Thesis (Ph.D., Mechanical Engineering) -- University of Idaho, 2015 | New fuel, cladding, and structural materials offer the potential for safer and more economic energy from existing and advanced nuclear reactor designs. However, insufficient data are available to characterize these materials in high temperature, radiation conditions. To evaluate candidate material performance, robust instrumentation is needed that can survive these conditions. Furthermore, the nuclear industry increasingly relies on computer models to predict the behavior of components and systems in both normal and off-normal conditions. Current measurement techniques cannot resolve physical phenomena with sufficient resolution to match the level of detail current models are capable of achieving. New sensors and measurement techniques are needed to validate these models. Irradiation testing of new, high performance fuels and materials for advanced reactor designs will require sensors capable of operation in conditions unsuitable for other, commonly used temperature sensors.
The objective of this research is to enable deployment of Ultrasonic Thermometers (UTs) in irradiations of ceramic and metallic fuels. Research was broken into two main areas; out-of-core development and testing of the UT and its components in a laboratory environment and in-core assessment of the radiation tolerance of the magnetostrictive transducers used to generate and sense the acoustic signals.
Significant progress was made toward the deployment of an ultrasonic thermometer for in-core experiments. Appropriate materials were identified for applications below 1000 °C and between 1000 and 2500 °C. A new, high frequency transducer was developed and used to improve spatial resolution of the ultrasonic thermometry system.
An irradiation test was initiated to identify transducer materials that can survive in a high radiation environment. It is the first to include both piezoelectric and magnetostrictive materials, and is scheduled to surpass other ultrasonic transducer irradiations in terms of total fluence. The included transducers were operated during irradiation and the test capsule was heavily instrumented with real time sensors, resulting in a high degree of confidence in the results. The results shows ultrasonic transducers based on magnetostrictive materials to be highly resistant to degradation caused by neutron and gamma radiation.