Uranium Ore Mining Research Articles

The effect of grain size on the radon emanation rate

Tailings produced during mining and milling of uranium ores represent potentially large volumes of low level radioactive materials. A typical environmental problem associated with mill tailings is radon emanation. Covering tailings is widely applied to reduce radon exhalation rate. In this paper, the fractal theories and field covering tests are used to study the fractal characters of size distribution of six types of covering materials, including waste rock, sand, laterite, kaolin, mixture of sand and laterite, and mixture of waste rock and laterite, and their influences on radon exhalation. The size distributions of uranium tailings and the six aforementioned covering materials all exhibit a good fractal structure. The contents of fine grain increase with the increasing value of fractal dimension. The results of field radon measurement show that the radon emanation rate of tailings without covers is 14.7–18.6 Bq/m2 s. Covering tests were carried out of the six abovementioned covering materials with thickness of 0.4 m, 0.8 m, 1.2 m, 1.6 m and 2.0 m. The results indicate that the application of these materials for cover layers can decrease the radon exhalation rate markedly. The effectiveness of a cover layer in reducing radon exhalation is related to its fractal texture of size distribution. Under the same thickness conditions, the attenuation coefficient of radon exhalation rate increases with the increasing fractal dimension of size distribution of covers. The empirical expressions of the attenuation coefficients in relation to fractal dimension D of size distribution and thickness x of covers is obtained for evaluating the effectiveness of final covers for uranium tailings impoundments.

(n,f)-radiography as a means to investigate plants for their contamination with natural and technogenic uranium

Plants which grow in an area where uranium mining took place have been investigated for their uranium content by applying neutron-fission radiography [(n,f)-radiography]. The uranium was either assimilated by the plant from uranium-bearing soil or deposited at the leaves by uranium-bearing dust particles. Human activities like mining and refinement of uranium ores release technogenic uranium in the environment and increase the concentration of this α-emitting element. The technogenic uranium contributes to radioactive pollution. In addition to the natural amount of uranium in dust, water and the fertile (humus) soil layer, the technogenic uranium may increase the effect of uranium on the human organism. In order to perform efficient radiation protection, one has to obtain knowledge about the sources of radiation. The discovery of open sources which release uranium to the environment is of great importance because of the large biological effect of the α-particles emitted by the uranium. Leaves, roots and soil have been sampled at different locations in the territory of a former uranium ore mine, in the surrounding area and in a forest at the edge of the city of Ronneburg, where a small plot is known for its high natural uranium concentration. The plastic foil “Lavsan” was used as track detector, and the irradiation was performed with a fluence of 10 16 neutrons cm −2. (n,f)-radiography applied to plants yields information about the presence of local α-emitting sources of uranium and their location. The density of the fission fragment tracks enables the estimation of the uranium concentration.

Influence of Shallow Mine-Workings on the Radon Concentrations in Houses: A Problem of Old Mining Regions

Abstract In some regions of the German New Federal Lands, residues from early mining characterise the radiological situation and can also influence the radon concentration in buildings. Construction on waste rock with increased radium concentration, the use of waste rock as building material and construction above shallow mine shafts and adits are important in this connection. In Saxony, for instance, one has to reckon with probably hundreds of buildings that may be influenced by radon from shallow mine workings. Very short-term changes of radon concentrations in buildings over several orders of magnitude was well as their close temporal correlation with the underground airflow clearly indicate influences from underground. In Schneeberg and Schlema, fluctuations of radon concentration in buildings of several 10,000 Bq.m-3 within one hour were observed. In Schneeberg, the old mine was ventilated artificially by installing a ventilator with an output volume of 500 m3min-1. Thus the radon concentration in buildings of the central city area has been reduced. In Schlema, the radon rich shafts of early mining are ventilated at present by the still active ventilation system of the suspended uranium ore mining. In 1992, during the first six months, 4.5 x 109 m3 of mine air with a radon activity of 6.3 x 1014Bq were extracted from the mine. If the mine ventilators are switched off, radon concentration in buildings over mine shaft increases sharply by two orders of magnitude.

