Results of the indoor radiological survey at the W.R. Grace Co., Curtis Bay site, Baltimore, Maryland

The W.R. Grace Company, Davison Chemical Division, conducted developmental research and extraction of thorium from monazite ore at its Curtis Bay facility in Baltimore, Maryland, during the 1950s under contract to the Atomic Energy Commission (AEC). Only one of the numerous buildings on the site was used for these operations. A 1979 aerial survey of the site for the Department of Energy (DOE) indicated that a comprehensive ground survey was required to determine whether or not any contamination remained from the AEC activities in that building. A radiological scoping survey performed later that year for DOE by a team from the Measurement Applications and Development Group of the Health and Safety Research Division, Oak Ridge National Laboratory (ORNL), disclosed surface contamination (alpha) levels in excess of DOE criteria on all five levels of the building. As a result of this finding, two additional surveys were performed in 1986 by ORNL at the request of DOE to evaluate any present or potential health risk. They are detailed in this report. The results of the 1986 surveys revealed several areas having elevated levels of radiation as a result of significant quantities of thorium on some building surfaces such as floors and ceiling beams. Most areas were small spots and in locations of low occupancy; thus, the possibility for significant exposure to workers was judged to be low. To confirm this evaluation, annual radiation exposure estimates for workers frequenting the few, larger contaminated areas on the site were derived using ORNL survey data and occupancy factors provided by the W.R. Grace Company. Estimates ranged from 27 to 41 mrem/yr or a maximum of 41% of the basic dose limit of 100 mrem/yr for members of the general public. 2 refs., 14 figs., 8 tabs