Assessing braze quality in the actively cooled Tore Supra phase III outboard pump limiter

The quality of brazing of pyrolytic graphite armor brazed to copper tubes in Tore Supraʹs phase III outboard pump limiter was assessed through pre-service qualification testing of individual copper-tile assemblies. The evaluation used non-destructive hot-water transient heating tests performed in the high temperature, high pressure flow loop at Sandiaʹs Plasma Materials Test Facility. The surface temperatures of tiles were monitored with an IR camera as water at 120 °C at about 2.07 MPa (300 lbf in−2) passed through a tube assembly initially at 30 °C. For tiles with braze voids or cracks, the surface temperatures lagged behind those of adjacent well-bonded tiles. Temperature lags were correlated with flaw sizes observed during repairs based upon detailed two-dimensional heat transfer analyses. “Bad” tiles, i.e. temperature lags of 10–20 °C depending upon a tileʹs size, were easy to detect and, when removed, revealed braze voids of roughly 50% of the joint area. 11 of the 14 tubes were rebrazed after bad tiles were detected and removed. Three tubes were rebrazed twice.