In Situ Uranium Mining Process (ISR)
ISR uranium mining is responsible for nearly all U.S. uranium. Because of the large number of ISR uranium projects on the horizon in the United States, the in situ (ISR) uranium mining method will provide U.S and global utilities with tens of millions of pounds of newly mined uranium by 2020.
Questions and Answers:
How did the uranium actually get into the sandstones and become a roll front deposit?
Natural processes caused the uranium deposit to be in the aquifer. The uranium was deposited by the naturally flowing ground water. Uranium is still being carried by ground water flowing to the deposits. The flowing ground water is also naturally leaching parts of the deposit and re-depositing it a short distance away. This is really a very common natural process that’s happening in many aquifers. (Click Here to see Illiustration)
When you mine using the ISR method, do you destroy or contaminate an aquifer where you are mining?
There are thousands of uranium deposits throughout the world of varying quality in sandstones, which are also aquifers. Only a few hundred of these will contain sufficient uranium to eventually be mined. It’s there, and if it is mined, most of the uranium that was in the aquifer will actually be removed from the aquifer instead of staying there. The in situ (ISR) mining process simply reverses the natural process that placed the uranium there in the first place. It’s really a pretty simple process. The restoration process, after the mining is completed, actually returns the aquifer back to its pre-mining conditions. There is no way the aquifer is contaminated or destroyed (by ISR mining). (Click To See Illustration) Opens “ISL Mining Process-Scale.jpg”
Many environmentalists claim that by removing the uranium, you are changing the aquifer. Is the aquifer much different than before mining took place?
It’s not a lot different. **
How do you know where in the deposit to inject the fresh oxygen?
On one side of the deposit is what we call altered or oxidized sands. On the down dip side of the deposit are the reduced sands. There is no oxygen in those sands. Any fluid that carries uranium into the reduced sands is going to use up the oxygen and immediately deposit the uranium by natural processes. The mining process adds additional oxygen to the water in the deposit itself to cause the uranium to go into solution. Then, it can be pumped up to the surface.
How do you control the water flow during the ISR mining process?
The fluid flow is controlled by pumping the production well at a greater rate than the injection wells which are injecting the fluid. In other words, we create a flow to the production well because it is being pumped at a greater rate than the fluid being pumped into the surrounding injection wells. By doing this, we end up with a certain amount of ‘bleed.’
(Click To See Illustration) Opens “ISL Mining Process.jpg”
What is the solution you’ll be using during the ISR process?
This will be just the addition of carbonate and oxygen to normal ground water. The carbonate could be in the form of simple bicarbonate of soda or the gaseous carbon dioxide itself. The solution being used has been described as not much different than Perrier® water.
But, other areas in the world rely upon sulphuric acid in the in situ recovery uranium mining method.
Sulphuric acid will not be used as part of our in situ recovery process. The sandstone deposits in Utah and Wyoming are very suitable for alkaline-type in situ mining. It is a lot easier to clean up and to restore the aquifer afterwards.
Tell us about constructing an ISR well field for mining the uranium.
The wells are installed similar to most common water wells – with PVC piping. PVC casing would be cemented in place, and then piping similar to that used for irrigation would be used to transport the water to the injection wells. Similar piping would take the same water, coming out the production well, when moving it to the ion exchange column. When you come right down to it, this is basically a water plant. You are dealing with piping and water and oxygen and bicarbonate of soda. (Click To See Illustration) Opens “ISL Mining Process.jpg”
What processing follows extraction of the of the solution?
A uranium project requires a Central Processing Plant. The ‘mother plant,’ as it is called in the trade, can complete the entire processing cycle from uranium extraction through loading the resin, stripping the uranium from the resin with a solvent (elution), precipitating, drying and packaging.
There have been concerns about water use in certain parts of the United States. Will your company be consuming large amounts of water?
Consumption will be really low because in situ mining is basically a closed process. We use the ground water that is in the uranium deposit itself. We pump it out. We bring it to the surface. We charge it with the oxygen and bicarbonate of soda. Then we recirculate it back through the formation. Ninety-nine percent or more of the water stays in the formation. We only have to take out and dispose of one-half to one percent of the water that we are producing.
While ISR mining how does your company ensure that radiation does not escape beyond the aquifer and contaminate the ground water people or livestock drink?
The key is a very extensive monitoring program through a system of monitoring wells very close and surrounding the well field. These surround the well fields. Shallow monitor wells watch over any overlying drinking water aquifers. The mining process is done by pumping at such a rate so it brings the flow toward the production wells themselves. This assures the ground water flow is not moving the mining solution away from the production wells. The monitor wells also assist the state government and the Nuclear Regulatory Commission in assuring that we have our fluid flow under control. (Click Here to See Illustration) Opens “7-Well Spot Pattern.jpg”
What happens when the bells go off or the alarm sounds at the monitor wells?
If any of the wells give a suggestion of the potential of mining solutions getting into the vicinity of the monitor wells, immediately stop the injection of solutions, and use ‘overpumping’ to draw the solutions back into the mine area. Monitor wells are there to ensure we can see what’s happening in the area. They are there to enable us to ensure our operations are being done properly. If a solution does happen to get into the monitor well, that’s not really such a bad thing. It’s telling us we need to make some corrections and move forward. Monitor wells help us develop better controls in the natural system we are dealing with.
How do you restore the water back to it pre-mining quality?
The aquifer is usually restored using reverse osmosis, reduction or bio-remediation. More than 99 percent of the water used in the mining process is recirculated. It’s put back in the aquifer after it is restored at the surface. It’s just the new volumes of newly restored water that are pumped back through the mined area to assure that it’s returned to pre-mine conditions. Only the small volumes of water, which are left with more concentration, may be either evaporated or distilled to create a solid waste for disposal.
How can the environmentalists be assured that the water will be restored to its pre-mining conditions?
State laws require 100-percent bonding for reclamation. The bonds are a result of a calculation which determines what it would cost the state to compete restoration if the company was not able to do any more work in restoring the mine.
