Neutron Dosimetry and Mechanical Properties Changes Monitoring by Magnetic Response of Fe and Ni Wires

Magnetic properties may be a useful means for monitoring the evolution of irradiation-induced damage in materials which are inherently ferromagnetic. Such materials include pure iron and nickel which are commonly used in a variety of irradiation applications for fluence or spectrum analysis. One such application is for fluence monitoring in Charpy coupon surveillance packets. This study examines the magnetic response of both iron and nickel wires which have been irradiated to doses up to 3.6 {times} 10{sup 19} cm{sup {minus}2} (E > 1MeV) in such surveillance packets at reactor ambient irradiation temperatures of approximately 290 C. The results show that large changes in magnetic response are found for magnetic properties which are sensitive to materials microstructure. The changes are predominantly to decrease the magnetic remanence and coercivity with dose. These changes saturate at the highest doses examined in this study. Though direct microstructural examination is needed to confirm the hypothesis, the results are consistent with the development of a large population of defect structures (vacancy and interstitial clusters) which evolve with irradiation dose.