Influence of Shallow Mine-Workings on the Radon Concentrations in Houses: A Problem of Old Mining Regions

In some regions of the German New Federal Lands, residues from early mining characterise the radiological situation and can also influence the radon concentration in buildings. Construction on waste rock with increased radium concentration, the use of waste rock as building material and construction above shallow mine shafts and adits are important in this connection. In Saxony, for instance, one has to reckon with probably hundreds of buildings that may be influenced by radon from shallow mine workings. Very short-term changes of radon concentrations in buildings over several orders of magnitude was well as their close temporal correlation with the underground airflow clearly indicate influences from underground. In Schneeberg and Schlema, fluctuations of radon concentration in buildings of several 10,000 Bq.m-3 within one hour were observed. In Schneeberg, the old mine was ventilated artificially by installing a ventilator with an output volume of 500 m3min-1. Thus the radon concentration in buildings of the central city area has been reduced. In Schlema, the radon rich shafts of early mining are ventilated at present by the still active ventilation system of the suspended uranium ore mining. In 1992, during the first six months, 4.5 x 109 m3 of mine air with a radon activity of 6.3 x 1014Bq were extracted from the mine. If the mine ventilators are switched off, radon concentration in buildings over mine shaft increases sharply by two orders of magnitude.

Cancer Factories: America's Tragic Quest for Uranium Self-Sufficiency

This government-bashing book deplores the lack of safety in the mining of uranium ore and selected other events. The author uses a broad brush to condemn the Atomic Energy Commission (AEC) and the US Public Health Service (USPHS) for abuse of discretionary authority in pursuing a risky national security policy involving a with the devil. This pact was allegedly a conspiracy of silence from 1945 to 1978, which resulted in the deaths of hundreds of uranium miners from lung cancer. The author cites alleged injuries in several other cases, such as mock germ warfare tests over cities, the Tuskegee syphilis experiment, and a number of radiation experiments, which he attributes to similar abuses. The book includes no interviews with persons directly involved in the pact. Knowledge of their motives and attitudes would be important. The four main points on which the book's thesis rests are (1) most radiation scientists

Transfer of210Pb and210Po to the environment during mining and processing of uranium ores

Transfer of210Pb and210Po from an uranium mine and mill to the environment was studied by measuring their concentrations in different stages of uranium extraction technology, in waste products from the mill and in environmental waters. A slightly modified radiochemical method was used for210Po and210Pb determination.

Problems of Anthropogenic Influences upon the Landscape in North Bohemia

The paper treats of harmful influences of the industrial sprawl, of ecological processes and phenomena interfering with socio-economic functions of the North Bohemian landscape. Great attention has been paid to special ecological problems related to open-cast mining, brown-coal preparation, uranium-ore mining, development of power stations, chemistry, land other industrial branches. According to the degree of anthropogenic influences owing to complex multi-line land use and conforming with ecological aspects, three types of regions have defined in the North Bohemian region.

Exposures from mining and mine tailings

The mining, milling and tailings management of uranium ores results in environmental radiation exposures. This paper describes the sources of radioactive emissions to the environment associated with these activities, reviews the basic approach used to estimate the resultant radiation exposures and presents examples of typical uranium mind and mill facilities. Similar concepts apply to radiation exposures associated with the mining of non-radioactive ores although the magnitudes of the exposures would normally be smaller than those associated with uranium mining.

