Development of Brazed W/Stainless Steel First-Wall Component with ODS-Cu Intermediate Layer for High-Temperature Wall in QUEST

抄録

A medium-scale tungsten (W)-sheet/stainless steel (SUS) first-wall component with an oxide dispersion strengthened copper (ODS-Cu; GlidCop^®) intermediate layer was developed using the advanced brazing technique (ABT) for high-temperature first-wall applications in the Kyushu University Experiment with a Steady-State Spherical Tokamak (QUEST). To ensure its reliability, the component’s thermal response was first evaluated in a vacuum test chamber, demonstrating a uniform surface temperature distribution up to 400°C with no problematic outgassing. Following these tests, the component was installed in the QUEST first-wall and subjected to temperatures up to 350°C during plasma operations from April 2 to 18, 2024. Surface inspections and elemental analyses performed after the campaign confirmed that the brazed interfaces remained robust; no further delamination or cracking occurred beyond the minor exfoliation initially observed after fabrication, despite long-term thermal loads and plasma-wall interactions. These results demonstrate the technical feasibility of using brazed W-sheet components for high-temperature first-wall applications in steady-state tokamaks.