Uranium sources

The bacterial leaching of uranium minerals is complex. This is because of the fact that uranium minerals are not sulfides and are not, therefore, directly attacked by the bacteria. However, the uranium sources usually have a substantial pyrite content which can be bac-terially oxidized to give an acidic ferric sulfate solution which is an effective leaching medium for uranium minerals. The reactions involved in the system can be shown in a simplified form as ... 

Uranium dioxide occurs in mineral uraninite. Purified oxide may be obtained from uraninite after purification. The commercial material, however, also is recovered from other uranium sources. Uranium dioxide is obtained as an intermediate during production of uranium metal (See Uranium). Uranyl nitrate, U02(N03)2, obtained from digesting the mineral uraninite or pitchblende with concentrated nitric acid and separated by solvent extraction, is reduced with hydrogen at high temperatures to yield the dioxide. 

Uranium source of a particles (embedded in a lead block to absorb most of the radiation)... 

In vivo counting systems are calibrated using tissue-equivalent phantoms. These phantoms have shapes similar to the human torso and are made of polystyrene or other tissue equivalent material. Standard uranium sources of known activity are inserted into the phantom at locations where uranium would be expected to accumulate in a human body (DOE 1988). Relationships are determined between the uranium activity measured by the detection system and the known activity in the phantom (DOE 1988 HPS 1996). 

In cases of radioactivity measurements of an a-emitter such as Am or uranium source electrodeposited onto a metal disk, a simple 2k a counting with a gas flow proportional counter is practical, and a reasonable accuracy can be expected. If the applied potential to the proportional counter is set at the a-plateau region, the counter responds only to a-particles. Since the backscatter of a-rays is small (a few percent) compared with that of P-rays, and the value can be estimated as a function of the atomic number of the backing material, the radioactivity, (, can be readily obtained from the observed counting rate, n, by the following simple relation ... 

Stuckless, J.S. and Nkomo, I T., 1978. Uranium-lead isotope systematics in uraniferous alkali-rich granites from the Granite Mountains, Wyoming implications for uranium source rocks. Econ. Geol., 73 427-441. 

World Health Organization (WHO) (2001) Depleted Uranium Sources, Exposure and Health Effects. Geneva Department of the Protection of the Human Environment, World Health Organization. 

Sea water is actually a very low grade uranium source, however, the advantage of the dissolved state and the almost inexhaustible quantities of uranium should be kept in mind. Moreover, it should be emphasized that the uranium concentration in sea water is relatively high compared to other heavy metals as for instance gold or thorium. Common metals like chromium, manganese, copper, or cobalt occur in sea water in lower molar concentrations than uranium (Table 1). 

Uranium produced from the uneconomic sources listed in Table 5.16 would cost several hundred dollars per pound and is not economic at present. If the uranium-fueled fast-breeder reactor becomes economic, it would generate so much electricity per ton of natural uranium that Chattanooga shale and even Conway granite irdght be used as economic uranium sources. These sources are estimated to contain 5 million and 6 to 9 million MT of uranium, respectively. Environmental problems from the large amount of earth disturbed in mining these low-grade sources would be severe. 

One approach to getting more power out of existing uranium sources and potentially reducing radioactive waste is a fast breeder reactor. This type of reactor is so named because it creates ( breeds ) more fissionable material than it consumes. The reactor operates without a moderator, which means the neutrons used are not slowed down. In order to capture the fast neutrons, the fuel must be highly enriched with both ura-nium-235 and plutonium-239. Water cannot be used as a primary coolant because it... 

A target area is most closely defined by sharp changes in pH and Eh (or dissolved oxygen) and by dissolved radon and radium. The latter two elements may be used to calculate the minimum product of grade times thickne.ss that could produce the anomaly. The most conservative assumption is that the well penetrates the centre of the mineralization. The farther the water travels to the well, the larger is the uranium source for a measured concentration of radon. 

Besides the resources estimated at 130/kg there exist other uranium sources, generally with a lower content and at a higher extraction cost. These are either an extension of conventional uranium deposits cultivated at 130/kg or conventional deposits the extraction cost of which exceeds 130/kg because of their limited size, deep location or presence in remote areas. Examples of these additional uranium sources are the vast high-cost resources associated with the Elliot Lake deposits in Canada, the 5000-10000 ton of uranium at costs of more than 130/kg in Italy, the 12000 ton contained in granitic rocks at a cost of 130- 260/kg in Namibia, the 141000 ton contained in the conglomerates and the 46000 ton in the surface sediments in South Africa at a cost of 130- 260/kg and the vast quantities of uranium contained in the sandstones of Colorado, Wyoming and New Mexico. 

Other additional uranium sources, associated with unconventional deposits or exploited as a by-product of other minerals (e.g. copper and gold), are those found in old mine dumps (gold mines in South Africa), phosphate rocks (Morocco, the U.S.A. and the U.S.S.R.), with a content ranging from 0.001 to 0.07%, in copper deposits, such as the porphyry coppers , in marine black shales with a content ranging from 0.001 to 0.008% (the U.S.A. and Sweden), in coal and lignite deposits with a content normally of 0.001%, exceptionally reaching 1% (the U.S.A.), in monazite deposits with 0.3% (India, Brazil, Australia and Malaysia), in igneous rocks, such as the alkaline intrusives distributed in various parts of the world, and, as has already been mentioned, in sea water. 

Stuckless J. S. Bunting J. A. and Nkomo I. T. U-Th-Pb systematics of some granitoids from the northeastern Yilgarn Block, Western Australia and implications for uranium source rock potential. J. geol. Soc. Aust., 28, 1981, 365-75. 

WHO, 2001. In W.H.O. Department of Protection of the Human EnvironmenL Depleted Uranium Sources, Exposures, and Health Effects World Health Organization, Geneva, Switzerland. 

For uranium source preparation, 50 pL of Nd solution (1 mg Nd VmL) was added to the separated uranium (the eluate) followed by an amount of TiCla (15%) drop by drop to change the colour of the solution to purple, then excess 1 mL was added to keep uranium in the tetravalent state. Five mL of 40% HF solution was added to the sample and left for 30 minutes prior to filtration using 0.1 pm polypropylene membrane filter. The sample was dried, mounted on a stainless steel disc and counted using the a-spectrometer. 

---