Measurement and modeling of strain fields in zirconium hydrides precipitated at a stress concentration

Allen, Gregory B.; Kerr, Matthew; Daymond, Mark R.

doi:10.1016/j.jnucmat.2012.06.037

Cited by 12 publications

(5 citation statements)

References 32 publications

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“…With the recent drive towards higher fuel burn-ups and therefore increased in-reactor fuel lifetimes, long term corrosion resistance and the absorption, by the cladding, of hydrogen produced during corrosion have become increasingly important [1]. As the solubility limit for H in Zr is exceeded, Zr-hydrides precipitate in the cladding alloy leading to cladding embrittlement [2,3]. This problem is particularly apparent after removal from the reactor; as the cladding cools, the hydrogen solubility drops and further brittle Zr-hydrides precipitate, which can lead to delayed hydride cracking [4].…”

Section: Introductionmentioning

confidence: 99%

The effect of Nb on the corrosion and hydrogen pick-up of Zr alloys

et al. 2017

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Zr-Nb alloys are known to perform better in corrosion and hydrogen pick-up than other Zr alloys but the mechanism by which this happens is not well understood. Atomistic simulations using density functional theory of both tetragonal and monoclinic ZrO2 were performed, with intrinsic defects and Nb dopants. The overall defect populations with respect to oxygen partial pressure were calculated and presented in the form of Brouwer diagrams. Nb is found to favour 5 + in monoclinic ZrO2 at all partial pressures, but can exist in oxidation states ranging from 5 + to 3 + in the tetragonal phase. Nb5+ is charge balanced by Zr vacancies in both phases, suggesting that contrary to previous assumptions, Nb does not act as an n-type dopant in the oxide layer. Clusters containing oxygen vacancies were considered, Nb2+ was shown to exist in the tetragonal phase with a binding energy of 2.4 eV. This supports the proposed mechanism whereby low oxidation state Nb ions (2 + or 3+) charge balance the build-up of positive space-charge in the oxide layer, increasing oxygen vacancy and electron mobility, leading to near-parabolic corrosion kinetics and a reduced hydrogen pick-up. Previous experimental work has shown that tetragonal ZrO2 transforms to the monoclinic phase during transition, and that during transition a sharp drop in the instantaneous hydrogen pick-up fraction occurs. The oxidation of lower charge state Nb defects to Nb5+ during this phase change, and the consequent temporary n-doping of the oxide layer, is proposed as an explanation for the drop in hydrogen pick-up during transition

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Section: Introductionmentioning

confidence: 99%

The effect of Nb on the corrosion and hydrogen pick-up of Zr alloys

et al. 2017

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“…Some research papers have been found on numerical modelling of hydrogen and hydrides distribution in zirconium alloy [8], numerical modelling of hydrides growth [9] and hydrides shape and orientation [10] in zirconium alloy in the presence of hydrogen using the finite element method. More papers can be found on fracture modelling of zirconium alloy with hydrides [11][12][13], etc. In fracture modelling papers, authors do create finite elėement models where one or few zirconium hydrides are embedded in zirconium matrix, and this is similar to what we used in the numerical prediction of mechanical properties of zirconium alloy with hydrides.…”

Section: Introductionmentioning

confidence: 99%

Numerical prediction of mechanical properties of zirconium alloy with hydrides using finite element method

Janulionis¹,

Dundulis²,

Kriūkienė³

et al. 2018

energetika

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During nuclear power plant (NPP) operation, degradation effects like ageing, corrosion, fatigue, and others may significantly impact component integrity. One of the degradation mechanisms is hydrogen absorption. High levels of hydrogen in zirconium alloys can lead to the formation of zirconium hydrides and that can influence material properties. Therefore, determination of material properties under different levels of hydrogen concentration in zirconium alloys is important. It is not always possible to conduct an experimental testing. Therefore, there is a need for alternative methods for determination of material properties. This article presents the numerical prediction of material properties of zirconium 2.5% niobium alloy with hydrides.According to the objective of the work, numerical prediction was performed using the finite element (FE) method. This was done by creating a finite element model of zirconium hydride embedded in zirconium alloy. The geometry and size of hydride were measured from a real specimen. The size of zirconium alloy surrounding the hydride was selected in such a way that hydride volume part in the model would match experimental measurements. The prognosis results were compared with the experimental data.

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“…The absorption of hydrogen can lead to a severe reduction of the life of zirconium alloys as it results in embrittlement. [1][2][3] It was previously determined that the source of embrittlement are zirconium hydride precipitates and considerable effort was devoted to keep the hydrogen concentration low and/or ensure that the hydrides have appropriate orientations. 4 Interestingly, presently zirconium hydride is included in hydride fuels due to its good stability under irradiation conditions and has become the focus of numerous studies.…”

Section: Introductionmentioning

confidence: 99%