Deuterium retention in the elements of plasma facing components for the DEMO first wall

The fully reduced activation brazing alloy TiZr4Be and a tantalum intermediate layer are considered to be used for joining tungsten (W) to reduced-activation ferritic-martensitic steel (RAFM) for future DEMO reactor application. Deuterium retention in the W-Rusfer joints and separate elements was investigated with the focus on the intermediate brazing layer. The samples were exposed in deuterium gas ( p = 1- 10 4 Pa, T = 30 0-60 0 C) and plasma discharge ( T = 600 C). An acceptable deuterium concentration was observed after gas exposure at the pressure of 1 Pa, that is relevant to operating conditions of future fusion devices, however the brazing alloy and tantalum accumulate a large amount of deuterium in the case of the pressure above 100 Pa that leads to failure of the joint. The D retention after D plasma irra-diation was substantial, but nearly independent on the fluence and the thickness of the W layer due to absorption from surrounding D 2 gas. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The study investigates the use of fully reduced activation brazing alloy and tantalum intermediate layer for joining tungsten and reduced-activation ferritic-martensitic steel. The deuterium retention in the joints and separate elements was studied, and it was observed that an acceptable deuterium concentration can be achieved under specific operating conditions but higher pressure leads to joint failure.