Neutron irradiation effects on properties of insulator coatings for ITER in-vessel components

Insulator coatings are used in ITER to reduce currents flowing from the first wall modules to the vacuum vessel and between the limiter plates. Al2O3 and Al2MgO4 are proposed as an insulating materials. Coatings should be sprayed by plasma on the surfaces of first wall keys, flexible cartridge and on the lateral sides of the ITER port-limiter plates. This paper deals with the investigation of electrical and mechanical properties of insulator coatings including irradiation effect. Specimens were manufactured from austenitic stainless steel 18Cr–10Ni–Ti and titanium alloy ΠT-3B grade. Insulator coatings made from Al2O3, Al2MgO4 and Al2O3 + 13%TiO2 have been tested. The NiCr intermediate layer has been used to provide better adhesion of insulator coatings with the substrate. The specimens were irradiated in IVV-2M reactor at the temperature 240 °C. The irradiation dose was ∼0.16 dpa. The electrical conductivity and break-down voltage of coatings were measured before and after irradiation. Appearance of cracks was also studied after compression loading up to 200 MPa.