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By L. C. Bartel

Geologic features such as structure (faults, folds, fractures, etc.), water bearing zones, aquifers, pemeability variations, and porosity variations are important for mine planning and in situ energy recovery processes. Features important for planning a mine will be important for planning the recovery of energy by in situ processes. Various geophysical techniques might be used to obtain the necessary geologic information. In this paper, case histories will be discussed of the use of electromagnetic geophysical surveys at a potential underground coal gasification site and a potential tar sand oil recovery site to obtain pertinent geologic information. Results show that the controlled source audio- frequency magnetotelluric technique shows promise for mapping faults and natural fracture systems when there is a sufficient resistivity contrast.

Jan 1, 1982

By R. L. Frederking

Geological remote sensing is, "....the study of the Earth utilizing electro-magnetic radiation (EMR) which is either reflected or emitted from the land surface in wavelengths ranging from ultra-violet (0.3 micrometre) to microwave (3 metre)."1 Selected examples which illustrate a variety of successful geologic applications include lithologic mapping, 2 engineering soils mapping,3 tectonic interpretation,4 and mineral and petroleum exploration.5 This report examines the applicability of remote sensing for bauxite exploration in northeastern Mississippi. Specific objectives were to map lithologies of northeastern Mississippi from LANDSAT imagery, to determine the utility of LANDSAT imagery for delineating and mapping known deposits of bauxite, and to discover and map new bauxite deposits.

Jan 1, 1977

By R. W. Hagemeyer

By way of background. it is important to keep in mind that the information presented in this paper relates specifically to synthetically produced precipitated calcium carbonate (PCC) fillers. Natural calcium carbonate fillers manufactured by grinding limestone, marble and chalk, though having similar chemical and physical analyses to PCCs, normally contribute somewhat different performance properties in paint, paper and polymer systems. Many factors have been cited and numerous theories have been proposed for the observed differences. Particle size parameters, surface chemistry and particle morphology are the items most frequently mentioned. A discussion of this subject is beyond the scope of this paper.

Jan 1, 1989

By S. Vijayan

Despite the limited demand for rare-earth elements, as well as yttrium and scandium, in conventional applications, the emergence of ne~ high-technology applications such as supermagnets, lasers and superconductors is expected to result in significant demand for some of these elements. This paper examines the anticipated applications and demands for rare-earth elements over the next decade and their implications on the utilization of available resources. Process methods for the recovery of rare-earth elements from conventional and unconventional resources are reviewed in the context of their growing demand. Challenges facing the industries in meeting this opportunity are also discussed.

Jan 1, 1988

By R. K. Mehta, M. G. Bersch

Characterization of an ore or mill product is routinely performed by time consuming and tedious chemical analyses, sink-float separations, etc. Additionally, these types of tests do not provide data concerning the interrelations and interlocking of the mineral constituents. This paper discusses some of the applications and capabilities of the Minerals and Material Science Research Center at The University of Alabama. Back-scattered electron images of coal, oil shale, complex suldfide, and tantalium ores were acquired using a JEOL 8600 electron microprobe with a NORAN (formerly Tracor Northern] 8500 image analysis system. Methods of analysis and typical results are discussed.

Jan 1, 1992

By Ian McFeat-Smith, Robert J. Fowell

Roadheader machines have a specific place in modern tunnelling, not simply as a compromise between drill and blast techniques and full face machines, but as an economic and versatile form of mechanised tunnelling where the method of excavation is easily integrated with tunnelling operations. In the past, roadheaders have been subjected to misuses by engineers who failed to realise that, as in all mechanised tunnelling, a planned and systematic approach is essential if the full potential of these machines is to be gained. An increasing awareness of this, together with the introduction of the more powerful roadheader carrying their cutting potential into the hard range of rock is changing this situation and now makes the prospect of using roadheaders particularly attractive (1). The advantages gained by employing these machines can be considerable and Table 1 lists some of them. This table illustrates that from both cost, and installation points of view, the roadheader has considerable benefits over the full face machine. However, the principal advantage gained is in broken ground where heavy supports can be installed immediately at the tunnel face. In addition, access for planned maintenance and repairs to most working parts of the machine is at a premium and average machine utilisations of 40 - 60% can be expected. In comparison to drill and blast methods, up to 40% better progress can be regularly achieved, and the subsequent savings in overbreak costs alone would more than pay for the cost of a roadheader used to drive a 3km long tunnel. As with full face machines, ground disturbance is minimal and for short tunnels in urban areas a road-

