potential energy for each unit of thorium is 25% to 33% lower,” he adds.
The approximate cost of a single standalone Gen-3 light water reactor (LWR) for each megawatt of installed capacity is in the region of $5 400/kW. It is estimated that the first standalone Gen-4 thorium modular reactor will cost about $5 000/kW of installed capacity. As additional modules of the thorium modular reactors (TMRs) are built and standardisation allows the builders and the subsystem equipment suppliers to become more efficient, it is estimated that the cost will be reduced to $4 500/MW, or nearly 20% less.
Mulder argues that TMRs have an advan- tage over LWRs, as the latter is characterised by infrequency of construction. Further, owing to the simplicity of the design of the thorium modular reactor, which scales up arithmetically rather than geometrically, larger modules of the TMR, ranging between 40 MW, 80 MW and 165 MW, can be built at similar cost for each unit of power delivered to the grid, without significant additional research and development (R&D).
“The economics of the TMR are compelling. They are less expensive to build, commission, operate and decommission than a comparable LWR. An important part of the savings is that TMRs have a short construction period of about two years, compared to LWRs, which take 6 to 10 years to build,” Mulder comments.
The estimated available thorium reserves within the earth’s crust are three or four times the world’s uranium reserves. Combined with its greater energy efficiency, as a high-temperature reactor, it can be shown that there are at least enough thorium reserves to last about 4 500 years.
Companies such as nuclear energy pioneer Lightbridge, of the US, and Norwegian thorium initiative Thor Energy are creating awareness of and consolidating incentives to build more thorium plants.
However, Mulder feels that there is still much to be done in this regard. He says that, in South Africa, awareness is being created at the Postgraduate School of Nuclear Science and Engineering at the NWU’s Potchefstroom campus. “This is unique in Africa and the only institution in South Africa that awards a Master of Engineering or Master of Science degree in nuclear engineering,” he adds.
At its Mafeking campus, the university has initiated a research programme in the environmental and industrial applications of nuclear methods, as a part of the Centre for Applied Radiation Science and Technology .
The school also has a chair in nuclear sciences and engineering and the R&D focuses on nuclear technology, including high-temperature gas-cooled reactor technology, the thermal hydraulics of nuclear reactors and the coupling effects associated with neutronics and core thermal hydraulics behaviour.
Mulder adds that, to date, the school has deliv- ered 40 master’s level students, while there are currently about 70 students enrolled. Dr Werner Van Antwerpen, a former PhD student at the school, also won the coveted European Nuclear Educational Network award as the best PhD student in 2009.