One of the important environmental issues raised recently in regard to coal ash reuse for highway construction purposes (e.g., embankment development) is that of worker, and public, exposure to radiation which might possibly be emitted by these types of residuals. Radiation emission is, in fact, a natural phenomenon for most materials, both natural and man-made, but in the case of coal ash residuals the process of combustion produces an inevitable concentration of radionuclides from the original virgin coal. INDOT’s corresponding environmental concern consequently focuses on the following basic question: does this magnification of radionuclides found within these coal ash residuals cause sufficiently high levels of radiation to impose harmful effects due to exposure? This research project subsequently addressed the associated issue of radiation emission by coal ash residuals generated within the State of Indiana, covering both fly ash and bottom ash materials. Samples were obtained at sixteen (16) different coal-fired power generating facilities within Indiana and subjected to a quantitative analysis of their associated gamma-ray emission levels. After identifying the responsible radionuclides, a conservative approximation was then developed for the worst-case potential occupational exposure with construction employees working on this type of highvolume, coal ash embankment. In turn, these potential emission levels were compared to those of other traditional construction materials and other common sources. The observed results indicated that these coal ash residuals did contain levels of gamma-ray emitters that were, in fact, higher than those of traditional construction materials (i.e., clay, sand, brick, and limestone). However, these levels of gamma-ray emission were not excessively high, and considerably below the limits respectively promulgated for public exposure and occupational exposure by the Environmental Protection Agency (100 mrem/yr for a single man-made source) and the Nuclear Regulatory Commission (5 rem/yr).

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coal ash, radiation emission, environmental quality, waste reuse, highway construction, SPR-2175

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Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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