Non-destructive evaluation of nuclear fuel rods using neutron radiographyat the Tehran Research Reactor

Three fresh fuel rods containing pellets inside zirconium tubes with three different enrichments and different dimensions have been evaluated using neutron radiography examinations at the Tehran Research Reactor. To obtain the information of the internal structure of the fuel rods, two different imaging methods, based on using single coated radiography film and phosphorous imaging plate were applied. The quantitative and qualitative evaluations of the fuel rods have been made using neutronic images of these examinations. In the qualitative evaluation of the images, the internal components of the fuel rod, such as pellets, springs, and end plugs, were well visible. The single coated radiography film had a better spatial resolution rather than the image plate so that the internal details of the rods and the gaps between the pellets were clearly detectable. In the quantitative evaluation, the pellets dimensions, the gaps between pellets, and the dependence of the absorption cross-section with the pellets enrichment have been measured and compared with the manufacturer specifications. This information was in good agreement with each other.