Radioactive Materials in Biosolids: Dose Modeling

Abstract

The Interagency Steering Committee on Radiation Standards (ISCORS) has recently completed a study of the occurrence within the United States of radioactive materials in sewage sludge and sewage incineration ash. One component of that effort was an examination of the possible transport of radioactivity from sludge into the local environment and the subsequent exposure of humans. A stochastic environmental pathway model was applied separately to seven hypothetical, generic sludge-release scenarios, leading to the creation of seven tables of Dose-to-Source Ratios (DSR), which can be used in translating from specific activity in sludge into dose to an individual. These DSR values were then combined with the results of an ISCORS survey of sludge and ash at more than 300 publicly owned treatment works, to explore the potential for radiation exposure of sludge workers and members of the public. This paper provides a brief overview of the pathway modeling methodology employed in the exposure and dose assessments and discusses technical aspects of the results obtained.

An Evaluation of the Radioactive Content of Ashes Obtained from the Use of Fuels from Recycled Materials by Co-Processing in the Cement Industry

“…The estimated annual effective dose rates for the ashes, calculated using Radiation Protection 122 (RP 122) [29], were in line with other studies, with values between 0.02 mSv and 1 [9]. Similarly, the annual effective dose rates were consistent with those from probabilistic models like RESRAD, which estimated them to be 0.03 mSv y −1 [36]. These doses are significantly lower than the natural annual radioactive background of 2.4 mSv y −1 [37], indicating no radiological risk under the present study conditions.…”

Fate of 60Co at a sludge land application site

“…The fate of land-applied radionuclides contained in wastewatertreatment sludge has received considerable recent attention (e.g., Bastian et al, 2005;O'Connor et al, 2005;Wolbarst et al, 2006), and the practice of land application of these biosolids is expected to continue to grow because of the perceived economic and societal benefits . Radionuclides are either present naturally or enter the wastewater stream from numerous anthropogenic sources, such as combustion, fertilizer runoff, mining and smelting operations, leachate from disposal facilities, industrial byproducts, research institutions, and hospitals, as well as from atmospheric fallout.…”