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By Khaled Morsy

Cementitious seals are made of foamed cements with strength ranging from 100 to 600 psi. These cementitious seals are usually used at locations where the seal will be subjected to some convergence, assuming that this material can absorb entry closure without compromising the structural integrity of the seal. Prior to 2006, Lake Lynn Experimental Mine (LLEM) conducted full-scale tests on various cementitious seals designed to meet or exceed the 20-psi horizontal static load requirements of the old 30 CFR1 75.335. Both hydrostatic and dynamic loading tests were conducted. The structural response (pressure and displacement readings) obtained from these tests were recorded. The stability of the cementitious seal is based on balancing the load applied to the face of the seal from the explosion against the shearing resistance at the seal/rock interface. Therefore, the properties of the seal/rock interface, such as stiffness, cohesion, friction, etc. are critical to determine the stability of a cementitious seal. These properties are usually assumed by the researchers in their models. This paper emphasizes the importance of having the correct properties of seal/rock interface in the numerical modeling. FLAC 3D models were developed to simulate Celuseal2 cementitious seals subjected to both hydrostatic and dynamic loadings. Using the hydrostatic and dynamic loading test data conducted at LLEM, the static and dynamic properties of the seal/rock interface were back calculated. The FLAC 3D models showed good agreement with the test results.

Jan 1, 2009

By D. R. Lowe

Silicic volcanic ash and its alteration product, bentonite (montmorillonite and cristobalite), occur widely within sedimentary phosphate deposits. The genetic link, if any, between volcanism and phosphate deposition has yet to be satisfactorily established The phosphatic member of the Santa Margarita Formation (upper Miocene) in northwestern Ventura County, California, consists of approximately 15 per cent volcanic ash and bentonite. Ash and bentonite units greater than one foot thick can be subdivided into a lower zone of airfall origin and an upper zone of mixed ash and terrigenous detritus washed in from surrounding land areas. This upper zone also contains up to 20 percent phosphate pellets. These thick volcaniclastic units are typically overlain sharply by thin beds (less than 6 inches thick) of relatively pure, silica-cemented pelletal phosphorite. The shelf basin in which the phosphatic sediments accumulated was characterized by quiet, reducing but not euxenic bottom waters; Abundant decaying organic debris, mainly diatoms, served as a reservoir of readily available phosphate. The sudden influx of a large volume of silicic volcanic ash into this basin and its subsequent alteration to montmorillonite had two profound effects on thechemistry of the interstitial and bottom waters: (1) during alteration magnesium was removed from these waters and incorporated into the montmorillonite lattice, and (2) the pH of these waters increased as alteration progressed Both of these effects led to the crystallization in the bottom waters of carbonate fluorapatite. This accumulated as thin phosphorite beds immediately above the volcaniclastic units.

Jan 1, 1972

By G. B. Misra

Though installations of main mine fans vary widely, the commonest installation is of a surface exhaust fan connected to an upcast shaft some distance below its collar by a horizontal fan drift bending sharply. downwards near its junction with the shaft. The junction of the fan drift with the shaft often causes considerable shock pressure loss if not properly designed. In one of the major coal mines in India circulating 180 m3/s of air through the mine a pressure drop of 229 Pa out of the total fan pressure of 568 Pa occurred at this junction while in a smaller gold mine circulating 9.4 m3/s it was 147 Pa out of a fan-drift pressure of 382 Pa. With larger mines circulating larger volumes of air, ill designed fan drifts can lead to considerable wastage of the power of ventilation. Shock loss at the junction of fan drifts with exhaust shafts depends on (1) the angle of deflection of the bend, (2) sharpness of the corners (both inner and outer) at the junction, (3) the degree of contraction of the flow-stream which depends on the cross- sectional area ratio of the shaft and the fan drift as well as the amount of leakage through the shaft collar. It must be noted here that the friction pressure loss in the bend is negligible compared to the shock pressure loss.

Jan 1, 1980

By F. Gonzalez, A. Zambrano, J. Schwoebel, S. Kravits

Significant lost time delays were experienced by Carbonifera de Nueva Rosita, S.A. de C.V. ("CNR") during mining development of the Pasta de Conchos Mine ("the Mine") near Nueva Rosita, Coahuila, Mexico. Furthermore, methane gas concentration in the return air course had exceeded 1.0 percent. Resource Enterprises, Inc. ("REI") was contracted by CNR to recommend an approach to reduce methane emissions at the Mine. In order to recommend a degasification approach, REI and CNR obtained geologic and reservoir characteristics of the Double coal seam, Olmos Formation. A vertical core hole was drilled to obtain core samples to determine gas content (average 8.4 cm3/gm) and to conduct a slug test to estimate permeability (34 md). This information was used to simulate gas productivity and drainage effectiveness. The simulation indicated that underground horizontal boreholes would remove significant quantities of gas in advance of mining in a reasonable period of time. Based on the results of the simulation study, an underground degasification drilling program was initiated at the Mine. In a six month period, five long in-mine degasification boreholes were drilled in advance of CNR's three to five years mining projections. Peak gas production from the five boreholes (approximately 2,750 cumulative meters) had exceeded 45,000 m3/D. Results to date have indicated a general reduction in methane concentration in the return air course below 0.8 percent.

