EXCLUSIVE TO SIGHTLINE U3O8 – The method in which a mining company intends to extract ore greatly affect the construction and operational costs of the project as well as the execution risks involved. In the case of uranium, mining is accomplished through conventional methods (open pit or underground mining) or via In Situ Recovery (ISR). Having said that, it is also important to remember that depth and mining method are only two of the factors used in establishing the economic value of a project and in and of themselves do not necessarily reflect a direct implication in the profitability of a mine.
Open Pit Mining*
When uranium ore is found near the surface, generally less than 100 metres deep, it is typically extracted by the open-pit mining method.
Open-pit mining begins by removing soil and waste rock on top of the ore, to expose the hard rock. Then a pit is excavated to access the ore. The walls of the pit are mined in a series of benches to prevent them from collapsing. To mine each bench, holes are drilled into the rock and loaded with explosives, which are detonated to break up the rock. The resulting broken rock is then hauled to the surface in large trucks that carry up to 200 tonnes of material at a time.
When ore is located more than 100 metres below the surface, underground mining methods are more economical than mining by open pit.
The first step in underground mining is to access the ore. First, miners dig vertical shafts to the depth of the ore, then cut a number of tunnels around the deposit. A series of horizontal tunnels offer access directly to the ore and provide ventilation pathways. All underground mines are ventilated, but extra care is taken with ventilation in uranium mines, to minimize the amount of radiation exposure and dust inhalation. In most underground mines, the ore is blasted and hoisted to the surface for milling.
In a few places, geologic conditions allow uranium to be dissolved from ore directly, by pumping mining solutions underground, bringing it back to the surface, and extracting the dissolved uranium. With this in-situ recovery process (“in situ” meaning “in the original position or place”), there is limited environmental disturbance of the surface. The surrounding rock remains in place, while the dissolved uranium is pumped to the surface, and then circulated through a processing plant for extraction.
Within our UComparables list, there are eight companies planning to recover uranium via open pit mining, two companies combining open pit and underground methods, two companies using strictly underground and three companies using the ISR method.
* Source: Canadian Nuclear Association