According to the World Nuclear Association, 21 percent of the world?s uranium production came about from ISL mining in 2004. We conducted interviews with some of the world?s top ISL experts, including the father of ISL, to help you better understand how uranium is currently mined for the world?s nuclear power plants.
uranium mining, ISL, nuclear energy, energy, heap leach, mining, Wyoming, Texas, Australia, geology
It?s time to rewrite the history books. In Situ Leach Mining (ISL), or Solution Mining, was not first commercially started in Bruni, Texas in 1973 by Westinghouse, a consortium of oil companies and others. The birthplace of ISL was never South Texas, as some have claimed. It was begun in Wyoming, about 16 years before an ISL operation was started in Texas. Why there has been a whitewash over the true history of ISL is not our concern. This series is an in-depth investigation into how and why ISL mining came about, how it has been tested over a period of nearly 50 years, and why this type of uranium mining will play an important role in providing U.S. utilities with the raw fuel to power nuclear reactors for the next few decades.
In this modern era of uranium mining, extremely skilled engineers, hydrologists and geologists establish ISL mining operations. Most insiders compare an ISL operation to a water treatment plant. It?s really that simple to understand. However, as with every modern industrial operation, the roots of ISL mining came about in a less genteel or sophisticated manner. In 1958, Charles Don Snow, a uranium mining and exploration geologist employed by the Utah Construction Company, was investigating a Wyoming property for possible acquisition for his company. During the course of that visit, he discovered a new method of uranium mining and helped pioneer its development into the modern form of ISL.
Since 1957, R.T. Plum, president of Uranyl Research Company, had been experimenting with a leach solution on his property at the Lucky June uranium mine. ?They mixed up the sulfuric acid solution and just dumped it on the ground, and soaked it through the material and collected it in a little trench at the end,? Charles Snow told StockInterview. It wasn?t very scientific. Snow added, ?They were just learning how, and I observed it and thought that the application could be made through some of the ore that we had in the Lucky Mc mine.? The company was mining uranium this way because it was below the grades miners were used to, when mining. As Snow noted, ?It was not worth mining.? But it was practically at the surface. He explained what they were doing at the Lucky June, ?There was an area where uranium leached out to the surface in a small area, and it had a clay under-bed. These people put solutions onto the surface, collected the solution, and ran it by resin beads to absorb the uranium.?
While they only recovered about $3600 worth of uranium, roughly 600 pounds, Snow was impressed. He later wrote an inter-office memorandum in July 1959, with the subject header: ?Recovery of Uranium from Low Grade Mineralization using a leach in place process.? In his conclusion, Snow recommended, ?From the preliminary information available, it appears that it will be possible to treat very low grade mineralization for recovery of uranium at a large net profit.? He explained the process to his bosses, encouraging them to consider this as an option:
?In brief, the process introduces a leach solution onto the surface of the ground and allows the solution to percolate down through the area to be leached. The solution is then recovered from wells and circulated through an ion exchange circuit with the barren solution being returned to the leach area. Recovery of the uranium is made by stripping from the ion exchange medium.?
He wanted the Utah Construction Company to try this method of mining where there was low grade mineralization. Snow succeeded in convincing his bosses. That began yet another innovation for Utah Construction Company, the same company which helped construct the Hoover Dam, decades earlier, before it got into the uranium mining business.
Utah Construction Becomes the
First Commercial ISL Miner
Newspaper reports, through the 1960s, illustrate that ISL mining was in full bloom more than a decade before anyone in Texas began a commercial ISL operation. On June 18, 1964, the Riverton Ranger newspaper reported, ?The Shirley Basin mine is on a standby basis. The timbers are being maintained and the water pumped out. Total production comes from solution mining.? Between 1962 and 1969, ISL was the only method producing uranium at Utah?s Shirley Basin Wyoming. Later in that same article, under the section entitled, ?Gas Hills Solution Mining,? it was reported, ?The Four Corners area is ?mined? by solution mining techniques similar to those employed at Shirley Basin.? Credit for this new mining method is also reported in that same article, ?Lucky Mc introduced the heap leach process of recovering values from low grade ores in 1960.?
