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Ultrasonic test of carbon composite/copper joints in the ITER divertor

TitleUltrasonic test of carbon composite/copper joints in the ITER divertor
Publication TypeArticolo su Rivista peer-reviewed
Year of Publication2013
AuthorsRoccella, S., Cacciotti E., Candura D., Mancini A., Pizzuto A., Reale A., Tatì Angelo, and Visca E.
JournalFusion Engineering and Design
Volume88
Pagination1802-1807
ISSN09203796
KeywordsAcoustic attenuation, Artificial defects, Carbon composites, High heat flux components, Non destructive testing, Non-destructive control, Nondestructive examination, Pulse-echo technique, Tubes (components), Ultrasonic techniques, Ultrasonic testing, Ultrasonic waves, Ultrasonics
Abstract

The vertical targets of the ITER divertor consist of high flux units (HFU) actively cooled: CuCrZr tubes armoured by tungsten and carbon/carbon fibre composite (CFC). The armour is obtained with holed parallelepiped blocks, called monoblocks, previously prepared and welded onto the tubes by means diffusion bonding. The monoblock preparation consists in the casting of a layer of copper oxygen free (Cu OFHC) inside the monoblock hole. Each HFU is covered with more than 100 monoblocks that have to be joined simultaneously to the tube. Therefore, it is very important to individuate any defects present in the casting of Cu OFHC or at the interface with the CFC before the monoblocks are installed on the units. This paper discusses the application of non-destructive testing by ultrasound (US) method for the control of the joining interfaces between CFC monoblocks and Cu OFHC, before the brazing on the CrCrZr tube. In ENEA laboratory an ultrasonic technique (UT) suitable for the control of these joints with size and geometry according to the ITER specifications has been developed and widely tested. Real defects in this type of joints are, however, still hardly detected by UT. The CFC surface has to be machined to improve the mechanical strength of the joint. This results in a surface not perpendicular to the ultrasonic wave. Moreover, CFC is characterized by high acoustic attenuation of the ultrasonic wave and then it is not easy to get information regarding the Cu/CFC bonding. Nevertheless, the UT sharpness and simplicity pushes to perform some further study. With this purpose, a sample with artificial defects induced on the CFC/Cu interface during the Cu casting, has been manufactured and investigated, both by pulse-echo technique and by different techniques. The results obtained by the UT on this sample are reported and compared with X-ray method. © 2013 Elsevier B.V.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-84884980259&doi=10.1016%2fj.fusengdes.2013.05.078&partnerID=40&md5=f88a29151de0e1a6185db44e4c4e22f0
DOI10.1016/j.fusengdes.2013.05.078
Citation KeyRoccella20131802