Chronic Release of Tritium from SS316 at Ambient Temperature: Correlation Between Depth Profile and Tritium Liberation

One conceivable option for the disposal of tritium-contaminated stainless steel consists in its storage at ambient temperature in a purged containment. To assess this option several stainless steel 316 specimens, previously loaded at elevated temperatures with 0.8-8.5 MBq of tritium, were flushed continuously with dry argon (water partial pressure 0.073 Pa) for extended periods of time. The released tritium (more than 99 % in the form of tritiated water (HTO)) was collected in bubblers and monitored periodically by liquid scintillation counting. After an initial fast liberation a fairly constant rate of the order of 0.2 % per day established. Tritium depth profile in the SS specimens could be simulated by a diffusion limited desorption model. The rate determining step for tritium release appears to be bulk diffusion.