Nuclear energy is a controversial subject for many people. Although traditional nuclear energy, derived from uranium or plutonium, has been hailed as a reliable, low-carbon energy source, it has also raised significant objections from environmentalists, the public, and policymakers alike. Many of these objections have related to nuclear energy’s overall safety, its high costs, limited resource availability, and considerable issues with its long-term waste management and environmental impacts.
This is why the nuclear industry is interested in alternative fuels for future nuclear reactors, and one candidate may be thorium, which has been gaining scientific interest for some time.
Thorium is a naturally occurring, silvery, and slightly radioactive metal that was named after Thor, the god of thunder in Norse mythology. The metal is significantly (three to four times) more abundant than uranium is in the Earth’s crust, but to date, it has had very little use as a power source. There are a few reasons for this, though the most important is that thorium is not fissile, which means it cannot sustain a nuclear chain reaction like isotopes of uranium (particularly uranium-235).
However, there are ways to use thorium to create fissile materials suitable for fuel. Thorium-232 is the only naturally occurring thorium isotope, but it is fissionable rather than fissile. This means it needs high-energy neutrons to undergo fission – a process where an atomic nucleus is split into smaller nuclei, releasing large amounts of energy. However, irradiating thorium-232 so that it absorbs a single neutron allows it to transmute into uranium-233, a fissile material that can be used to fuel nuclear reactors.
This is known as the breeding process, and usually takes place in special reactors known as breeding reactors, which are designed to create more fissile material than they use.
This is one of the reasons why nuclear researchers are interested in it. Because of its natural abundance across the world, it could become a potential replacement for uranium and be used to create energy over the long term. At the same time, uranium-233, the primary fission material produced from thorium, is harder to use for weapons purposes than uranium-235 or plutonium-239. This means there is less of a risk its wider use will pose a proliferation risk.
The thorium fuel cycle also produces less long-lived radioactive waste compared to the uranium and plutonium cycle, which potentially makes it much more environmentally friendly too.
“Because of its abundance and its fissile material breeding capability, thorium could potentially offer a long-term solution to humanity’s energy needs,” Kailash Agarwal, a Nuclear Fuel Cycle Facilities Specialist at the International Atomic Energy Agency (IAEA) said in a 2023 statement regarding an IAEA report on thorium.
“Many countries consider thorium as both a viable and very attractive option for generating power and meeting their growing energy needs.”
However, there are challenges here as well. The most obvious issue relates to the breeding process. Thorium requires a neutron source to create uranium-233, necessitating the use of an initial fissile material to start the process (e.g. uranium-235 or plutonium). It is also expensive to extract, despite its abundance in the Earth. Due to uranium’s current predominance, there is not much demand for thorium extraction on its own. Instead, it tends to be a by-product, and requires extraction methods that are currently more expensive than those used for uranium.
This, however, could change if the demand for thorium changed in the future.
At the same time, the nuclear industry is not currently set up to deal with thorium as a fuel. In order to accommodate it, existing uranium-focused reactors would either need to be retrofitted (which is also expensive) or new facilities would need to be developed. At present, commercial thorium reactors require advanced technologies, like molten salt reactors, which are not widely used. Further research, development, and testing of thorium-powered installations is needed before thorium is likely to push uranium from its position in the industry.
Despite these challenges, the global demand for energy continues to rise alongside the need to achieve global climate objectives. We desperately need alternative sustainable sources of reliable energy, so thorium may yet get its chance to perform in the future.
Source Link: Could Thorium Offer Long-Term Potential As A Nuclear Energy Source?
