Emanation coefficients for Rn in sized coal fly ash

Area of Science:

• Environmental Science
• Radiochemistry
• Geochemistry

Background:

• Coal fly ash is a byproduct of coal combustion.
• Radon-222 (Rn) is a naturally occurring radioactive gas.
• Fly ash can contain radioactive elements, including those that decay to Rn.

Purpose of the Study:

• To evaluate radon-222 emanation coefficients in sized coal fly ash samples.
• To determine the influence of fly ash source and particle size on Rn emanation.
• To assess the potential for Rn release from inhaled fly ash particles.

Main Methods:

• Utilized a modified "sealed-can, gamma-only" technique.
• Separated diffusible and nondiffusible Rn using charcoal adsorption.
• Measured Rn and its daughter 214Bi via gamma-ray spectrometry.

Main Results:

• Emanation coefficients for Rn in fly ash ranged from 0.007 to 0.098.
• Values were dependent on fly ash source and particle size.
• Emanation coefficients and specific activities generally decreased with increasing particle size.

Conclusions:

• A small fraction of Rn in lung-deposited fly ash is expected to be removed by exhalation.
• Fly ash particle size and source are critical factors in Rn release.
• Understanding Rn emanation is important for assessing inhalation risks from fly ash.