Reversing Mother Nature, Part Three

We talked to North America’s leading In Situ Leach (ISL) uranium mining engineers, and had them explain exactly how ISL worked. Most of the significant ISL operations in the United States were designed and/or constructed by these engineers. They explained how ISL mining is really just reversing the process of Mother Nature.

CLEANING UP THE PROJECT

Not so fast. Shipping the uranium out of the ISL plant isn’t the final step. The water has to be cleaned up, the property returned to its original condition. If done properly, then the footprint of the ISL uranium operation should have been nearly erased. In an earlier article, “Wyoming Uranium: Now and the Future,” we talked to Pat Drummond at Smith Ranch about this process:

The company is meticulous in restoring the landscape as well. Any restoration work on the surface is called “reclamation.” That can involve farming. “When we start a well field, we have to, by license, remove the topsoil and store it somewhere,” Drummond explained. “When we go back to reclaim the property, we take all the pipes out, we take the houses down, and cut our wells off. It’s all identified. We put an ID marker on the well. In 50 years time, when Farmer Joe comes around and wonders what was there, the state can say, ‘That was a uranium well.’ From the time we’ve stopped mining, we put everything back to normal.”

The one item we did not address at the time was cleaning up the water after the orebody has been mined out. Why is restoring the water back to background important? “In the mining process, you’re basically elevating sulfate,” explained Anthony. “You’re also elevating calcium because you’re lowering the pH a little bit, down to 6.5 to 7. Because you run it across the ion exchange circuits, you get a little leakage of chlorides into the lixiviant.” Subsequently, the water will have sulfate, chloride, calcium and bicarbonate circulating within it. “When you add carbon dioxide, you’re forming bicarbonate,” Anthony noted. “These are the major ion groups you are elevating during the mining process.” He also added that in some projects, you may get arsenic, vanadium and/or selenium. “They all go into the solution so that at the end of your mining process, these ions will be elevated above their baseline values.” The water will need to undergo a purification process to return them back to a quality consistent with baseline values.”

What does the ISL operator do with the water once the facility has mined out the uranium? There are three options, which we discussed with Glenn Catchpole, who has also set up previous ISL operations. In 1996, Catchpole was the General Manager and Managing Director of the Inkai uranium solution mining project in Kazakhstan. He is currently the Chief Executive of Uranerz Energy. “Here’s my order of priority: If you have a receiver formation for deep disposal on your project, that’s my first choice.” Sometimes, a project may not have access to a deep disposal aquifer, warned Catchpole.

The water is sent down the receiver formation, down about 4000 feet. “You’re usually sending this water to a formation that is very briny, a poorer quality than what you’re sending down,” Anthony pointed out. Another option, according to Catchpole, would be operations ponds, or evaporating ponds, where the water is evaporated. A third option is “land applied.” Catchpole explained this was for land application. “You take your waste stream, you treat it to remove the certain level of impurities, according to the government requirement, and then you’re allowed to disperse it on the land surface, as if you were irrigating.” When applied to the land, it is soaking into the land. “It’s growing grass, and it’s going into the groundwater system,” concluded Catchpole, “Whatever water quality standard they allow for you to put that water in the land, they want to ensure it doesn’t accumulate some particular chemical over time that is going to build up and contaminate the land.”

Generally, during the restoration process, the water is circulated through the barren orebody about eight times. It’s another instance of pore volumes – eight more times through the sandstone formation. Anthony explained, “Normally, the first pore volume is evacuated and disposed of via a disposal well.” But he warned, “This will cause an inflow of surrounding native water back into the mine zone. The resulting water is pumped to the surface and processed through a reverse osmosis unit.” Anthony compared this to the desalination of seawater. “The reverse osmosis equipment acts like an ‘ion filter,’ allowing pure water to pass through a membrane and filtering out ions of sulfate, calcium, uranium, bicarbonate and so forth,” Anthony explained.

Two streams of water are produced by the reverse osmosis unit. One stream is called “product water,” and is normally consistent with drinking water quality. The smaller stream of water is called “brine.” It contains, according to Anthony, “95 percent of all the dissolved ions that were in solution.” He said, “The brine is disposed down a deep well into an underground formation, which is typically not suitable for any use.”

