DETERMINATION OF RADIOACTIVITY IN AND RADON EMANATION COEFFICIENT OF SELECTED BUILDING MATERIALS AND ESTIMATION OF RADIATION EXPOSURE FROM THEIR USE (RADON, RADIUM)

CARMELA HERNANDEZ PAREDES, Purdue University

Abstract

Building materials commonly used in the construction industry and those that were manufactured with waste products of the phosphate industry, waste products from the phosphate industry, and phosphate ores were examined for radioactivity content. Each material was analyzed for Ra-226, Ra-228, and K-40 by gamma-ray spectrometry. The measured radionuclide concentrations for the building materials examined ranged from 0.2-3.9 pCi g('-1) for Ra-226, 0.3-1.8 pCi g('-1) for Ra-228, and 2.3-37 pCi g('-1) for K-40. Waste products of elemental phosphorus manufacture had activity concentrations that ranged from 4.2-54 pCi g('-1) for Ra-226, 0.3-1.0 pCi g('-1) for Ra-228, and 1.4-6.6 pCi g('-1) for K-40. The activity concentrations for phosphate ores from Tennessee and Montana were 5.3 and 36 pCi g('-1) for Ra-226, 0.5 and 0.6 pCi g('-1) for Ra-228, and 4.8 and 9.0 pCi g('-1) for K-40, respectively. The emanation coefficients for the building materials examined ranged from 6.86 x 10('-4) - 5.99 x 10('-2). Those for the waste products of the phosphate industry ranged from 2.21 x 10('-4) - 3.06 x 10('-2). The phosphate ores had emanation coefficients in the order of 10('-2). The emanation coefficients for mineral wool and wall-board slightly increased when measured at a relative humidity of 100% instead of 0%. No dependence of emanation coefficient on humidity was observed for Tenn. phosphate slag. An available computational model predicted the concentration of Rn-222 and its daughters in room air arising from building materials to be less than normal background levels at low ventilation rates. Under specified conditions, the indoor working level (WL) values ranged from 4 x 10('-5) - 3 x 10('-3) WL at 0.06 air change per hour (ach) and from 4 x 10('-6) - 3 x 10('-4) WL at 0.05 ach. These levels result in an increased risk for lung cancer induction of 1 to 27 cases per year per million which is less than the expected incidence rate of 40 cases per year per million exposed to the assumed average background radon daughter exposure. One can conclude that the use of these materials would not constitute a significant risk to the occupants of a home.

Degree

Ph.D.

Subject Area

Environmental science

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