Jan 1, 1993

By Mike D. Adams

Testwork was conducted on loaded carbon samples from a small gold mine in South Africa. It was shown that a 75% saving in reagent consumption in the Zadra elution circuit could be achieved by adopting a cyanide-free elution approach, i.e. by cutting back the NaCN level from 1 % to nil, and the NaOH level from 3% to 1 %. This process change was also shown to result in a 20% improvement in the elution kinetics. Furthermore, it was also shown that a 50% enhancement in elution rate over the current situation could be achieved by use of an eluant containing 0.5% NaOH and 0.15% NaCN, corresponding to an 84% saving in reagent consumption. A further improvement in elution kinetics was found to occur by increasing the NaCN level to 3%, but this would lead to a concomitant increase in reagent consumption, due to the decomposition of cyanide at high temperatures. The presence of base metals loaded onto the carbon was also found to have a significant effect on the elution. Copper tends to adsorb as Cu(CN)2- during the adsorption stage, and acid washing converts this species to CuCN. Copper in this form is not eluted during cyanide-free elution, whereas it is eluted during a conventional cyanide elution, consuming the initial cyanide in the process. The elution data was analysed and the fit to a simple model was verified.

Jan 1, 1995

By W. R. Mackenzie, C. A. MacDonald

Oxide copper was discovered in 1946 at Guelb Moghrein. Early work culminated in the construction in 1970, by a consortium headed by the Anglo American group, of a project producing copper concentrates from 1,000,000 tonnes per annum of oxide ore. The process used was the TORCO (Treatment Of Refractory Copper Ores) process, which reduced oxide copper minerals to elemental copper by roasting in fluidised beds at 800°C with salt and coal. The roaster product was then floated to yield a high grade smelter concentrate, which was exported. The project closed in 1976, due to low copper prices and increased energy prices, leaving an open pit, the old TORCO plant, a water pipeline, and more than 2,000,000 tonnes of tail­ings, which contained remnant copper, as well as an average of 3 git of gold. After several attempts to recommence operations at Akjoujt, recovery of gold from the old TORCO tailings was started in 1992 by a joint venture company known as MORAK (Mines d'Or d'Akjoujt). This company comprises General Gold Resources N.L. of Australia, who are the managing partner, SAMlN (La Societe Arabe des Mines d'Inchiri) and the International Finance Corporation. Because the tailings are high in copper (0.1-0.3% Cu), the project used the 'Hunt' process, which uses a combination of cyanide and ammonia to leach gold while suppressing copper extraction. The gold is recovered from leach liquor by carbon absorption.

Jan 1, 1996

By R. A. Holmes

Although manganese is a metallic element and is widely dispersed in nature, it never occurs except as a compound in combi¬nation with other elements. Use of such compounds in the production of glass is known to have occurred in early Egypt. The dioxide of manganese was considered a compound of iron until 1774 when C.W. Schule first recognized it as an element. In the same year, a Swedish mining engineer, J.G. Gahn, became the first to isolate manganese. In 1856 development of the Bessemer process of steelmaking gave economic importance to manganese, and later, in 1882 Robert Hadfield discovered the benefits of high manganese steels. GEOLOGY Physical Properties Elemental manganese is a silver-gray metal, resembling iron but harder and more brittle and used primarily in alloys (both ferrous and non-ferrous) and a wide variety of chemical compounds. Some of the physical properties of manganese include: melting point¬1 245°C; boiling point-2 150°C; density at 20°C-7.43 g/cm3; specific heat at 25.2°C-O.115 cal/g; latent heat of fusion-63.7 cal/g; hardness on Mohs scale-5.0; linear coefficient of thermal expansion from 0 to 100°C-22 x 10-6. Mineralogy There are over one hundred minerals that contain manganese. These minerals vary from those with compositions that are pre¬dominantly manganese to those having only minor percentages of manganese. Distribution of Deposits Manganese ore deposits are found worldwide and were formed in various geological environments, but only a rather limited num¬ber of deposits have high grade manganese ore in sufficient quan¬tities to be mined and utilized economically on an industrial scale. It is worth noting the fact that almost all of the significant deposits can be classified into two types of deposits: marine chemical sed¬imentary deposits, and residual (secondary) enrichment deposits. There are, however, a much larger number of geological types but these are not of commercial significance at this time. Sedimentary deposits are the most common and are usually stratiform or lenticular. Manganese minerals were formed by a chemical process during the deposition of marine sediments. They usually contain manganese oxides and carbonate minerals, some¬times interbedded together or with other sedimentary rocks such as limestone or shale. Examples of this type of deposit are the Russian ore bodies of Nikopol and Tchiatoura, as well as the Kalahari deposits in South Africa and deposits of Groote Elyandt in Aus¬tralia. Residual deposits were formed in a different way: by alteration of existing manganese deposits or by concentration of the manga¬nese minerals when other minerals were washed away by weath¬ering or ground water processes. The Nsuta deposit in Ghana, the Amapa deposit in Brazil, the Moanda deposit in Gabon, and nodules in the residual clays of the US Southern Appalachians are examples of this type of geological process. In the case of the Ghana and the Amapa deposits, this is only true for the outer layers of the deposit containing oxide minerals, the inner part being comprised of car¬bonate minerals including manganese carbonate, probably from marine origin. Some sedimentary and residual-type deposits have been metamorphosed, giving rise to small high grade ore bodies. These deposits are regionally metamorphosed, occurring in mar¬bles, slates, quartzites, schists, and gneisses. Some of these deposits, such as the Franklin, NJ, deposit are rich enough to be commercial without secondary enrichment; however, most of the exploitable deposits have been secondarily enriched. Due to the diversity and complexity of manganese deposits, both with respect to deposition and chemistry, a wide range of impurities are almost invariably present in the ores. Table 1 shows that the reserves (i.e., a measured resource that can be economically and legally extracted) are estimated at 814 x 106 tons of contained Mn, which equates to more than a 100 year supply at the current level of production. The reserve base is made up of the marginally economic reserves and sub-economic re¬sources and are some 4.5 times greater than the proven reserves. Also apparent from study of Table I is the fact that some 75% of manganese reserves are found in two countries, the USSR and South Africa. On the other hand, North America (i.e., the United States and Canada) have few significant deposits. The largest deposit, or at least one of the largest, in the United States is located at Chamberlain, SD. This deposit is sedimentary

