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

Abstract

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 560h 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 560h 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.