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Monitoring of the ground air for the presence of radon gas is another 2 method that has shown some promise in ore detection. A measurement of the alpha activity is made in auger holes 1.
This method has been shown to detect radon over uranium-bearing ore covered by considerable thickness of overburden. The uranium minerals occur as pore fillings, replacements of woody tissue or other carbonaceous matter, and as a cement between quartz grains or along fractures.
Uranium deposits occur in either of two modes, stratiform or vein type. Approximately 95 percent of the Nation's reserves is found in the strati- form type consisting of sandstone and conglomerate, limestone, and lignite formations. The deposits lie parallel to the bedding plane and have large lengths and widths as compared to their thickness. Vein-4 type deposits occurring at steep angles along fractures and structural faults account for the other reserves.
The principal known deposits of uranium ores in the United States are 4 located in three major districts: Table 1 shows the percentage distribution of ore reserves by resource region as of January The distribution of ore reserves by State is shown in Table 2, while uranium ore production in the four leading States from through is shown in Table 3.
Ore reserves now known lie in over a thousand individual deposits in the Western States; however, half of the reserves are in fifteen deposits containing over a million tons of ore. The ore grade ranges from less than 0. Figure 1 shows the geographical location of the ore reserves by resource region. Geo- graphical locations of the major uranium mining districts in the Western States are shown in Figure 2.
Probably less than five percent of the total prospectable acreage in the area had been explored as of January Some deposits of ore are expected to occur in the High Plains area of Texas, but will likely be less productive than the Coastal Plains. The Uravan mineral belt in the Colorado Plateau contains vanadium-bearing minerals, making it profitable to recover both uranium and vanadium from the ore. Much of the uranium ore contains molybdenum in quantities sufficient for economic recovery.
Canadian companies are conducting exploration activities in the United 9 States. Rio Algom Mines Limited is developing a mine in the Lisbon Valley district, about 30 miles southeast of Moab, Utah, and is partici- pating in an extensive exploration program in Wyoming with Mitshubishl Metal Mining Company.
Several major uranium-producing companies 12 from the United States are becoming involved in Canadian uranium exploration activities in anticipation of future uranium requirements. Many new companies are entering the field of uranium exploration; the number of companies exploring for uranium more than doubled from through The discovery rate from exploratory drilling in the previous uranium-producing areas has been about six pounds of uranium oxide per foot drilled.
Recently, exploration has spread into previously unexplored areas and, combined with the search for deeper deposits, has resulted in a reduction in the discovery rate to about three pounds of uranium oxide per foot drilled.
Uranium has been found and produced in 17 States, but 95 percent has been from Arizona, Utah, New Mexico, and Wyoming. The eastern two-thirds of the United States has many sedimentary deposits similar to those in the uranium-producing areas. As exploration activities spread into the newer areas, new bodies of ore may be discovered to greatly expand reserves. About 40 percent of the United States has potential for producing uranium ore. Drilling activities have increased rapidly since Table 4 shows the surface drilling from through with the projected drilling plans for through The previous peak in drilling was in when 9.
In comparison, drilling from through I was only 52 million feet. Table 5 shows both exploratory and surface drilling for the period through The exploratory drilling has increased at a much faster rate than developmental drilling, indicating a rush to find new reserves for future demands. The previous high in exploratory drilling was in when 7.
Table 6 shows the distribution of the surface drilling by States. Of interest is the high drilling activity in Texas for new reserves. While producing only five percent of the uranium, it ranks second in drilling activity. This may be an indication of a forthcoming rise in production rate. Shallow deposits were more readily located by airborne or ground surveys and more economical to mine. As these deposits become depleted, exploration at deeper depths will be required.
Table 7 shows the drilling statistics for the Western United States. From I through the average depth per hole drilled was feet. The average depth of drilling has steadily increased through the years from feet in to feet in From to the average depth more than doubled. Table 8 shows the distribution of ore by depth for the year Approximately 65 percent of the ore reserves lie at depths of less than feet allowing recovery by open pit mining. The ore is more concentrated at two zones: Table 9 shows the distribution and grade of ore reserves by mining method as of January Underground mines are located in all the uranium-producing States except Texas.
