Development of tungsten fiber-reinforced copper composite pipes for EU-DEMO Divertor target

Within the roadmap of the EU-DEMO reactor design pursued by the EUROfusion Programme, R&D activities are promoted for the technological development of Plasma Facing Components. A dedicated task aims at consolidating and verifying the current target concepts envisioned for DEMO Divertor, derived from the reference ITER-like W-monoblock concept and the back-up solution with tungsten fiber-reinforced copper (Wf-Cu) composite pipes. ENEA has undertaken a research activity to support the back-up concept, finding alternative technological solutions for monoblock-pipe joining to reduce the use of materials having high activation and/or degradation under neutron irradiation. In particular, the possibility of joining the blocks to the pipe without brazing alloy has been investigated. An impregnation procedure consisting of copper casting with the simultaneous impregnation of pre-wrapped W fibers and the junction of the W monoblocks in a single process has been developed. A crucial point is the realization of high-quality composite tubes, having dimensions as close as possible to the ones of the standard CuCrZr tubes currently envisaged for DEMO Divertor, as well as a Cu matrix in which the content of defects and imperfections is reduced as much as possible. For this purpose, a set of samples having a DEMO Divertor target cooling tube shape are fabricated, and their quality is assessed through non-destructive (ultrasonic testing) and destructive (i.e., metallography) examination techniques.