LIBRETTO-4: Understanding and modeling tritium transport under irradiation

LIBRETTO-4 irradiation experiment with in situ T production in eutectic alloy LiPb inside EUROFER97 capsules was performed at the High Flux Reactor (HFR), Petten. Two identical capsules at two temperature ranges (500-550 deg. C and 300-350 deg. C) tested the tritium permeation rate through pre-oxidized ferritic-martensitic EUROFER97 into a He + 1000 H2 vppm cooling channel. A second channel with similar flowing gas composition obtained the tritium released from the LiPb and permeation through the internal wall of austenitic steel AISI316L. A 2-dimensional mathematical model has been developed. The model simulates tritium fluxes in capsule materials for variable experimental conditions (generation rates, gas pressures and flow rates) for a 27 days cycle. Modeling provides a consistent physical picture of release-rate mechanisms within the capsule. Tritium transport data under irradiation in capsule's material have been derived.