CONCLUSION

For all the lip service and media attention paid to the environmental movement in terms of financial support, recognition and respect, it is the ISL miner who cares more about the environment, about preserving Mother Nature. Environmentalists remain ignorant of, or care not to publicize, the dangers of coal-fired electrical generation. Mining and burning coal to generate power for industry and residential electricity poses a greater threat to Mother Nature than ISL mining and nuclear power-generated electricity. No more evident a case in point is New Mexico, where the Navajo Nation “banned” uranium mining, because their president was misled by environmentalists in believing ISL uranium mining could pose a threat to groundwater. At the same time, the Navajo Nation enjoys over $100 million in coal royalties each year, as their air is polluted by carcinogens filling their air from coal mining in the San Juan Basin and coal-fired plants, which produce most of their electricity. It is time for the world’s environmentalist movements to wake up and smell the air they are breathing.

Unfortunately, ISL uranium mining will not replace conventional uranium mining in many deposits across the world. According to the World Nuclear Association, ISL mining accounted for 21 percent of worldwide uranium mining in 2004. “The overriding constraint of ISL is the technology is only applicable to selected uranium deposits,” Stover cautioned. “It’s those deposits wherein the uranium ore resides in a permeable environment, where you can flow water through the deposit and where you can bring the dissolved oxygen and carbon dioxide into contact with the uranium.” Stover explained that, during the evolution of ISL mining, a number of projects failed because the uranium was associated with organic material, was not accessible to the leaching solution, or the uranium was tied up in clays or shale-like material. “They were not able to flow fluid through it,” explained Stover. “The key issue at the onset is a careful characterization of the host environment in which the uranium exists.”

The key advantage to ISL is the far lower capital costs to start up a project, compared to the hundreds of millions required for a conventional mining and mill complex. For example, UR-Energy’s William Boberg and Uranerz Energy’s Glenn Catchpole both believe they can install an ISL operation on their Wyoming properties for as little as $10 million. Labor costs are also less. Doug Norris pointed out, “In its heyday, the Highland mine probably had 4,000 working in it.” By comparison, Cameco’s Smith-Highland ranch in Wyoming may soon ramp up to nearly 100 employees. “We’re talking about installing a centralized water treatment plant supported by a large number of water wells, typically completed with PVC,” Stover explained. “That’s in contrast with conventional mining, where you have extensive earth moving, in the case of an open pit or extensive underground workings, and a more complicated, much larger processing plant.”

In terms of environmental impact, ISL offers something sensible to the environmentalists. “ISL is much less intrusive, and it is short lived,” Stover said, echoing the sentiments of all who have been involved in this type of uranium mining. “It’s acceptance by the general public is much more favorable,” he concluded.

What does the future hold for ISL uranium mining in the United States? “Up until 2004, prices were flat,” Norris pointed out. “The economic picture has just now switched to where mines can start coming on again, but it does take years to properly define where the ore is. It takes a lot of geologic drilling and time to decipher it. Then there are the regulatory requirements, and that can take several years. Even if everybody reacted right now to what’s out there, it would still be several years, upwards of five years, before production jumped from its existing rate to 10 to 20 million pounds at the most.”

Reversing Mother Nature, Part Two

We talked to North America’s leading In Situ Leach (ISL) uranium mining engineers, and had them explain exactly how ISL worked. Most of the significant ISL operations in the United States were designed and/or constructed by these engineers. They explained how ISL mining is really just reversing the process of Mother Nature.

ISL EXTRACTION AND PROCESSING

During ISL mining, water is pumped to the surface from production wells that contain uranium in very low concentrations, on the order of parts per million concentrations. The next step in the ISL process is to extract the uranium dicarbonate. Extraction is done by chemically exchanging ions inside a processing facility. “The ion exchange process is very analogous to a home Culligan® water softener,” Anthony revealed. “It removes hardness or calcium from the water by replacing it with sodium, using ion exchange resins. If you go to Lowe’s or Home Depot, and buy a water softener, you basically have a home version of a uranium extraction plant.” The main difference is your water softener will have a cation exchanger. “For a uranium plant to function properly, you need to use an anion exchange resin, which is specifically designed to load uranium,” Anthony clarified.

