23 Jun (NucNet): Thorium technologies require “significant further investigation”, but options for thorium’s introduction into the nuclear fuel cycle should be kept open because its use could improve the medium-term flexibility of nuclear energy and its long-term sustainability, a report says.
The report, by the OECD’s Nuclear Energy Agency, says options that need to be looked at for using thorium include:
- Using thorium as a means of burning plutonium, and possibly other higher actinides, as an option for plutonium management;
- The possibility of reaching higher conversion factors in thermal or epithermal neutron spectra, using thorium-based fuels, in evolutionary Generation III+ systems, with the aim of recycling the fissile material from used fuels;
- Examining the promising physicochemical characteristics of thorium dioxide, which would offer improved performance of thoria-based fuels over current fuel designs.
The report says the development of new fuels or new reactor concepts is a time- and resource-consuming process “likely to span several decades”.
Any industrial application of thorium as a nuclear fuel would continue to require the input of fissile material from the existing uranium/plutonium cycle until the required amounts of uranium-233 could be produced to ultimately make the thorium cycle self-sustaining, the report says.
Thorium fuel R&D initiatives are being funded by some countries concerned with long-term nuclear energy sustainability, the report says. “However, given their cost and the lack of clear economic incentives for nuclear power plant operators to pursue this route, industrial development activities for thorium remain somewhat limited at present.”
The report says that since the beginning of the nuclear era, significant scientific attention has been given to thorium’s potential as a nuclear fuel. Although investigations have been carried out on thorium-based fuels, and thorium-fuelled power reactors have operated in the past, the thorium fuel cycle as a whole has never been fully developed.
Thorium, a naturally occurring slightly radioactive metal, is more abundant than uranium, and research is being carried out into its potential use in nuclear reactors in a number of countries, notably China, India, Russia, Norway, Canada, the US and Israel.
The thorium fuel cycle has several potential advantages over a uranium fuel cycle, including thorium's greater abundance, superior physical and nuclear properties, better resistance to nuclear weapons proliferation and reduced plutonium and actinide production.
Thorium-based fuels and fuel cycles have been used in the past, but have yet to be commercialised.
According to the International Atomic Energy Agency, existing estimates of thorium resources total more than 4.5 million tonnes (reserves and additional resources). US mining company US Rare Earths has said deposits of highly concentrated thorium in the US would be large enough to supply the power needs of the entire country for centuries using thorium-fuelled nuclear reactors.
The NEA report is online: http://bit.ly/1QoGhGT
