PNNL

Abstract

Three irradiations have been performed in the Swiss Spallation Neutron Source (SINQ) to establish a materials database for mixed proton and neutron fluxes for future spallation neutron and other accelerator sources. Materials included in the second irradiation, STIP-II, included mainly austenitic and martensitic steels. Samples of 316LN, F82H, Al, and Zircaloy-2 from STIP –II have been analyzed for their total helium and hydrogen contents and their release characteristics. In terms of total gas content, the helium and hydrogen results are similar to those observed earlier from STIP-I. Specifically, the helium contents tended to be somewhat higher (up to 50%) than calculated for both low and high dose samples. 3He/4He ratios were generally in agreement with expectations except for the Ziracaloy-2 which showed very low values, likely from increased 3He generation from decay of irradiation-generated tritium. Hydrogen contents on the other hand tended inversely with dose, suggesting increased hydrogen loss at the higher dose (and higher temperature) locations from diffusion. Hydrogen levels in the Zircaloy were considerably higher than expected (~10,000 to 25,000 appm), suggesting additional pickup of hydrogen from the irradiation environment. Hydrogen levels in the aluminum were similar to predicted. Helium and hydrogen release measurements from the temperature ramp experiments showed considerable levels of deuterium and tritium species which generally mirrored those of hydrogen. Hydrogen release occurred from about 300 for the aluminum to about 800 °C for the Zircaloy-2. For the Ziracloy-2 and the steels, helium release began to occur at about 1100 °C, which is consistent with previous measurements on irradiated steels. For the aluminum, helium release began at just under 600 °C.