Emission Tomography
CANDU FUEL - Cs137 migration
large depression activity in the middle of the rod
accumulation of Cs137 in the last mm of the rod
lack of pellets interfaces
Cs137 Axial Profile
An example of the application of the EGCT method for the detection of failed rods will be given. Here we present two examples of tomographic reconstruction and radial profiles for two CANDU fuel pins.
Cs137 - Intact Rod Cs137 - Failed Rod
25 x 25 pixels slit width = 0.25 mm projection angles = 5
The radial profiles are clearly different. In the intact rod maximum emission is localized in the core region of the rod while the failed rod shows a significant migration of the volatile Cs137 isotope towards cooler regions, in this case the pellet-clad interfaces. Indeed, if a fuel rod failure does occur, this causes a release of fission products into the primary coolant system and penetration of the coolant in the pellet interfaces. Complex chemistry is taking place. Same information is displayed, in a more subtle way, in the reconstructed cross sections above. Most visible is the elevated concentration of Cs137 isotope at the clad perimeter.