International Society for Industrial Process Tomography

Improved Backscatter Correction Model for High Attenuation Gamma-ray Tomography Measurements

R.B. Spelay¹*, S.A. Hashemi¹, R.S. Sanders², B.T. Hjertaker³

¹ Saskatchewan Research Council, Pipe Flow Technology Centre^TM, Saskatoon, SK, Canada

² University of Alberta, Dept. Chemical and Materials Engineering, Edmonton, AB, Canada

³ University of Bergen, Dept. Physics and Technology, Bergen, Norway

^*Email: ryan.spelay@src.sk.ca

ABSTRACT

In this study a state of the art Gamma-ray Tomography unit (GRT) at the Saskatchewan Research Council’s (SRC) Pipe Flow Technology Centre^TM was used to measure the solids concentration distributions of high density, high attenuation clay/water/sand slurries in 4 in. (100 mm) diameter recirculating pipe loop. The presence of neighbouring radiation sources on the GRT results in a scattered radiation contribution to the total intensity measured at each detector. The backscattered radiation decreases the signal-to-noise ratio of the measured radiation intensity and introduces error in the measured tomography data and the reconstructed tomograms (Maad et al., 2008). Because of the high attenuation of the materials being measured, in some cases the backscatter contribution was a significant fraction of the total radiation measured at each detector. To correct for the scattered radiation contribution in the measurements, a test campaign was undertaken to characterize and model the backscattering for the GRT unit at SRC. The scattered radiation was measured experimentally from empty pipe, water filled pipe and a number of flowing clay/water/sand slurry tests at mixture densities ranging from 1206·kg/m³ to 1580·kg/m³. A semi-empirical backscatter correction model has been developed which allows the backscattered contribution at each detector to be calculated iteratively based on the measured uncorrected attenuated radiation intensity.

Keywords backscatter, correction, gamma-ray tomography, slurry

Industrial ApplicationMining and Mineral Processing, Slurry Pipeline Research