Oxidation of stainless steel 316 and Nitronic 50 in supercritical and ultrasupercritical water

Abstract

Corrosion of stainless steel 316 and Nitronic 50 exposed to supercritical and ultrasupercritical water was studied as a function of temperature and exposure time. Post-exposure surface analysis was performed using Raman and X-ray photoelectron spectroscopies to determine the chemistry of the oxides formed as a result of the exposure. When exposed to supercritical water, Nitronic 50 and stainless steel 316 were observed to have similar weight gains; however, stainless steel 316 was found to gain less weight than Nitronic 50 in exposure tests performed in ultrasupercritical water. Stainless steel 316 developed surface films primarily composed of iron oxides, while the surface of Nitronic 50 contained a mixture of iron, chromium and manganese oxides. Based on these analyses, the differences in weight gain and oxidation characteristics of the two materials are attributed to the higher concentration of Cr and Mn in Nitronic 50 compared to stainless steel 316.

Early oxidation of Super304H stainless steel and its scales stability in supercritical water environments

“…5, which indicates that the inner layer consisted primarily of chromiumrich spinels, while magnetite phases were main components of the outer layer. The absence of hematite phase can be explained by higher temperatures [7], lower oxygen content less than 2 ppm [22], and/or insufficient exposure times for second oxidation of the magnetite [6,11,23]. The occurrence of wustite (FeO) phases was not detected, even when the testing temperature was as high as 580 C. This phenomenon can be attributed to solid reaction between FeO and Cr 2 O 3 .…”

“…As displayed in Fig. 1 (Run 5 and 6), when initial pH value changed from 8.5 to 7.3, the grain size and quantity of oxide particles formed at two conditions did not show obvious differences, which from a certain extent, implies that the outer layer of duplex oxide layer may grow mainly by solid growth mechanism [5,6,9] rather than metals dissociation/ oxides precipitation mechanism [18,19]. The former deems that the growth of outer oxide layer is by means of metal ions diffusing outward through inter scales, and then reacting with gas species at scales/environment interface, while the latter believes that the dissolved metal cations combine with anions such as OH À in aqueous environments to form oxides or hydroxides, they then precipitate on specimens surface to form and/or thicken the outer layer.…”

Stress corrosion cracking behavior of 310S stainless steel in supercritical water at different temperature

“…Supercritical‐water‐cooled reactor (SCWR) is considered as one of the most promising Generation IV nuclear reactors due to its simplified design and excellent thermal efficiency . Supercritical water (SCW) is used as the coolant in SCWR, which can operate above the critical point of water (374 °C, 22.1 MPa) . Accordingly, a pressure vessel type thermal spectrum SCWR concept named CSR1000 is proposed by Nuclear Power Institute of China .…”

“…[1][2][3][4][5] Supercritical water (SCW) is used as the coolant in SCWR, which can operate above the critical point of water (374°C, 22.1 MPa). [6][7][8][9] Accordingly, a pressure vessel type thermal spectrum SCWR concept named CSR1000 is proposed by Nuclear Power Institute of China. [10][11][12] The inlet and outlet coolant temperatures are 280 and 500°C, respectively, while the maximum temperature of fuel cladding can reach 620°C.…”

Accelerated estimation of corrosion rate in supercritical and ultra-supercritical water

“…10,11 SAE stainless steel 316 (SS316), Nitronic 50 (N50), Inconel 625 (I625), and Inconel 718 (I718) were chosen for the tests because they are used extensively in high-temperature power plants. 4,7,8,[12][13][14][15][16][17][18][19][20][21][22][23][24] This research aims to establish a method for evaluating corrosion rates in pure SCW and to reduce the test time to less than 24 h.…”