When it comes to mining method and approach employed for any
particular uranium deposit, the decision is governed by the
nature of the orebody, safety, environmental andeconomic
considerations. Over the last 60 years, developments have changed
uranium mining to include production methods which had
previously been absent from the industry landscape. In 2009, the
breakdown of reported production was as follows: conventional
underground and open pit mining at 57 percent; in situ leach (
) mining at 36 percent and by-product mining at 7 percent.
Investors will note that Olympic Dam was classified as by-product
rather than in underground category for reporting purposes.
the Olympic Dam
ore body controlled by
) as the world's largest resource of low-grade uranium,
accounting for about 66 percent of Australia's reserves plus
resources. Uranium occurs with
in a large hematite-rich granite breccia complex overlain by
flat-lying sedimentary rocks.
Uranium mining methods have been changing. In 1990, 55 percent
of world production came from underground mines, but this shrunk
dramatically to 1999, with 33 percent at the time. Since the year
2000, new Canadian mines have increased the global representation
of underground mines again.
For the 2009 reporting period a total of 18,262 tonnes was
produced by ISL operations, representing 36 percent of world
total production, a share which has risen steadily from 16
percent in 2000. The distribution of this ISL production was
collectively allocated between 13,473 tonnes of uranium from
Kazakhstan, 2429 tonnes of uranium in Uzbekistan, 1217 tonnes of
uranium in USA, 583 tonnes of uranium in Australia and 560 tonnes
of uranium in Russia.
Production costs and shortfall
In an exclusive interview with
, Amir Adnani, Chief Executive Officer of
Uranium Energy Corp.
) discussed the cost advantages of ISL mining projects compared
with conventional and open pit mining techniques. "When you look
at some of the feasibility reports prepared and published by some
of the lower grade deposits that are open pit situations in
Namibia…you are looking at costs from between $40-$50."
Adnani also cited concern for the longer term price incentives
for uranium production, "firms like RBC Capital have come out and
said that the sector needs at least $80 per pound uranium…the
average cost of production for these projects is about $60 per
pound, people are not going to get into this business just to
break even. They need to have return on capital and it's got to
, a sector analyst and chairman of BGF Equities in Sydney
suggests a more conservative figure of "$60 per pound uranium
oxide figure is the minimum required to encourage new mines."
The World Nuclear Association reports production from world
uranium mines currently supplies only about 75 percent of the
requirements of power utilities, and most analysts would agree
that a sustainably higher price for uranium could be required to
help resolve this gap to satisfy reactor needs, initial core
requirements and inventories for new reactors.
Underground and open pit mining
Conventional open cut mining, involving a large pit and the
removal of overburden in addition to considerable waste rock is
most suitable where orebodies have been deposited close to the
surface. Underground mining is usually employed, when the
orebodies are deeper, involving the construction of access shafts
and tunnels but with less waste rock removal and less
environmental impact. In either case, grade control is usually
achieved by measuring radioactivity as a surrogate for uranium
detects associated radioactive minerals which are decay products
of the uranium, rather than the uranium itself.
These conventional mining techniques involve removing
mineralized rock from the ground, breaking up the ore and
treating it to remove the minerals being sought. The associated
mines have a mill where the ore is crushed, ground and then
chemically treated with sulfuric acid called "lixiviant" or
"leachate" added to dissolve the uranium oxides and liberate the
uranium from the crushed rock. Some mills employ carbonate
leaching instead of sulfuric acid, depending on the orebody.
Following this process at the mill of a conventional mine the
uranium is then separated by ion exchange before being dried and
At Ranger in north Australia, Rossing in Namibia, and most of
Canada's Northern Saskatchewan mines through to McClean Lake, the
orebodies have been accessed by open cut mining. Other mines such
as Olympic Dam in Australia, McArthur River, Rabbit Lake and
Cigar Lake in Northern Saskatchewan, and Akouta in Niger are
underground, up to 600 metres deep. At McClean Lake and possibly
Ranger, mining will be completed underground.
In situ leach mining
In situ leaching (
), also known as solution mining or in situ recovery (
) in North America, involves leaving the ore where it is in the
ground, and recovering the minerals from it by dissolving them
and pumping the pregnant solution to the surface where the
minerals can be recovered. Consequently, there is little surface
disturbance and no tailings or waste rock generated. However, the
orebody needs to be permeable to the liquids used, and located so
that they do not contaminate ground water away from the orebody.
The leaching solution dissolves the uranium before being pumped
to the surface treatment plant where the uranium is recovered as
ISL uranium mining was first tried on an experimental basis in
during the early 1960s. The first commercial mine began operating
in 1974. Today most uranium production from
and the United States comes from ISL mining. Several projects are
licensed to operate in Wyoming, Nebraska and Texas with most of
the operational mines dating from the 1990s. They are relatively
small, producing under 1000 tonnes per year, but combined they
provide most of the uranium production within the United
Uranium ISL uses the native groundwater in the orebody which
is fortified with a complexing agent and in most cases an
oxidant. It is then pumped through the underground orebody to
recover the minerals in it by leaching. Once the pregnant
solution is returned to the surface, the uranium is recovered in
much the same way as in any other uranium plant (mill).
In Australian ISL mines (Beverley and the soon to be opened
Honeymoon Mine), the oxidant used is hydrogen peroxide and the
complexing agent sulfuric acid. Kazakh ISL mines generally do not
employ an oxidant but use much higher acid concentrations in the
circulating solutions. ISL mines in the USA use an alkali leach
due to the presence of significant quantities of acid-consuming
minerals such as gypsum and limestone in the host aquifers. Any
more than a few percent carbonate minerals means that alkali
leach must be used in preference to the more efficient acid
Some ore, usually very low-grade, is treated by heap leaching.
Here the broken ore is stacked on an impermeable pad and
irrigated with acid or alkaline solution. The pregnant liquor
from this is treated to recover the uranium, as with ISL.
By product methods
Where uranium is recovered as a by-product, for instance, of
copper or phosphate, the treatment process is likely to be more
complex. At the Olympic Dam deposit, cross-price elasticity
becomes important on the production side, as the scale and
allocation of resources is contingent upon future expectations
for a series of resources.
Uranium Mining Techniques
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