As early aslarge ore reserves had been developed, but as the requirements for uranium decreased, production experienced a down- ward trend from through Exploration activities were halted and many mills were closed. As the nuclear power industry began to grow, increased exploration activity in resulted in more new reserves discovered than those mined in that year.
The reserve estima- tion from through is shown in Table Should the market price rise substantially, reserves can be increased by mining lower grade ore containing as little as 0. Phosphates in Florida have a uranium content of 0. Marine shales range from 0. New technology in mining and milling processes may make mining of low grade 15 7 Table 7. Exploratory Developmental Table 8. The leach- ing of uranium from low grade copper dumps and recovery from phosphate fertilizer is projected to supplytons of uranium oxide through the year Another source of uranium may be the surplus stockpiled uranium con- centrate held by the Atomic Energy Commission.
The AEC stopped procurement at the end of with 40, to 50, tons of stockpiled uranium oxide. Release of the surplus for commercial use may begin inbut be controlled so as to protect uranium producers.
State of the Art : Uranium Mining, Milling, and Refining Industry
Should a shortage develop due to nuclear power demands, the surplus could serve to alleviate the situation. Nuclear energy for the production of electricity has become economically competitive with other types of energy. It is believed that practically all of the demand for uranium for non- military purposes to the end of the century will be to fuel nuclear power reactors.
Uranium's greatest advantage as a fuel for the production of t electricity is that an enormous amount of energy is stored in a compara- tively small space. One pound of uranium has the same energy potential as three million pounds of coal.
After years of development by govern- ment and industry, the manufacturing facilities in the United States are capable of producing an estimated 20 large nuclear power reactors each 15 year. Duringfive new nuclear power reactors began operations with 14 more under contract, making a year-end total of central station nuclear power reactors under contract, under construction, or operable in the United States.
It is predicted that penetration of the electric 18 utility market by nuclear power plants will increase from less than one percent of the total generation into 25 to 30 percent inand 1 12 range from 40 to 60 percent in the year Only one percent of the uranium portion of the uranium oxide con- centrate is consumed in the nuclear reactors presently in use. In contrast, the breeder reactor will actually produce more fuel than it 13 consumes.
The breeder reactor will produce fissionable plutonium- and uranium from uranium and thorium, respectively. The ultimate effect of utilizing the breeder reactor will be to reduce the amount of uranium required, thereby increasing the currently predicted uranium depletion times from decades to centuries.
Another advantage is that the breeder reaction is relatively insensitive to cost of uranium oxide, thus allowing mining and milling lower grade ores at a higher market price to provide additional ore reserves. The Liquid Metal Fast Breeder Reactor has been chosen by the Atomic Energy Commission as the prime contender for reactors of the future 14 and a development program is under way to perfect its design.
This type of reactor should compare economically with reactors now in opera- tion, and use the nuclear resources more efficiently than present reactors, Additionally, it will be able to operate on reprocessed spent fuel from present reactors, thus eliminating uranium isotopes and plutonium from the current and perplexing waste disposal problem. Should breeder reactors be introduced in the early 's, the effect on the uranium requirements will probably not be evident until the end of the century.
Should plutonium be reserved for breeder fuels, the demand for uranium to fuel light water reactors would increase. Also a large amount of uranium will be required for the initial fueling of these new reactors. Plutonium recycle in thermal reactors is planned to start inthus reducing annual requirements. Many uncertainties in requirements for 19 the late 's and the 's exist, such as the timing of commercial fast breeder reactors.
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A substantially greater amount of uranium will be required, but a close estimate is difficult at this time. Table 11 shows the projected domestic uranium requirements through the year The requirements include the initial fuel for reactors under construction and makeup fuel for operating reactors. Requirements for operating reactors ranged from 15 percent of the total annual requirements into 60 percent in Current figures for the number of nuclear power plants to the end of the century indicate a steeply rising annual demand for uranium far beyond the capacity of existing mills.
