Ultrasonic testing of plasma-facing ITER components with use of a innovative equipment

Transcription

1 Ultrasonic testing of plasma-facing ITER components with use of a innovative equipment Dmitry V. Lyanzberg 1, Tamara M. Guryeva 1, Radmir N. Giniyatulin 1 and Andrey N. Bulavinov 2 1 Efremov Institute of Electrophysical Apparatus, St. Petersburg, Russia, lyanzberg@sintez.niiefa.spb.su 2 I-Deal Technologies GmbH, Saarbrucken, Germany, info@i-deal-technologies.com Abstract Efremov Institute of Electrophysical Apparatus (NIIEFA) is large Russian developer and manufacturer of high-heat-flux plasma-facing components (PFC) of the First Wall Panels (FWP) and of the Divertor for the ITER project. Non-destructive testing of the ITER PFCs is obligatory procedure because of extreme operating conditions and high requirements to quality of manufacture. The FWP and Divertor components represent geometrically difficult multi-layered constructions made from various materials: stainless steel, tungsten, beryllium, copper, bronze. The components are manufactured by different joining methods, i.e. brazing, casting, explosion welding, hot-isostatic pressing. The welded joints of components represent austenitic seams of difficult configurations with limited zones of access executed by various technologies of argonarc and laser welding. The paper illustrates the experience of use of innovative technologies and equipment for the solution of problems of ultrasonic testing. The robot-based immersion equipment is used for ultrasonic testing of multi-layered joints (tungsten/copper/bronze, beryllium/bronze, bronze/steel) in the ITER objects having the curvilinear surface for input of ultrasonic waves. In the report the authors consider the features and advantages of use of the robotic equipment in combination with the Phased Array technology. The specialized scanner and the specialized probe with surface adapted under the internal diameter of a tube are used for in-tube ultrasonic testing of the multi-layered joint (bronze/copper/tungsten). The paper includes the examples of acoustic images that characterize the quality of materials and various joints in multilayered ITER PFCs. The welded joints executed by argon-arc and/or laser welding are tested using the modern equipment of manual ultrasonic testing with use of Phased Array technology and the scanning devices with visualization of testing results. The analysis of use of the innovative equipment and comparison of testing results from foreign participants of the ITER project allows to draw a conclusion about informativity and relevance of ultrasonic testing technologies at manufacture of the ITER components in Russia. 1. Introduction The International Thermonuclear Experimental Reactor (ITER) is the international project, the main aim of which is to prove the feasibility of producing energy from the fusion process. In the context of the RF international commitments the JSC NIIEFA manufactures and delivers to the ITER site the high-heat flux in-vessel ITER components, Creative Commons CC-BY-NC licence

2 namely, the Divertor DOME and first wall panels (FWP), coil PF-1, protective switching equipment. Of importance is to develop industrial non-destructive testing (NDT) technologies for the ITER components to ensure the required quality of non-standard products. The in-vessel DOME and FWPs are geometrically complicated components produced by different joining methods (casting, high-temperature brazing, Hot Isostatic Pressing (HIP), explosion welding, laser welding, argon-arc welding) from variously combined materials (tungsten W, beryllium Be, copper Cu, bronze CuCrZr, stainless steel SS 316L(N)) (1). Fig. 1 shows the external view of the ITER DOME and FWP. Figure 1. External view of the ITER DOME and FWP The design solutions, as well as materials and technologies for multi-layered joints are determined by high thermal, electromagnetic and neutron loads on the ITER plasmafacing components. With consideration for numerous destructive factors affecting the quality of materials and their joints the ITER components must be subjected to nondestructive testing. The JSC NIIEFA has developed the NDT basic complex, which includes technological equipment, programs, techniques and certified personnel ensuring the required quality of the ITER components according to the requirements of EN ISO for NDT. The following NDT methods are applied: ultrasonic testing (UT), radiographiс testing (RT), visual testing (VT), penetrant testing (PT) and eddy current testing (EC). The most actual and innovative are UT technologies of multilayered (bimetallic and trimetallic) joints of dissimilar materials for the ITER plasma-facing components. 2. Ultrasonic testing of ITER plasma-facing components The ITER plasma-facing components are made as two-, three- and four-layered structures consisting of armoring tiles (W and/or Be), heat-sink panels (Cu and/or CuCrZr) and bearing support (SS) made by different technologies. The character of possible defects (small-opening lack of penetration between layers, differently oriented cracks in joined materials), geometrically complicated and large-size ITER plasmafacing components, as well as the experience in the performed studies define the automated UT as the most informative and reliable NDT method. To comply with the ITER regulations concerning assessment of real defects in materials and on the interfaces of multi-layered joints the following is used in the UT equipment: 2

