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Query: UMLS:C0205700 (ash)
 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A stockpile probe based on backscattered gamma-gamma-ray technique was tested for the determination of coal ash. A centralized tool employing a gamma-ray source of very low radioactivity (1.85 MBq) was used. This logging tool was tested using 137Cs and 133 Ba sources with a 37 mm (diameter) by 75 mm NaI (TI) scintillation detector. Ten source-detector configurations were analyzed using 137Cs, and another nine source-detector configurations are analyzed, using 133Ba source, both for four geophysical models, having a borehole diameter of 90 mm. Regression analysis on the laboratory logging data for each studied configuration was carried out in order to establish calibration equations for ash prediction. The optimum configuration for the logging stockpile probe using 137Cs source was determined to be 80 mm source to detector spacing, and 80 mm iron thickness shielding. This configuration gives the best results for ash prediction. The root mean square (rms) deviation for ash is 1.52%. The optimum configuration for the logging stockpile probe using 133 Ba source is determined to be 85 mm source to detector spacing, and 50mm iron thickness shielding. This configuration gives the best results for ash prediction, where the rms deviation for ash is 1.47%.
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PMID:Optimization of low activity spectrometric gamma-gamma probes for ash determination in coal stockpiles. 1279 72

Seven types of common building materials and by-products of coal-fired power plants collected from Baoji, West China, were analysed for the natural radioactivity of 226Ra, 232Th and 40K using gamma ray spectrometry with an NaI(Tl) detector. The average activity concentrations vary from 23.0 to 112.2, 20.2 to 147.5 and 113.2 to 890.8 Bq kg(-1) for 226Ra, 232Th and 40K, respectively. The measured activity concentrations for these radionuclides were compared with the data reported from other countries and with the worldwide average activity of soil. As a measure of radiation hazard to the people, the radium equivalent activities, total annual effective dose and activity concentration index were estimated. The radium equivalent activities of the studied samples are below the internationally accepted values. The calculated total annual effective dose and the activity concentration index of seven types of common building materials are <1 mSv y(-1) and 1, respectively. But fly ash and bottom ash exhibit the higher values that exceed and be close to the acceptable values, respectively. This study shows that the measured building materials do not pose any significant source of radiation hazard and are safe for use in the construction of dwellings. Nevertheless, when fly ash and bottom ash are used in dwelling construction, it is important to assess their radiation potential.
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PMID:Radionuclide content and associated radiation hazards of building materials and by-products in Baoji, West China. 1792 11

Coal and its by products often contain significant amounts of radionuclides, including uranium which is the ultimate source of the radioactive gas radon. Burning of coal and the subsequent emission to the atmosphere cause the re-distribution of toxic trace elements in the environment. Due to considerable economic and environmental importance and diverse uses, the collected fly ash has become a subject of worldwide interest in recent years. In the present study, radon exhalation rate and the activity concentration of (238)U, (232)Th and (40)K radionuclides in fly ash samples from Durgapur thermal power plant (WB) have been measured by "Sealed Can technique" using LR-115 type II detectors and a low level NaI (Tl) based gamma ray spectrometer, respectively. Radon exhalation rate varied from 360.0 to 470.0 mBq m(-2)h(-1) with an average value of 406.8 mBq m(-2)h(-1). Activity concentrations of (238)U ranged from 84.8 to 126.4 Bq kg(-1) with an average value of 99.3Bqkg(-1), (232)Th ranged from 98.1 to 140.5 Bq kg(-1) with an average value of 112.9 Bq kg(-1) and (40)K ranged from 267.1 to 364.9 Bq kg(-1) with an average value of 308.9 Bq kg(-1). Radium equivalent activity obtained from activity concentrations is found to vary from 256.5 to 352.8 Bq kg(-1) with an average value of 282.5 Bq kg(-1). Absorbed gamma dose rates due to the presence of (238)U, (232)Th and (40)K in fly ash samples vary in the range 115.3-158.5 nGy h(-1) with an average value of 126.4 nGy h(-1). While the external annual effective dose rate varies from 0.14 to 0.19 mSv y(-1) with an average value of 0.15 mSv y(-1), effective dose equivalent estimated from exhalation rate varies from 42.5 to 55.2 microSv y(-1) with an average value of 47.8 microSv y(-1). Values of external hazard index H(ex) for the fly ash samples studied in this work range from 0.69 to 0.96 with a mean value of 0.77.
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PMID:Estimation of radon exhalation rate, natural radioactivity and radiation doses in fly ash samples from Durgapur thermal power plant, West Bengal, India. 1846 12