Dissolution rate of uraninite and uranium roll-front ores

The dissolution rate of uraninite crystals and of uranium roll-front ore samples has been measured in bicarbonate solutions at 25 degrees C, pH 7.0 to 8.2, and variable oxygen pressure. The rate law determined for uraninite crystals in highly undersaturated solutions is d[U]/dt = (kA/V)(O 2 ) (super 1/2) . A more complete rate law applicable over all uranium concentrations up to saturation is d[U]/dt = (kA/V)(O 2 ) (super 1/2) (U s - [U])/U s , where A is the surface area in cm 2 , V is the volume of solvent in liters, [U] is the measured molal concentration of U(VI) in solution, U s is the saturation concentration, (O 2 ) is the partial pressure of oxygen in atmospheres, t is the time in minutes, and k is the rate constant with a value of 4.9 (+ or -2.2) X 10 (super -5) (mole)(l)(m) (super -2) (atm) (super -1/2) (min) (super -1) . In this specific system, the rate-limiting step for uraninite dissolution is cleavage of the oxygen-oxygen bond in adsorbed oxygen. Parabolic rate behavior observed in some of our experiments is attributed to rapid initial dissolution of hexavalent oxides and fine-grained material. Our derived rate law for uraninite crystals applies very well to our dissolution data for uranium roll-front ores. Our rate law and experimental approach can be used to model the following processes: the formation and migration of roll-front ores, solution mining of uranium ores with oxygenated, bicarbonate solutions, and dispersion of uranium about mining sites and ore and tailings dumps.

Modern trends in the development of hydrometallurgical processes for extracting uranium from ore

The authors conduct a review of hydrometallurgical procedures for the mining and processing of uranium ores and the extraction of uranium from the feed material, including leaching, crushing, ion exchange, oxidation, solid-liquid separation, and other techniques. Leaching solutions as well as ion exchangers and oxidizers are comparatively assessed for their effects on the purity and properties of the product as well as on the mining and processing environment. Water recirculation in feed materials plants is discussed from the standpoint of water conservation and pollution abatement.

Uranium effects on the growth of soybean (Glycine max (L.) Merr.).

Some naturally occurring radionuclides accumulate in appreciable amounts in plants, adversely affecting their growth. One such radionuclide is uranium, which is released to the environment from the mining and processing of uranium ores and the increased use of phosphate fertilizers. Because phosphate fertilizers are commonly used in agriculture, there is a need to evaluate uranium uptake by crop species. Hence, the present study was conducted to measure uranium taken up by soybean during germination and early growth and to determine its effects on the germination and chlorophyll content of the leaves.

Application of Solution-Mineral Equilibrium Chemistry to Solution Mining of Uranium Ores: ABSTRACT

Modern methods of solution mining are typically accompanied by gains and losses of mass via reagent consumption by rock-forming minerals and subsequent clay-mineral formation. A systematic approach to alleviation of such problems involves the application of leach solutions which are in equilibrium with the host-rock minerals but in disequilibrium with the ore-forming minerals. This steady state can be achieved by solution composition adjustments within the systems K2O-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O. Uranium ores from the Grants mineral belt of New Mexico containing 0.15 to 1.0% U3O8 were collected for investigation. Small-scale (<= 1 kg) column leaching experiments have been conducted to compare results of conventional leaching systematics with those obtained with solutions in equilibrium with the matrix minerals. Application of these principles will have considerable bearing on future in-situ leaching of uranium ores. End_of_Article - Last_Page 693------------

Letters to the editor

I must take issue with several statements in your March 1976, editorial. It does not follow that because I advocate the development of nuclear power that I am an advocate of the arms race, nor that I advocate wasteful consumption. I believe that the mining of uranium ore and the ultimate disposal of radioactive wastes imposes less of an exploitive burden on the earth than the available practical option, which is the consumption of fossil fuels. I most resent the statement, "… nuclear power proponents unquestioningly and without discussion assume…" I personally find the evidence that electric energy consumption will increase to be persuasive. I did not arrive at that conclusion without question or discussion, and I cannot believe that the thousands of engineers who share my view are the naive, sophomoric technologists your statement implies.

Accumulation of Natural Radionuclides in the Bottom Sediments and by Aquatic Organisms of Streams

AbstractThe accumulation of natural radioisotopes by aquatic organisms and bottom sediments was studied in two small rivers, one uncontaminated and the other polluted by effluents of uranium ore mining and milling.Parabolic regressions between the water and uppermost sediment content of both uranium and total beta activity (corrected for 40K content) is presented and demonstrates the water cumulative capacity of organically rich sediments. For 226Ra no significant differences between sediments with different organic content were found. The 226Ra content of bottom sediments is expressed as a power function of radium and calcium concentration in the water.In the given reaches, 53% and 85% of uranium and over 90% of 226Ra and total beta activity (corrected for 40K) was accumulated in the upper two centimetres of sediments and biomass of aquatic vegetation. Filamentous algae, plankton, aquatic bryophyta and macrophyta from the present and other published data showed rather higher cumulation capacities as compared with bottom sediments.

