Much faith is being placed in the ability of nuclear energy to alleviate the environmental and energy supply burdens arising from the consumption of fossil fuels, but now concerns are starting to emerge about the long-term supply of uranium.
Chris Davis, CEO of Perth-based uranium miner Energy Minerals Australia, says that the majority of reactors in use around the world are extremely inefficient at converting energy, and that the continued widespread reliance on them could threaten global reserves of uranium. "If we carry on consuming uranium at this rate we could run out in 100 years," he warns.
There are currently 436 nuclear reactors around the world, consuming a total of 60,000t of uranium oxide, or yellowcake, a year. However, demand is tipped to increase sharply over the next few years in line with the growing popularity of nuclear energy as a cheaper, cleaner alternative to fossil fuel-based energy.
Scores of new reactors are planned throughout Europe, Asia, the UAE, Russia and the US in the next five to ten years. Most will be modelled on the current generation of thermal-spectrum, or water-cooled reactors, which today produce most of the world's nuclear energy, with some 99.3% of the uranium fed into them rendered inert and useless.
"The [uranium] industry is having to face up to the gross inefficiency of older reactors," says Mike Angwin, head of the Australian Uranium Association.
Fast neutron (FNR) and fast breeder reactors (FBR)
Since the 1950s, scientists have been developing so-called fast neutron reactors (FNRs) that convert non-fissionable uranium in the fuel into fissionable plutonium. Neutrons shoot about at a much faster rate, which leads to the burning and conversion into energy of what would normally have become waste.
A small number of FNRs are in operation around the world, some in the commercial production of electricity, but it is the next phase of this technology that is expected to utterly transform the nuclear sector over the next few decades.
Fast breeder reactors (FBRs) are essentially a more powerful version of FNRs in that they produce more plutonium than they consume. The fast reactor has no moderator and relies solely on fast neutrons to cause fission, which for uranium is less efficient than using slow neutrons. A fast reactor therefore usually uses plutonium as its basic fuel, since it fissions sufficiently with fast neutrons to operate.
At the same time the number of neutrons produced per fission is 25% greater than from uranium, and this means that there are enough (after losses) not only to maintain the chain reaction but also continually to convert U-238 into more Pu-239. In traditional thermal spectrum reactors, it is the U-235 isotope which is used to produce energy; however uranium oxide contains just 0.7% of it, the remainder being U-238.
Furthermore, the fast neutrons are more efficient than slow ones in doing this breeding. These are the main reasons for avoiding the use of a moderator. The coolant is a liquid metal (normally sodium) to avoid any neutron moderation and provide a very efficient heat transfer medium. So, the fast reactor "burns" and "breeds" fissile plutonium.
Fast breeder potential
Experts say that fast breeder reactors have the potential to convert uranium into energy 60 times more efficiently than thermal spectrum reactors and could extend global uranium supplies by several centuries. They also produce a fraction of the radioactive waste and are able to run on waste from other sources, such as long-lived actinides recovered from used fuel out of ordinary reactors, as well as military plutonium.
"In 40 or so years we will reach the point where we will have negligible volumes of radioactive waste," says Dr Eric Lilford, a partner and energy expert with Deloitte in Australia.
The issue of waste is expected to become a major driver for the uptake of fast breeder reactors as governments face mounting community and political opposition to large scale waste dumps. President Barack Obama's recent decision to cancel plans for the storage of nuclear waste at Yucca Mountain in Nevada, US, indicated that the world's biggest user of nuclear energy now accepts that it needs to find an alternative.
In addition to reactors that effectively eat their own and other plants' radioactive waste, new technologies aimed at improving the process of uranium enrichment could help to alleviate some of these concerns. Among the ideas showing promise are gas centrifuge and laser.
Future fast breeders
Investment in fast breeder reactors rose sharply five years ago when the price of uranium shot to record highs after several years in the doldrums, and many countries now have advanced programmes to bring them online.
Many in the industry are watching with interest the Chinese experimental fast reactor (CEFR) project, which is being coordinated by the Russian-Chinese Nuclear Cooperation Commission. China and Russia are also working together to build two fast-spectrum reactors in China based on the design of the BN-800 fast breeder reactor being built at Beloyarsk in Russia and due to start up in 2012. The project is expected to lead to bilateral cooperation between China and Russia on fuel cycles for fast reactors.
India is hoping that fast breeder technology will underpin its accelerating nuclear energy programme, with the Department of Atomic Energy (DAE) expected to go live with a large-scale prototype reactor this year. India has indicated that it wants to build several hundred fast breeder reactors to meet its growing energy demands.
France wants to convert more than half of its nuclear reactors to fast breeder technology over the coming decades, but has faced a number of setbacks. The Superphénix predecessor, Phénix, at Marcoule, is the only commercial-scale fast breeder reactor to have been in operation. It was, however, shut down in 2009 following sodium leaks and fires and a series of potentially serious reactivity incidents.
Japan's Monju fast breeder reactor experienced similar problems and has been lying dormant since being closed due to public pressure in the mid 1990s.
There are some who say that the environmental problems with fast breeder reactors have been overstated, and that they are in fact safer than many other types of reactor. This is largely due to their highly robust design, needed to encase vastly more fissile activity, not to mention hellish temperatures, sometimes as high as 500°C.
As a result, fast breeder reactors are, on paper, significantly more expensive to build than thermal reactors, and early-stage teething problems have created cost blowouts, sometimes forcing programmes to close.
This new investment in FNR and FBR technology resumes where the industry left off in the 1980s when freefalling uranium prices eroded the business case for their construction. It's fair to say therefore that the future of fast breeder reactors is very much dependent on a higher uranium price. The fact that the spot market price for uranium continues to be lower than the long-term contract price does auger well.
Deloitte's Eric Lilford concludes optimistically: "The coming year will be an exciting one for the development of fast-spectrum nuclear reactors. We expect to reach many important milestones."