Automatic X-ray inspection for the HTR-PM spherical fuel elements

• An automatic X-ray inspection method is established to characterize HTR pebbles.
• The method provides physical characterization and the inner structure of pebbles.
• The method can be conducted non-destructively, quickly and automatically.
• Sample pebbles were measured with this AXI method for validation.
• The method shows the potential to be applied in situ.

Inefficient quality assessment and control (QA&C) of spherical fuel elements for high temperature reactor-pebblebed modules (HTR-PM) has been a long-term problem, since conventional methods are labor intensive and cannot reveal the inside information nondestructively. Herein, we proposed a nondestructive, automated X-ray inspection (AXI) method to characterize spherical fuel elements including their inner structures based on X-ray digital radiography (DR). Briefly, DR images at different angles are first obtained and then the chosen important parameters such as spherical diameters, geometric and mass centers, can be automatically extracted and calculated via image processing techniques. Via evaluating sample spherical fuel elements, we proved that this AXI method can be conducted non-destructively, quickly and automatically. This method not only provides accurate physical characterization of spherical fuel elements but also reveals their inner structure with good resolution, showing great potentials to facilitate fast QA&C in HTM-PM spherical fuel element development and production.