Radium-226 liberation from uranium ore processing mill waste solids and uranium rocks into surface streams. II. The effect of different chemical composition of surface water.

The control of the radioactivity level of surface water contaminated by radioactive waste from uranium ore mining and processing revealed higher concentration of dissolved radium in places several kilometres far from the place of the outlet of the wastes than in the outlet itself. After the finding that the pH of surface waters does not play the main role in releasing radium from the sediments, we experimentally studied the influence of inorganic salts concentration. Homogenized and dried samples of uranium ores and sediments were shaken with distilled water together with 1 N, 0.1 N and 0.01 N concentrations of BaCl2, SrCl2, MgCl2, CaCl2, LiCl, NaCl, KCl, (NH4)2SO4, Na3PO4, K3PO4 and MgCO3 salts. It was found, that 95–100% of radium bound in sediments was released in 1 N solutions of KCl and NaCl salts, dependent on their structure and mineralogical composition. Positive effect on the leachability of radium has also CaCl2 solution.

Radium-226 liberation from uranium ore processing mill waste solids and uranium rocks into surface streams. I. The effect of different pH of surface waters.

Intensive uranium ore mining and processing cause increasing contamination of surface waters with natural radioactivity not only of a pertinent residing region, but often of large areas. Most of the radioactive wastes penetrating into surface waters (mine waters, effluents from uranium ore processing mills, wash down from dumps and overburdens) contain radioactive isotopes bound before all to sedimenting matter. This paper presents the results of experimental studies of the dependence of radium release bound in radium ore and sediments on different concentrations of hydrogen ions in surface waters. Dried homogenized samples of uranium ore and sediments containing 226Ra to 14 pCi/g, 84 pCi/g and 540 pCi/g were shaken for 15, 30, 60, 180, 300 and 480 min with water of a pH modified in the range of 1–13. Radium was leached in 15–30 min of shaking in the maximum amount when pH was 1 (to 22%). With the increasing of pH the amount of released radium decreased to pH 9.

Radioactivity in Foods

There is little doubt that atomic energy will assume an important role in our civilization, and it is appropriate that future possible hazards should be evaluated. At the present time, it can be concluded that there is no reason for any change in our nutritional habits or food technology as a result of fall-out contamination. Research must continue, however, so that recommendations can be made to minimize the intake of radioactive contamination should this ever become necessary. Although environmental contamination now existing is due almost entirely to fall-out from nuclear weapons, peacetime operations may become increasingly important as sources of radioactive contamination. In addition to fall-out, small quantities of radioactive materials may be released into the environment as a result of such operations as mining of uranium and thorium ore and fuel processing; reactor installations in power plants, submarines, ships, and aircraft (normal operations and accidents); and radioisotope applications in

Radioactivity in foods.

There is little doubt that atomic energy will assume an important role in our civilization, and it is appropriate that future possible hazards should be evaluated. At the present time, it can be concluded that there is no reason for any change in our nutritional habits or food technology as a result of fall-out contamination. Research must continue, however, so that recommendations can be made to minimize the intake of radioactive contamination should this ever become necessary. Although environmental contamination now existing is due almost entirely to fall-out from nuclear weapons, peacetime operations may become increasingly important as sources of radioactive contamination. In addition to fall-out, small quantities of radioactive materials may be released into the environment as a result of such operations as mining of uranium and thorium ore and fuel processing; reactor installations in power plants, submarines, ships, and aircraft (normal operations and accidents); and radioisotope applications in

Radioactive Contamination of the Environment in the Cincinnati Area

use of radioisotopes in industry, medicine, and research institutions ; mining and chemical processing of uranium ore; nuclear reactors for power production or research ; chemical processing of spent reactor elements for the recovery of nuclear fuel ; fallout due to testing nuclear devices. Information pertaining to the location of these sources in a particular area is made known to state boards of health