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By A. W. Hall

Cylindrical plastic scintillators were investigated for efficiency in detecting neutron-induced prompt gamma rays. Scintillator performance was compared on the basis of half-resolution and peak-to-trough ratios for gamma spectra obtained from Co-60 (1.17 and 1.33 MeV), Th-228 (2.62 MeV), and PuBe (4.43 MeV). Various sizes of Pilot Chemical scintillators (types B, F, M, and Y) were tested. The best half-resolution, 7.7 percent for PuBe, was achieved with a 5-by 5-inch Pilot Y?scintillator and dual photomultipliers. Comparison with sodium iodide (NaI) scintillators and the use of plastic scintillators for on-stream analysis of sulfur in coal is discussed. Plastics were found to be unsuitable for on-stream analysis of materials having complex prompt gamma ray spectra; however, they could conceivably be used for those yielding Simpler spectra.

Jan 1, 1974

By M. L. Whisman

The Bureau of Mines developed and tested in the laboratory several innovative techniques for reclaiming used lubricating oil. These processes included percolation through both chemically treated clay and ion-exchange resins, distillation through batch and continuous wiped-wall vacuum apparatus, treatment with solvent extraction systems, and chemical removal of impurities with chelating agents. In each treatment, the criteria of evaluation was oil recovery and reduction of acidic and metallic components. Both vacuum distillation and solvent treatment ranked high in their abilities to remove acidic and metallic components of the used oil with good oil recoveries. A combination of the two techniques gave the best overall results in terms of quality evaluations made by established bench tests. The methods were not ranked according to economic practicablity.

Jan 1, 1974

By M. Shabbir

A study was made to determine the optimum conditions for precipitation of uranium from mill solutions using hydrogen peroxide. Precipitation tests were made on both synthetic and actual mill solutions. Parameters studied included amount of hydrogen peroxide, initial pH, reaction pH, time, and temperature. Also investigated was the effect of varied amounts of vanadium, molybdenum, and sulfate in the test solution on uranium precipitation and product quality. The optimum conditions for complete precipitation and high product quality were (1) the use of 150 percent of the stoichiometric requirement of hydrogen peroxide, (2) initial pH of 1.0, (3) reaction pH between 3.4 and 5.0, (4) 4 hours reaction time, and (5) ambient reaction temperature. The excess hydrogen peroxide requirement is partially dependent on the amount of impurities present in the feed solution. The hydrogen peroxide process appeared applicable to treatment of the several mill eluate and strip solutions tested. The experimental studies also indicated that the hydrogen peroxide technique gives substantially better product quality than that produced by ammonia precipitation.

Jan 1, 1974

By P. T. Brooks

A process for extracting 69 percent of the vanadium from weathered Nevada dolomitic shale containing about 1 percent V205 was developed on a laboratory scale by the Bureau of Mines. The process essentially is comprised of salt roasting, leaching with dilute sulfuric acid, solvent extraction, and precipitation of vanadium as ammonium metavanadate. Carbonaceous unweathered shale was less amenable to treatment. A preliminary cost estimate for mining and processing 1,500 tons per day of weathered shale indicated a production cost of about 1 dollar per lb of V205. Considering recent sales at nearly $1. 75 per lb of contained V205, larger scale testing to obtain more definitive process design and evaluation data may be warranted.

Jan 1, 1974

By Russell R. McLellan

As part of an effort to develop new or improved placer mining technology in the Tertiary gold-bearing channel gravel of northern California, the Bureau of Mines conducted investigations at the old Badger Hill placer mine in Nevada County, Calif., to collect data and information regarding drilling and sampling methods and deposit characteristics. Sampling studies involved the collection and processing of 400 tons of large-and small-volume samples from drill holes, underground workings, surface pits, and blasthole rounds. A total of 355 samples averaging 2,296 pounds per sample provided reasonably accurate data for analysis of the gold distribution. These studies indicated that the bulk of the gold is within 40 feet of bedrock in stacked, lenticular zones of cemented gravel that are largely confined to the relatively narrow, meandering course of the deepest portion of the bedrock channel. Drilling studies involved the testing of truck-mounted rotary, buckett and vibratory drills, none of which proved to be a completely versatile tool for sampling quickly and reliably both consolidated and unconsolidated gravel..

