Monitoring of a radiation recovery in neutron-irradiated RPV steel by using the magnetic methods

The effects of a neutron irradiation on the magnetic parameters of a reactor pressure vessel (RPV) steel with different microstructures, partially due to a difference in the steel refining processes were investigated. The samples were irradiated in a research reactor with a fluence of 4.5 × 1019 n/cm2 at 288 °C. The measurement of the Barkhausen noise (BN) was conducted to explore the relationship between the microstructural state and the domain wall motion. The BN profiles of the unirradiated samples showed a consistent change with the microstructure (grain size, carbide morphology, lath width), but the neutron-irradiated sample did not show a consistent change with microstructural state. The radiation hardening and recovery characteristics have been investigated by using the Vickers hardness method, and the relationship between the BN and the microhardness is obtained for four different steels. The linear relationship between mechanical and magnetic properties can be used as a nondestructive evaluation for radiation damage.