Multi-modal tomographic imaging system for poolside characterization of nuclear test fuels: Design considerations and studies

Testing and qualification of advanced nuclear fuels involve an iterative process of prototyping, in-pile irradiation testing, and in/ex situ examination. Fuel restructuring and fission product migration during burnup are among the most important aspects of fuel evolution and affect several important performance characteristics (e.g., heat removal, accident tolerance, and fission product retention). Poolside nondestructive characterization techniques provide fuel developers with tools to understand fuel evolution at different time points of burnup. A design for a compact, submersible, and multi-modal (transmission and emission) gamma-ray tomography system for imaging irradiated nuclear fuel is presented herein. Detector selection, collimator geometry and fabrication, mechanical design, imaging protocol, and acquisition protocol are discussed. Modeling calculations showed that sub-millimeter resolution could be achieved in a matter of hours in both transmission and emission tomography images. Several design compromises and fabrication challenges are discussed to further the development of future submersible gamma-ray tomography instruments.