Existing mills produced 13, tons of uranium oxide inas seen from Table The projected annual requirements will reach this level inas seen in Table 11, will double byand triple by New mines and processing mills will have to be placed in operation if the projected requirements are to be met.
An eight-year forward reserve is needed to assure an adequate supply of ore for the requirements; hence, each year the addition to the reserves must equal the annual requirements eight years later. Many of the earlier mines were one-man operations producing small quantities of ore.
The ore was hauled from the many locations to a processing mill some distance away. The ore production rate in was 75 percent of that in I, despite the fact that the operating mines had decreased to 30 percent of the figure. This was due to the larger companies taking over the majority of the smaller mining operations. There were 25 mills in operation in that produced 17, tons of uranium concentrate. The number of mills decreased to 15 indue to the lowered demand. In anticipation of the increased demand for uranium as a fuel for nuclear power, two new mills were placed in 20 Table Two more acid leach-solvent extraction plants were placed in operation in Continental Oil Company opened a mill near Falls City, Texas, with a capacity of 1, tons of ore per day, and Humble Oil and Refining Company began operations at a mill near Douglas, Wyoming, with a capacity of 2, tons of ore per day.
An alkaline leach plant with a tons of ore per day capacity was also placed into operation in by Rio Algom Corporation near La Sal, Utah. Table 13 lists operating mills, location, and capacity at the end of The locations of the Colorado River Basin mills are shown in Table Only three of the mills are still in operation. Although operations have ceased at 14 of the mills, waste tailings piles containing potential radioactive pollutants remain at the sites.
Continental Oil Company Utah: Rio Algbm Corporation Washington: Federal American Partners Petrotomics Co. Humble Oil and Refining Co. Reactivated early in In there were 25 open pit mines and underground mines being worked. Open pit mining is used where the ore deposits are near the surface and covered with loose, easily removable soil.
Some open pit mining may be done at depths of more than feet; but usually, below feet, under- ground methods are preferred. The ratio of overburden to ore removed in uranium mines is unusually large as compared to other types of mining with ranges from 8: The expense of removing the larger amounts of overburden is justified by the greater value of the product being recovered. Conventional earth-moving equipment is used for mining: The size of the mining operation determines to some extent the equipment employed.
In some small ore bodies backhoes are the most economical means of digging and loading ore. Ground water intrusion has been a problem in many of the open pit mines. The water is pumped from the mine to keep the floor surface workable. A trench several feet deep may be dug around the periphery of the pit floor and as the ground water drains from the pit floor into the ditch, it is pumped front,the mine. As the ore is removed to the level of the ditch depth, the process is repeated.
The water is discharged to the surface to seep into the ground or drain into nearby creeks or rivers. About 70 percent of the New Mexico production is underground. The largest ore bodies mined by underground methods measure as much as half a mile in length, several hundred feet in width, from 5 to feet thick, and are located several hundred feet below ground. Many of the smaller deposits are mined using simple adits in canyon walls with removal of ore by wheelbarrows.
Most mines require shaft entry, but some ore is mined using inclines and adits. Shafts, located at depths of feet, are generally concrete-lined for lowered maintenance. Stoping methods are generally used with various forms of room and pillar methods.
When possible, waste or low grade ore is left as pillars. Tunnels extending from the shaft are supported by steel plate, timber, or concrete, depending on ground conditions and permanency of the tunnel. The ore bodies are outlined by underground long-hole drilling of to feet from the underground shaft and tunnels. New tunnels are placed from the long-hole drilling data. The mine is continually developed in this manner until the vein is depleted. Ground water from the ore bodies is pumped to the surface for discharge or used as process- ing water in the mill.
The volume of water pumped from mines may range from to 3. Lack of proper ventilation in uranium mines constitutes a hazard since radon, a radioactive gas, is produced as one of the daughter products of uranium.