3 - mathematical algorithms for processing of diffraction waves excited and/or generated in the tested object (2) (3); - Full-Matrix-Capture (FMC) method for measurement of ultrasonic data and Sampling Phased Array (SPA) method for tomographic processing of measuring data (4). At the JSC NIIEFA the ultrasonic testing of multilayered joints is provided by automated UT systems based on the FAZUS interference scanning flaw detector (ISFD), Roboscan-3D-UT robotized UT complex (Germany) and Tube Inspector-3D- UT system for in-tube testing (Russia/Germany). 2.1 UT based on FAZUS ISFD The automated ISFD-based equipment employs the acoustic holography method based on the interference method for imaging of the tested object by acoustic waves. The advantages of the holographic interferometry methods are three-dimensionality and precise presentation of the testing results, high noise immunity, possibility to process and to analyze the obtained information in the off-line (post-processing) mode. The methods of the holographic interferometry allow one to detect and to measure weakly reflecting discontinuities by changes not only in the amplitude but also in the phase of the acoustic field. (2) In addition to the assessment of the material joint quality by the amplitude indications (amplitude C-scans) the UT based on the FAZUS ISD provides layer-to-layer analysis of the tested object by the so-called interference C-scans taking into account both the amplitude and the phase of the wave field scattered by the tested object. Fig.2 shows the tested object made as a tungsten-copper joint by the casting technology. The opportunities of the layer-to-layer analysis are illustrated by the example of UT results for a W/Cu joint. Fig. 2b - interference C-scan of a tungsten layer with evaluation of cracks and crack nuclei; Fig. 2c - interference C-scan of the W/Cu casting interface; Fig. 2d - interference C-scan of copper layer with evaluation of pores and intercrystalline structure. Figure 2. UT images of casting joint of blanks (a tested object, b interference C-scan of W layer, c interference C-scan of casting joint, d interference C-scan of Cu layer) The analysis of the UT results by the interference C-scans might reveal discontinuities, which, according to the specified test procedure, are not detected on the amplitude C- scans as defects, but are potential defects, as verified by the control testing after various 3

4 tests, the thermal ones including. The potentially dangerous detected defects can be measured, when the sensitivity is corrected at the post-processing stage, thus obtaining more information on the quality of the material joint. According to the ITER regulations for the ultrasonic testing the potentially dangerous detected zones should be recorded, measured and their propagation should be further analyzed. The method of processing of the UT results on the basis of the FAZUS ISFD produces reliable results confirmed experimentally by further metallographic studies. This method has proved to be good when analyzing the quality of such joints as CuCrZr/SS joint made by the explosion welding or HIP technology, W/Cu/CuCrZr and Be/CuCuCr joints made by the brazing technology. 2.2 Innovation approach in the UT based on Roboscan-3D-UT The automated UT of the ITER components with a geometrically complicated surface requires the flexibility of scanning manipulators ensuring the optimal orientation of the acoustic waves relative to the tested object. Achievements of robotics in the accuracy of positioning and in development of data transfer interfaces determine the possibilities for robots to be applied for UT technologies. Introduction of up-to-date robotized systems for UT of geometrically complicated and large-size ITER components is optimal for solution of NDT problems. The ITER regulations specify the requirements for visualization of the tested object by the UT results in the online mode (possibility of ultrasonic tomography), for postprocessing analysis and archiving of UT results. The robotized ultrasonic tomography determines high requirements for the scanning systems, as it is necessary to process the ultrasonic data obtained simultaneously from different positions of the tested object. Six-dimensional tracking of the position in real time at a high measurement accuracy not less than 0.1 mm and at a scanning speed of several hundred mm/s is not a typical requirement for industrial robotized system used currently, for example, for cutting, welding and «pick-and-place» operations. Specific synchronization interfaces between robot motion control and UT hardware are needed to provide fast and accurate data acquisition that is appropriate for tomographic reconstruction purposes. (4) The JSC NIIEFA jointly with the I-Deal Technologies GmbH (Germany) has developed and introduced the Roboscan-3D-UT robotized immersion UT complex.(fig.3), where an industrial six-axial robot produced by the KUKA company is used as a manipulator. 4

5 Figure 3. Roboscan-3D-UT robotized immersion complex The control unit of the KUKA KR AGILUS manipulator ensures reading of ultrasonic data with a repetition frequency up to 1 khz. The three-dimensional reconstruction of tested object data is realized by the SPA method. This SPA method provides the reconstruction of ultrasonic data with a high spatial resolution in the real time mode. The SPA method makes it possible to reconstruct the surface profile by ultrasonic data from one of the measuring cycles and to correctly reconstruct the UT tomographic image of the tested object. The three-dimensional presentation of the tested object is obtained by combining the UT images of sections (B-scans) in all measuring positions. The UT tomographic image of the tested object is reconstructed on the basis of a CAD model of the tested object. The advantages of the Roboscan-3D-UT robotized complex are the automatic detection and evaluation of the detected defects according to the sensitivity calibration, where the rejection criteria are the sizes of indications and their geometrical positions. The possibilities of detection and evaluation of defects are illustrated by the example of the robotized UT of the W/Cu/CuСrZr joint (Fig.4). 5