Jan 1, 1979

By Raimo Matikainen, Pekka Särkkä

HISTORY The history of mining in the Outokumpu Co. shows continuous development of small and medium-sized mines, coupled with a permanent improvement in min¬ing methods and mechanization. Tables 1 and 2 provide a brief outline of the major events over the years of operation. Some of the mines have had relatively short lives as in the case of Nivala, Korsnas, Kylmäkoski, the surface pits of the Kotalahti, Vuonos, and Hammaslahti mines, and some very small pits. The sequence in which the mines started opera¬tions is shown in Table 1 and production increases in Table 2. GEOLOGICAL FRAMEWORK Most of the ore deposits in Finland (see Fig. 1) are situated in middle Precambrian (1500 to 2300 m.y.) formations corresponding to the Baltic shield. The ores and country rocks are generally firm, with a minimum compressive strength of 60 MPa (8700 psi). The sulfide ores, of importance to the national econ¬omy, can be divided into copper-nickel deposits, asso¬ciated with basic and ultrabasic rocks (1900 m.y.), and the sulfide ores found in well-preserved Svecokarelidic crystalline schists (1800 to 2300 m.y.) which contain varying amounts of copper, zinc, cobalt, nickel, and lead. Over 90% of the sulfide ore mined to date in Fin¬land and existing in the known ore reserves belongs to deposits situated in the main sulfide ore belt. This belt extends diagonally across the country over a breadth of Table 1. Sequence in Which Mines Began Operations 1913 Mining started at the Outokumpu mine (now called Keretti) 1928 Large scale systematic exploitation started in the Outokumpu mine Opening of mines: 1942 Nivala mine (1942-54) 1943 Yiojärvi mine (1943-66) 1947 Orijärvi mine (1947-54) (Mining started in 1757) 1948 Aijala mine (1949-58) 1952 Metsämonttu mine (1952-58 and 1964-74) 1954 Keretti's new mine plant 1954 Vihanti mine 1959 Kotalahti mine 1961 Korsnäs mine (1961-1972) 1962 Pyhäsalmi mine 1966 Virtasalmi mine 1967 Kemi mine 1970 Hitura mine 1971 Kylmäkoski mine (1971-74) 1972 Vuonos mine 1973 Hammaslahti mine 1978 Vammala mine Table 2. Ore Production of the Outokumpu Oy Mines Year 1000 t of Ore 1913-1928 252 1929-1954 13 075 1955 1 105 1960 1 784 1965 2 627 1970 3 269 1975 5 825 1976 5445 1977 4 939 1978 5 766 1979 5905 40 to 150 km, from Lake Ladoga to the coast of the Gulf of Bothnia. The main sulfide ore belt includes the Outokumpu copper-zinc, the Kotalahti nickel-copper, the Pyhäsalmi copper-zinc, and the Vihanti zinc ore zones. The Outokumpu ore district occurs in a mica schist area about 60 x 100 km, in association with belts of metamorphic Svecokarelidic quartzites, black schists, dolomites, skarn rocks, and serpentinites. The main ore minerals are chalcopyrite, pyrrhotite, pyrite, and sphalerite. In addition there are nickel and cobalt minerals such as cubanite and cobalt-pentlandite, which have been of economic importance. In this area, Outokumpu Oy exploits the deposits at Keretti and Vuonos. The latter was discovered as an extension of the Keretti ore field about 6 km to the northeast. The Kotalahti geological formation extends across nearly 400 km. The host rock of these mostly pipelike deposits is generally serpentinite, pyroxenite, or norite. The main ore minerals are pyrrhotite, pentlandite, and chalcopyrite. In this zone, the deposits of Kotalahti, Hitura, and Virtasalmi are at present under exploitation by Outokumpu Oy. The Vihanti geological formation is located in west¬ern Finland and is about 40 km wide and some 200 km long. The rock associations are crystalline schists including dolomites, mica schists, mica gneisses, gray¬wacke, and acidic or basic volcanic rocks, which change generally, in connection with the mineralization, into skarn and cordierite-anthophyllite rocks. The host rocks are dolomite, skarn, graywacke, and quartzitic rock and the principal minerals are sphalerite, chalcopyrite, galena, pyrite, and pyrrhotite. The accessory minerals are mainly cubanite, arsenopyrite, molybdenite, and native gold and silver. The two largest ore bodies being exploited at pres¬ent by Outokumpu Oy are the Vihanti mine, which pro¬duces zinc, lead, and copper, and Pyhäsalmi, which con¬tains copper and zinc. Deviating from the sulfide ore types described earlier is the Hammaslahti copper ore located in the southeast-

