(A) study on theIrradiation effect of reactor materials using micromagnetic technique

Abstract

Conventional magnetic and micromagnetic measurements were conducted to evaluate the radiation damage and damage recovery in SA508-3 reactor vessel (RPV) steel, and due to thermal ageing of Inconel 600 steam generator tube material. The B-H hysteresis loop of the the neutron irradiated SA508 steel showed that the coercive force (Hc) increased in two stages with neutron dose, a relatively slow increase up to a dose of $10^{14} n/cm^2$, followed by rapid increase by 15.4 % for a $10^{16} n/cm^2$ dose sample compared with that of the unirradiated one. The change of maximum induction (Ms) also showed a similar trend to that of coercivity. The Barkhausen noise amplitude (BNA) reflecting the domain wall motion decreased also in two stages, a slow decrease up to $10^{14} n/cm^2$ irradiation, followed by a rapid decrease of 37.5 % at $10^{16} n/cm^2$. The decrease in BNA may be attributed to the increase in the number of impassable defects possessing a large retarding force. The results indicate that the Barkhausen noise is more sensitive than the conventional magnetic properties, such as coercive force, remanence and maximum induction. Effects of neutron and proton dose on the magnetic properties of RPV steel was investigated. The damage depth profile of proton irradiated specimen showed a high damage gradient suggesting complex defect structure at around maximum peak of 380 μm. The magnetic properties of neutron irradiated samples were varied in two stages with doses. The Hc and Ms induction increased slowly up to a neutrom dose $1.5 \times 10^{-7} dpa$, followed by a rapid increase up to $1.5 \times 10^{-5} dpa$. The change of magnetic properties of proton irradiated specimen also showed a characteristic trends depending on proton dose. The Hc increased up to a proton dose $0.8 \times 10^{-2} dpa$ then decreased up to $1.2 \times 10^{-2} dpa$. Similarly, the Ms increased up to a dose $0.2 \times 10^{-2} dpa$ then decreased up to $1.2 \times 10^{-2} dpa$. However,...