Helium analysis from the DHCE-1 simulation experiment

The combined effects of high helium transmutation rates with the displacement damage produced by high energy fusion neutrons remains the key issues in the evaluation of the performance and lifetime limits of candidate vanadium alloys for fusion first-wall structure applications. A dynamic helium charging experiment (DHCE) has been developed as a unique method for investigating the effects of fusion-relevant helium generation rates on the properties of vanadium alloys irradiated in a fission reactor neutron spectrum. In this simulation, decay of tritium in the vanadium alloy to helium during fission reactor irradiation is used to provide constant He/displacement damage ratios characteristic of a fusion neutron environment. A proof-of-principle experiment (DHCE-1) was conducted in the FFTF reactor. Detailed calculations of the predicted helium concentrations in unalloyed vanadium and the reference V–4Cr–4Ti alloy included in the DHCE-1 indicate quite good agreement with experimental results and demonstrate the validity of the DHCE technique.