Jan 1, 1982

By V. R. Degner

Given: the process tonnage, performance objectives, and plant floor area, the paper will outline the metallurgical and machine hydrodynamic scale-up procedures for translating the lab flotation test results to the design of a full size flotation machine installation, including the machine number, size, and arrangement. Machine selection considerations for rougher, scavenger and cleaner duty, and special considerations relative to specific applications, will be summarized where appropriate. The value of kinetic modeling in quantitative metallurgical (lab to full size machine) scale-up will be reviewed considering a coal installation, and design information for additional applications such as copper, molybdenum, iron, phosphate, and potash will be discussed.

Jan 1, 1986

By Gregory E. Korbin

The effectiveness of pre-reinforcement as an immediate stabilization measure as well as its contribution to the permanent stabilization of a tunnel were studied through the use of physical (Figure 1) and numerical models (1). Physical models were designed for the investigation of two pre-reinforcement systems: first, reinforcing far ahead of the main excavation (Figure 2); second, spiling reinforcement ahead of the face (Figure 3). In both cases, the use of reinforcement was responsible for permanently stabilizing an otherwise unstable opening. Data from the physical models were used to calibrate a numerical model from which additional information on long term behavior, methods to account for the capacity of a pre-reinforcement system, and the mechanisms involved were ascertained. These studies indicated that pre-reinforcement can stabilize a rock mass effectively as it reduces deformations and thereby deterioration due to strain softening, provides rock mass confinement leading to increased available strength, and maintains rock arch continuity allowing for increased tangential stress in the immediate vicinity of the opening. Field studies verified the capacity of spiling reinforcement to restrain initial deformations.

Jan 1, 1976

By W. T. Robertson

My charge is to review briefly "Coal In The Electric Utility Industry - Present and Future." Thus, I will not dwell on the overall energy picture, other than to express what most others involved in the energy picture know - we're in trouble! Several years ago, speaking to another engineering society, I said, "Much has been and yet will be said and written about the energy situation in our Country." What an understatement! The energy question has reached crisis proportions and is a top priority item at the highest level of government, Unfortunately, it will be in that situation for some time to come. Many factors created this complex problem, and we all share some of the blame. But I am perplexed when I read in the popular press that environmental factors are unrelated to the energy crisis when I know this to be untrue. In the recent past all forms of energy have been cast in the role of villain, particularly coal with its problems of surface mining, mine safety, acid water drainage, sulfur content, and a multitude of other adverse factors relating to the environment in one way or another. As you know, the sulfur situation has led to the closing of numerous mines, resulting in the lessening of our mining capacity. Today, along the Eastern Seaboard, 60 to 70 million tons of coal are displaced by imported oil, primarily to meet air standards. Even in the Midwest, utilities sitting on enormous coal reserves are converting to other fuels or hauling low sulfur coal thousands of miles from the western Mountain States. [We will hear more about this coal from another speaker on the program this morning.]

Jan 1, 1973

By C. M. McCulloch

More and more mining underground is being conducted using the longwall method. Likewise, many new surface mines use area or mountaintop removal methods. These methods can have a significant impact on surface and groundwater resources. The overall study of the effects on surface and groundwater from mining is referred to as the probable hydrologic consequences (PHC) determination of mining and reclamation. Collection and interpretation of information concerning groundwater and surface water quality and quantity, as well as detailed geologic analysis, is required to adequately define the impacts of mining. This paper discusses the present day requirements and methodology of preparing a PHC for a large mining operation in the eastern coalfields.

Jan 1, 1995

By Raj K. Rajamani

In ball milling the rates of breakage vary primarily with the size distribution of powder in the mill. In wet grinding viscosity of the slurry varies continually as size distribution changes and hence the breakage rates change. In this study a simpler estimation scheme is used to determine breakage rates in batch grinding. Using an approximate solution to the batch grinding equation, acceleration and deceleration of breakage rates of all individual size classes is determined when the grinding environment is varied. Experimental results with limestone and copper ore show time-dependent breakage rates under both dry and wet grinding conditions. In general the breakage rates increase for coarse sizes and decrease for fine sizes with increase in the fines present in the mill. Such variations have strong implications in closed-circuit grinding.

