Tip:
Highlight text to annotate it
X
Underground uranium mining is, in principle, not any different from any other hard rock
mining. And, indeed, other ores are often mined in association with uranium, for example,
copper or gold or silver. However, particular attention to the ventilation of the mine is
required to limit dose to the workers from radioactive radon that’s emitted from the
uranium decay daughters. Once the ore body has been identified, the
shaft is sunk in the vicinity of the ore veins and cross cuts are driven horizontally to
the veins at various levels, usually every 100-150 meters. Similar tunnels known as drifts
are driven along the ore veins from the cross cut. The next step is to drive tunnels, known
as raises when driven upward and winds when driven downward through the deposit from level
and level. These raises and winds are subsequently used to develop the stopes, where the ore
is mined in the veins. The stope, which is the workshop of the mine, is the excavation
from which the ore is extracted. Two methods of stope mining are commonly used: the cut
and fill method and open stoping method
The space remaining following the removal of ore after being blasted is filled with
waste rock and cement
In the shrinkage method, just sufficient broken ore is removed via the chutes below to allow
miners to work from the top of the pile, to drill and blast for the next layer to be broken
off, eventually leaving a large hole. Another method, known as room and pillar (see
the picture) is used for thinner, flatter ore bodies. In this method, the ore body is
first divided into blocks by intersecting drives, removing ore whilst doing so, and
then systematically removing these blocks, leaving sufficient pillars for the roof support.In
situ leaching (ISL), sometimes referred to as in situ recovery (ISR) or solution mining,
is performed by pumping liquid, either weak acid or weak alkaline, depending upon the
calcium concentration in the ore, down through injection wells placed on one side of the
deposit of uranium through the deposit, then up through recovery wells on the opposite
side of the deposit. By this, they can recover the ore by leaching it from the rock in the
ore body. ISL is also used on other types of metal extraction, for example, copper.
ISL is often cost effective because it avoids excavation costs and it may be implemented
much more quickly than conventional mining; however, it is not suitable for all uranium
deposits, as the host rock must be permeable to liquids, such as is the case with sandstone.
In situ leaching is the only type of uranium mining currently being done in the United
States as of 2006.