Laser surface melting of nickel-based alloy reduces nickel release in the primary cooling system of a nuclear power plant

Abstract

The surface of Ni-based alloy 690 was treated using a sub-microsecond pulsed laser in order to reduce the amount of nickel released when the surface is exposed to the primary cooling system of pressurized water nuclear reactors. A 2D array of laser treatment parameter sets was investigated. The results on sample surfaces was characterized using interferometric microscopy, Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectrometry (GDOES) and X-ray Photoelectron Spectrometry (XPS). The treatment leading to a continuous and defect-free chromine surface having the minimum nickel content over about the first two nanometers and no subsurface chromium depletion was selected for the nickel release test. This selection criterion proved to be very efficient as the total amount of nickel released in a standard qualification test using a simulated primary coolant was reduced, compared to a non-treated surface, by a factor of 7 during the heating phase and by a factor of 3.7 on average over the whole month-long test.