The Vacuum Tight Threaded Junction (VTTJ) is an innovative vacuum-compatible non-welded junction developed and patented by Consorzio RFX. This technique is used to join not easily weldable materials, such as copper and stainless steel, to manufacture components exposed to vacuum conditions in nuclear fusion experimental devices. Presently the technique is used for two experiments; the Source for Production of Ion of Deuterium Extracted from Rf plasma ( SPIDER) and the Megavolt ITer Injector and Concept Advance (MITICA). SPIDER and MITICA are two prototypes under
construction in Padua (Italy) aimed at testing and optimizing the future operation of the International Thermonuclear Experimental Reactor (ITER) heating neutral beam injectors. ITER will be the first fusion device to produce net energy and will include two neutral beam injectors. SPIDER is the full-size radio frequency negative-ion source and MITICA is the full-scale prototype of the ITER heating neutral
beam injector. These two facilities are actively cooled by ultrapure Water (UPW) to electrically insulate in-vessel components that are biased to high voltage levels. Actively cooled components, made of copper or copper alloys, are connected to stainless steel piping by means of VTTJs. The VTTJ has been tested up to 500 bar internal pressure and up to 700 °C, showing excellent leak tightness in
vacuum conditions and high mechanical strength. However, no investigations on the metal release performance of this junction in UPW have been carried out. In this work, sectioned VTTJ prototypes revealed that there are area exposed to high water velocity (up to 7 m/s) as well as small stagnant water regions. This paper presents the first experimental results for stainless steel and copper samples
exposed to stagnant UPW at ambient temperature to investigate their general corrosion behavior as found in the VTTJ. Trace metal analysis using Inductively Coupled Plasma Mass Spectrometry (ICPMS) was used to quantify the release of metals when stainless steel and copper are either exposed separately to UPW or when they are coupled together in stagnant conditions.