Development of a Solid Content Sensor Based on Low-level X-ray Sources

Abstract

The focus of this thesis is to develop a solid content sensor based on low-level X-ray sources to monitor the settling process of FFT (Fluid fine tailings) in oil sands tailings ponds and provide calibration data for a light scattering sensor built for the same purpose. In this study, high-resolution spectrometry based on a CdTe (Cadmium Telluride) detector was used to measure the X-ray attenuation by FFT samples with solid content at different wt% (weight percent). Two experiment setups were designed for a 0.9 μCi 241Am and a 1 μCi 133Ba source. Based on the considerations of measurement performance and licensing regulations, the 1 µCi 133Ba source was finally selected for further development, and the monitoring parameter was based on the intensity ratio of 31 keV and 81 keV peak. Mass attenuation calculations were used to verify the experimental results. Comparison of the calculated and measured X-ray / gamma (γ) ray transmission results shows the experimental results are between the upper and lower limits formed by photoelectric absorption and total attenuation cross-sections. GEANT4, a Monte Carlo based simulation code, which calculates the transmission of radiation through matter, was used to simulate the results of this study. The experimental results and simulated results are in good agreement. The effect of measurement error of FFT chemical composition, measured via ICP-MS (Inductively Coupled Plasma Mass Spectrometry), was evaluated to be within ± 2 wt% in solid content. This simulation predicted transmission results within several percent by considering all the geometry factors of the real setup. The transmission is sensitive to chemical composition which should be determined by ICP-MS composition analysis for accurate predictions. An inexpensive detection system based on Lutetium-yttrium oxyorthosilicate (LYSO) fluorescent crystals and Multi-pixel photon counters (MPPC) was developed and characterized with the 1 μCi 133Ba. It was found that such an inexpensive detector system can work effectively and should offer a viable technique for carrying out solid content analysis of settling ponds in the field.