Investigations of tungsten heavy alloy (WHA) for use on SPARC*

Tungsten based materials have been chosen for SPARC’s plasma facing components (PFCs). However, the brittle nature of pure tungsten makes it difficult to work with in a tokamak environment. This has motivated an evaluation of WHA for use in SPARC. WHA remains ductile even at room temperature and has been successfully deployed in a tokamak environment on ASDEX-Upgrade. However, there is a current gap in literature on the compression structural properties of WHA and the behavior of WHA when subjected to heat flux loading at magnitudes expected for SPARC transients. Previous tests have shown that the WHA, compared with pure tungsten, has a lower temperature failure mode due to the use of Ni and Fe binder materials. Testing indicates that WHA behaves in a ductile manner under compression loading. In addition, high heat flux testing carried out at the Applied Research Laboratory electron beam facility indicates a significant ejection of material when exposed to moderate heat flux levels (>100 MW/m² for durations of <100 ms). Though, when exposed to higher heat flux levels (~500 MW/m² for durations of <30 ms), surface melting in both WHA and pure tungsten is observed although with some distinguishing behavior.