Jan 1, 1994

By G. Le Bel

Discussion by G. Le Bel The paper proposes three methods to determine optimum lifetime of a mining project 1. The conclusion is that the three methods arrive at the same optimum production rate (by coincidence). It is also stated that: "The stochastic and option pricing models, in addition to providing a more realistic optimum mine life than the traditional NPV (net present value) calculation, showed that the example project has the potential for substantially higher return. By explicitly considering a project's potential risks, the stochastic or option pricing techniques can more accurately describe its probable investment performance." This discussion is intended to demonstrate that: •It is no coincidence that the three methods arrive at the same optimum production rate. • The stochastic and option pricing models do not provide a more realistic optimum mine life than the traditional NPV calculation. •The potential for a substantially higher return is misrepresented. First, a review of investment decision theory in mining is needed. Net present value is the preferred performance measure because of the flexibility offered when comparing various alternatives. However, it presents the following disadvantages: • The discount rate selection is not straightforward. • The NPV obtained represents a deterministic characterization of the variables included in the cash flow calculations, i.e. a single-point estimate. Discount rate selection The opportunity cost of capital represents the rate of return that would be obtained if the capital was instead invested in other opportunities considered to exist. Such opportunities must be bypassed if the available capital is invested in the project studied 2. If these other opportunities carry risk similar to the project under analysis (for example, if they are other mining projects), there is no need to add incremental [ ] risk factors. On the other hand, if these opportunities are represented by the acquisition of government bonds yielding 7%, a risk premium factor must be included. The types of risks associated with a mining venture are shown in Table 1. Together they represent the "business risk" of being a mining company. The individual project risk is important to investors if it differs substantially from the business risk of the company and that of the other investments in mining ventures that we must pass up to invest in this particular project. A risk premium or discount would then be required. This can be illustrated by the following example. Consider that a company has two investment alternatives: one is the Cavender hypothetical project located in Nevada, and the other is the same project located in a civil war zone of central Europe. The second project requires a risk premium factor on the discount rate. Conversely, a project showing highly uncertain returns that are negatively correlated with the returns of the firm's other assets may decrease the company's corporate risk. Deterministic character of NPV calculation The cash flows used in NPV calculations are obtained from a set of variables. These variables are estimated using one parameter obtained from the engineering studies. Each parameter is thus a single value that is often termed a "realistic" or "best estimate" as opposed to "optimistic" or "pessimistic." However, considering that each variable can assume a range of values between the

Jan 1, 1994

By Gaither H. Kitchell

Introduction Fire assaying is an ancient method of determining the amount of gold and silver in geological materials. Today's commercial, mining, school, and private fire assaying laboratories still use this basic assaying method. One of the primary reagents used to collect gold and silver from the ore is litharge (PbO), or lead oxide. The Federal Occupational Safety and Health Administration's (OSHA) and the Nevada Division of Occupational Safety and Health's (OSH) have a lead standard. It states that a person exposed to airborne lead at concentrations greater than 50 µg/m3 (1.4 µg per cu ft) of air over an eight-hour period has gone beyond the permissible limit for health safety. It is not uncommon to get airborne lead concentrations of 1400 µg/m3 (40 µg per cu ft) in the flux/sampling area or 900 µg/m3 (25 µg per cu ft) around the gas/ electric furnaces during the fusion and cupelling phases. Therefore, any individual working in these areas for more than 30 days per year without proper protection is a likely candidate for lead poisoning. Lead In A Human Lead enters the body as a toxic substance by breathing it into the lungs and upper respiratory tract and by getting lead particles into the digestive system through ingestion. Smoking, eating, drinking, chewing tobacco and gum, or wiping a lead-contaminated hand across the mouth are all potential ways forgetting lead into the body. Lead taken in large quantities can actually kill a person in a matter of days. This is rare, however. The real hazard of lead overexposure is for the unsuspecting person who works in an unsafe lead environment for months or years. This individual can slowly receive damage, sometimes permanent, to the central nervous system, gastrointestinal tract, kidneys, blood, gums, and reproductive system. Safe Blood-Lead Level The Lead Standard states that the maximum safe blood-lead level is 40 µg/100 g (40 µg per 3.5 oz) of whole blood. It recommends 30 µg/100 g (30 µg per 3.5 oz) if a person is of child-bearing age. People not working around lead products normally have a blood level of less than 10 µg/100 g (10 µg per 3.5 oz). A person not adequately protected can exceed 40 µg/100 g (40 µg per 3.5 oz) in a few weeks by fire assaying only 100 samples per day per week. Studies show that some individuals have developed lead-related diseases with blood-lead levels less than 80 µg/m3 (2.3 µg per cu ft). Lead Poisoning Symptoms There is a long list of symptoms associated with lead poisoning. The most common are: a prolonged, sweet, metallic taste in the mouth; loss of appetite; anxiety and irritability; weakness and dizziness; nausea and tremors; and insomnia. Preventive Measures Based on the lead standard, a number of preventive measures can be taken to ensure that fire assay laboratory personnel frequently exposed to lead are protected against overexposure. First, the actual lead concentration within the assaying area should be determined. In Nevada, one can contact the Department of Industrial Relations, Division of Occupational Safety and Health for assistance in monitoring any laboratory. The agency will also recommend ways to protect against lead. This agency does the monitoring and provides an educational class on lead safety. This type of agency can be found in other states. Commercial consulting firms are also available, but they are expensive. Regardless of the technique used to determine lead concentrations, it is most likely that the average fire assay area exceeds the 50 µg/m3 (1.4 µg per cu ft) lead concentration limit. This is considered unsafe.