Jan 1, 1974

By Mark I. Copeland

This study was conducted by the Bureau of Mines to determine the effect of steel reheating practices in burning natural gas on the amount of silicon required to prevent the formation of copper on steels containing up to 1 wt-pct Cu. Formation of copper, which causes surface hot shortness, was readily prevented by as little as 0.3 wt-pct Si and by 2 vol-pct excess oxygen in the furnace atmosphere when reheating steels containing up to 0.8 wt-pct Cu. Up to 0.8 wt-pct Si content and careful control of reheating conditions were necessary for steels containing 1 wt-pct Cu. Best conditions for these steels were reheating to 2,200° F (1,205° C) in burning gases containing 2 vol-pct excess oxygen, and then to higher temperatures in gases of 6 vol-pct excess oxygen. Slag and mold wash were not detrimental on steels reheated for 8 hr by a soaking-pit-type furnace schedule, but they were problematical on steels heated for 2 hr by a pusher-type furnace schedule. The effect of silicon contents on scaling rates also was determined.

Jan 1, 1974

By James J. Snodgrass

The Bureau of Mines has investigated vibration levels produced by blasting at four underground sites to establish how such factors as type of explosive, delay blasting, charge weight, and geology affect amplitudes of ground motion. A summary of the work is presented and the results of further analysis of the data are discussed. Square root scaling was found applicable to two of the underground sites and could be applied with minor error to all the sites. Comparison of empirical propagation equations in the different rock types indicates that although the site effect is apparent, the combined data may be used as a basis for engineering estimates of vibration amplitudes from subsurface blasting in many different rock types. Recommendations for predicting and minimizing vibration amplitudes from underground blasts are given.

Jan 1, 1974

By C. Daniel Kealy

Dissolved and suspended solids are present in the free water of tailings ponds. This Bureau of Mines study was designed to identify the influences of the slime zone in preventing these solids from reaching the environment outside the tailings pond. The finite-element method was used to determine the rate of discharge of subsurface water from the Van Stone tailings pond in northern Washington. The slime zone was sampled and tested for the first time, and results were interpreted and incorporated into the mathematical model. Computer results were verified by installing and monitoring piezometers in the field and by a simulated (16- by 1/2- by 3 foot) laboratory model. Output from the numerical model defined critical seepage zones and revealed that proper pond design and maintenance can reduce pond seepage losses to a minimum. Minimization of seepage requires maintaining the pond water level over the slime zone. Sufficient physical, chemical, and limnological data were collected and analyzed to conclude that the only realistic reflection of synergistic effects is obtained by study of the indigenous biota in combination with quantitative chemical and physical data. Proper planning and management of the milling and waste disposal operations are the key to minimal pollution.

Jan 1, 1974

By W. T. Abel

The Bureau of Mines tested 48 materials for their ability to absorb H2S from hot simulated producer gas (1,000°-1,500° F). The material found best from the standpoint of absorption capacity, durability, and amenability to regeneration was sintered pellets of 75 percent fly ash-25 percent Fe203. The performance of this absorbent under simulated and actual conditions is described. The effect of absorbent composition, absorbent temperature, steam content of the gas, and tar vapors and dust in producer gas is discussed.

Jan 1, 1974

By E. D. Calvert

The room temperature tensile properties of commercially pure titanium and seven titanium alloys prepared by skull casting were determined in the as-cast and heat-treated conditions. Data were compared with property data from tensile tests on wrought alloys of the same compositions in the as-worked and heat-treated conditions. The alloys evaluated were Ti-5Al-2.5Sn, Ti-6Al-4V, Ti-6Al-4V-lSi, Ti-6A1-2Sn-4Zr-2Mo, Ti-6A1-6V-4Zr-4Mo, Ti-6A1-6V-2Sn, and Ti-11.5Mo-6Zr-4.5Sn. Test specimens were prepared from both static and centrifugal castings and from plate fabricated by forging and rolling vacuum-melted ingots. The data indicate that the alpha and alpha-beta alloys have strength properties in the as-cast condition that are reasonably close to the strength properties of their wrought counterparts in the as-worked condition. An exception to this was the Ti-6A1-6V-4Zr-4Mo alloy for which insufficient data were available to form any firm conclusions. Fine-grained cast structures of Beta III (Ti-11.5Mo-6Zr-4.5Sn) were shown to be generally stronger in the as-cast condition than the wrought alloy in the as-worked condition except for the yield strength of one structure that was unusually low. Heat treatment of this alloy produced properties that were unpredictable. Indications are, however, that optimization of heat treatment parameters for each cast structure could produce strength properties equal to that of wrought materials.

