Acceptance tests of iter vertical target divertor full scale plasma facing units fabricated by HRP

ENEA and Ansaldo Nucleare S.p.A. (ANN) have being deeply involved in the European International Thermonuclear Experimental Reactor (ITER) development activities for the manufacturing of the inner vertical target (IVT) plasma-facing components of the ITER divertor. During normal operation the heat flux deposited on the bottom segment of divertor is 5-10 MW/m² but the capability to remove up to 20 MW/m2 during transient events of 10 seconds must also be demonstrated. This component has to be manufactured by using armour and cooling pipe materials defined by ITER. The physical properties of these materials prevent the use of standard joining techniques. In order to overcome this difficulty, ENEA has set up and widely tested a manufacturing process, titled Hot Radial Pressing (HRP), suitable for the construction of these components. The last challenge is now to fabricate, by means the new HRP facility, a full scale prototype of the IVT for the final qualification and ENEA-ANN are now involved in the F4E-OPE138 contract where the fabrication of this component. The tolerances and acceptance criteria of the IVT plasma facing units (PFU) are fixed by ITER/F4E and are very tight. The objective of manufacturing a PFU that satisfies these requirements is an ambitious target. The final acceptance control to check the component compliance with the acceptance criteria is performed by ultrasonic water gap technique. A new equipment suitable for the final control of PFUs by ultrasonic was developed in ENEA with the purpose of speeding up the testing whilst mantaining the required technique resolution.