Jan 8, 1985

By Werner Hofmann

INTRODUCTION The attempt to interprete lung cancer incidence caused by inhaled radon decay products in items of radiation dose raises the question of the relevant dose. The various dosimetric approaches published by now are characterized by an increasing complexity in the structure of the models used. Ranging from organ doses to microdosimetric specific energy distributions in the cells at risk, a significant trend from the macroscopic to the microscopic scale can be observed. Since tumors originate preferentially in the basal cells of the lobar and segmental bronchial epithelium, these cells are regarded as the critical target for inhalation carcinogenesis. The evaluation of basal cell doses is, therefore, the main objective of lung dose assessments. Various dosimetric models have been published in the past (Altshuler, Nelson and Kuschner, 1964; Haque and Collinson, 1967; Harley and Pasternack, 1972; Hofmann, Steinhäusler and Pohl, 1979, 1980; Jacobi, 1964; Jacobi and Eisfeld, 1980; James , Greenhalge and Birchall, 1980). Due to incertainties of physical and biological parameters involved and the application of different anatomical and physiological models the claculated doses are varying up to one order of mangitude. Independent of the choice of these dosimetric models applied to the calculation of lung doses, deposition, clearance and resulting dose are affected essentially by the properties of the inhaled aerosol as well as by personal characteristics. Both the properties of the exposed individual as well as of the inhaled environmental atmosphere have to be considered in radiation protection. It is the main objective of this paper to illustrate the influence of both parameter sets on basal cell doses by varying the above parameters. PERSONAL CHARACTERISTICS Though it might be more convenient for radiation protection calculations, the biological "man" cannot be represented by a uniform standard man. In Tab. 1 these personal characteristics which cause the variability of man are listed together with the region of their effectiveness. In the following the influence of these parameters will be discussed with regard to lung dose assessments. Besides these factors the great biological variability of all anatomical and physiological parameters involved as well as pathological alterations due to lung diseases cause additional variations in lung dosimetry. [ ] Age Age can be considered as the most important personal factor influencing the anatomical structure of the lung between birth and about 15 years of life. This period is characterized not only by an enlargement of already existing respiratory units but also by structural changes. Besides these anatomical alterations deposition is strongly dependent also on respiration parameters, such as tidal volume (TV) and respiratory frequency (RF). Whereas RF decreases with progressing age in an exponential manner, TV increases significantly resulting finally in a growth of the respiratory minute volume (RMV). Also mucus clearance in the infant might be more effective than in the adult, though no reliable experimental data are available. Superposing all these age-dependent changes mean basal cell doses are higher for children by about a factor of 2 than for adults living in the same radioactive environment (Hofmann, 1981). In the adult the following alterations of respiration standards with age are reported: total lung capacity diminishes with age, functional residual capacity is unchanged or increases with age and the dead space rises slightly with age (ICRP, 1975). The influence of these lung capacities on deposition, however, can be regarded as insignificant. Due to the ageing process mucus velocities my be considerably smaller in older people. This effect can also be superposed by the simultaneous influence of ciliatoxic effects of cigarette smoke and air pollutants or other bronchial diseases. Since the lower age limit for occupational exposure is about 18 years, age can be disregarded in the uranium mining industry for the determination of radiation doses, though lung cancer induction is significantly dependent on age.

Jan 1, 1981

By H. Lyn Bourne

Daily everyone depends on the great variety of glass products, so much so that glass is often taken for granted. In fact most people do not realize how versatile glass has become. Consider the various uses and then try to imagine a day in which we are not influenced by glass. Common uses include container ware, table ware, window glass, lead crystal, automobile glass, and fiber glass. Several less common, but important, uses include laboratory ware, pharmaceutical, TV bulbs, light bulbs, glass ceramics, optical glass, fiber optics, and laser glass. Corning, Inc., a leader in specialty products, uses nearly 1 000 different compositions to manufacture about 60 000 different products (Edwards and Copley, 1977). Glass is such a complex product that-definitions vary and exceptions can be found for most definitions. Glass is an inorganic amorphous (non-crystalline) solid. Most glasses are produced by melting of a mixture of oxide raw materials, and then cooled to room temperature. Soda-lime-silica composition.s account for about 90% of all glasses melted (Anon, 1973). The properties of the glass product come mainly from its chemical composition. All of the different glasses require melting a combination of raw materials and forming the molten material into the desired shape. Both the melting and the forming processes use sophisticated technology and these technologies require experts to manage these production systems. The manufacturing process is continuous and takes place in tonnage quantities, so adjustments in the batch to achieve the desired finished product requires a great deal of expertise. Raw materials are fed to the batch mixing area in very large quantities (tons in most cases). As a result, impurities in the range of 0.1% result in addition of that impurity within the molten glass in kilogram amounts. More than twenty different industrial minerals are consumed in the manufacture of various kinds of glass (O'Driscoll, 1990). This chapter describes the major and minor ingredients of the various glass batches. It discusses the roles of the various oxides in the glass batch and most importantly considers the mineral raw materials which supply the glass industry. Each of the raw materials is described in detail in other chapters so the geology and mineralogy sections are kept brief here. Container glass, by far, accounts for the most production; followed by flat glass, fiber glass, and specialty glass of which table ware accounts for the greatest tonnage. [Table 1] shows the general production data for 1987 through 1990. Statistics for many of the uses do not appear because production volumes are small compared to the major uses. The glass industry is organized in four categories: containers, flat glass, fiber glass and specialty glass. The US Department of Commerce, Bureau of Census, publishes production data about the glass industry in three different categories: 1) glass containers, 2) consumer, scientific, technical and industrial glassware, and 3) flat glass. The Bureau has very complete statistics about the glass industry in these three categories but they report production data in different units according to industry standards. Therefore, [Table 1] gives the production data in dissimilar units. The production of most glass articles follows similar steps. The raw materials are mixed and the resulting batch is fed into the furnace. In soda-lime-silica glasses melting begins between 600 and 900°C. At these temperatures CO, and other gasses are released which create bubbles in the molten glass. To remove the bubbles and insure complete melting the temperature is raised to between 1 500 and 1 600°C. This is the melting-refining stage during which the refining agents in the glass batch serve to aid in the release of gas bubbles, homogenize the melt, and prevent the formation of scum on the surface of the molten liquid. At the conclusion of the melting-refining stage the glass is too fluid for working and the melt is cooled to about 1 100°C to attain the proper viscosity for working and forming to begin. After the glass article has been made, it must undergo annealing (slowly and uniformly reheated and cooled) to remove thermal stresses that were created during the forming process.

