Irradiation and testing of SPAULRAD-S for fusion-magnet applications

This report describes work on the irradiation and testing of a fusion magnet insulator material, SPAULRAD-S, which is made from S-glass cloth and polyimide. Circular disks 11.1 mm diameter by 0.46 mm thick were irradiated in two facilities, the Advanced Test Reactor (ATR) at the Idaho National Engineering Laboratory and the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. Neutron fluences attained in these irradiations were 3.41 x 1023 n/m2 (E > 1 MeV) and 3.17 x 1024 n/m2 (total) for the ATR and 1.9 x 1021 n/m2 (E > 0.1 MeV) and 2.8 x 1021 n/m2 (total) for the IPNS. In addition a gamma dose of 3.0 x 109 Gy was obtained in the ATR irradiation. Temperatures of 325 K and 4.2 K were used for the ATR and IPNS irradiations, respectively. Post-irradiation tests included static compression, compression fatigue, and electrical resistance. No failures were observed in static compression tests when the specimens were loaded to a maximum attainable stress of 2750 MPa. Only one of five specimens from the ATR irradiation group failed in fatigue after cycling to 640 MPa for 277,500 cycles. No failures were observed for the IPNS specimens when cycled to the same maximum stress for 646,640 cycles. No change in electrical resistance was observed for the IPNS irradiation group compared to the control specimens (6 x 1011 Ohms) whereas a decrease by a factor of ten was found for the ATR group. These results are very encouraging for the use of SPAULRAD-S in fusion reactor magnets