Characterization of the Oxide Films Grown at 260°C in a Simulated Secondary Coolant of a Nuclear Reactor

This paper presents the characteristics of superficial films formed on carbon steel A106 B samples machined from an original tube of a secondary circuit of a CANDU Nuclear Power Station not exposed to the coolant. The oxide layers were grown on a set of coupons over 77 and 560 h periods in static stainless steel conditioned autoclaves at 260°C simulating AVT conditions: I) degassed (hydrazine + ethanolamine) solution and II) degassed (hydrazine + morpholine) solution. The oxide films were studied using SEM, DRX and chemical descaling to evaluate metal corrosion, adherent oxide thickness and oxide release. Up to 560 h of testing, the samples exposed to medium I) showed a slightly lower metal corrosion and oxide release, although of the same order of magnitude for the two media.