Jan 1, 1994

By M. Kalin, C. Steinberg

We have worked on several flooded pits from coal-mining activities in the former East Germany, as well as ones associated with hard- rock mining, including the B-zone pit discussed in the above technical paper. We found the paper to be a useful summary, but, unfortunately, it failed to give an adequate comparison of the physical limnology of the flooded pits, which is an essential component. While the title suggests that the primary focus of the review is physical limnology, it appears that it is essentially pit-lake chemistry being presented. Physical limnology requires that factors such as fetch, latitude, light penetration, relation to ground water table, methods of flooding and the physical shape of the pits be defined. These physical aspects of a pit interact with the chemical and biological processes taking place in it, all of which contribute to the character of a water body. Few of these physical aspects are presented, however. The conclusion that the authors reach suggests that meromixis may be a condition that would serve as an effective containment mechanism for contaminants in a pit. Although this may be desirable, such limnological conditions are not clearly supported by the data presented for any of the pits. These data should be summarized to facilitate comparison between the same structural units of the pit water - the epi- and metalimnion for example. The thermocline depth is a reflection of the physical forces mixing the water body, and pit dimensions affect these forces. Due to the use of different scales in Figs. 2 through 5, it is difficult to determine whether the thermocline is at the expected depth, because the fetch is not given. Moreover, the status of a water body cannot be determined unless measurements cover a period of at least one year, and depth profiles are completed to represent the entire depth of the pit. This shortcoming is most notable in the case of the Berkeley pit, where data are given for depths of only 20 and 35 m (66 and 115 ft), although the pit is reported to be 242 m (794 ft) deep. Limnological data to define the status of the pit water have to be collected at regular intervals, for the same parameters. The authors present temperature measurements for 1-m (3.3-ft) intervals, but fail to use that interval for other parameters, such as dissolved oxygen or, in some cases, for contaminant concentrations. Furthermore, the profiles for the deepest part of the pit display only part of the picture, because pits are rarely conical. Profiles can be considered to represent the status of a water body only after other stations in the pit have been monitored regularly and the consistency is determined. For example, fresh water, which can enter a pit at any depth, would interfere with the proposed meromictic conditions. Similarly, organic material at the bottom of a pit, such as the fish-waste deposited in the Gunnar pit, contribute to oxygen consumption. Oxygen depletion alone is not indicative of meromixis. It is interesting to note that the Dpit arsenic concentrations could possibly be slightly higher than the B-zone pit concentrations at depth, although this is difficult to determine accurately when a log scale is used for the D-pit and not for the B-zone pit. In our investigations, we noted arsenic removal in the B-zone pit bottom water, which was due to the formation of particles that are relegated to the newly forming sediment in the bottom of the pit. Particle-carrying contaminants form due to a combination of geochemical and biological factors and TSS contributed from erosion of the upper parts of the pit walls, whereas the settling out of particles from the water column is controlled by the physical conditions or turn over, for example. during ice cover in the B-zone pit. Although meromictic conditions for flooded pits may be desirable at decommissioning, this would depend largely on the physical conditions of the pit, because, under no circumstances, would this water be of desirable ground-water quality. Under meromictic conditions, acidity, if an environmental issue, may be reduced by microbial acid-neutralizing activity, and several heavy metals may form more or less stable sulphitic compounds. These may stay suspended in the water if conditions are such that they are not relegated to the sediments, i.e., in the absence of turnover. These processes do not take place in meromictic conditions only, but meromixis does require autochthonous and/or allochthonous organic substrate supplies, which are generated under aerobic conditions. Specific limnological (biological, chemical and physical) features of the pit lake under consideration have to be defined, such that water quality parameters can be predicted, and the objectives of the decommissioning activities, environ-

