Analysis of coal slag for naturally occurring radioactive material

Samples of aerosolized coal slag were collected during an abrasive blasting operation to determine the concentration of naturally occurring radioactive materials (NORM) in the respirable and nonrespirable fractions. Each slag fraction was analyzed using alpha and gamma spectrometry. Since the slag is insoluble, it was necessary to dissolve samples completely by fusion with potassium fluoride and, after additional transposing and separation, mount the precipitate containing radium (Ra), the main radioactive component in NORM, on a membrane filter for alpha counting. The concentration of 226Ra in coal slag was independent of the particle size fraction and equal to 2.28 picocuries/gram (pCi/g) +/- 0.43 pCi/g, which is approximately twice the typical concentration of NORM in uncontaminated soil. Analysis of NORM by gamma spectrometry identified low concentrations of uranium, thorium, and potassium, all primordial radioactive materials that are commonly encountered in normal background soil. Integral exposure to workers from inhalation of NORM during abrasive blasting with coal slag is extremely low and could be essentially eliminated by use of appropriate respiratory protection. External radiation exposure to workers handling large quantities of NORM-contaminated coal slag during shipping or storage is also low, but would vary depending on the concentration of NORM in the slag.