Development and Evaluation of Mineral Insulated Diagnostic Probes Subjected to High Dose Neutron Irradiation

40941 November 18, 1996 Delta M Corporation Nuclear systems, including high power accelerators and fission and fusion power plants, rely on diagnostic sensors and probes to monitor and control operation. A problem common with these systems is their lack of reliability when subjected to intense radiation. For example, it is common for thermocouples to prematurely fail under neutron irradiation, and it has been shown that diagnostic coils and sensors which are currently in use in fusion systems will be unacceptable in the next generation fusion power plants. This lack of reliability is caused by an irradiation induced degradation in the insulating material used in these components. Specifically, neutron and gamma irradiation can cause both an immediate, transient degradation as well as a permanent degradation in the resistive capability of insulating material. This project will examine the permanent degradation in the insulating capability of mineral insulated diagnostic probes used in fusion systems in order to understand the conduction mechanisms of mineral insulated probes subjected to neutron irradiation environments. For several combinations of materials and processing parameters, the radiation induced electrical degradation (RIED) will be quantitatively measured. The most radiation resistant combinations will be carried into Phase II. Anticipated Results/Potential Commercial Applications as described by the awardee: The mechanisms responsible for the degradation in mineral insulated cables should be understood, and concrete radiation hardened diagnostic probes, to be used in fusion systems such as ITER, will be identified.