Abstract
Abstract Supercritical Water-cooled Reactor(SCWR) whose operating environment exceeds the critical pressure and temperature of water (22.4MPa and 374℃) has been considered by the Gen-IV Nuclear Energy System International Forum as an option for future light water reactor(LWR). The main advantages over the current LWR include: (1) higher thermal efficiency (2) more compact thermal component (3) combination of existing LWR plant and SCP fossil power plant technologies and (4) higher safety. However, the irradiation and change of water chemistry in the core of SCWR will affect the structural integrity and cladding materials. In this study, nickel-based superalloy HR-224 was pre-oxidized in flowing air at 982℃ for 100hr to establish a continuous and dense α-Al2O3 layer. Then it exposed in supercritical water (SCW) environment with 8.3 ppm oxygen content at 700℃ and 24.8MPa for cyclic oxidation testing up to 1300h. According the result of oxidation thickness, calculated mass gains (w) in the samples as a function of test duration (t) could be fitted by an equation of Δw=2.72×〖10〗^(-3) t^0.7089. In addition, after pre-oxidizing process, triple scales were observed, consisting of an outer layer of Ni(Cr, Fe)2O4 spinel, a middle layer was Cr2O3 and an inner layer of α-Al2O3. This scale structure remained unchanged after it was exposed in SCW environment after 1300hr. The thickness of α-Al2O3 layer increased with increasing duration of time. The thickness change (Δd) with exposure time (t) can be described as a function of Δd = 3.26×〖10〗^(-2)×t^0.55. The results show that the pre-oxidizedα-Al2O3 layer is thick enough to maintain good adherence and provides a better corrosion resistance for long exposure time in SCW.