SNAP Environment Simulation Problems

The development of components for the SNAP (Systems for Naclear Auxiliary Power) program requires life-testing under fast neutron and gamma irradiation in ultra-high vacuum at temperatures to 1200F for periods up to one year. Thermal-vacuum evaluation is first performed followed by irradiation testing at levels to 1019 nvt (E> 0.1 Mev.) and 1010 r (Gamma) at operating temperature and pressure. The practical problems involved in conducting a successful component irradiation program include considerations of material compatibility with the irradiation and temperature levels, proper selection and operation of vacuum equipment, and the establishment of procedures which provide the cleanest possible conditions within the siamulation chamber. This paper discusses the above problems and the modifications which were required in both materials and vacuum pumping equipment. Materials phenamena related to the combined vacuum-temperature-irradiation environment are also presented. Discussion is made of the technical problems experienced in the combined environmental tests of two SNAP 10A control drum actuators coupled to two control drum position sensors.