Jan 1, 1974

By M. B. Shirts

Bench-scale studies were made on a reductive hydrometallurgical procedure to convert chalcopyrite flotation concentrate to copper metal or a readily leachable sulfide. Reductive conversion of chalcopyrite and dissolution of iron and sulfur were accomplished in hydrochloric or sulfuric acid solution by the addition of metallic copper, iron, or lead. Use of metallic copper as the reductant enabled extraction of 95 and 46 percent of the iron and sulfur, respectively. The products were ferrous iron, hydrogen sulfide, and a copper sulfide. Use of metallic iron or lead as the reductant enabled extraction of 95 percent of both the iron and sulfur. The products obtained with metallic iron or lead were ferrous iron, hydrogen sulfide, and metallic copper.

Jan 1, 1974

By W. L. Brien, O&apos

Molybdenum alloys with good strength properties at elevated temperatures were produced by the powder metallurgical internal oxidation method previously applied to tungsten and known as oxyreaction strengthening. Commercial molybdenum powders were blended with 0 to 10 pet of a reactive powder, ZrMo2. The effects of composition, blending procedure, and sintering conditions on strength properties at elevated temperatures were studied. Strengthening was attributed to zirconium in solid solution with molybdenum and to the presence of submicrometer particles of Zr02. Several alloys had tensile strength and stress-rupture properties com-parable with those of the best commercial alloys. The maximum tensile strengths obtained were 92 kpsi at 1,200° C and 53 kpsi at 1,316° C. The maximum stress-rupture life at 30 kpsi and 1,200° C was 145 hours.

Jan 1, 1974

By Harold H. Fukubayashi

The effect of various zinc electrowinning solution impurities on the surface morphology of deposited zinc was investigated. Impurities studied included Al, Ag, Cd, Co, Cr, Cu, Ge, Mn, Ni, Sb, Sn, Ti, Pb02, PbSO4, and HC1. Also, the effect of animal glue, gum arabic, and Na2SiO3 additives on the deposited zinc surface structure was studied. Results were compared with deposits from a pure electrolyte consisting of H2SO4 and Zn+2, 200 and 65 gpl, respectively. Zinc was deposited on a Al cathode, 99.9 pct pure, using Pt anodes. Time, temperature, current density, and impurity concentrations were con¬troller The bulk of the tests were conducted at 40° C and 75 A/ft2 (82 mA/cm2). A scanning electron microscope (SEM) was used to examine the surface morphology. X ray diffraction techniques were used to determine crystal orientation and nondispersive X-ray spectrometer analyses were employed in an attempt to locate impurity concentrations on the zinc deposit when pitting or re-solution occurred. The impurities were categorized by their effect on current efficiency, morphology, and apparent mechanism of H2 evolution from the cathode.

Jan 1, 1974

By G. L. Hundley

An anhydrous chlorination process has been developed by the Bureau of Mines for the production of copper, ferric oxide, and sulfur from chalcopyrite. The first part of the process is a chlorination step in which elemental sulfur and a mixture of iron-copper chlorides are produced. This paper describes the second step of the process in which the copper and iron chlorides are reacted with oxygen to selectively convert the iron chloride to ferric oxide and chlorine leaving the copper in the chloride form. The chlorides are pulverized and dropped countercurrent to a flow of oxygen in a vertical 20-cm-diam. reactor at 800° C. By leaching with brine, the copper chloride may be separated from the insoluble iron oxide and reduced to copper powder by electrowinning. It has been demonstrated that 70 to 80 pct of the iron can be converted to oxide in a single-stage operation with a chlorine content in the offgas of 80 pct. After removal of the oxygen, this chlorine could be recycled to the chlorination step. A two-stage operation will convert 98 to 99 pct of the iron in the mixture to insoluble oxides. The offgas from the second stage contains 70 pct chlorine.

