Development of microstructure and irradiation hardening of Zircaloy during low dose neutron irradiation at nominally 358 °C

► An incubation dose of 5.8-11 × 1023 n/m2 was needed for loop nucleation to occur. ► Irradiation of Zircaloy at 358 °C resulted in less irradiation than for 260-326 °C irradiations. ► Irradiation of Zircaloy at 358 °C resulted in a lower 〈a〉 loop density than for 260-326 °C irradiations. ► There is evidence that the irradiation hardening can decrease with dose over certain ranges. ► Irradiation induced voids were observed in very low numbers in the Zircaloy-2.