Emanation Coefficients for Rn in Sized Coal Fly Ash

Abstract

Emanation coefficients for 222Rn in sized samples of dry coal fly ash were evaluated as a function of source and particle size using a modification of the "sealed-can, gamma-only" technique. The emanation coefficient is defined as the fraction of Rn atoms that escape the solid particles of a source. Diffusible Rn was separated from nondiffusible Rn by adsorption on charcoal, and each was measured independently by gamma-ray spectrometry of the Rn daughter, 214Bi. Samples of ash from eastern bituminous coal, western bituminous coal and mid-western bituminous coal with aerodynamic equivalent diameters of less than 15 micron were examined, and the measured emanation coefficients ranged from 0.098 down to 0.007. These values were dependent on both the size and source of the fly ash. The emanation coefficients and the specific activities generally decreased monotonically with increasing aerodynamic equivalent diameter. For unfractionated standard fly ash, SRM 1633a, from the U.S. National Bureau of Standards, the emanation coefficient for 222Rn was found to be 0.018. The results suggest that only a small fraction of the Rn in lung-deposited fly ash will be removed by exhalation.

Radiological characteristics and investigation of the radioactive equilibrium in the ashes produced in lignite-fired power plants

“…This should be attributed to the smaller grain size of the fly-ash collected there, which results in an increase of the surface-to-volume-ratio that allows for higher radon emanation power. These conclusions are consistent with those of Kalkwarf et al (1985), who have determined the emanation coefficient of 222 Rn for fly-ash samples of different origin, as a function of their size, and concluded that emanation coefficients depend both on the source and the size of fly-ash, and furthermore they generally decrease monotonically with increasing particle size. 3.…”

ICRP Publication 137: Occupational Intakes of Radionuclides: Part 3

“…Duport and Edwardson (1984) reported values between 0 and 0.5 for micron-sized samples of uranium ore dust. Kalkwarf et al. (1985) measured radon emanation coefficients in the range 0.001–0.1 for coal fly ash particles in sized fractions from less than 0.5 µm to 11–15 µm.…”

Investigation of the Effect of Hydrothermal Waters on Radionuclide Activity Concentrations in Natural Marble with Multivariate Statistical Analysis

“…Among building materials, natural marble is in common use [4][5][6][7][8]. Long-term whole-body exposure to radiation due to the use of such granite and marble materials in Symmetry 2020, 12, 1219 2 of 21 buildings can affect the health of the individuals using them [9,10]. Therefore, it is very important to compare the natural radioactivity levels of marble ( 226 Ra, 232 Th, and 40 K) and their associated radiological impact indexes with the accepted limit values.…”

“…Several studies have been conducted to reveal the reason why the radioactivity of the samples depends on the grain size. Some differences may be observed depending on the type of sample investigated [11][12][13][14][15][16][17].…”