Deployment and In-Reactor Testing of an Instrument for Real-Tme Monitoring Thermal Conductivity Evolution of Nuclear Fuels

Thermal conductivity of nuclear fuels directly ties to the reactor safety and efficiency. Because of the microstructure defects generated and evolved in the extreme reactor environment, thermal conductivity of nuclear fuels reduces significantly during the reactor operation. Currently the experimental efforts on understanding such effects are primarily from the post-irradiation-examination (PIE) testing. However, an important type of phonon scatters, point defects, anneal at high temperature after the reactor shutdown and before PIE can be performed. In order to fill this technical gap, we developed an instrument that can perform real-time thermal conductivity measurements in reactor. Here we presented the latest testing results of this instrument in Massachusetts Institute of Technology Research Reactor (MITR). The final objective is to provide the routine measurement capability of thermal conductivity of nuclear fuels and materials in reactor. It will make better understandings of the scattering mechanisms between defects and thermal carriers possible, and help predict the fuel performances in reactor.