Aging of Pd Under Tritium: Influence of 3He Generation and Associated Mechanisms

An experimental and theoretical study has been conducted to improve the understanding of the Pd tritide aging process. Tritide aging due to tritium radioactive decay produces 3He which create nanobubbles in the metal matrix. Pd samples are aged up to 20 years to cover the three steps of aging: bubble nucleation (similar to few days), bubble growth (similar to few years) and 3He massive release (over 10 years, depending on the initial tritium loading). All the experimental measurements are used as input/output data for the theoretical aging mechanism modeling. The bubble nucleation/growth modeling is improved thanks to these additional data. A sample aged over 20 years has been fully characterized which allows proposing a mechanism and the corresponding modeling for the last step of the aging process: the 3He release. The models provide a material behavior that agrees with microscopic and macroscopic observations.(c) 2023 Elsevier B.V. All rights reserved.