Jan 1, 1999

By John D. Abbatt, H. B. Newcombe

The Eldorado Epidemiology Project formally began in late 1978. It consists of a retrospective cohort study, to be followed by and to leave in place the mechanism for a prospective cohort monitoring program. These present and future activities are intended to merge into one another. The current study includes all Eldorado employees past and present for whom records are available. The objectives of the undertaking are - 1) to obtain cause-and-effect, dose-response data with which to evaluate the risks to workers in radon and radon daughter containing atmospheres, and to provide additional quantitative information on which to base possible improvements in working conditions; 2) to identify any dead employees of E.N.L. whose cause of death suggests that a potential compensation claim right exists for their survivors, and to similarly identify living ex-employees of E.N.L. whose work histories and states of health suggest potential compensation claim rights. The nature of the study has been determined by the history of Eldorado, which will be described briefly. Eldorado began (as Eldorado Gold Mines) in the late 1920's, operating relatively unsuccessfully in Manitoba. In 1930-31 the emphasis shifted from gold to uranium, and what became the Port Radium mine was first staked. From the very early 1930's until 1942 the company's purpose was almost entirely devoted to the mining of pitchblende - uranium ore - from the Port Radium site, and the extraction of radium from this ore at the Port Hope refinery in Ontario, a process from which the uranium was a largely stockpiled byproduct. In 1942 the company was requested by the Canadian government to accelerate the production of ore, and of uranium. At the same time, all its stockpile of uranium (then being stored in silos as a "waste" product which might later "come in") was acquired for the Manhattan Project. In 1944 the company shares were bought by the Canadian government and the company itself became Eldorado Mining and Refining (1944) Limited; it has operated as a Crown corporation ever since. The name was changed to Eldorado Nuclear Limited in 1968. The Port Radium mine was closed in 1960, and since 1953 the Beaverlodge uranium mine complex has operated on the northern shores of Lake Athabasca. Radium production was discontinued in 1954 when the radium circuit was taken out of the refinery, and since that time the refinery's products have been various types of refined uranium (uranium dioxide, uranium trioxide and uranium hexafluoride) plus metallic uranium. The refinery, of course, processes the company's own yellowcake but as it is one of only five refineries in the western world, most of its work consists of custom refining for a large variety of customers. In addition to the mining and the refining operations, there have been three other divisions involved, and these are, respectively, Aviation, R. & D., and Exploration, in addition to the financial, corporate, administrative and support activities. MATERIAL AND METHODS The human study population (Abbatt, J.D. et al., 1980) consists of all Eldorado employees who have ever worked for E.N.L. and for whom records are available. The total nominal roll to December 31, 1980 is approximately 21,000 and consists of employees of the Mining, Refining, R. & D., Aviation and Exploration Divisions, as well as a relatively small number of other employees (Head Office, etc.). The basic epidemiologic design, as has been mentioned, is for a retrospective cohort study merging into a prospective cohort study, and depending very heavily upon automated record linkage and file matching. The original design called for an initial assembly of the bulk of the nominal roll, prior to the first of two matches with the National Mortality File. The first of these two matches is now complete and the second is to be separated from it in time by 18 months to two years. The second match will be the definitive match prior to the analysis, the interpretation of the data, and the publication of the results. The period between the two matches was designed to permit completion of the nominal roll, including: - addition of previously missing individuals and groups, elimination of duplicates, and amplification of identifying information, - assembly of work histories and exposure information for each individual, - digestion and application of lessons and modifications resulting from the first match with the National Mortality File at Statistics Canada, - preparation of files for the definitive second match. The analysis of data will be carried out by the National Cancer Institute of Canada Epidemiology Unit based at the University of Toronto. This group, with whom Eldorado Nuclear has a memorandum of understanding, have for a variety of reasons, including their familiarity with record linkage and their expertise, been members of the Project Team since

Jan 1, 1981

By K. A. Brunk

This paper describes Newmont's research, operations, history and experience with pre-treatment of preg robbing carbonaceous ores. The chemistry, physics and kinetics of chlorine treatment are described. Present operations, control strategy and projected changes are discussed. Included is a summary of the adsorption of chlorine into pulps and off-gas scrubbing.

Jan 1, 1987

By G. Swartz, R. J. Brison, R. A. Wyman, J. P. Vandenhoeck, S. E. Khalafalla

Magnetic fluids are commonly composed of ultrafine submicron particles of magnetite (Fe3O4) dispersed in either a kerosene or a water carrier medium with oleic acid as a protective colloid. The unique property of these fluids is that when the magnetic particles are attracted to a magnet the carrier medium moves along with the particles so that the liquid also appears magnetic. The availability of a fluid whose gross behavior changes sharply in a magnetic field without affecting its rheologic characteristics is becoming critical for many technologic applications. About two gener¬ations ago suspensions of relatively large, micron-sized ferromagnetic particles in oil proved useful in clutches, brakes, and dashpots. These were called magnetic clutch materials, and their viscosities were highly dependent upon the applied magnetic field, in contrast to true mag¬netic fluids which retain their fluidic characteristics under all applied fields and field gradients. While the term "ferrofluid" was used by Rosensweig and Kaiser&apos; to designate a magnetic colloid composed of a dispersed magnetic ferrous material, the more general term, "mag¬netic fluid," is preferred. This is because these fluids may contain ferro- or ferrimagnetic substances, such as cobalt, nickel, gadolinium, dysprosium, or magnetic ferrites in carrier liquids, such as hydrocar¬bons (kerosene), silicones, water, fluorocarbons, etc. Preparation of Magnetic Fluids Magnetic fluids were first prepared by Papell and Faber, at the NASA Lewis Research Center, Cleveland, Ohio, by tumbling ferrite materials for several weeks in a carrier medium (such as kerosene) and a dispersing agent (such as oleic acid) with steel balls. Rosensweig et al.1 compared the stability of their ferrofluids obtained from both metallic iron and the magnetic oxides of iron, Fe3O4 and yFe2O3. They found that, although the saturation magnetization of iron is 3.5 times greater than that of magnetite, its colloidal solutions deterio¬rated much more rapidly. The iron particles were undoubtedly rapidly oxidized to a nonmagnetic state due to the enormous surface area of these colloidal particles. Because the properties of these fluids are highly dependent on particle size and may acquire opposite characteristics by small incre¬ments in that size, more controllable methods of preparation have been developed recently by Khalafalla and Reimers.6 In one method metastabilized pyrophoric wiistite is ground to colloidal size in a kerosene oleic acid mixture, and then it is disproportionated to colloi¬dal magnetite and iron at temperatures just below the eutectoidal temperature of wüstite stability (570°C); thus, t < 570°C 4 FeO t > 570°C Fe + Fe30, (1) Because of its antiferromagnetic characteristics, the precursor wüstite is much easier to grind than magnetite. Another method3 avoids grinding entirely and utilizes a peptiza¬tion technique from ferrous materials in the molecular state of aggrega¬tion. This latter procedure has resulted in preparation of strong fluids at considerable savings in cost.

