163it’s been estimated that the low-grade uranium resource is more than 1000 times greater than the 22 million tons we just
assumed. Deffeyes and MacGregor (1980) estimate that the resource of uranium in concentrations of 30 ppm or more
is 3×1010 tons. (The average ore grade processed in South Africa in 1985 and 1990 was 150 ppm. Phosphates typically
average 100 ppm.)
Here’s what the World Nuclear Association said on the topic of uranium reserves in June 2008:
“From time to time concerns are raised that the known resources might be insufficient when judged as a multiple of
present rate of use. But this is the Limits to Growth fallacy, ... which takes no account of the very limited nature of
the knowledge we have at any time of what is actually in the Earth’s crust. Our knowledge of geology is such that we
can be confident that identified resources of metal minerals are a small fraction of what is there.
“Measured resources of uranium, the amount known to be economically recoverable from orebodies, are ... dependent
on the intensity of past exploration effort, and are basically a statement about what is known rather than what is there
in the Earth’s crust.
“The world’s present measured resources of uranium (5.5 Mt) ... are enough to last for over 80 years. This represents a
higher level of assured resources than is normal for most minerals. Further exploration and higher prices will certainly,
on the basis of present geological knowledge, yield further resources as present ones are used up.”
“Economically rational players will only invest in finding these new reserves when they are most confident of gaining
a return from them, which usually requires positive price messages caused by undersupply trends. If the economic
system is working correctly and maximizing capital efficiency, there should never be more than a few decades of any
resource commodity in reserves at any point in time.”
[Exploration has a cost; exploring for uranium, for example, has had a cost of $1–$1.50 per kg of uranium ($3.4/MJ),
which is 2% of the spot price of $78/kgU; in contrast, the finding costs of crude oil have averaged around $6/barrel
($1050/MJ) (12% of the spot price) over at least the past three decades.]
“Unlike the metals which have been in demand for centuries, society has barely begun to utilize uranium. There has
been only one cycle of exploration-discovery-production, driven in large part by late 1970s price peaks.
“It is premature to speak about long-term uranium scarcity when the entire nuclear industry is so young that only one
cycle of resource replenishment has been required.” www.world-nuclear.org/info/inf75.html
Further reading: Herring (2004); Price and Blaise (2002); Cohen (1983).
The IPCC, citing the OECD, project that at the 2004 utilization levels, the uranium in conventional resources and
phosphates would last 670 years in once-through reactors, 20 000 years in fast reactors with plutonium recycling, and
160 000 years in fast reactors recycling uranium and all actinides (Sims et al., 2007).

165Japanese researchers have found a technique for extracting uranium from seawater. The price estimate of $100 per kg
is from Seko et al. (2003) and [y3wnzr]; the estimate of $300 per kg is from OECD Nuclear Energy Agency (2006, p130).
The uranium extraction technique involves dunking tissue in the ocean for a couple of months; the tissue is made of
polymer fibres that are rendered sticky by irradiating them before they are dunked; the sticky fibres collect uranium
to the tune of 2 g of uranium per kilogram of fibre.

–The expense of uranium extraction could be reduced by combining it with another use of seawater – for example,
power-station cooling. The idea of a nuclear-powered island producing hydrogen was floated by C. Marchetti. Breeder
reactors would be cooled by seawater and would extract uranium from the cooling water at a rate of 600 t uranium per
500 000 Mt of seawater.

166Thorium reactors deliver 3.6×109 kWh of heat per ton of thorium. Source: www.world-nuclear.org/info/inf62.html.
There remains scope for advancement in thorium reactors, so this figure could be bumped up in the future.

–An alternative nuclear reactor for thorium, the “energy amplifier”... See Rubbia et al. (1995), web.ift.uib.no/
~lillestol/Energy Web/EA.html, [32t5zt], [2qr3yr], [ynk54y].

–World thorium resources in monazite. source: US Geological Survey, Mineral Commodity Summaries, January 1999.
[yl7tkm] Quoted in UIC Nuclear Issues Briefing Paper #67 November 2004.
“Other ore minerals with higher thorium contents, such as thorite, would be more likely sources if demand significantly
increased.”