Evaluation of residual tritium in stainless steel irradiated at SINQ target 3

A MW spallation target will need an accurate amount of tritium generation in materials for post irradiation experiments. A high-energy proton of 580 MeV generates a variety of constituents in the SINQ target mainly through spallation reaction, and these constituents included helium and hydrogen isotopes. For the SINQ target hydrogen and helium are generated to hundreds appm H and tens appm He, respectively. However, tritium gas production has not yet been reported. Evaluation of tritium gas generation in the specimens of target 3 was done by calculation. Results were compared with gamma spectrum measurement of austenitic and martensitic-ferritic steels three and a half years later after irradiation. Good agreement was obtained for activity of the main isotope. Residual tritium measurement was carried for the austenitic stainless steel specimens irradiated below 250 °C by the thermal desorption method four and a half years later after irradiation. An ion chamber monitored the tritium concentration. Water bubblers collected all tritium after oxidation of tritium by the oxidation catalysts. It is found that a release of tritium began over 250 °C and the ratio of residual tritium to generated one is estimated to be less than 20%.