Jan 1, 1991

By K. Nuttall, S. Vijayan, A. J. Meinyk, R. D. Singh

For conventional applications, there is limited demand for rare earth elements as well as yttrium and scandium. But the emergence of new high technology applications such as supermagnets, lasers, and superconductors should result in significant demand for some of these elements. This article examines the anticipated applications and demands for rare earth elements over the next decade. It also looks at the implications on the use of available resources. In the context of a growing demand, process methods are reviewed for the recovery of rare earth elements from conventional and unconventional resources. And the article also discusses the challenges facing the mining industry in meeting this opportunity. Reserves and reserve base The rare earths (RE) are a homogeneous group of metallic elements occupying the area from lanthanum to lutetium in group IIIB of the periodic table. Yttrium and scandium are also included with the rare earths because of their chemical similarities and common existence in nature. These 17 elements and their atomic numbers are shown in Table 1. The rare earths are widely distributed in low concentrations throughout the earth's crust (Hedrick, 1985). They occur in many rock formations including basalts, granites, shales, and silicate rocks at concentrations of 10 - 300 ug/g. They also occur in more than 160 discrete minerals. Most of these are rare, but may contain as much as 60% rare earth oxides (REO). More than 95% of the REO occurs in three minerals: monazite and bastnasite for the light rare earths and xenotime for yttrium and the heavy rare earths. Apatite and multiple-oxide minerals, such as euxenite and loparite, are also commercial sources of the lanthanides and yt-trium. Rare earths do not occur in nature in the elemental state. And, except for scandium, they do not occur in minerals as individual compounds. Bastnasite and monazite are the two major minerals used commercially to supply most of the rare earths (Hedrick, 1985). Bastnasite is a key raw material source for the cerium subgroup elements. The largest known bastnasite deposit occurs with iron ore minerals in China. The second largest deposit is situated in California. Typical rock analyses of the fluorocarbonate mineral bastnasite deposit in California show about 15% bastnasite. The REO content of that is about 50%. Monazite is present in beach sands in many parts of the world. This includes India, Brazil, Australia, South Africa, the

Jan 1, 1989

By Stephen J. Reynolds

Arizona's geologic history is complex, resulting in a diversity of rock types and earth materials, including those of commercial interest. Regional variations in geologic history gave rise to three geologic provinces and an inequitable distribution of both metallic and nonmetallic mineral wealth. The Colorado Plateau is largely composed of flat-lying Paleozoic and Mesozoic sedimentary rocks and late Cenozoic volcanic fields and sedimentary deposits. Associated resources include gypsum, halite, sylvite, clays, specialty sand, flagstone, volcanic products, and aggregate. The adjacent Transition Zone features a large expanse of Proterozoic rocks, economically important Devonian and Mississippian carbonate rocks, and Tertiary volcanic and sedimentary materials. Nonmetallic resources in this province include facing and dimension stone, aggregate, decomposed granite, chrysotile asbestos, gypsum, clay, barite, fluorspar, zeolites, and limestone used for lime, cement, and railroad ballast. The Basin and Range Province has the most complex geologic history and, therefore, the most diverse assemblage of industrial mineral occurrences. These include halite, gypsum, clay, aggregate, decomposed granite, diatomite, zeolites, perlite, pumice, kyanite, limestone, marble, stone, and others. In addition, young stream deposits yield vast quantities of sand and gravel, Arizona's most economically important nonmetallic mineral commodity.

Jan 1, 1987

By John A. Herbst

Mathematical models of mineral processing unit operations have been developed and used for a variety of purposes. Models, defined as equations which mathematically approximate the behavior of process units, are being employed in simulators to evaluate proposed flowsheets, to investigate flowsheet modifications, to study the effect of variables on circuit behavior, to optimize the performance of circuits off-line, and to compare alternate control strategies (Mular and Herbst, 1978). Models developed for mineral processing operations may be placed in one of two general categories: phenomenological (based on mechanism) and. empirical (based on experimental data only). Dynamic models (including time as a variable) .are useful for control studies, while steady-state models (independent of time) are employed in flowsheet evaluations. Phenomenological models are potentially more flexible and accurate than empirical models. However, models constructed from theoretical knowledge are less easily developed compared to empirical expressions fitted statistically to experimental data. The latter apply only over the range of data acquired. Most often, models used in practice are the result of a combination of theoretical and empirical approaches.

