Host: The Japan Society of Mechanical Engineers
Name : The 30th International Conference on Nuclear Engineering (ICONE30)
Date : May 21, 2023 - May 26, 2023
Betavoltaics are direct energy conversion devices that deliver low, microwatt power for long-lasting, uninterruptable applications. Betavoltaics utilize beta particles, similarly to how photovoltaics utilizes photons, by absorbing energy from emitted particles into the semiconductor p-n junction that converts the kinetic energy into electrical energy. One of the viable radioisotopes for betavoltaics is tritium, which is gaseous at standard temperature and pressure. In order to properly utilize tritium for betavoltaics, tritium must be stored in a solid matrix via chemical bonding as a metal tritide. In order to manufacture high quality films, the kinetics of tritium uptake must be understood to evaluate the stress-strain fields and other material properties of the films during hydrogen loading. One model to predict tritium uptake in thin films is the diffusion-limited Mintz-Bloch model. In the Mintz-Bloch model, a tritide layer, more commonly known as a ”blocking layer”, grows at the active surface of the metal interacting with tritium. To reach the metal to chemically bond, tritium atoms must diffuse through the interstitials of the growing tritide layer. Even though the Mintz-Bloch model is proven to be descriptive for hydride layer growth in solid films, the kinetics of the growing hydride layer have not been verified in literature. This paper validates the Mintz-Bloch model by utilizing diffusion constants found in literature and comparing the model to three separate sets of experimental loadings by Shuggard, Efron and Adams. In all three sets of experimental data, the MintzBloch model followed closer with the experiment kinetics as the loading temperature approached 300°C. While the trend of initial parabolic trending to linear uptake showed well for all three experimental sets, the time to fully load a titanium thin film based on the Mintz-Bloch model was 48% short for Shuggard at 250°C, 20.11% short for Efron at 250°C and 14.6% short for Adams at 160°C.