6 Figure 4. Automated 3D evaluation of the UT results The testing results are finally approved by a system operator using universal instruments for the analysis of 3D-images. The opportunities of the high-technology robotized UT have been verified by the results of the control carried out on the prototypes of the ITER in-vessel components. 2.3 In-tube UT based on Tube Inspector -3D-UT system Within the framework of the ITER project new structural and technological developments are tested for compliance with the requirements imposed on the ITER invessel components. Ultrasonic testing was carried out at performing a work on the effect of thermal loads on the quality of multilayered joints of the Divertor Vertical Targets at different stages of High Heat Flux Testing (HHFT). The objects of researches represent the technological mock-ups consisting from tungsten (W) monoblocks joined to a bronze (CuCrZr) cooling tube (internal diameter 12 mm, outer diameter 15 mm) through a layer of copper (Cu) from 0,5 mm to 1,5 mm thick. In-tube UT is carried out using the Tube Inspector-3D-UT equipment. The Tube Inspector-3D-UT system consists of a ultrasonic electronics unit of the robotic complex Roboscan-3D-UT, a specialized scanning device and a in-tube focused single-element probe (15 MHz) with a surface adapted for the internal diameter of a bronze tube. The scanning device provides immersion UT of a multilayered joints by rotary-translational motion of the ultrasonic probe with a specified measuring raster inside the tested object. Using the example of the in-tube UT results of the multilayered CuCrZr/Cu/W joint, the possibility of detecting and evaluating defects before and after the various stages of HHFT of one of the technological mock-ups are shown (Fig. 5). 6

7 Figure 5. UT images of casting joint of technological mock-up after various stages of HHFT (a tested object, b C-scan before HHFT, c C-scan after 3 rd HHFT) The ultrasonic image represent a C-scan of the CuCrZr / Cu (bronze / copper) joint of the tested object, consisting of 7 monoblocks. According to the ITER regulations for components of Divertor Vertical Targets, the threshold sensitivity of ultrasonic testing is set as the size of the indication on the C-scan from the flat-bottomed hole Ǿ2 mm on each of the boundary of the multilayered joint. The possibilities for reconstructing ultrasound images using ultrasonic electronics of the robotic complex "Roboscan-3D-UT" are confirmed by the detection of an internal surface condition of the bronze tube during the analysis of the in-tube UT results of the CuCrZr/Cu/W joint. Figure 6 shows an example of the ultrasonic image of damages on an internal surface of a bronze tube and their measurement made by a video-endoscopic method. Figure 6. UT images of casting joint of technological mock-up and image of bronze tube damage (made by video endoscope) 7

8 The analysis of in-tube UT results executed at different stages of HHFT is of great importance when determining dependences of quality of new modifications of plasmafacing components on the thermal loadings specified in the ITER project. 3. Conclusion The NDT complex has been realized at the JSC NIIEFA, which should assure the quality of the components manufactured and delivered by the Russian Federation in the framework of the ITER project. The automated and robotized system for ultrasonic visualization has been tried out on the geometrically complicated multi-layered invessel ITER components, namely DOME and FWPs. The three-dimensional presentation of the results, solution of defectometry problems, analysis of the UT results in the post-processing mode offer advantages, when estimating the quality of the manufactured products and their acceptance, as specified in the ITER regulations. References 1. I.V. Mazul, R.N. Giniyatulin, A.A. Gervash, T.M. Guryeva et al. Technological challenges at ITER plasma facing components production in Russia, Fusion Engineering and Design, v , 2016, p Egorov N., Gurieva T., Application of ultrasonic interference scanning flaw detector, В мире НК 3(45), pp 38-43, Lyanzberg D., Gurieva T., Belyaev A., Ultrasonic testing of ITER in-vessel components, In: 11th European Conference on Non-Destructive Testing (ECNDT 2014), October 6-10, 2014, Prague. 4. Bulavinov A., Pinchuk R., Gurieva T., Lyanzberg D., Lider A., Demyanuk D., Sednev D., Zhvyrblya V., Filippov G., Robot-based In-Process Examination of ITER Dome and First-Wall Panels based on Novel Ultrasonic Tomography Approach, In:19 th World Conference on Non-Destructive Testing (WCNDT 2016), June 13-17, 2016, Munich. 8