High resolution ultrasonic inspection of different high heat flux components for future thermonuclear fusion devices
M. Sheerer, P. Hahn, L. Plöchl, M. Rödig, I. Smid, Forschungszentrum Julich, Julich, Germany
ABSTRACT
High heat flux components for future thermonuclear fusion devices such as divertor's or limiter's will be exposed to heat loads up to 5 MW/m2 in steady state operation, and up to 30 MW/m2 under transient conditions. To remove the deposited heat actively cooled components consisting of Carbon-Fibre-reinforced-Carbon (CFC) armour connected to a copper-base or refractory metal heat sink are selected. Different joining technologies like high temperature brazing, diffusion bonding, electron beam welding or active metal casting are applied to connect the plasma facing armour with the heat sink material. One important task is the non-destructive testing of the integrity in the interface between the armour and the heat sink, as well as the inspection of defects in the cooling system. A high resolution ultrasonic inspection system using transducers with frequencies up to 100 MHz was used to visualise defects like pores or cracks n the interface and in the bulk materials. Depending on the material, resolutions down to 20 mm are achieved. A 4-dimensional motorised axis positioning system is used to scan different shape of specimens. The system works in impulse echo mode to create a 3-dimensional picture of the probe using the time of flight method for the determination of the depth. In order to inspect the whole interface of long cylindrical components, a special positioning unit was produced to scan lengths up to 1 meter from inside the coolant tube. Different divertor modules were ultrasonically inspected and the results were correlated using other non-destructive or destructive methods like thermography or metallography. A very good agreement between the ultrasonic inspection and the other methods is achieved, which is of interest for a reliable NDE of nuclear components before assembly.
Publication Source: First International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components , 20 - 22 October 1998, Amsterdam, Netherlands. Held by the Joint Research Centre of the European Commission. Publisher:Woodhead Publishing Limited
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