Jan 1, 1974

By Lewis V. Wade

This report provides background information concerning a mine roof simulator currently being considered by the Bureau of Mines. The simulator is a mechanical device with the ability to simulate the forces and displacements associated with mine roof over an area 20 by 20 feet. The topics covered in the report include a conceptual description of the system, definition of system capabilities, discussion of how such capabilities were decided upon, description of available control modes, and a comparison between the mine roof simulator facility and similar facilities existing elsewhere.

Jan 1, 1974

By Henry E. Blake

The Bureau of Mines has been engaged in a continuing research effort to develop processes for increasing the recovery and utilization of fluorine from low-grade resources. This current research has shown that over 98 percent of the fluorine in phosphate rock is extracted when the ore is treated with excess phosphoric acid in the presence of water vapor at 150° to 180° C. More than 80 percent of the fluorine can be recovered as fluosilicic acid, which can then be converted to commercially useful hydrogen fluoride or fluorspar by previously developed Bureau processes. Extraction of P205 from the ore was about 98 percent in batch tests and 90 percent in semicyclic tests.

Jan 1, 1974

By F. P. Miknis

Previous studies at the Bureau of Mines have shown that broad-line nuclear magnetic resonance (NMR) techniques have potential applications for rapid evaluation of oil-shale deposits. In a continuation of this study the techniques of pulsed NMR have been applied in a similar manner. The basis for the pulsed NMR oil-shale assay method lies in the assumption that the free induction decay (FID) amplitude following a 90° pulse is proportional to the potential oil yield. This assumption was tested on two groups of oil-shale samples, numbering 141 and 263 samples, from two different oil-shale cores. For both groups of samples a small number were selected as calibration samples. Free induction decay amplitude measurements were made on the 141 and 263 samples. The best least-squares regression line was obtained for the calibration samples, and the oil yields of the remaining samples were calculated using the slopes and intercepts obtained in the regression analyses. The agreement between measured and calculated oil yields was good, the indexes of determination being 0.93 and 0.89 for the groups of 141 and 263 samples, respectively.

Jan 1, 1974

By George S. Koch

A mathematical simulation model has been devised to guide the layout of underground mine workings, drill stations, and drill holes that are established in order to search for tabular ore bodies. Developed and tested for elliptical ore shoots in fissure veins in the Galena mine, Coeur d'Alene district, Idaho, the model can also be applied to ore bodies contained within sedimentary beds (for instance, many types of uranium, copper, and gold ore bodies) or other tabular structures. Programed for a time-shared digital computer, the model contains both stochastic and deterministic variables. Stochastic or natural variables include the number of ore shoots and their sizes, orientations, locations, and values. Deterministic or controllable variables include (1) locations and costs of workings; (2) drill-station locations and costs; and (3) drill hole azimuths, inclinations, lengths, and deflections, if any. For various assumptions about the stochastic variables, the model is run while the controllable variables are changed deliberately. Thus, layouts are devised to determine the percentages of the total number of assumed ore shoots found at different costs. In order to choose among the various layouts, cost-effectiveness measures are calculated.

Jan 1, 1974

By T. C. Wesson

The need for elemental-analysis information on coal mine dust for use in health and safety research prompted this study by the Bureau of Mines. Neutron-activation and X-ray fluorescent techniques were used to obtain five-element analysis (silicon, aluminum, iron, calcium, and magnesium) on 444 samples from 68 coal mines in 10 States. From these analyses, the average composition of the dust in coal mines was determined. The contribution of the primary dusting material (limestone dust) to the makeup of coal mines was shown. Regional differences in mine-dust composition were indicated.

Jan 1, 1974

By R. L. Schmidt

Research conducted over the past 20 years in France, Great Britain, and the United States on the use of the large-hole burn cut has established cer¬tain advantages for this system. Advantages include longer pull and more complete fragmentation from blast rounds. However, research is needed to establish a set of parameters for optimum performance. As part of the Bureau of Mines Advancing Mining Technology for Marginal Resources program, the Twin Cities Mining Research Center, Twin Cities, Minn., acquired a horizontal rotary drill capable of boring holes up to 24 in. in diameter. This was used for a series of underground experiments at White Pine mine, White Pine, Mich., during 1973. Exceptional results were obtained with a 12-1/4-in void hole that yielded up to 18 ft of pull in a 10- by 20-ft drift, Fragmentation was excellent, and the compactness of the muck pile facilitated loading.

Jan 1, 1975