Tritium retention behavior in tungsten exposed to off-normal plasma condition

A first series of experiment concerning off-normal plasma events were performed under a US-Japan collaboration program. The off-normal plasma event was simulated by introducing nitrogen gas into the DT plasma. The tritium retention amount and thermal desorption behavior of tritium from tungsten exposed pure DT plasma and nitrogen introduced DT plasma was investigated as a function of nitrogen flow rate. As a result. It was found that tritium retention increased and the tritium release temperature rose with increasing nitrogen flow rate. Surface analysis by X-ray photoelectron spectroscopy was also carried out for tungsten specimens after thermal desorption. The effective chemical change on the surface chemical composition or chemical state was not observed between DT and nitrogen introduced DT plasma.