More energy and water will be needed to extract and process high-grade uranium in the future, according to a new study. So what will this mean for those advocating nuclear power as a green technology?
News analysis Environmental costs of nuclear power are likely to increase as high-grade uranium becomes harder to find, according to new research that has been challenged by the uranium industry.
The findings form part of the debate over what part nuclear power will play in supplying future energy needs.
Australian researchers writing in the journal Environmental Science and Technology say that the average grade of the uranium extracted from mines around the world has gradually declined over the past 50 years.
That trend is likely to continue, says lead author Dr Gavin Mudd from Melbourne's Monash University.
This means mining companies will have to use more energy and more water to extract the ore and process it for use in power stations.
"Ore grade is one of the most sensitive predictors of carbon and water cost," Mudd says. "It's pretty clear that in the long term, the ore grade will decline."
Mudd and his co-author Dr Mark Diesendorf from the University of New South Wales in Sydney gathered data from government publications, company reports and other sources from the US, Canada, Australia and elsewhere. The earliest documents date from the late 1940s.
They then charted the average ore grade over time, and the amount of energy and water needed to produce a set amount of uranium oxide.
Energy debate
Advocates for nuclear power argue that as more plants come online to replace gas or oil-fired power stations, the fewer greenhouse gas emissions.
As such, they argue, nuclear power is an important weapon in the fight against climate change.
In 2007, for example, an Australian government inquiry recommended that 25 nuclear power plants could be built around the nation by 2050.
The then-Prime Minister John Howard committed A$12.5 million to assist research to develop advanced reactor designs for deployment by about 2025.
But Mudd and Diesendorf say the debate has been characterised by a lack of real facts and figures on the total environmental impact of nuclear power, a problem their paper begins to address.
"There is such poor data on this," Mudd says. "In sustainability terms, we believe we are mining a finite resource but there's no real data around on it."
Where high-grade uranium ore is used, it has been argued that carbon emissions from the nuclear fuel cycle are much less than those of an equivalent gas- or coal-fired power station.
But the question is how long that will continue to be the case.
"The rate at which ore grade declines depends on exploration, technology and the rate at which production increases," Mudd says.
A nuclear future?
The Australian Uranium Association disagrees and a spokesperson for the industry group questions the researchers' assumptions.
"The assumption appears to be that we are currently mining all the known resources of uranium, beginning with the most easily recoverable ore and working through to the ore that is more difficult," the spokesperson says.
"Even if this were the case, the International Energy Agency has estimated that known world reserves of uranium ore of good enough quality to deliver net energy benefits are sufficient to fuel nuclear-generated electricity production for 85 years.
"[This is] even with no improvement in current reactor technology nor the introduction of new technology."
The industry in Australia has only recently begun putting a large effort into exploration, the spokesperson says.
Its spending on exploration rose from A$10.5 million in 2003-2004, to A$50m in the first quarter of 2007-08, he says.
"It is reasonable to expect that as the exploration effort increases, the volume of known recoverable ore will increase."
Compared with coal?
Dr Ron Cameron, chief of operations at the government-funded Australian Nuclear Science and Technology Organisation, says that carbon emissions for nuclear power are many times less than for coal over the full process, from mining the fuel, processing it and generating electricity from it.
"So it would need very big changes [in the total environmental impact of nuclear energy] to alter this picture."
He also says that the future growth in nuclear power will involve reprocessing fuel that has already been used in power stations.
"This recovers 95% of the uranium and means that the push for new sources is less important and extends the 'limited' reserves by many thousands of years."