This project concluded on 30 June 2008.
Thorium is an alternative to conventional nuclear fuels, such as uranium and plutonium and offers the following advantages:
- almost all natural thorium is usable in a reactor compared with 0.7 per cent of natural uranium
- the residue material from thorium-fuelled reactors is difficult to reprocess into weapons-grade material
- unlike uranium, thorium requires a source of neutrons to start and maintain a nuclear fission reaction, which is the process of splitting atoms to release large amounts of energy.
While there is considerable development work required before the thorium fuel cycle can be commercialised, there is renewed interest in thorium fuel because less radioactive residue is produced and there is potential to re-use some of the radioactive by-products generated by conventional uranium-fuelled nuclear reactors. Currently, thorium fuels are used to varying degrees in some research reactors in India and Russia. Research is continuing in Russia, China, Norway, France and other countries on the use of thorium fuel in some current uranium fuelled nuclear reactors and regulatory approval for the use of thorium fuels may be gained within 10 years. Meanwhile, India is in process of developing a thorium fuelled Advanced Heavy Water Reactor.
Exploration for thorium to date has been minimal and, prior to this project, there were no comprehensive records of resources, mainly because of a lack of large-scale commercial demand. Most of the known thorium resources in Australia are in the monazite component of heavy mineral sand deposits, which are mined for ilmenite, rutile, leucoxene and zircon. This project has undertaken a review of Australia's thorium resources and the geochemical processes controlling the distribution of the element in the Earth's crust. As part of this review Geoscience Australia has upgraded Australia's thorium resource database and provided a summarised report on thorium resources in Australia's Identified Mineral Resources 2009. The report on Australia's thorium resources, together with a summary of the latest developments in thorium fuelled nuclear reactors, is updated annually in Australia's Identified Mineral Resources on-line publication.
- An improved understanding of the status and distribution of Australia's thorium resources for use in the determination of government policy and industry investment decisions
- A better understanding of the geochemistry of the thorium cycle in the Earth's crust.
A general understanding of the crustal distribution of thorium in Australia was gained from Geoscience Australia's OZCHEM dataset which has information on 56 000 rock, regolith and drill hole samples which have been analysed for thorium. Figure 1 shows the distribution of the 56 000 sample sites and where samples returned an analytical result of 50ppm or greater thorium content.
The display of thorium distribution in Figure 1 is limited to those geological provinces in which Geoscience Australia has carried out surveys in the past. Most of the geological provinces which were not sampled and analysed for thorium are sedimentary basins with limited geochemical sampling. The existing data was supplemented with data from Geoscience Australia's Baseline Geochemical Survey to obtain geochemical analyses for more than 60 elements, including thorium, at an average density of one site for around 5000 square kilometres throughout Australia.
- An enhanced understanding of the status and distribution of Australia's thorium resources for use in determining government policy and industry investment decisions and their potential as an alternative nuclear fuel source.
- Upgraded the thorium resource database and provided a summarised report on thorium resources in the publications, A Review of the Geochemical Processes Controlling the Distribution of Thorium in the Earth's Crust and Australia's Thorium Resources and Resources and geology of Australia's thorium deposits