And what is this magical “ion exchange resin”? The resin is comprised of little polymer beads, which are charged particles having an affinity for uranium anions. “There are literally millions of these small resin beads in a vessel, which can adsorb low concentration of uranium in solution,” said Anthony. Adsorption is when something is attracted to something else or clings to it, like static electricity.

Why do you have to process uranium like this? “In essence, the ion exchange process is a beneficiation (reduction) process that concentrates large volumes of low concentrate uranium solution into a much smaller volume containing a much higher concentration of uranium,” said Anthony. In other words, the beneficiation is just concentrating the uranium from the large volume of water in which it is mined into a more compact form. The preferred means is through an ion exchange.

Anthony gave a real-life example of the beneficiation process, “Three million gallons of wellfield solution containing dilute concentrations of uranium, of 100 parts per million minus 0.10 grams/liter, is passed through a bed of ion exchange resin. This might take 24 hours to achieve if the solution is flowing at 2,500 gallons per minute. After this length of time, the resin becomes loaded with approximately 2,500 pounds of uranium.”

STRIPPING THE URANIUM

Stripping the uranium is called the elution process. This is done through a chemical exchange of positively and negatively charged ions. Resins are classified by the charge on the active sites. “The active sites on the resin are positively charged for anion resins and negatively charged for cation resins,” Norris enlightened us. “The resin’s ability to extract chemical ions from a solution is derived from what’s called an active site,” he continued. “In our case, chloride ions obtained from ordinary tale salt are used to stabilize or temporarily neutralize this positively charged active site.” The negatively charged chloride ion sticks to the positively charged site, held in place by what Norris called “electrostatic forces.” When the negatively charged ions, such as uranyl dicarbonate, are placed in contact with the solution, it will kick off the chloride and replace that with the uranyl dicarbonate.

That was the chemistry lesson. Anthony summed it up in a nutshell, “They just displace it. There’s a greater affinity for the chloride ion to the resin than there is for the uranium. So, the uranium is stripped from the resin bed.” The processing facility chemically strips the loaded uranium from the resin by soaking the entire package of uranium-laden resin in a salt bath solution. “The volume of salt solution is on the order of 10,000 gallons resulting in a solution concentration of 30 grams/liter uranium,” Anthony said, describing the process of how the uranium becomes concentrated. “The stripped uranium solution concentration is magnified 300 times more than the wellfield solution,” he informed us. “The concentration level can now be economically processed for recovery: precipitation, dewatering, drying and drumming for a nuclear facility.”

GETTING URANIUM INTO THE DRUM

After the uranium has been removed from the solution, it is precipitated. At this point in the processing stage, you have yellowcake slurry. Up close, it looks like a sort of yellowish and wet, runny cement mixture. The dewatering process does just that, it removes the water from the yellowcake mixture.

“I use a filter press, a device that is designed to separate solids from solutions,” explained Anthony. Filter presses are extensively used in various types of food, chemical and drug processing across the world. “The uranium solids, now looking more like yellowcake, are retained in the filter press, where they can be washed and later air dried, before drying them to a powder with a low temperature vacuum dryer,” said Anthony taking us step by step through this process.

So what is the filter press and how do you end up with the finished yellowcake when you’re done? “It’s a series of plates and hollow frames, or it could be a series of recessed chambers,” Anthony answered. “Filter cloth is draped over the plates or chalked in the recessed chambers. The yellowcake slurry is pumped through the filter allowing the liquid phase to pass through the filter cloth, trapping the uranium oxide inside the device.” Anthony likes to pack the filter press up with as much yellowcake as it can hold. “It is then washed with clean water to displace the chloride ions to a low level,” Anthony explained. If you don’t remove the chloride concentrations to the acceptable level required by an uranium enrichment facility, a fine is assessed against that shipment.

The final steps include conveying the yellowcake to the vacuum dryer. The uranium oxide’s color depends on how high or low a temperature is used to dry the “yellowcake.” Patrick Drummond, the Smith-Highland Ranch plant superintendent, showed us pure uranium oxide dried at high temperatures. It was nearly black. After the drying process is complete, the uranium is packaged up in DOE-approved 55 gallon drums and transported to an enrichment facility. It is then when the enriched uranium can finally be used to power a nuclear reactor and provide an inexpensive source of electricity.