Detector Noise in X-ray Computed Tomography Examinations of Irradiated Tristructural Isotropic (TRISO) Fuels

Idaho National Laboratory, USA

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Published online: 6 November 2025

Abstract

Tristructural isotopic (TRISO) fuel is a promising next-generation fuel form for advanced nuclear reactors. TRISO fuel consists of sub-millimeter diameter uranium-bearing fuel kernels encapsulated in multiple layers of carbon and ceramic materials. As part of the assessment of TRISO fuels, post irradiation examination (PIE) is performed to provide information on changes in microstructure, mechanical properties, and potential degradation. X-ray computed tomography (XCT) is a nondestructive technique that collects a series of two-dimensional radiographs as a function of sample rotation and mathematically reconstructs them into a three-dimensional dataset that provides volumetric information on the sample’s internal features. This work focuses on PIE of irradiated TRISO fuels using XCT with a focus on examining the impact of highly radioactive fuels on the images generated with the instrument’s CsI detector. Despite examining samples with over 2.00 Sv/hr on contact, techniques such as frame-averaging as well as a lack of interaction of high-energy gamma-rays with the detector ensure there is no noticeable impact on the quality of the CT images due to detector noise.