Without adequate ventilation the gas will concentrate in i7 18 levels considered hazardous to the miners' health. Concern has been expressed that uranium miners may be 26 subject to an increased risk of lung cancer due to radon and its daughters. Epidemiological studies of lung cancer among miners have been under way by the U. Public Health Service for some years. Uranium is extracted from the solution by chemical means. Since the Utah Construction and Mining Company has been using a solution mining process routinely to extract uranium from an under- 20 ground ore body in Shirley Basin, Wyoming.
Certain conditions must exist for solution mining of uranium: Uranium ore must lie in a generally horizontal bed underlain by a relatively impermeable stratum. The ore must occur below the static water table. The direction and velocity of regional waterflow must be known. Mineralogy of the ore must be determined to choose the proper leaching and extracting process. The well locations and the inflow-effluent rates must be carefully planned using regional water flow data and experimental drilling.
The Shirley Basin mining operation is composed of three inflow wells up- gradient from a production well with the center inflow well directly up- gradient on the regional ground water flow direction.
The remaining two inflow wells are located on radii diverging at an angle of 75 degrees from one another, equally spaced from the center inflow well. The distance from the inflow wells to the production well is approximately 25 feet. Sodium chlorate may be added as an oxidant to increase the leaching efficiency.
The flow of solution is continued until the concentration of uranium in the leach solution decreases, indicating the leach zone is depleted. Approximately one month is required for depletion of a zone with three to five well patterns in operation simultaneously. Uranium recovery approaches percent except when multiple-horizon areas occur, and upper horizons are not underlain by impervious layers.
The uranium-bearing liquor, containing between 0. The loaded column is stripped with a mixture of nitric acid, sodium nitrate, and sulfuric acid. The barren leach solu- tion is discharged as waste to a tailings pond with no outflow. The strip solution is then precipitated with a lime or magnesium slurry at pH 7. The slurry is shipped to the mill for further purification. The decant, containing neutral nitrate salt, is recirculated to eluate makeup with nitric acid.
Solution mining costs approach or exceed those of open pit mining but are lower than those of underground mining.
The operation is much safer for mining personnel, however. Disadvantages are that the proper ground conditions for recovery must be present for utilization of the process. Also, in poor recovery zones, injected solution may be lost in multiple ore horizons and underground fractures, thus becoming a contaminant to ground waters. Solution mining can be used on mined-out stopes and tunnels of underground mines by flooding with leach solution and then pumping the loaded solution out of the mine for extraction of the uranium.
Natural leaching of uranium ore by the ground water results in uranium concentrations containing up to ten parts per million that may be extracted by ion exchange processes. Certain acid tolerant bacterial species are capable of further oxidizing ferrous sulfate to ferric sulfate, which in turn oxidizes the insoluble tetravalent uranium to the acid soluble hexavalent state.
In practice, mines are flooded with water which gradually decreases in pH to between 1. The pregnant mine water is pumped to an ion exchange extraction circuit for uranium separation.
Studies in Canada have been conducted to determine whether the bacterial? Sul- furic acid requirements for leaching were reduced from 80 pounds per ton to 25 pounds per ton.
Underground bacterial leaching has been used in Canada with success, but is unlikely to supersede conventional mining and milling methods due to the long period of time required for 22 efficient leaching. The chief uses have been to scavenge worked-out mines, caved areas, or low grade materials above or below ground that are uneconomical to treat by conventional methods. The process also holds promise for the recovery of uranium from material rejected by flotation, heavy media, electronic sorting, or other upgrading processes.
The bacterial leaching of United States ores may never be effective because most presently known reserves contain insufficient pyrite and an abundance of neutralizing calcium carbonate. Stockpiles of low grade ore removed from mines may be profitably proc- essed by heap leaching. A typical heap leaching pile is constructed by grading the ground at the site area to a smooth sloping surface.
The area, approximately feet wide by feet long, is covered by a polyethylene sheet of six mil 29 thickness, Four-inch perforated plastic pipe is placed parallel to the width at 18 foot centers.
