The Effects of Nuclear Radiation on High Temperature Thermistors

High temperature thermistors, 100°C to 600°C, were tested before, during, and after irradiation in the Ground Test Reactor at The Nuclear Aerospace Research Facility, General Dynamics/Fort Worth. The radiation environment was held constant at 2.2 × 1010 nf/cm2-sec (nf = fast neutrons with energy> 2.9 Mev) and 4.2 × 108 ergs/ gm(C) hr ¿ for a period of 91 hours. Resistance as a function of temperature was measured for high, medium, and low resistance type thermistors. No permanent damage was observed, but transient effects were severe at high resistance values. The transient effects were due to ionization of the air and the thermistor material by the nuclear environment. The ionic conduction in the thermistor material was highly temperature dependent.