Post-irradiation analysis of SINQ target rods by thermal neutron radiography

Cylindrical lead rods from the SINQ spallation neutron source target have been investigated by thermal neutron-radiography/-tomography using a setup for highly activated samples and dysprosium loaded imaging plates. 2D radiography and 3D tomography results have been obtained from lead target rods from SINQ Target-5 irradiated for 2 years, corresponding a total proton charge accumulation of 10.85 Ah. This was the only non-destructive evaluation method capable to visualize macroscopic material changes induced by proton and/or neutron irradiation. The size and location of defects were identified and areas of interest could be selected for further destructive testing. The high sensitivity of neutrons for hydrogen makes this technique particularly useful when looking for metal hydrides. The formation of lens-shaped zirconium hydride blisters has been identified at the steel/Zircaloy interface of a lead rod with a combined steel/zircaloy cladding. Qualitative and quantitative information has been derived from this neutron radiography inspection.