The pipe is covered with one foot of gravel followed by emplacement of low grade ore to a depth of approximately 25 feet. The top of the pile is graded and divided into sections of feet by 60 feet with dikes made from the ore. A sulfuric acid solution is placed in the diked sections of the pile, allowed to percolate through the ore, collected by drainage from the pipes, and removed to storage tanks. The uranium is extracted from the leach solution by conventional solvent extraction or ion exchange methods.
Waste acidic solutions are recycled through the pile for maximum leaching efficiency. The final strip solu- tion contains approximately 25 grams of uranium per liter that may be further processed by a mill.
Airborne radiation surveys are made during the operation of the system to check for radon in the air. The pile, containing approximatelytons of ore, is abandoned as leaching operations are completed. The residual material contains less than 0. Western Nuclear's facility produces approxi- mately 12, pounds of uranium per month at the Day Loma heap leach site.
The milling process may be broken down into separate circuits; each of the operating mills is composed of various combinations of circuits as shown in Table The organic extractants and precipitating agents utilized are listed in the respective columns. Uranium precipitates containing sodium impurities are further purified by acid dissolution followed by reprecipitation with ammonia.
As far as possible, the process solutions are recovered and recycled in the milling processes. The remainder is discharged as waste to the disposal area along with leached sands and slimes and dissolved constituents from the ore. Flow diagrams of various milling processes are shown in Figures 3 through 9.
The flowsheets reflect only the sand-slime discharges to the tailings pond. Recycling of process solutions within the plant is not shown because of mill variations in volume, chemical content, and point of discharge to tailings pond. Unrecycled process solutions are used to carry sand and slimes to the tailings area. Additional water is added as necessary to supplement process solutions in slurrying the solids for transport to the tailings pond.
Excessive chemical buildup in the recycled mill solutions from the dissolution of minerals in the ore is prevented by discharging a portion of the solution to the tailings pond and replenishing that volume with additional water and chemicals.
A number of mills reuse tailings pond water following removal of the suspended solids. Utah Construction and Mining Co. C The loaded strip solution is combined with the loaded strip solution from the alkaline-RIP circuit for precipitation.
Blend- ing is performed to provide a grade of ore with more uniform physical characteristics and uranium content. Radiometric analysis of the ore as loaded onto the trucks establishes the grade which varies from less than 0. The ore may be stockpiled in a manner to provide a uniform grade of approximately 0. Ores can be hard, slimy, or sandy, which may cause difficulty in the milling circuits. Hard ores limit the capacity of the grinding circuits, slimes interfere in ion exchange circuits, and sandy ores settle too rapidly in pipelines causing plugging.
Blending eliminates extremes and allows a smoothly flowing process to be main- tained. Jaw crushers ranging from 15 to 40 inch size are used as primary units but may be bypassed for fine ore. Grizzly circuits are employed to screen and remove undersize material from the crushing circuit, bypassing the fine ore to storage bins.
Both impact-type and cone or gyratory crushers are also used as required by ore type. Moisture content is important in the crushing operation and should be in the range of five to ten percent. Some ore must be dried before crushing by either kiln drying or natural drying. Some mills employ a roasting circuit for use with special types of ore.
Pretreatment of lignite ores by roasting improves the leaching character- istics. Improved settling and filtration characteristics of clay minerals 40 are obtained by roasting. Vanadium-bearing ores require a salt-roasting process to improve the solubility of vanadium. Carbonaceous ores are roasted to remove organic carbon and prevent contamination of leach solutions.
The roasting circuit is bypassed when not needed with the ore going directly from the crushing to the grinding circuit. The ore is carried by belt-type feeders at the desired feed rate to the grinding circuit and sampled at some point between the crushing and grinding circuit for laboratory analysis.
Rod mills and ball mills are used almost exclusively for grinding the ore to approximately 28 mesh for an acid leach process and mesh for an alkaline leach process. Water is added to obtain a slurry of approximately 65 percent solids for grinding. Recycled acidic wash solutions from other plant circuits are sometimes added to reduce the water requirements. Classifiers are some- times placed in a closed circuit with the grinding equipment to size the ore and return coarser particles for further grinding.
