Locating Radiation Hazards and Sources within Contaminated Areas by Implementing a Reverse Ray Tracing Technique in the RadBall™ Technology

Abstract

RadBall™ is a novel technology that can locate unknown radioactive hazards within contaminated areas, hot cells, and gloveboxes. The device consists of a colander-like outer tungsten collimator that houses a radiation-sensitive polymer semisphere. The collimator has a number of small holes; as a result, specific areas of the polymer are exposed to radiation, becoming increasingly more opaque in proportion to the absorbed dose. The polymer semisphere is imaged in an optical computed tomography scanner that produces a high resolution three-dimensional map of optical attenuation coefficients. A subsequent analysis of the optical attenuation data, using a reverse ray tracing technique, provides information on the spatial distribution of gamma-ray sources in a given area, forming a three-dimensional characterization of the area of interest. The RadBall™ technology and its reverse ray tracing technique were investigated using known radiation sources at the Savannah River Site's Health Physics Instrument Calibration Laboratory and unknown sources at the Savannah River National Laboratory's Shielded Cells facility.

Characterizing Doe Hanford Site Waste Encapsulation Storage Facility Cells Using Radball

“…A complete RadBall TM deployment and retrieval process consists of six individual steps illustrated in Figure 4 Stanley and Holmes 2010;Farfán et al 2011). These steps were slightly modified to account for the submerged RadBall TM deployments at WESF.…”

“…Savannah River National Laboratory (SRNL) addressed key aspects of the testing and further development of an innovative technology, RadBall TM ; originally developed by the National Nuclear Laboratory (NNL) in the United Kingdom Stanley and Holmes 2010;Farfán et al 2010aFarfán et al , 2010bFarfán et al , 2010cOldham et al 2010;Farfán et al 2011). The RadBall TM technology presents a significant opportunity to expedite initial characterization of radiologically contaminated facilities with respect to ALARA concerns, initial decontamination strategies, and costs associated with the decontamination efforts.…”

Improving the Presage® Polymer Radiosensitivity for Hot Cell and Glovebox 3D Characterization

“…(Stanley 2008). To characterize photon sources, the ideal RadBall \ absorbed dose is between 1.5 to 3.0 Gy (Farfán et al 2012a). The exposure time to achieve this dose depends on the source strength, number of sources, and distance between RadBall \ and sources.…”

“…The polymer semisphere is imaged in an optical-CT scanner (Oldham 2006;Oldham et al 2010), which produces a 3D map of optical attenuation coefficients. The orientation of the opacity track provides the positional information regarding the source, which is achieved by using a reverse ray tracing technique (Farfán et al 2012a). The activity of the detected source is assessed by quantifying the magnitude of the opacity change that follows a linear relationship with respect to absorbed dose.…”