Improvements To Segmented Gamma Scanner Matrix Correction Techniques

Segmented gamma scanning is a well established technique for the non-destructive assay of gamma emitting radioisotopes in drummed waste. The accuracy of all segmented gamma scanner systems is strongly affected by their ability to correct for varying gamma absorption in waste matrices. The BNFL Instruments team at Sellafiel has developed two advanced matrix correction techniques, which have been implemented in the DrumScan TM segmented gamma scanner to overcome limitations in conventional techniques. The first technique uses a measurement of multiple gamma ray energy lines from a EU transmission source in order to provide a correction in nuclides whose principle energy lines span a wide range from the measurement of a single transmission source. The second technique uses a combination of a transmission measurement and the drum weight in the innovative \"TransWeight\" algorithms to determine a correction for gamma absorption in dense highly stratified wastes. Practical experience has shown that the most accurate correction for gamma absorption in drum matrices is achieved by the intelligent combination of these techniques with the conventional differential photopeak absorption and weight correction techniques, thus ensuring that an accurate assay is achieved.