Jan 1, 1985

By David M. Parkes, Mike Fisher

In 1947, coal production in Western Canada was 10 Mt (11 million st) which predominantly came from 120 underground mines. By 1968 production was down to 1 Mt (1.1 million st). Production in 1981 was back up to 29 Mt (32 million st), but only 1.5 Mt (1.7 million st) of the total was from underground mines. In fact, because of competition from open-pit mines, only two underground mines were operating in 1981-the McIntyre and B.C. Coal mines. While several other underground mines are being planned, this article will deal with only the two in production. Geology The geology in Western Canada is frequently complicated; hence only more regular deposits are mined. Coal is generally thick, often steeply pitched and usually soft or well cleated. The 5000-km (3,100-mile) coal belt that runs from the Yukon to Mexico is well developed in Western Canada. It is divided into two distinct regions-the Rocky Mountain Lower Cretaceous coals and the mostly uniform level Upper Cretaceous coals of the plains area to the east. Isolated pockets of coal occur at Vancouver Island and Hat Creek. Hat Creek&apos;s massive 300-m (984-ft) thick geologically recent lignite deposit is 250 km (155 miles) inland. Geography The infrastructure of Western Canada is shown in Fig. 1 along with the locations of the two mines. Both rely on exports of premium low volatile metallurgical coal mostly to the Pacific Rim. The rail distance from both mines to port is 1100 km (684 miles)-accounting for a significant portion of the sales cost of the coal. Mining Methods Two main mining methods are used-room and pillar and hydraulic. Longwall has been attempted and is being considered again. In the past, a simple hand method used gravity to help mine most of the coal on steep pitches. Levels were driven in the seam, rising slightly to assist in draining. On the advance, mining would start at the upper level, usually from adits driven in the side of the mountain. Rooms or angles were driven up 100 m (328 ft) at a suitable angle for the coal to flow down. On retreating out of the level, the pillars would be taken, starting from the highest point, using batteries to stop coal or rock flushing down the room. Batteries consisted of three to six stout wooden posts set at an angle to resist material flow. Coal loading was directly from chutes at the bottom of raises into 1- to 2-t mine cars hauled by diesel or battery locomotives. Often output was restricted by the supply of empty cars. Mechanization began in the 1960s but was difficult in these conditions. Mines such as Canmore and Coleman continued operation into the 1970s but closed because steep seams, high methane emissions, and faulting made mining difficult. McIntyre Mines The McIntyre mines are located 360 km (224 miles) west of Edmonton, Alberta, in the foothills of the

Jan 4, 1983

By Donald Whittaker

Severe climatic conditions in mines are normally associated with working at depth. More precisely, it is a matter of working in regions of high strata temperature, since, for example, some coal mines in the Ruhr have strata temperatures at 1000 m which are matched only at 3 times that depth in the South African gold mines. In Britain we are perhaps fortunate in encountering strata temperatures in our deeper coal mines some 10-15 K lower than at the same depth in the hot mines of the Ruhr. Nevertheless the problems of high temperatures and humidities in UK mining operations, which in the past have been confined to a few specific sites, have in recent years become more widespread, and there is every reason to suppose that the trend will continue. Clearly strata temperature is not the only .causative factor. Long ventilation circuits serving districts remote from the shaft must also play a part, while the heavy use of machinery and the rapid, rates of excavation of modern mining methods are obviously important. It is necessary to understand the mechanisms of all such factors, and to measure their magnitudes and fluctuations, if remedial measures are to be properly designed or predictions made which are accurate enough to be of use in ventilation planning. This paper presents the results of a long-term (and continuing) investigation carried out in several mines to measure the major sources of heat and moisture on longwall districts and trunk conveyor roadways. The variation with time of these sources is reported, and the resultant effect on the climate is considered. In their investigations of the heat exchanges occurring in a whole mine Oakes and Hinsley (1955-56)1 listed and estimated the magnitudes of a large number of heat sources. Some of these, namely autocompression of the air in the shaft, diesel engines and compressed air mains, do not apply to the present investigations, which refer to longwall districts with conveyor transport and no compressed air supply. Others, such as oxidation of coal and, desorption of methane, have not been taken into account in the measurements, but are discussed later. One other source, the importance of which was pointed out by Gracie and Matthews (1975)2, is the coal on the conveyor, a form of strata heat emission, but one which is strongly dependent on the rate of coal production. The heat emissions measured in the present investigations were the energy consumed by electrical machinery, the heat conducted from the strata and the heat lost by the conveyed coal. Most of the emitted heat was removed from the district by the ventilation air, and was measured by continuously recording the enthalpy of the air at fixed stations. The heat removed by service water, supplied for machine cooling and dust suppression, was also measured. Account was of course taken of the relatively minor changes in level around the districts, in terms of the potential energy gained or lost by the coal and by the ventilation air (autocompression).

Jan 1, 1980

By Michael L. Cramer, Kunsoo Kim

INTRODUCTION The Columbia River Basalt beneath the Hanford Site is one of several rock types being considered by the U.S. Department of Energy for the first commercial high-level nuclear waste repository. The Basalt Waste Isolation Project (BWIP) has been carrying out a comprehensive investigation to assess the feasibility of constructing a repository in basalt and to develop technology required for repository engineering and site characterization. Development of a nuclear waste repository requires a number of design considerations not usually necessary in the planning of conventional underground structures. Principal among these is the thermally induced stress field resulting from waste emplacement. This thermal stress, super- imposed on the preexisting in situ- and excavation- induced stress fields, needs to be evaluated in the design process due to the sensitivity of waste emplacement density to this factor. The nature of this thermally induced stress field is dependent on several factors, including the temperature distribution around the repository openings, the thermal properties of the rock mass, and the deformability of the rock mass. Re1iable performance of the repository structure is largely determined by the ability to under- stand the above rock mass characteristics and predict the underground opening response to waste emplacement based on this understanding. To gain an understanding of this rock mass behavior in a repository condition, the BWIP has conducted a large-scale heated block test in basalt at the Near-Surf ace Test Facility (NSTF) on the Hanford Site. This paper presents the results from the elevated temperature phase of the block test in which the thermal, mechanical, and thermo- mechanical response of the closely jointed basalt rock mass was evaluated as a function of stress and loading orientation at varying temperatures up to 200 oC. SITE GEOLOGY The NSTF test areas, including the block test site, are located in the entablature zone of the Pomona basalt f low. The Pomona flow entablature is structurally typical of most flows in the Columbia River Basalt Group in that it is characterized by long, undulating, polygonal columns up to 2.4 m in length. Columns vary from 15 to 30 cm in diameter, averaging about 20 cm. Over their length, columns can vary in dip by 150 to 200. The column structures are dissected by subhorizontal cross joints that are generally discontinuous and seldom cross columnar joint boundaries. Spacing of the cross joints also averages about 20 cm. A representative joint pattern taken from mapping of the tunnel wall near the block test site is shown in figure 1. Application of the Rock Mass Rating System (Bieniawski, l979) to the block test site yielded an overall value of 62. The corresponding value from application of the Q-system (Barton et al., 1974) is 8.7 (Cramer and Kim,1985). The NSTF is approximately 50 m below the surf ace. However, this depth is sti1l above the water table and conditions are generally dry. Interstitial water exists as the result of percolation of meteoric water from the surface.

