Pulsed thermography using infra-red TV for in-reactor structural inspection

Over recent years infra-red thermal imaging has been used successfully inside nuclear reactors to assess the state of the vessel insulation and its attachment to the vessel wall. This paper describes an enhancement of the technique whereby other mechanical structures in the reactor can be tested for soundness by applying a relatively long thermal pulse and post processing the captured images to reveal cracks or weld discontinuties. This technique has proved to be a rapid and cost effective non-contact inspection technique which can be used as an alternative to NDT or other mechanical contact testing. Examples are given where the technique has probed relatively large steel structures for oxide jacking damage and even seen through 4 mm steel plate to reveal failures in visually concealed welds. Work on radiation hardening and other modifications to the cameras is also reported. (Author)