Land Area Surveys Using High Resolution Scintillator (NaI) Detector Arrays
C. Stephan1; J. Gonsky1; E. Eloskof1; M. Wendling2; C. Domingo3; and T. Macchiarella3 (1Tetra Tech FW, Inc.; 2Eberline Service; 3Base Realignment and Closure, Program Management Office, West)
Tetra Tech, FW, Inc. performed a radiological characterization survey at Installation Restoration (IR) Sites 1 and 2 of the former Alameda Naval Air Station (Alameda Point), Alameda, California to define the nature and extent of residual radioactive material at these former disposal areas. IR Sites 1 and 2 are closed waste disposal areas that cover approximately 188 acres of land. The Navy operated a radium paint shop at Alameda Point that repaired and maintained radioluminescent devices in the 1940s, 1950s, and 1960s. Disposal of radioluminescent devices containing radium-226 was not controlled by specific procedures until the late 1960s. Prior to that time, it was common practice throughout private industry and the military to dispose of devices by burial in landfills. To provide input to the Feasibility Study (FS) for these sites, which includes steps for analyzing in detail the nature of site contaminants, a high-density radiological survey was performed. The survey approach involved a suite of investigative tools that included scan surveys using high-resolution scintillator (NaI) detectors, biased soil sampling, and field gamma spectroscopy analysis. NaI detectors coupled to a data logger were the primary radiation detection systems used during the scan surveys. An array of four detectors was attached to all- terrain vehicles (ATVs). The scan speed was targeted to collect one data point per square foot of land area surveyed. Areas with elevated radioactivity were further investigated by performing static measurements, biased soil sampling and analysis and field gamma spectroscopy. Data collected during the characterization surveys were used to define the nature and extent of the residual radioactive material at IR Sites 1 and 2. The survey system included a precision global positioning system and a high precision laser-assisted ranging and data logging. This allowed over three million measurements to be collected at each site. The survey approach at this site showed that by using a combination of high-density surface scans, biased soil sampling, and field gamma spectroscopy, large land areas can be quickly characterized to provide input into modeling and planning activities. The work described herein demonstrated the usefulness of this technique in characterizing residual radioactive material, and thus ensuring public safety, at former military sites undergoing transfer to the public.
