Tritium Ageing Studies for "LMJ Target" Applications: Poliymide and CHx Membranes Permeation Results

As part of the French Inertial Confinement Fusion (ICF) program, CEA has developped Cryogenic Target Assemblies (CTAs) for the Laser MegaJoule (LMJ). These targets are filled by permeation with high pressure deuterium-tritium gas mixture. The evolution of the materials physical properties, particularly organic ones (PI and CHx), which compose the target is unknown in these hard conditions. The polyimide and CHx membranes permeation was studied in this context. The hydrogen and helium permeation parameters are unaltered for polyimide membrane after tritium ageing in the 20 K-300 K temperature range:

K_He = 3.10^-14 exp(-16040/RT) mol.m^-1.s^-1.Pa^-1

K_H2 = 2.10^-14 exp(-16950/RT) mol.m^-1.s^-1.Pa^-1

First results for the CHx hydrogen permeation parameters without ageing tritium have been obtained:

K_H2 = 7.10^-13 exp(-10550/RT) mol.m^-1.s^-1.Pa^-1

New CHx permeation results after tritium ageing are shortly waited.