In-situ measurement of tritium accumulation and decontamination of tungsten

Tritium accumulation on surfaces, also known as the memory effect, has a wide range of implications for operating and maintaining fusion reactors, astroparticle physics experiments using tritium, and tritium analytics. At Tritium Laboratory Karlsruhe (TLK), the Tritium Activity Chamber Experiment (TRACE) was designed and built to investigate the tritium memory effect of a variety of materials. With TRACE, it is possible to expose samples to high-purity tritium at ambient temperature and measure their retained near-surface activity in-situ via beta-induced X-ray spectrometry (BIXS). Within this work, the relative memory effect of two tungsten samples — one pre-contaminated — after a cumulative exposure to tritium of 2100 mbar ⋅ h was determined. The time evolutions of their activity prove the repeatability of the experiment. Attempts were made to decontaminate one of the samples in-situ. During continuous evacuation, merely 20% of its near-surface activity could be desorbed at a bake-out temperature of 200 °C.