Out-reactor nodular corrosion behaviour of zircaloys

Ramasubramanian, N.

doi:10.1016/0022-3115(83)90197-6

Cited by 28 publications

(10 citation statements)

References 4 publications

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“…This may also be one of the main reasons for the non-existence of a standard laboratory test for assessing nodular corrosion susceptibility of Zr alloys. This paper discusses these complex phenomena of Zr oxidation and the role of oxidants in the light of our results on nodular corrosion (parametric studies on the currently used laboratory tests and morphological investigation), long term oxidation kinetics of Zircaloy-2 and Zircaloy-4 and our earlier results on local enhanced oxidation of Zr-Nb alloys [10] and similar observations in the literature [1,[4][5][6][7][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]].…”

Section: Introductionsupporting

confidence: 71%

“…In addition, different alloys respond differently to a given reactor environment [1,7,10,11]. Localized enhanced oxidation has been observed in different Zr alloys under different water chemistry conditions and after varied exposure periods [1,6,7,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24]. These include nodular corrosion and shadow corrosion phenomena [1,6,7,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] in Zircaloys (Zr-Sn alloys with Fe, Cr, and Ni) prevalent in boiling water reactors (BWRs) and local enhanced oxidation in two-phase Zr-Nb alloys [1,10].…”

Section: Introductionmentioning

confidence: 99%

“…These phenomena have been observed both in-pile and out of pile [1,10]. However, the mechanism of nodular and shadow corrosion of Zircaloys in reactors in a multi oxidant scenario has been hypothesized [1,6,7,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] to be different than that occurring out of reactor. An obvious demonstration of the above statement may lie in the context of accelerated laboratory tests available for assessing nodular corrosion susceptibility of Zircaloys.…”

Section: Introductionmentioning

confidence: 99%

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Localized oxidation of zirconium alloys in high temperature and pressure oxidizing environments of nuclear reactors

Kumar

Aggarwal

Beniwal

et al. 2013

Materials & Corrosion

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This paper presents the results of parametric studies on the existing test procedures to assess nodular corrosion susceptibility of zirconium (Zr) base alloys. The parameters included the level of dissolved oxygen (DO) in the steam, exposure time, and type of exposure. The alloys studied were Zircaloy‐2, Zircaloy‐4, Zr–2.5Nb, and Zr–1Nb. A two‐step test procedure involving prefilming at 410 °C followed by nodule growth at 510 °C in deaerated steam (using demineralized water) was found to be the most representative for Zircaloys and none of the test conditions produced nodules on Zr–Nb alloys. Presence of high dissolved oxygen was found to suppress nodule formation in Zircaloys. A detailed investigation on the morphology of individual nodules and nodule cross section is presented. Mechanism of nodular corrosion, in particular and localized oxidation of Zr alloys at 400 °C, in general, in oxidizing environments of nuclear reactors has been discussed in the light of the present results of nodular corrosion. Long term oxidation of Zircaloy‐2 and Zircaloy‐4 under low and high DO conditions are reported and compared with our earlier results on the effect of dissolved oxygen on the long term oxidation and hydrogen pick‐up behavior of Zr–Nb alloys.

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Section: Introductionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Localized oxidation of zirconium alloys in high temperature and pressure oxidizing environments of nuclear reactors

Kumar

Aggarwal

Beniwal

et al. 2013

Materials & Corrosion

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“…Ramasubramanian [118] assumed that the intermetallic precipitates of the second phase within a growing oxide are the sites of nodule nucleation. Ramasubramanian [118] assumed that the intermetallic precipitates of the second phase within a growing oxide are the sites of nodule nucleation.…”

Section: Nodular Corrosionmentioning

confidence: 99%

“…Ramasubramanian [57,118] proposed the following model to explain the oxidation behaviour of Zircaloys in steam at high temperatures and accelerated oxidation of the nodular type at high steam pressures:…”

Section: Nodular Corrosionmentioning

confidence: 99%

Corrosion of Zr Alloys in Water and Steam

1994

Materials Science Monographs

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The oxide, Zr0 2 , is formed by the reaction of Zr with water. Water molecules dissociate on the oxide surface, the oxygen formed diffuses through anion vacancies in the oxide to the metal-oxide boundary, where part of the oxygen dissolves in the metal and part reacts to form new oxide. As the oxide has a greater volume than the metal from which it was formed, strain is produced at the boundary. Hydrogen formed in the reaction partly diffused through the oxide into the metal.The process of oxidation of Zr and its alloys in water and steam passes through several stages with correspondingly different laws for the rate of oxide growth as a function of temperature and the corrosion exposure time. In the initial stage, especially at low temperatures, the oxide growth has a complex character, controlled by either a logarithmic or parabolic rate law. This period is a result of localized oxidation of the grain boundaries and of intermetallic species, preferential oxidation of some grains, etc.At temperatures above 300 °C, the oxidation rate is controlled by a cubic or parabolic law. Black, adhering and non-stoichiometric Zr0 2 is also formed. After a certain period of time, given by the oxidation conditions, a change occurs in the oxidation kinetics, appearing as a break on the kinetic curves, after which the oxidation kinetics obey a linear law. This is mostly accompanied by the formation of white or light grey (light brown) oxide, that adheres poorly to the metal and peels off.The increase in the mass of the Zr alloys sample with time can be expressed by the relationship ΔΜ = kt n (9.1)where Am is the mass increase per unit surface area, t is the oxidation time, k is the oxidation rate constant, and n is a dimensionless coefficient. The corrosion process is affected by a great many factors, the most important of which are: the chemical composition of the Zr alloy, both alloying elements and impurities in the metal, the metal structure determined by the technology of alloy working, the quality of the alloy surface, determined by the technology, the composition of the corrosive medium, the influence of radiation, especially the flux and the fluence of fast neutrons. 9.

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