ISR Uranium Mining: A New Method Explained

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ISR uranium mining is responsible for nearly all U.S. uranium mining (except for recovery through phosphates). More than 20 percent of global uranium mining now comes from the in situ recovery method, predominantly through In Situ Leach (ISL) mining in Kazakhstan and in Australia.

ISR uranium mining is responsible for nearly all U.S. uranium mining (except for recovery through phosphates). More than 20 percent of global uranium mining now comes from the in situ recovery method, predominantly through In Situ Leach (ISL) mining in Kazakhstan and in Australia. Because of the large number of ISR uranium projects on the horizon within the next ten years, both in the United States, Kazakhstan and Australia, 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.

We discussed the basics of ISR uranium mining with Bill Boberg, chief executive of UR-Energy, whose company plans to mine Wyoming's Lost Creek and Lost Soldier uranium deposits using the in situ recovery uranium mining method in 2008. We discussed many of the environmental type questions our readers wanted more information about.

StockInterview: How did the uranium actually get into the sandstones and become a roll front deposit?

Bill Boberg: Natural processes caused the uranium deposit to be in the aquifer in the first place. The uranium was deposited by the naturally flowing ground water when the natural oxygen in the ground water was exhausted due to natural chemical reactions with minerals and organic material contained in the sands of the aquifer itself. 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.

StockInterview: When you mine using the ISR method, do you destroy or contaminate an aquifer where you are mining?

Bill Boberg: There are probably 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).

StockInterview: Many environmentalists claim that by removing the uranium, you are changing the aquifer. Is the aquifer much different than before mining took place?

Bill Boberg: It's probably not a lot different. The formation of uranium deposits in the sandstones is a result of oxygenated ground waters that came from the surface, carrying uranium which is deposited when the oxygen is depleted or finally exhausted. The deposit is in place in the sandstone. As fresh oxygen is brought down to that point, it will re-dissolve and move the uranium further along.

StockInterview: How do you know where in the deposit to inject the fresh oxygen?

Bill Boberg: 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. The area of reduced sand that is downstream from the deposit is still there. It is the contact between the altered or oxidized sand and the reduced sand that causes the uranium to be precipitated into the sand itself. As the natural ground water flow carries the uranium into the reduced sands, natural processes will cause the uranium to precipitate out of the ground water, if there is some that did not get pumped to the surface and recovered during the mining operation.

StockInterview: How do you control the water flow during the ISR mining process?

Bill Boberg: 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.' The majority of the ground water is returned to the aquifer on a regular basis. About one-half to one percent of the water used in the system is actually 'bled' out because we are pumping the production wells at a greater rate - between one-half to one percent greater rate than what we are injecting. That's how we control the flow from the injection wells into the production wells.

StockInterview: What is the solution you'll be using during the ISR process in Wyoming?

Bill Boberg: This will be an alkaline solution - basically 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. The solution is not something out of the realm of normal ground water, and would cause no one any problem. The combination of the carbon dioxide or bicarbonate of soda and oxygen in the ground water is really quite a benign solution. But, it changes the chemical character sufficiently that it causes the uranium to go into solution. It's really just reversing the process that caused uranium to be deposited in the first place. Uranium is precipitated in a 'reduced form.' The alkaline solution just reverses the deposit-forming process by using the water already in the deposit. Adding oxygen to it enables the uranium to go into solution, and then be brought up to the surface. There the uranium is stripped out on the polycarbonate resin in the ion exchange column.

StockInterview: But, other areas in the world, such as Kazakhstan, rely upon sulphuric acid in the in situ recovery uranium mining method.

Bill Boberg: Sulphuric acid will not be used as part of our in situ mining process. The sandstone deposits in Wyoming region are very suitable for alkaline-type in situ mining. The use of acid for in situ mining is considered suitable only under certain geologic conditions, particularly in areas of very poor water quality. Where we've got good water quality in the areas of Wyoming where we would be mining, alkaline is a far more suitable means of in situ mining. By using alkaline it is a lot easier to clean up and to restore the aquifer afterwards. Acids can react on many things besides uranium. They can dissolve pyrite, sulphides and other minerals in the sandstone. Acid can release a lot more undesirable things into the formation that can make it more difficult, in some cases, to recover the uranium, and make it more difficult to do a proper restoration job. The alkaline process is a lot cleaner process, and it's a lot easier to restore the aquifer.

StockInterview: Tell us about constructing an ISR well field for mining the uranium.

Bill Boberg: 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. There's not much of anything that is going to cause anybody a problem.

StockInterview: There have been concerns about water use in certain parts of the United States. Will your company be consuming large amounts of water when mining at Lost Creek or Lost Soldier?

Bill Boberg:
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.

StockInterview: 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?

Bill Boberg: The key is a very extensive monitoring program through a system of monitoring wells. These surround the well fields. Shallow monitor wells watch over any overlying drinking water aquifers. The monitor wells are very close to the well field. 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. From a mining company's viewpoint, it would be a huge waste if we could not control the fluids. We would have a huge expense in not being able to have the fluids go where we want them to. As a result, we carefully set up the process to make sure the fluids are moving the way we need them to go. The monitor wells assist us in knowing that we have control of the water flow. The monitor wells also assist the state government and the Nuclear Regulatory Commission in assuring that we have our fluid flow under control.

StockInterview: What happens when the bells go off or the alarm sounds at the monitor wells?

Bill Boberg: If any of the wells give a suggestion of the potential of mining solutions getting into the vicinity of the monitor wells, we would 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.

StockInterview: How do you restore the water back to it pre-mining quality?

Bill Boberg: The aquifer is usually restored using the reverse osmosis process. It is a super-filtering process. We can also use other techniques, like reduction or bio-remediation. But, reverse osmosis is probably the one that would be more commonly used. 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. Or, they would be disposed of in a licensed disposal well.

StockInterview: Could you explain the deep disposal process?

Bill Boberg: Deep disposal is an activity which is strictly licensed and monitored by the states. It's not for just when the mining activity is completed, but probably something to be used throughout the mining activity. What this amounts to is this: the waste water is injected into a very deep rock unit. The disposal well is too deep and with such poor water quality that it could never be used for drinking water. These wells are commonly 6,000 or more feet in depth. The containment qualities of the deep disposal rock unit have to be able to contain the disposed water without a potential for leakage into other rock units. This is a common and well-accepted method for fluid disposal. It is strictly licensed and monitored. We are currently evaluating both our project areas, through the use of old oil and gas drill logs, in the area for rock units which could be favorable for the installation of deep disposal wells. As I said before, the deep disposal well is for a small percentage of the whole volume of water that will be handled.

StockInterview: How can the environmentalists be assured that the water will be restored to its pre-mining conditions?

Bill Boberg: Wyoming and Nebraska have a similar law, which requires 100-percent bonding for reclamation. The bonds are a result of a calculation, depending on various qualities of the deposit and how the mining will be conducted, which determines what it would cost the state to compete restoration if the company went bankrupt, or was not able to do any more work in restoring the mine. It is a complete 100-percent bonding that is determined in advance. It's probably in the range of tens of millions of dollars, which would be required for the bonding.

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