In discussions and presentations on rare earths and their extraction and processing, junior mining and exploration companies are frequently asked to discuss how they plan to handle and “dispose” of any thorium present in the deposit [especially if the deposit contains monazite]. The presence of thorium in such deposits is usually perceived to be at best a nuisance and at worse, a potentially costly regulatory problem, because of its slightly radioactive nature.
And yet, it wasn’t always the case that thorium was perceived to be a problem. Many of the rare earth deposits known today, were discovered by geologists and others looking for either uranium or thorium-bearing minerals. Former thorium-producing mines are now being re-examined and re-vamped as rare earth mines.
Thorium was at one time the subject of significant research as part of the development of nuclear fuel cycles. It ultimately lost out to uranium as the metal of choice for such processes, primarily because the uranium fuel cycle was particularly suited to the production of materials for use in weapons manufacture. Thus the decline in interest was a result of political, not technical reasons.
In recent years, however, there has been a resurgence of interest in the use of thorium for a modernized version of the nuclear fuel cycle. According to the Thorium Energy Amplifier Association  [ThorEA], there are a number of reasons for this:
- Thorium is over three times more plentiful than uranium and the process of extracting it from minerals is relatively straightforward;
- Thorium has a higher energy density than uranium. According to ThorEA, there is enough energy in 5,000 tonnes of thorium to provide total global energy needs for one year;
- Fuel cycles that use thorium are inherently proliferation-resistant [ironically the very reason why thorium fell out of favor with the industrial-military complex decades ago], with negligible plutonium production;
- Such fuel cycles have better nuclear characteristics, better radiation stability and longer fuel cycles than uranium fuels;
- It is possible to use thorium fuel cycles to effectively destroy legacy plutonium and other nuclear waste products.
A number of systems have been proposed in order to develop a thorium fuel cycle. A couple of weeks ago, ThorEA published a report on one such concept  – the Accelerator Driven Subcritical Reactor of ADSR. Without getting bogged down in the details, an ADSR system couples a nuclear reactor core with a high energy proton accelerator. While not a new concept, the ThorEA report revisits the concept and analyzes the feasibility of such a system as a means of generating electricity.
If, realistically, nuclear power generation has to remain a central plank of any future energy development program to either reduce carbon dioxide emissions or the burning of fossil fuels, it seems to me that the advantages of a thorium-based fuel cycle significantly outweigh those associated with uranium-based systems. While certainly a long term project, developing such cycles would also simultaneously provide a destination and future customers for the thorium currently discarded as a waste product of the rare earth extraction process. Surely a win-win for all concerned?
You can download a copy of the ThorEA report from here  – well worth a look.