Swelling of CLAM steel irradiated by electron/helium to 17.5 dpa with 10 appm He/dpa

To investigate irradiation/helium effects on microstructure of China Low Activation Martensitic (CLAM) steel, single beam (e−) and dual-beam (e−/He+) irradiation to 17.5 dpa with 10 appm He/dpa at 400 °C and 450 °C on CLAM steel was carried out with high voltage electron microscope HVEM. Evolution of microstructure was in situ observed during irradiation and annealing procedure. Preliminary results showed that size and density of voids and helium bubbles increased with irradiation dose. And swellings of voids and bubbles are ∼0.5% and 1–1.5%, respectively after irradiation.