RADIOLOGICAL ASSESSMENT OF THE UTILIZATION OF FLY ASH IN CONCRETE FOR BUILDING CONSTRUCTION AND THE PARAMETERS AFFECTING RADON-222 EMANATION FROM FLY ASH CONCRETE
Abstract
Rn-222 is a major source of radiation exposure to the general public. In this study, the Rn-222 area exhalation rates and the maximum area exhalations for concrete containing fly ash or Ra-226 water were measured. Various concrete samples were fabricated with fly ash of known radium content as a cement substitute. Other samples were prepared with one of three concentrations of Ra-226 water solution added into the concrete mix. A newly designed "Indoor/Outdoor Emanation Chamber", which consisted of two consecutive chambers with a cylindrical concrete specimen located between them, was used in this study. Air samples were assayed for Rn-222 at various elapsed times by using the scintillation cell technique. The Ra-226 concentrations for the fly ash used in this study ranged from 3.42 pCi/g to 7.55 pCi/g depending upon the source of the ash and the particle size. Doses were calculated for occupants of a hypothetical house built with concrete of the type studied. Doses to the basal cells of the bronchial epithelium and the mean dose to the lung were 2.10 rad/yr and 0.37 rad/yr for standard concrete, up to 4.28 rad/yr and 0.76 rad/yr for fly ash concrete, and 3.26 rad/yr and 0.58 rad/yr for the concrete made with 25 pCi/L radium-226 water. The risk associated with utilization of standard concrete in an unventilated house was estimated to range from 560 to 1316 fatal cancers in million population. Utilization of fly ash as a cement substitute could increase the number of fatal lung cancers up to 2680. Introducing 25 pCi/L Ra-226 water into concrete will increase the fatal cancer rate up to 2042 in a million population. This study suggests that homes constructed with concrete containing fly ash or radium water could significantly increase the exposure to Rn-222 and its daughters. Utilization of fly ash as a cement substitute needs to be carefully monitored. The portion of cement replaced by fly ash and the origin of the fly ash would affect the amount of Rn-222 exhalating into houses. The water used in manufacturing concrete should be examined in order to avoid high Ra-226 content. (Abstract shortened with permission of author.)
Degree
Ph.D.
Subject Area
Environmental science
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