A detector system for non-contact imaging of contamination patterns

A detector system for non-contact imaging of patterns on radioactively contaminated surfaces has been developed and tested at AECL Chalk River Laboratories. The detector system incorporates a collimated gamma detector mounted on a computer-controlled pan-tilt head to sequentially scan a square grid and generate a colour-mapped image of the radioactivity distribution. The detector used is a cadmium telluride diode based X-ray and gamma spectrometer. Traditional contact auto-radiography techniques and the use of expensive gamma cameras are not favoured in this application because of high ambient gamma fields and potentially high surface contamination levels. In one application, the non-contact radiograph-like images capture dispersal patterns of particulate contamination that falls off the outside surfaces of a waste package onto the bottom plate of the transfer flask containing the waste package. The images are being used to assess the effectiveness of techniques to reduce the amount of contamination on waste packages. The images are also being used to assess the effectiveness of techniques to retain the contamination on the bottom plate. (author)