Application of neutron imaging plate and neutron CT methods on nuclear fuels and materials

Advanced neutron radiography techniques such as the neutron imaging plate (NIP) and neutron computed tomography (NCT) methods have been investigated in the practicability for the postirradiation examination (PIE). In current works, an unirradiated fuel rod was examined by NIP and NCT methods in order to collect the fundamental data for applying these techniques to the PIE. A fuel rod used is composed of seven-enriched UO₂ and two-natural UO₂ pellets with controlled sizes and shape that are loaded into a Zircaloy tube. The neutron radiography tests were performed by NIP and NCT methods at the 2nd Thermal Neutron Radiography Facility (TNRF-2) in the Japan Research Reactor (JRR)-3. In the NIP image of the fuel rod, the difference in the size, shape, and enrichment between the UO₂ pellets is obviously recognized. In the case of NCT method, the images clearly show the detailed shape of the cross section in both enriched and natural pellets; and difference in the enrichment between those pellets is also observed. In addition, size difference between fuel parts of specifications and those in NCT images is evaluated.