Jan 1, 1986

By M. Measures, W. A. Napier, C. Pomroy, J. M. Jardine

INTRODUCTION In most uranium mines the concentration of uranium in the ore is low enough that inhalation of dust does not present a radiological problem. Conversely in the mills there is a potential inhalation hazard from inhaled uranium in concentrated form, namely "yellowcake" and other compounds intermediate between the ore and the final product of the mill. It was generally assumed that the solubility of yellowcake placed it in the category of Class D materials. This plus the fact that the uranium is non-enriched led health physicists to assume that the potential health hazards were a result of the uranium&apos;s chemical properties rather than its radiological properties. Bioassay programs have thus been limited to routine urine sampling at a weekly or monthly frequency. In most cases when a high reading was obtained, subsequent sampling within one or two days showed a rapid return to low levels, therefore tending to confirm the class D nature of the material. Two developments over the last few years have however suggested that modifications to this simple bioassay program may be necessary and practical. Firstly, a number of studies on the solubility of uranium mill products, from ore to yellow cake, in simulated lung fluid (Eidson A.F., Mewhinney J.A., 1980) have shown that some of the material is not class D, but class W or even Y. This raised the possibility that, while the urine levels rapidly decreased, indicating rapid excretion of the class D component, the W and Y components remained in the lung. Thus an unsuspected lung burden could have been accumulated. The second development, the ready availability of [in vivo] counting facilities with which to make direct measurements of uranium lung burdens, offered a means of confirming the hypothesis of unsuspected lung burdens. A study was therefore initiated to correlate lung burdens with urinary excretion. METHOD A total of 79 subjects from 3 uranium mills participated in the study. They were brought to the Ottawa laboratories of the Radiation Protection Bureau in groups of 4 or 6, over a period of several months. In Ottawa, [in vivo] thorax measurements were performed, and a urine sample collected. Each subject also brought with him a urine sample that had been collected the previous day. All samples were split, for analysis by both R.P.B. and the mill laboratory. [Concentrations of Uranium Dust] Results obtained by mills A, B and C for concentrations of uranium in air at various locations are given in table 1. Samples taken at mill B were obtained using continuous sampling with a midget impinger over a six hour period. Samples taken at mills A and C were 5-minute gravimetric samples. [Subject Selection] The subjects were selected to represent a wide range of work history in terms of both length of employment and type and location of job, as shown in table 2.

Jan 1, 1981

By I. Jashnani, J. R. Lawter, D. B. Lindsay

INTRODUCTION It is a generally recognized obligation of owners and operators of underground mines in the United States to protect the health of miners against the potential carcinogenic effect of airborne alphaemitting radionuclides, in particular the shortlived radioactive daughter-products of 222Rn. In meeting this obligation, a number of strategies are available, and it is largely up to the operator to decide what combination of methods he will use. Because the officially accepted theory of the mechanism by which radon and its short-lived progeny cause cancer of the respiratory system, the objective in controlling this health hazard is to limit as far as possible the inhalation of the three daughter products, 218Po, 214Pb, and 214Bi. (214Po, the fourth nuclide in the chain, is so short-lived that its alpha-decay occurs almost instantaneously after the beta-decay of its parent, 214Bi.) The reasoning in this theory leads to the conclusion that the alphadecay of radon itself causes essentially negligible physiological damage, and that the amount of daughter product activity attributable to decay of radon within the respiratory system is also very small. As every ventilation engineer in this business knows, however, focusing remedial actions exclusively on the daughter products themselves is choosing the hard way, and will probably never lead to effective control of this health hazard in underground mining activities. The reason for this troublesome fact can be seen in Figure 1. Let us say that we have air containing 222Rn and its short-lived daughters in near-equilibrium, a not-uncommon condition in the air of a poorly ventilated underground mine, and that we wish to purify it by removing only the toxic daughter products. If we have been very thorough in our purification efforts, we might expect to achieve a 99% reduction of the Working Level (WL) measurement. Figure 2 allows us to examine closely the early regrowth of WL&apos;s in this freshly cleaned air. Within the first five minutes, for instance, the WL&apos;s are back to 10% of their full equilibrium value, and ten minutes later the level has more than doubled and is on its way to an almost complete defeat of the clean-up effort by the end of the next hour. It is quite clear from this simple illustration that no matter how effective an air-cleaning system may be if it is directed only at the selective removal of the toxic trio, 218Po, 214Pb and 214Bi, its beneficial effect will be quite temporary. A truly effective attack on the problem must always include methods aimed at the control of the unruly parent, radon. Then, even if its progeny have an inalienable "right to life", their brief lives will not be spent in the miners&apos; lungs. The object of the present paper is to show how state-of-the-art environmental air

Jan 1, 1981