Integrated 2D and 3D vision system delivers non-contact inspection for nuclear fuel pellets

Findings from joint research undertaken by China Jiliang University and CNNC Jianzhong Nuclear Fuel Element Co., Ltd. have been published in Acta Metrologica Sinica, published by the Chinese Society for Measurement. The technology combines two-dimensional contour imaging and three-dimensional point cloud scanning to capture nine key geometric parameters at a single workstation, addressing persistent industry drawbacks associated with conventional inspection including surface damage to components, low throughput and incomplete data capture. The innovation supplies a high-precision metrology solution to support intelligent manufacturing within the nuclear fuel sector.

Domestic nuclear power construction is accelerating amid wider energy transition efforts. Uranium dioxide fuel pellets function as core reactor components, and dimensional accuracy directly governs assembly clearances, heat transfer performance and long-term operational safety. Traditional workflows rely on contact instruments such as vernier calipers and displacement sensors that require separate inspection stations. 

Physical contact carries risks of surface abrasion, while manual operations bring inconsistent results and extended cycle times. Existing vision-based solutions are generally limited to cylindrical or end-face measurements and cannot reconstruct complete three-dimensional geometry, creating a long-standing gap for integrated high-precision inspection hardware.

Stringent micrometre-level tolerances, distinctive dished end-face geometry and requirements for non-destructive mass production inspection formed the starting point for the collaborative research programme.

The research team has developed a coordinated hardware platform integrating telecentric two-dimensional imaging and line-laser three-dimensional scanning, paired with self-developed upper computer control software. Three operational modes are available: standalone two-dimensional inspection, three-dimensional scanning and combined full-dimension measurement. Complete geometric data covering cylindrical surfaces and end faces can be gathered without repeated re-fixturing. The two-dimensional module uses sub-pixel contour extraction algorithms to measure diameter, height, chamfer and perpendicularity. 

A proprietary geometric neighbourhood filtering algorithm reduces redundant point cloud data by 70 per cent while preserving critical dished-surface features, significantly accelerating calculations for dish diameter, depth and shoulder width.

Field testing confirms robust operational performance. Routine inspection focusing only on cylindrical parameters takes six seconds per pellet, while full-dimension checks incorporating three-dimensional topography require approximately eighteen seconds. Measurement precision for end-face dimensions surpasses ±0.02 millimetres. Repeatability trials show standard deviations for reference pellet diameter and height held below five micrometres. 

Simulated batch testing with random feeding demonstrates that variations across all measured parameters comply with the demanding IT5 tolerance standard applied in nuclear component manufacturing.

Supported by national research programmes, the project covers theoretical derivation, hardware and software development and full physical verification. It eliminates constraints inherent to contact inspection while meeting three core requirements: non-destructive handling, rapid throughput and high measurement accuracy. The integrated vision inspection system has been deployed on production lines at CNNC Jianzhong Nuclear Fuel Element Co., Ltd. Further work will target improved positioning robustness, simplified calibration workflows and faster point cloud processing to lift overall inspection throughput.

Deployment of the new technology will facilitate large-scale, high-quality intelligent manufacturing of nuclear fuel assemblies and strengthen precision metrology infrastructure underpinning secure, long-term operation of domestic nuclear power facilities.