BPX insulation irradiation program test results

BPX (Burning Plasma Experiment) toroidal-field coil insulation was radiation-tested to doses on the order of 3×10¹⁰ rad. Vacuum-impregnated materials, glass strand material, and Spaulrad-S sheet samples were tested. Vacuum impregnation with a Shell 9405 resin and 9470 hardener was used to produce bonded copper squares and flexure samples of both pure resin and resin with S-glass. The Spaulrad-S flexure samples demonstrated a loss of strength with irradiation, similar to previous results. The pure resin lost nearly all flexibility, while the S-glass-reinforced samples retained between 30% and 40% of the initial flexure strength. The S-glass strands showed a 30% loss of strength at the higher dose level when tested in tension. The bonded copper squares had a low room-temperature shear strength of approximately 17 MPa before and after irradiation. shear testing revealed that the low shear strength resulted from the polyurethane primer used. In later tests the epoxy-based primers and DZ-80 from Ciba-Geigy showed with shear strengths on the order of 40 MPa