designing the ground engineering system (GES) experiments. Extrapolation of these data to the SP-100 system full power operating lifetime of 7 years indicates that a minimum stress of 2.6 MPa in NblZr-Type A will result in a total creep strain of 2% at 1400 K. Additional data from NblZr-Type A and Type C creep tests during the remainder of the SP-100 project will result in a more accurate prediction of the allowable creep stress for both NblZr and materials. Reactors I&C Subsystems Status The components and the configuration of the reactor I&C subsystem are shown in Fig. 19. The Reactor I&C preliminary design is complete, and was formally reviewed June 20 through June 23, 1989. The key development components are the multiplexers, sensors, reflector segment actuators and safety rod actuators. The multiplexers are required as close to the sensors and actuators as possible to provide amplification of the sensor signals and to reduce the mass of control cable from the actuators to the power conditioning and control hardware. Therefore the multiplexer electronic components must operate in a high neutron and gamma flux environment, i.e., total dose over 10 years is 4 X 1015 n/cm2 and 2.4 X 108 rads of gamma. The junction field effect transistor (JFET) devices and glass capacitors are being tested for these high neutron and gamma doses at much higher dose rates than the space system would experience in order to quickly screen these components. The n-type JFET devices were exposed to a total integrated gamma dose of 10 X 108 rads and showed little or no permanent damage. The p-type JFET devices all failed below 10 megarads (10 X 106 rads), but
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