Jan 1, 1979

By D. K. Jorgensen

The Bullfrog and Montgomery-Shoshone deposits, near Beatty, NV, have a combined drill-indicated reserve of 15.8 Mt (17.4 million st) of ore. Average grade is 3.5 g/t (0.103 oz per st) gold and 8.2 g/t (0.24 oz per st) silver. The deposits occur in Miocene volcanic rocks that underwent large-scale movement within a detachment-faulted terrane. The principal host to gold mineralization is a strongly welded rhyolitic tuff that experienced brittle deformation during plate movement. Open space fractures and breccia were filled with quartz, calcite, and adularia accompanied by lesser pyrite, gold, and acanthite. Gold occurs as micrometer-sized particles within and adjacent to the low-angle fault and along associated listric-normal and tear faults. The Bullfrog and Montgomery-Shoshone are volcanic-hosted, detachment fault-related, epithermal quartz calcite stockwork gold deposits. Bullfrog's minable reserve is 13 Mt (14.3 million st) of ore grading 3.8 g/t (0.11 oz per st) of gold. At Montgomery-Shoshone, 2.7 Mt (3 million st) minable tons at 2.5 g/t (0.072 oz per st) are present. Preproduction stripping has begun at the Bullfrog ore body. A 7.7-kt/d (8500-stpd) carbon-in-pulp (CIP) mill is under construction. In 1990, Bond Gold expects to be producing about 6.2 t/a (200,000 oz per year) of gold.

Jan 1, 1990

By Chester A. Rowland, David M. Kjos

INTRODUCTION Mineral ore comminution is generally a feed preparation step for subsequent processing stages. Grinding, the fine product phase of comminution, requires a large capital investment and frequently is the area of maximum usage of power and wear resistant materials. Grinding is most frequently done in rotating drums utilizing loose grinding media, lifted by the rotation of the drum, to break the ores in various combinations of impact, attrition and abrasion to produce the specified product. Grinding media can be the ore itself (autogenous grinding - primary and secondary), natural or manufactured nonmetallic media (pebble milling) or manufactured metallic media - steel rods, steel or iron balls, or a combination of autogenous media and steel balls (SAG milling). This chapter covers rod and ball mills utilizing manufactured metallic grinding media. MILL DESIGN The interior surface of rod and ball mills exposed to pulp and/or grinding media are protected from wear and corrosion by rubber, metallic or a combination of rubber and metallic wear resistant materials. Rod and ball mills essentially draw constant power, thus are well suited for use of synchronous motors with power factor correction capabilities as drive motors. A net of approximately 120 to 130 percent of running torque is required to cascade the charge in these mills. The pull-in torque is about 130 to 140 percent with the pullout torque to keep the motor in-step (in-phase) generally in excess of 150 percent. When rod and ball mill are started across-the-line the starting and pull-in torques result in inrush currents exceeding 600 percent which possibly result in high voltage drops. To deliver 130 percent starting torque to the mill the motor design must take into account the maximum anticipated voltage drop. Motor torque decreases as the decimal fraction of the voltage available squared. E.g., a motor rated 160% starting torque with a 10% system voltage drop will deliver 160% x or 129.6% torque to its output shaft When it is not possible or practical to start a fully loaded synchronous motor across-the-line it is possible to utilize the motor's pull- out torque to start the mill. By using a clutch, normally an air clutch. between the motor and the mill, the motor is brought up to synchronous speed before the clutch is energized. If the motor has an adequate amount (175 or greater) of pull-out torque the pull-out torque starts the mill without major disruptions on the electrical system. Since the energy release at initial cascade of the mill charge is an inverse function of acceleration time, a minimum acceleration time of 6 to 10 seconds or more is recommended to prevent damage to the mill or the mill foundation. Economics at the time of plant design and mill purchase determine the drive to be used. The simpliest drive is the low speed synchronous motor with speeds in the range of 150 to 250 RPM connected to the mill pinionshaft by either an air clutch or flexible coupling. Using a speed reducer between the motor and pinionshaft permits using motors having speeds in the range of 600 to 1000 RPM. In this speed range, if power factor correction is not required induction motors can be used; squirrel cage where there is no restriction on inrush current; slip ring where a slow start and low inrush current is required. Air clutches can also be used to ease starting problems with squirrel cage motors. In some areas of the world induction motors and starters are less expensive than synchronous motors at a sacrifice of motor efficiency and power factor correction. Dual drives, that is two pinions driving one gear mounted on the mill, become economical for ball mills drawing more than 3500 to 4000 horsepower (2600 to 3000 kilowatts). Further developments of the low frequency, low speed synchronous motors with the rotor mounted on the mill shell or an extension of one of the mill trunnions could improve the cost picture for these "gearless drives", making them practical for large ball mills. The percent of critical speed, which is the speed at which the centrifugal force is sufficiently large to cause a small particle to ad- here to the shell liners for the full revolution of the mill is given in mill specifications. Critical speed is determined from the following: Where D is mill diameter inside liners (specified in meters). Cs is critical speed in RPM. When D is specified in feet

