Availability of Usable Uranium
Uranium is present at an abundance 2 - 3 parts per million in the Earth's crust which is about 600 times greater than gold
and about the same as tin. The amount of Uranium that is available is mostly a measure of the price that we're willing to pay for it. At present the cost of Natural Uranium ($165 per kg) is a small component in the price of electricity generated by Nuclear Power. At a price of $US110 per kg the known reserves amount to about 85 years supply at the current level of consumption with an expected further 500 years supply in additional or speculative reserves. The price of Uranium would have to increase by over a factor of 3 before it would have an impact of the cost of electricity generated from Nuclear Power. Such a price rise would stimulate a substantial increase in exploration activities with a consequent increase in the size of the resource (as has been the case with every other mineral of value). The price of Uranium rose to a peak of over 300/kg in 2007 but has since declined to around $100 by mid 2010. Identified reserves of Uranium have increased by around 100% since the end of 2003.
However advanced technologies
are being developed which are far more efficient in their use of Uranium or which utilize Thorium
which is 3 times more abundant than Uranium. If perfected these technologies can make use of both the spent fuel from current nuclear reactors and the depleted Uranium stocks used for enrichment. Taken together these provide enough fuel for many thousands of years of energy production. This will mitigate the demand for newly mined Uranium.
Size of the Uranium Resource
Uranium is a dense metal found at an abundance of 2.8 parts per million in the Earth's crust.
It is a highly reactive metal that does not occur in a free state in nature,
commonly occurring as an oxide U3
Prices for Uranium in the world market are quoted in $US per pound of U3
The amount of Uranium commercially recoverable depends upon the market price of the metal.
The market price in mid 2010 is around US$100/kg, after peaking at over $300/kg in 2007. In the early 1990's the spot price of Uranium reached historical lows of less than US$22/kg .
The cost of mining Uranium is a very small factor in the cost of running a nuclear power station and so movements in the price have little effect on the price of the power produced.
The sources of uranium are: mining, commercial inventories (from earlier periods of oversupply), reprocessing of spent full rods from nuclear power plants and down blending (mixing of enriched uranium with natural or
highly enriched uranium from dismantled nuclear weapons. Consumption of uranium at the end of 1999 was 61600 tonnes of Uranium metal (tU) per annum  of which 56% is sourced from uranium mining.
The majority of the balance comes from stockpiles and down blending in former Soviet countries as they reduce or eliminate their stock of nuclear weapons.
The importance of this source and that of commercial inventories is expected to diminish over the next ten years.
Reasonably assured reserves
(or proven reserves) refers to known commercial quantities of Uranium recoverable with current technology and for the specified price. As well there are estimates of additional
reserves in extensions to well explored deposits or in new deposits that are thought to exist based on well defined geological data.
These are necessarily subject to a larger uncertainty, however, the historically low price of uranium over the past ten years has provided a disincentive to exploration.
This is beginning to be rectified as the price recovers.
Further exploration will reduce the uncertainty in the estimates of additional reserves.
There are around 4000 million tU in sea water at a concentration of approximately 3 parts per billion. Extracting this Uranium
is a significant challenge  but substantial progress has been demonstrated by Seko et al.
These researchers recovered approximately 1 kg of Uranium in a 16 square meter cage submerged for 240 days off the coast of Japan. A patent related
to these efforts has been granted. This technology has continued to be developed by Tamada
. He estimates that the cost of his process is currently $220/kg .
As of the beginning of 2003 World Uranium reserves were
- Reasonable Assured Reserves recoverable at less than $US130/kgU (or $US50/lb U3O8)  = 3.10 - 3.28 million tU [2,5].
- Additional reserves recoverable at less than $US130/kgU (or $US50/lb U3O8) = 10.690 million tU .
As of the beginning of 2005 World Uranium reserves were
- Reasonable Assured Reserves recoverable at less than $US130/kgU (or $US50/lb U3O8) = 4.7 million tU .
- Additional recoverable Uranium is estimated to be 35 million tU .
As of the beginning of 2009 identified World Uranium reserves were
- Reasonable Assured Reserves recoverable at less than $US300/kg = 6.3 million tU 
The substantial increase (almost 100%) from 2003 shows the results of the world-wide renewed exploration effort spurred by the increase in Uranium prices which commenced in 2004. This increase in activity has continued through to 2010.
Thus, the provable uranium reserves amount to over 100 years supply at the current level of consumption with current technology, with another 500 years of additional reserves. Around 24% of the proven reserves are in Australia.
With current technology, 235
U is the only fuel for nuclear reactors. Uranium-235 represents 0.72% of natural uranium. Future technological developments could allow other elements to fuel nuclear reactors.
Thorium-232 is a possible nuclear fuel and has a similar abundance to uranium, though there are as yet no commercial reactors operating
or planned that would utilize thorium. Fast breeder reactors could utilize both 235
U (Uranium-235) and 239
Pu (Plutonium-239) as a fuel.
Plutonium-239 is created when 238
U (99.27% of naturally occurring uranium) is bombarded with neutrons.
Plutonium-239 is a by product of nuclear power generation with the current mix of 235
U and 238
It is currently a waste product of concern due to its extreme toxicity and link to nuclear weapons.
If reactors could be made to utilize 239
Pu the potential of known reserves of uranium would be greatly extended since 238
U could then be turned into a fuel.
The Super Phoenix fast breeder reactor in France has demonstrated the technology.
Currently electricity from such a plant would cost around three times the amount per kilowatt as that from conventional nuclear power plants. Fast breeder reactors have a higher risk profile due to the need to handle large quantities of Plutonium,
and so present a different balance between utility and risk than the other types of reactors.
 The Market for Uranium: An overview of supply, demand and prices 2004--2025,
International Nuclear Inc., in Western Mining Corporations Ltd Target Statement (for the takeover by BHP),
 Survey of Energy and Resources 2001, World Energy Council (WEC)
 See van Leeuwen and Smith
and references within.
 Though the cost of extraction could be more than twice the current spot price of Uranium, the spot price is a function of the current, and speculated future, supply and demand situation and is virtually independent of the price of electricity finally produced from nuclear power.
 Supply of Uranium, World Nuclear Association, July 2005
 Global Uranium Resources, IAEA, June 2006
: Masao Tamada, Current status of technology for collection of uranium from seawater. Erice Seminar 2009