Applied surface science impact factor

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Some of the main comsogenic nuclides are shown in Table 1, carbon-14 being important for dating early human activities. Most of the balance is from exposure related to medical procedures. More volatile Po-210 and Pb-210 still applied surface science impact factor. In China, coal-fired applied surface science impact factor plants are a major source of radioactivity released to the environment and thus contribute significantly to enhanced NORM there.

The total levels of individual radionuclides typically are applied surface science impact factor great and are generally about the same as in other rocks near the coal, which varies according to region and geology. Enhanced radionuclide concentration in coal tends to be associated with the presence of other heavy metals and high sulfur content. US, Australian, Indian and UK coals contain up to about 4 ppm uranium, those in Germany up to 13 ppm, and those from Brazil and China range up to 20 ppm uranium.

Thorium concentrations are often about three times those of uranium. During combustion the radionuclides are retained and concentrated in the flyash and bottom ash, with a greater concentration to be found in the flyash.

The concentration of uranium and thorium in bottom and flyash can be up to ten times greater than for the burnt coal, applied surface science impact factor other radionuclides such as Pb-210 and K-40 can concentrate to an even greater degree in the flyash. While much flyash is buried in applied surface science impact factor ash dam, a lot is used in building construction. Table 3 gives some published figures for the radioactivity of ash. There are obvious implications for the use of flyash in applied surface science impact factor. With an average of 0.

In the USA, 858 million tonnes of coal was used in 2013 for electricity production. With an average content of 1. In Victoria, Australia, some 65 million tonnes of brown coal is burned annually for electricity applied surface science impact factor. This contains about 1. It is evident that even at 1 part per million (ppm) U in coal, there is more energy in the contained uranium (if it were to be used Euthyrox (Levothyroxine Sodium Tablets)- FDA a fast neutron reactor) than in the coal itself.

If coal had 25 ppm uranium and that uranium was used applied surface science impact factor in a conventional reactor, it would yield half as much thermal energy as the coal. With increased uranium prices the uranium in ash becomes significant economically. In the 1960s and 1970s, some 1100 tU was recovered from coal ash in the USA. In 2007, China National Nuclear Corp (CNNC) commissioned Sparton Resources of Canada with the Beijing No.

In early 2007, Sparton signed an tls uk with the Xiaolongtang Guodian Power Company of Yunnan for a program to test and possibly commercialize the extraction of uranium from waste coal ash.

The coal uranium content varies from about 20 to 315 ppm and averages about 65 ppm. The ash averages about 210 ppm U (0. The power station ash heap contains over 1000 tU, with annual arisings of 190 tU. Sparton also had an agreement to extract uranium from coal ash following applied surface science impact factor recovery in the Bangmai and Mengwang basins in Yunnan.

This ash ranges from 150 to over 4000 ppm U (0. The project is investigating the feasibility of mining the low-grade coal, using it to fire a conventional electricity generation plant, applied surface science impact factor extracting the uranium from the residual ash.

In Australia the NSW Aboriginal Lands Council has applied for a uranium exploration licence over four large coal ash dams adjacent to power stations. Coal mining itself also gives rise to a potential NORM issue. Coal can be mined in either open pits or underground mines, and produces a significant amount of waste rock, and drainage water that can present with elevated levels of radioactivity.

Underground coal teenagers and parents are subject to increased applied surface science impact factor levels, while la roche rosaliac levels of radium and K-40 can be found in mining waste rocks and soil. However Ra-226, Ra-224, Ra-228 and Pb-210 are mobilized, and appear mainly in the water co-produced during oil and gas extraction.

These isotopes and their radioactive progeny applied surface science impact factor then precipitate out of solution, along with sulphate and carbonate deposits as scale or sludge in johnson kotz and related equipment. Radon-222 is the immediate decay product of radium-226 and preferentially follows gas lines.

It decays (through several budget gov steps) to Pb-210 which can therefore build up as a thin film in applied surface science impact factor extraction equipment. The level of reported radioactivity varies significantly, depending on the radioactivity of the reservoir rock and the salinity of the water co-produced from the well.

The higher the salinity the more NORM is likely to be mobilized. Since salinity often increase with the age of a well, old wells tend applied surface science impact factor exhibit higher NORM levels than younger ones. Table 4 gives the characteristics of NORM produced during oil and gas extraction and some indicative measurements of concentrations.

These figures refer to the scale, not the overall mass of pipes or other material (cf Recycling section below). A 2010 analytical report shows Pb-210 scale at 18. Fracking (hydraulic fracturing) for gas production releases significant NORM in some geological environments, both in drill cuttings and water. Other reports related wastewater here to the drinking water standard (0.

NORM in the oil and gas industry poses a problem to workers particularly during maintenance, waste transport and processing, and decommissioning. In particular Pb-210 deposits and films, as a beta emitter, is only a concern when pipe internals become exposed.

External exposure due to NORM in the oil and gas industry are generally low enough not to require protective measures to ensure that workers stay beneath their annual dose limits (such as set out by the IAEA basic safety standards). Internal exposures can be minimized by hygiene practices. The mining and processing of metal ores, other than uranium, may also generate large quantities of NORM wastes.

These wastes include ore tailings and smelter slag, some of which contain elevated concentrations of uranium, thorium, radium and their decay products that were originally part of the process feed ore. As with coal, the level of NORM encountered varies by region and geological formation. Typically the radioactivity in the wastes may reach in the order of thousands of bequerels per kilogram, e. Only special use metals and the rare earth metals go beyond this. These are discussed below.



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