Jan 1, 1998

By Dennis L. Boley, Francesco Gallavresi, Donald A. Bruce

The authors describe novel aspects of ground reinforcement and treatment as related to soft ground excavation for tunnels throughout the world. Insitu reinforcement for cut slopes (soil nailing), as underpinning (reticulated micropiles), and as direct tunnel support (infilaggi) is introduced. Ground treatment focuses on new aspects of permeation grouting (by the tube'a manchette system), and on jet grouting-a very powerful and positive new technique. Recent developments in equipment, materials, methods and instrumentation are reviewed, with special reference to major tunnelling projects in Italy and Singapore.

Jan 1, 1987

By Roland Hoet

Mine operators, conveyor system designers, consultants, and manufacturers have had opportunities over the past decade to utilize various actively controlled technologies to drive complex underground conveyor systems. These technologies included several electrical drive solutions, mechanical drive solutions, and hydromechanical (fluid coupling) drive solutions. All of these technologies have their inherent advantages and disadvantages, and only after several years of operation can mine operators fairly evaluate the overall benefits (short term performance and cost vs. longer term operational and maintenance costs) of any particular drive. Far too often in today's world, decisions for new equipment are made with inadequate regard to issues concerning serviceability and maintainability. Many of the newer electrical technologies (primarily AC variable speed drives) which have been used in recent years were selected based on the perceived desirable benefit from variable speed operation. This technology, however, which differs sign8cantly between various manufacturers, is in a constant state of evolution which puts into question the manufacturers' ability for long-term product support. In addition, various forms of this technology have also generated some undesirable operational issues, including reduced motor life, harmonics for the power system, and mine communications problems. This technology is also extremely current-limited, which results in problems handling overload conditions, a frequent occurrence often resulting from a decline in the coal recovery rate (conveying more rock than coal). The fluid coupling, however, is based on a technology which has been used successfully in underground conveyor applications for decades. Although the base hydrodynamic technology is well proven and has inherently beneficial characteristics on conveyor applications, Voith has continuously improved on this technology to meet the increasing demands of today's challenging conveyor haulage systems. Recognizing a need in the market for a reliable, actively controlled drive system, Voith Turbo began development in 1996 of a new, actively controlled coupling which was targeted specifically for the higher powered, complex underground conveyors. Voith introduced the new TPKL Fill Controlled coupling product to the market in 1997, and the first two applications for this new technology were on multiple drive mpper booster applications on longwall panel conveyors. Since the successful startup of these two conveyor systems in 1998, Voith has supplied over 200 TPKL couplings to the mining industry worldwide, with over 150 in US coal mining applications alone. This paper will provide an overview of the TPKL's capabilities, performance, and reliability based on the TPKL's impressive installation base and operational history.

Jan 1, 2004

By A. MacG. Robertson

INTRODUCTION The tailings, or solid waste, remaining after uranium has been extracted from an ore and the liquid wastes associated with it contain both radioactive and other substances which, if released to the environment, may have a detrimental impact on man and his environment. Although the radioactivity of the waste is of natural origin, the mining and milling process results in bringing the radioactive ore to the surface, changing its chemical and physical form, increasing its mobility and, therefore, enhancing the potential radiological exposure to man. Exposure to radionuclides released from a tailings impoundment, while small as applied to any one generation, can be made large by counting far into the future, large enough to be the dominant source of exposure from the nuclear fuel cycle, Cunningham (1978). Increasingly it is being found that where the prime concern was initially the radionuclide releases, the release of other pollutants and contaminants may be of equal or greater concern. While there is a definite benefit, at least to present generations, resulting from the recovery of uranium, current and long-term concerns require that consequential present and future releases be kept as low as is reasonably achievable. Design practice, to minimize this release, is currently passing through a technical revolution; precipitated by public and institutional concerns. New techniques and methods are, therefore, being actively sought and continuously implemented. Because of the complexity of the pollutant release mechanisms and the sitespecific nature of each impoundment site and tailings product, a wide variety of site selection and design options have been implemented or considered. It is often possible to design a number of satisfactory tailings disposal schemes which differ widely in nature and cost. This paper outlines the principal areas in which options are available and discusses some of these options. Both operating and post-decommissioning conditions are consi-

Jan 1, 1980