An efficiency function model of segmented gamma scanning for measuring radioactive waste drum.

ABSTRACT

Segmented gamma scanning (SGS) is a fast and effective method for measuring radioactive waste drum. The efficiency calibration is directly related to the accuracy of reconstructed radioactivity. An efficiency function model and SGS efficiency calibration method are proposed for solving existing SGS efficiency calibration problems such as time lag, limited by experimental sources or difficult to effectively combine with SGS system. The SGS system model is established by the Geant4 to calculate the segment efficiency under different linear attenuation coefficients of medium and gamma energies. The efficiency calibration function is established with the function model and parameters. Waste drum samples are constructed with the polyethylene and point sources 137Cs/60Co to complete SGS experimental measurement, efficiency calibration and radioactivity reconstruction. The result shows that the relative deviation of the reconstructed activity of a single point source at different locations in the drum is -50.48% to 43.69% and it of multi-point sources in a segment or a drum is -27.88% to 3.57%. Experimental results verify the effectiveness of this efficiency function model and SGS calibration method.