Increasing the Sensitivity of Passive SiC Thermometry Through Nanocalorimetry Experiments

Determination of the sample temperature during irradiation experiments is crucial to the analysis and interpretation of subsequent characterization. Passive thermometry of in-reactor core experiments, through subsequent dilatometry of SiC temperature monitors, suffers from uncertainties that can be as large as ± 50 °C. Optimization of thermometry specimens, to reduce this uncertainty, requires accelerated irradiation testing and reduced sample geometry. However, developments in TM design are hindered by the time and significant cost of instrumented in-core neutron-irradiation campaigns and also by the dimensional requirements of dilatometry specimens. We propose to benchmark ion-irradiation of SiC as a surrogate for neutron-irradiation in order to shrink the required geometry of temperature monitors through nanocalorimetry of ultra-miniature specimens. The proposed work will validate the precise exploration of irradiation temperature of a SiC thermometry piece irradiated in HFIR at nominally 300°C and through well controlled and actively monitored proton and helium ion irradiations at 300°C of SiC. Together, these three conditions will demonstrate the use of nanocalorimetry to conduct passive thermometry at an increased spatial resolution of over 400x compared to current methodologies. This will enable the characterization of temperature gradients within in-core capsules and increase the fidelity with which reactor irradiations can be analyzed and interpreted. In addition, this proposal will establish the use of nanocalorimetry as a technique that can characterize defects that are below the resolution limit of electron microscopy, thus quantifying the most significant contributors to both swelling and degradation of thermal conductivity in irradiated SiC. The proposed work will require one day of ion irradiation and twenty days to produce specimens for nanocalorimetry. The outcome will be an advancement of the fundamental science behind radiation damage in SiC to better understand their limitations as temperature monitors.