Eddy current array developments for remote deployment on the ITER project

Abstract

The inspection of welds and components for nuclear applications can be more challenging due to extreme levels of radiation and temperature. A development project in collaboration with the UK Atomic Energy Authority (UKAEA) is being conducted to develop non-destructive testing (NDT) procedures for inspecting the remotely welded joints within the ITER facility. Initially, a feasibility study has been carried out to identify the most suitable non-destructive technique. Eddy current array (ECA), phased array ultrasonics and guided wave electromagnetic acoustic transducers (EMATs) were considered as candidate solutions and, following the feasibility study, ECA was selected to be taken forward for further development. Subsequently, dedicated high- and low-frequency array probes have been developed and tested to detect and size surface and buried defects employing encoder and calibration curves. The research has been extended to characterise defects such as tungsten inclusions using the phase angle. To avoid damage to the electronics in extreme environments, the ECA probe coils were separated from the excitation and data acquisition unit with 60 m coaxial coils to achieve a high signal-to-noise ratio. The results revealed that the ECA technique can successfully be deployed remotely for the detection and sizing of defects down to 3 mm in extreme environments.