Charles Snow explained how his company made the transition from underground mining to solution mining, ?The underground mining at Shirley Basin was very expensive, and we were having a lot of heavy ground problems.? The sandstone aquifers containing the uranium were uncemented and brittle, supported with timbers. ?In some places, it was too heavy to hold with timbers,? said Snow. ?We had to use steel sets underground, and it was even mashing the steel sets. So the expenses were getting very high.?
Water was flowing into the open drifts at prodigious rates. Snow recalled, ?Barney Greenly said, ?Let?s try solution mining over here.? They did a test, and it did operate quite well. They got some pretty good results. So the underground mine was shut down, and they went to a solution-mining program to produce the allocated pounds in the Shirley Basin area.? The procedure was tested for a few years before a full-scale commercial production began. This fulfilled 100 percent of Utah?s Shirley Basin uranium production allotment from the AEC.
There were problems at first. ?We started out initially using sulfuric acid, and we had some reaction with carbonates in the formation.? Sulfuric acid plus calcium carbonate produces calcium sulfate, and this plugged up the formation. Calcium sulfate is gypsum, which was insoluble in the leach solution. ?It tended to plug up the formation and reduce the transmissivity of the fluid from the input hole to the output recovery hole.?
To prevent interference with the porosity of the formation, Snow switched to nitric acid, but admitted, ?We were reluctant to use nitric acid because it was much more expensive than sulfuric.? But they did, because the nitric acid solution did not form gypsum. Unlike present-day ISL methods used in Texas, Nebraska and Wyoming, Utah Construction did not use a carbonated leaching solution in their solution mining. Nitric solution was used during the 1960s and continued until the Lucky Mc switched over to open pit mining.
It all started as a heap leach experiment. ?We had quite a bit of low grade in Lucky Mc,? Snow told us, ?so we thought we would try a heap leach experiment.? Results were good on the test, and Utah pioneered ISL mining. Snow wrote in an August 2, 1960 memo, ?The favorable results of the heap leach project and other research indicate that the process can be successfully applied in many of the low-grade areas to recover much of the mineralization.? Later in his report, Snow calculated reserves from random samples obtained from previous drilling at Lucky Mc, ?The estimated reserve for the block is 147,000 tons @ 0.0361 percent U3O8, or 106,616 pounds of U3O8.? He estimated the program would cost $111,471. Using a value of $6/pound for U3O8, the anticipated returns were calculated as follows:
50 percent recovery: 53,318 pounds: $208,377
25 percent recovery: 26,654 pounds: $ 48,453
That was just the start. By the end of the decade, Shirley Basin?s solution mining operation was producing U3O8 at comparable levels to present day production at any of the major U.S. ISL facilities. In a paper presented by Ian Ritchie and John S. Anderson, entitled ?Solution Mining in the Shirley Basin,? on September 11, 1967, at the American Mining Congress in Denver, Colorado, these Utah International executives explained the success of the Shirley Basin solution mining operation. In a summary explaining the company?s activities, we discovered the Shirley Basin operation not only filled the Atomic Energy Commission (AEC) allocation requirements from 1962 through 1969 but we learned of the sizeable commitments into the future Shirley Basin was to fill:
?In 1968 sales of uranium concentrate were made to purchases other than the AEC. One of the first sales was to Sacramento Municipal Utility District with a minimum of 950,000 pounds to a maximum of 1,100,000 pounds of uranium concentrate in 1971. Additional contracts were signed with General Electric Company and with Nordostschwerzerische Kraftwerke A.G. (Baden, Switzerland). The contracts called for delivery of 8,000,000 pounds of concentrate to GE between 1968 and 1975, and 500,000 pounds of concentrate to NOK commencing in July 1969.?
