Advances in neutron imaging for non-destructive testing: Developing techniques, challenges, and future directions

Neutron radiography is a non-destructive imaging tool that utilizes neutron beams for the investigation of the internal material structures. It offers a unique sensitivity for light elements such as lithium, boron, and most importantly hydrogen. Neutron radiography has evolved past its small accelerator experimental days of the early 1930s into highly advanced studies at large facilities such as research reactors and spallation sources. Neutron radiography facilities currently utilize scintillator-detectors, imaging plates, and high-resolution cameras, along with advanced image-processing techniques, in order to obtain higher spatial resolution and reduced noise. This imaging technique opens the doors for studies across a wide range of industries and applications, such as two-phase flow visualization, energy materials’ studies such as fuel cells and lithium-ion batteries, and analysis of objects of cultural heritage relevance. Modern-day neutron imaging suffers from limitations such as neutron source availability, safety and operational issues, elemental selectivity, and high computational demands for image reconstruction. Despite this, neutron radiography still remains a valuable complementary tool to conventional x-ray imaging, as it provides insights into structures and processes that are otherwise difficult to visualize. This review paper summarizes the evolution, advantages, and limitations of neutron radiography while also highlighting the many applications it has across multiple fields. It aims to consolidate recent advances while also providing a forward-looking perspective on the role of neutron imaging in the radiography field as well as a complementary imaging tool.