Development of Site-Specific Soil Cleanup Criteria: New Brunswick Laboratory, New Jersey Site

摘要

The potential human exposure which results from the residual soil radioactivity at a decommissioned site is a prime concern during D and D projects. To estimate this exposure, a pathway analysis approach is often used to arrive at the residual soil radioactivity criteria. The development of such a criteria for the decommissioning of the New Brunswick Laboratory, New Jersey site is discussed. Contamination on this site was spotty and located in small soil pockets spread throughout the site area. Less than 1% of the relevant site area was contaminated. The major contaminants encountered at the site were exp 239 Pu, exp 241 Am, normal and natural uranium, and natural thorium. During the development of the pathway analysis to determine the site cleanup criteria, corrections for the inhomogeneity of the contamination were made. These correction factors and their effect upon the relevant pathway parameters are presented. Major pathways by which radioactive material may reach an individual are identified and patterns of use are specified (scenario). Each pathway is modeled to estimate the transfer parameters along the given pathway, such as soil to air to man, etc. The transfer parameters are then combined with dose rate conversion factors (ICRP 30 methodology) to obtain soil concentration to dose rate conversion factors (pCi/g/mrem/yr). For an appropriate choice of annual dose equivalent rate, one can then arrive at a value for the residual soil concentration. Pathway modeling, transfer parameters, and dose rate factors for the three major pathways; inhalation, ingestion and external exposure, which are important for the NBL site, are discussed. (ERA citation 10:026948)