The single reason solution mining stopped, well before the first ?commercial? ISL operation began in Bruni, Texas in 1973, was because of the improved market forecast for uranium in the 1970s. Utah Construction switched to open pit mining because they needed to produce a lot more uranium. The nuclear renaissance of the 1970s demanded massive quantities of uranium to fuel the rapidly growing nuclear power industry.
Don Snow?s initial field tests, begun in the late 1950s, resulted in continuous production achieved by late 1962. Subsequently, production in the underground uranium mine was shut down by May 1962. The underground mine was maintained in a standby condition until 1965, when all underground operations were written off. Millions of pounds were mined by Utah Construction through its ISL operations in Shirley Basin. It wasn?t heap leaching.
Sufficient evidence confirms that Wyoming, not Texas, first pioneered commercial ISL mining. Not only were well fields designed as early as 1960, but the entire concept of an ISL ?water treatment? plant can trace its roots to Utah Construction?s pioneer work. Everything from injection wells to production wells were pioneered in the early 1960s. We challenged Charles Don Snow that some have claimed it was heap leaching, not ISL mining. Snow shot back, ?No, we drilled holes in the ground and the material had never been mined. We got our ideas, certainly, from heap leaching, which came from the copper industry.? Snow explained that after the solution mining experiment was successful, ?A recovery plant was designed and put into the hoist house, where they had had the underground mine. That was designed by Robert Carr Porter and Ian Ritchie.? Snow added, ?In fact, Ian Ritchie and J.S. Anderson have a U.S. Patent on the well completion procedures that we used at Shirley Basin.?
Snow pondered if his friend Jack Bailey may have exported the ISL technology to Texas. ?Jack Bailey was the Shirley Basin project manager for the underground mine when we switched over to solution mining,? Snow said. ?He later went to work for Chevron, and Chevron had operations in Texas. I believe they even experimented with solution mining. Now, whether or not Jack was directly involved, I don?t know.? As it is with history, many of the old-timers are gone. We were told Jack Bailey had had a stroke a number of years back, and did not trace this further. There may have been others. ?Some of the people from that area (Shirley Basin) had gone to Texas,? Snow recalled. ?There is documentation, it was published information, and a lot of people who went to Texas, came from the Wyoming area. So, I?m sure there wasn?t a paucity of information being transferred.? Ironically, the Westinghouse-led consortium, which included U.S. Steel and Union Carbide, among others, was called Wyoming Minerals. Now we know exactly why they chose that name.
While there have been a number of ISL operations built and operated in Texas, there may be little future for uranium mining in that state, unless there are new discoveries. By a few, Texas has been inaccurately called the ?home of ISL mining.? Perhaps that came about because ISL operations continued, during the uranium depression of the past two decades, with small amounts of production occurring in Texas. According to Energy Information Administration figures published in June 2004, uranium reserves in Texas stand at 23 million pounds of U3O8 based upon $50/pound uranium. By comparison, Wyoming and New Mexico reserves, using that same benchmark, reach as high as 363 million and 341 million pounds, respectively.
This may explain the rush by junior exploration companies, such as Strathmore Minerals (TSX: STM; Other OTC: STHJF), Energy Metals Corporation (TSX: EMC), UR-Energy (TSX: URE), Uranerz Energy (OTC BB: URNZ), Kilgore Minerals (TSX: KAU) and others, to Wyoming. The large quantities of pounds are in Wyoming, not Texas. It may also explain why Uranium Resources (OTC BB: URRE) has looked beyond Texas into New Mexico to develop its ISL operation, and Strathmore Minerals has quickly been advancing through its permitting stage on one of its properties in that state. It is fitting that the big past uranium producing states may again become tomorrow?s leading U.S. producers. In any event, the entire world of ISL mining owes a debt of gratitude to Charles Don Snow for his pioneering efforts in bringing a heap leach experiment into full fruition as modern-day in-situ mining.