Affiliations: [a] Nuclear Science and Engineering Directorate, Japan
Atomic Energy Agency, 2-4 Shirane, Shirakata, Tokai-mura, Naka-gun, Ibaraki,
Japan | [b] Sumitomo Metal Technology, Inc., Amagasaki,
Japan | [c] Institute of Fluid Science, Tohoku University, Sendai,
Japan | [d] Advanced Nuclear System Research and Development
Directorate, Japan Atomic Energy Agency, Ibaraki, Japan
Abstract: The authors previously reported that magnetic flux leakage data,
measured using a flux gate (FG) sensor, showed a correlation with the
irradiation-assisted stress corrosion cracking (IASCC) susceptibility of
neutron-irradiated austenitic stainless alloys. This paper presents a study
conducted to develop a diagnostic system that can detect IASCC precursors in
stainless steels by measuring the magnetic properties of the material. The eddy
current method and alternating current (AC) magnetization method were used, as
these will be more practical for use in actual reactors. Probes were developed
for these measurement methods, providing sufficient tolerance for environments
in nuclear reactors. An attempt was also made to improve spatial resolution by
manufacturing a smaller probe. A sensor system was designed for remote control,
performance tests were conducted by measuring neutron-irradiated specimens and
mock specimens, and magnetic data were evaluated by comparing the IASCC
susceptibility of the specimens. It was proved that the sensor system developed
in this study is capable of detecting IASCC precursors. Further developments
necessary for application in actual nuclear reactors and the mechanism of
correlation between magnetic properties and IASCC susceptibility were also discussed.
