First Wall Qualification Testing at SNL

The first wall of ITER will be a replaceable sandwich of beryllium tiles, water-cooled copper alloy, and a water-cooled stainless steel backing. The first wall will be subject to approximately 30,000 pulses of surface heating at levels of 0.2 - 0.5 MW/m² and 5 - 10 W/cm³ of volumetric nuclear heating. At these low heating levels, the main failure mechanism is predicted to be fatigue, particularly at the interface between the copper alloy and beryllium tile. Six different party teams are proposing to produce the first wall for ITER To qualify the processes and materials for producing the first wall, small mock-ups will be subject to fatigue testing at Sandia National Laboratories´ (SNL) Plasma Materials Test Facility and at a European Union test facility. We propose that the failure of a joining process is determined by an increase of surface temperature over nominal temperatures for a given surface heat flux. If the joint between a Be tile and Cu alloy degrades, the path from the heated surface to the coolant in the copper alloy increases, which should result in a higher surface temperature. This paper will document the test setup and preliminary analysis of the fatigue testing and failure criteria at SNL.