In some instances, the pulp density in the grinding circuit is different from that required for the leaching circuit and must be adjusted by means of cyclones and thickeners. Among these are the type of uranium mineralization, ease of liberation, and the nature of other constituent minerals present. The most important factor in choosing the leaching process, however, is based on the lime content of the ore. Sulfuric acid, rather than hydrochloric or nitric, is commonly utilized for leaching purposes due to its less corrosive nature and lower cost.
Uranium in the ore in the tetravalent form must be oxidized to the hexa- valent state before dissolution occurs. Iron present in the ore or intro- duced from wear of the metal in the grinding circuit serves as the principle oxidant. Sodium chlorate or manganese dioxide is employed for this purpose. The oxidation-reduction potential emf of the ore slurry is important and should lie within the range of to millivolts.
Failure to maintain uranium in the hexavalent state throughout the leaching process will result in premature precipitation. The ore slurry is pumped into the leach circuit maintaining a pulp density of 50 percent solids ground less than 28 mesh. Leaching is performed in a series of wooden tanks equipped with agitators. Sulfuric acid is added in an amount to maintain a free acid concentration ranging from 1 to 90 grams acid per liter 40 to pounds per ton. Higher acid concentrations are used for vanadium extraction due to its greater insolubility.
Nominees for director are selected based on their experience, knowledge, integrity, understanding of our business environment and the willingness to devote adequate time to Board duties. The Board uses the same selection criteria regardless of whether the candidate has been recommended by a stockholder or identified by the Board. When evaluating a candidate for our Board, the Board does not assign specific weight to any of these factors nor does it believe that all of the criteria necessarily apply to every candidate.
While our Board does not have a written policy regarding diversity in identifying director candidates, the Board considers diversity in its search for the best candidates to serve on our Board. The Board looks to incorporate diversity into the Board through a number of demographics, skills, experiences, including operational experience, and viewpoints, all with a view to identify candidates that can assist the Board with its decision making.
The Board believes that our current Board reflects a diverse mix of directors on a number of these factors. The Board did not receive any stockholder nominations during fiscal In the ordinary course, absent special circumstances or a material change in the criteria for Board membership, the Board will re-nominate incumbent directors who continue to be qualified for Board service and are willing to continue as directors.
However, the Board expects that it will seek to add additional independent directors in the future to regain compliance with NASDAQ listing standards. If a vacancy on our Board occurs between annual stockholder meetings, the Board may seek out potential candidates who meet the criteria for selection as a nominee and have the specific qualities or skills being sought for Board appointment.
Director candidates will be identified based on input from members of our Board, our senior management and a third-party executive search firm, if engaged. The Board will consider persons recommended by our stockholders in the same manner as a nominee recommended by our Board members, management, or a third-party executive search firm. Candidates meriting serious consideration will meet with other members of our Board, as deemed appropriate.
Based on this input, the Board will evaluate which of the prospective candidates is qualified to serve as a director and whether this candidate should be appointed to fill a current vacancy on our Board or presented for the approval of the stockholders, as appropriate.
The Board then will make a recommendation as to the person s who should be nominated to the Board. Rosen and Davis were initially appointed to the Board in Davis were initially identified as director nominees by an independent director. SPCH acted as the lead investor in a private placement of common stock that was completed in July Board Nominees for the Annual Meeting Each of the nominees listed in this Proxy Statement is a current director standing for re-election.
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We are exposed to a number of risks, including financial risks, strategic and operational risks and risks relating to regulatory and legal compliance. The Board will regularly discuss with management our major risk exposures and the steps management has taken to monitor and control such exposures, including the guidelines and policies to govern the process by which risk assessment and risk management are undertaken, and highlighting any new risks that may have arisen since they last met.
The Board manages exposure risks within various areas including: We have a policy of encouraging all directors to attend the annual stockholder meetings; all of the directors attended the annual stockholder meeting in person. The Code of Ethics is posted on our website at http: The information in this table is based solely on statements in filings with the SEC or other reliable information.