The influence of the air fraction in steam on the growth of the columnar oxide and the adjacent α-Zr(O) layer on Zry-4 fuel cladding at 1273 and 1473 K

Experimental study of oxidation in oxygen, nitrogen and steam mixtures at 850∘C of pre-oxidized Zircaloy-4

“…A mechanism, involving hydrogen trapping and concentrating in the porosities of the oxide close to the reacting surface, was proposed to explain hydrogen incorporation during steam oxidation of zirconium alloy at high temperature [25]. Owing to the strongly porous oxide formed in nitrogen containing atmospheres, the same mechanism was invoked in [24,26] and can also explain the present results.…”

“…The objective of the next section is to quantify this effect. Strong hydrogen incorporation during high temperature oxidation of Zircaloy-4 was already observed in nitrogensteam [20] as well as in air-steam mixtures [24]. A mechanism, involving hydrogen trapping and concentrating in the porosities of the oxide close to the reacting surface, was proposed to explain hydrogen incorporation during steam oxidation of zirconium alloy at high temperature [25].…”

Investigation of Breakaway Time Delay Phenomenon in Isothermal Test with Zircaloy-4 under Oxygen Atmosphere at 1000 °C

“…On the other hands, cracks are not observed, and a dark-colored oxide is observed for 180 and 200 mL/min conditions (Figure 5i,j, respectively), while a mixture of light-and dark-colored oxides were observed with no apparent cracks for 160 mL/min. The change in oxide colors from dark to light coincided with the kinetic transition, which was reported in previous studies [8]. Moreover, the cracks are generated when the accumulated stresses in the oxide scale are released progressively during the oxide phase transition from tetragonal to monoclinic [3,7,9].…”

“…Sci. 2022, 12, x FOR PEER REVIEW 7 of 10 oxide colors from dark to light coincided with the kinetic transition, which was reported in previous studies [8]. Moreover, the cracks are generated when the accumulated stresses in the oxide scale are released progressively during the oxide phase transition from tetragonal to monoclinic [3,7,9].…”

“…It should be noted that the porous oxides were only detected in light-colored oxides, and the dense oxides were observed in dark-colored oxides. Spotted cracks in the oxides and nearby metal oxide-metal interfaces were observed and were probably generated during the grinding and polishing steps due to the specimen's embrittlement [8]. 6 shows microphotography by an optical microscope (OM).…”