In-pile electrochemical measurements on AISI 304 and AISI 306 in PWR conditions – Experimental results

In-pile electrochemical measurements were performed in order to investigate the effect of radiation on the electrochemical corrosion behaviour of AISI 304 and AISI 316 in PWR primary water (400 ppm B and 2 ppm Li) at 300 °C. The corrosion potential was continuously monitored during the whole irradiation period. Polarization resistance measurements and electrochemical impedance spectroscopy were performed at regular intervals. Polarization curves were recorded halfway through and at the end of each reactor cycle. All measurements were performed on both an in-flux and an out-of-flux 3-electrode electrochemical cell, each containing a platinum high-temperature reference electrode and an yttrium-stabilized zirconia (YSZ) reference electrode. The results show a small influence of radiation on the corrosion potential. However, the impedance data show a marked difference between in-flux and out-of-flux. The Nyquist diagram shows one semi-circle and one flattened semi-circle of which a branch leaps off indicating an R-(R//C)-(CPE//RW) type equivalent circuit.