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

Abstract

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High temperature Zircaloy-4 oxidation in water vapour-containing environments examined with Raman imaging and labelled oxygen

“…Summarising the main published results, steam addition in air has only a moderate effect on the corrosion kinetics in the 700-900°C temperature range [7,15,17]. For higher temperatures, the dependence of the oxidation rate with the steam fraction is more pronounced [15,17].…”

“…The effects of nitrogen on the high temperature oxidation of zirconium alloys are now documented [3][4][5][6][7], even if they are not still completely understood. All the studies conducted so far have shown that right from 750-800°C, oxidation of pure Zr or Zr-based alloys is by far much faster in nitrogen-containing environments (oxygen and/or steam) than in nitrogen-free atmospheres.…”

“…On the other hand, cladding materials corrosion in atmospheres containing simultaneously both oxidizing species, steam and di-oxygen, has been less studied [7,[13][14][15][16][17]. In this regard, it is worth bearing in mind that the oxidation behavior of Zr alloys in water-vapor-containing environments may substantially differ from that in dry oxygen containing gases.…”

Raman imaging in corrosion science: High‐temperature oxidation of the zirconium alloys used in the nuclear industry as an example

“…[9][10][11][12] This process was evidenced in air, in air-steam mixtures, and for steam-nitrogen atmospheres. [10,11,[23][24][25] Only a very limited amount of nitrogen may initiate this particular process, as it was clearly evidenced varying the nitrogen content in oxygen/nitrogen and in steam/nitrogen mixtures. [9,10] To illustrate the effects of corrosion on Zircaloys, some typical macrographs of the samples before after some characteristic oxidation tests are shown in Figure 1.…”

Parallel mechanism of growth of the oxide and α-Zr(O) layers on Zircaloy-4 oxidized in steam at high temperatures

“…In this mechanism, the growth of the α-Zr(O) phase is not considered simply because at these temperatures, the quantity of dissolved oxygen in the metal is negligible. Lasserre [26] and Gestin [27] studied the oxidation kinetics of Zircaloy-4 at 850 °C in air and in air/steam mixtures. However, in presence of nitrogen the oxidation mechanism is altered and leads to a more severe kinetic transition due to the oxidation of zirconium nitride precipitates.…”