Study of the flux effect on nuclear pressure vessel steel by measurement of magnetic properties

TL;DR

This study investigates how flux affects the magnetic properties of nuclear pressure vessel steel, revealing correlations with microstructural changes and potential for monitoring material degradation in reactors.

Contribution

It demonstrates the sensitivity of magnetic properties to flux-induced microstructural evolution, providing a non-destructive method to assess steel degradation in nuclear reactors.

Findings

Coercive field varies with flux and microstructure.

Magnetic anisotropy distribution depends on flux.

Saturation magnetization correlates with accumulated damage.

Abstract

Since Reactor Pressure Vessel steels are ferromagnetic, they provide a convenient means to monitor changes in the mechanical properties of the material upon irradiation with high energy particles, by measuring their magnetic properties. Here, we discuss the correlation between these two properties (i.e. mechanical and magnetic properties) and microstructure, by studying the flux effect on the nuclear pressure vessel steel used in reactors currently under construction in Argentina. Charpy-V notched specimens of this steel were irradiated in the RA1 experimental reactor at 275{\deg}C with two lead factors (LFs), 93 and 183. The magnetic properties were studied by means of DC magnetometry and ferromagnetic resonance. The results show that the coercive field and magnetic anisotropy spatial distribution are sensitive to the LF and can be explained by taking into account the evolution of the microstructure with this parameter. The saturation magnetization shows a dominant dependence on the accumulated damage. Consequently, the mentioned techniques are suitable to estimate the degradation of the reactor vessel steel.