Hydride Formation in Zirconium Alloys

Motta, Arthur T.; Chen, Lei

doi:10.1007/s11837-012-0479-x

Cited by 85 publications

(46 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is well known that a nearly dense hydride layer (called hydride rim) usually appears near the outer surface of the zirconium alloy cladding materials in the reactor service conditions, mainly owing to the radial temperature gradient present during the operation. [27,28] This hydride layer was also observed in previous studies [13,27,29] and the current study ( Figure 6(a)) under the artificial gaseous hydriding conditions. However, in the current hydriding conditions [soaked at 723 K (450°C) for 5 hours in each thermal cycle], no significant temperature gradient could be present in the hydrided sample, given the fact that the sample size is in the order of millimeters.…”

Section: A Phase Identification and Quantificationsupporting

confidence: 90%

Observations on the Zirconium Hydride Precipitation and Distribution in Zircaloy-4

Wang

Garbe

et al. 2013

Metall Mater Trans B

View full text Add to dashboard Cite

Hydride precipitation and distribution in hot-rolled and annealed Zircaloy-4 plate samples artificially induced by gaseous hydrogen charging were studied primarily by neutron tomography, scanning electron microscopy (SEM), and SEM-based electron backscattered diffraction techniques. The precipitated hydride platelet (δ-ZrH1.66) at a hydrogen pressure of 20 atm was found following the {111}δ-ZrH1.66//(0001) α-Zr with the surrounding α-Zr matrix. The microstructural characterization indicated that hydrides with a relatively uniform distribution were precipitated on the rolling-transverse section of the plate, whereas, on the normaltransverse section, a hydride concentration gradient was present with a dense hydride layer near the surface. Further, the neutron tomography investigations clearly identified the nonuniform spatial distribution of hydrides. Thin hydride layers preferentially formed on the sample surface, and the concentrated hydrides precipitating at the edges/corner of the sample were observed. The causes for the localized hydride accumulation were also discussed. Disciplines Engineering | Science and Technology Studies Publication DetailsWang, Z., Garbe, U., Li, H., Harrison, R. P., Kaestner, A. & Lehmann, E. (2014 Hydride precipitation and distribution in hot-rolled and annealed Zircaloy-4 plate samples artificially induced by gaseous hydrogen charging were studied primarily by neutron tomography, scanning electron microscopy (SEM), and SEM-based electron backscattered diffraction techniques. The precipitated hydride platelet (d-ZrH 1.66 ) at a hydrogen pressure of 20 atm was found following the {111} d-ZrH1.66 //(0001) a-Zr with the surrounding a-Zr matrix. The microstructural characterization indicated that hydrides with a relatively uniform distribution were precipitated on the rolling-transverse section of the plate, whereas, on the normal-transverse section, a hydride concentration gradient was present with a dense hydride layer near the surface. Further, the neutron tomography investigations clearly identified the nonuniform spatial distribution of hydrides. Thin hydride layers preferentially formed on the sample surface, and the concentrated hydrides precipitating at the edges/ corner of the sample were observed. The causes for the localized hydride accumulation were also discussed.

show abstract

Section: A Phase Identification and Quantificationsupporting

confidence: 90%

Observations on the Zirconium Hydride Precipitation and Distribution in Zircaloy-4

Wang

Garbe

et al. 2013

Metall Mater Trans B

View full text Add to dashboard Cite

show abstract

“…Consequently, Zircaloy react with water, producing an oxide layer at the interface and hydrogen (H), of which a substantial fraction infiltrates into the cladding interior3. Due to the low solubility of H in α-Zr, which is the main component of claddings, hydrides precipitate in the cladding matrix456. Hydride formation can detrimentally affect the cladding integrity primarily in two ways.…”

mentioning

confidence: 99%

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

Zhang

Jiang

Bai

2017

Sci Rep

View full text Add to dashboard Cite

This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along is found to be slightly higher than that along , with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.The diffusion of hydrogen in hcp metals has attracted extensive research interests for both its scientific merit and technological importance. It is the rate-limiting step for solid hydrogen storage in Mg based alloys 1 and for mechanical property degradation in Ti 2 and Zr alloys 3 . For instance, Zr-based alloys such as Zircaloy2 and Zircaloy4 (denoted as Zircaloy) are widely used as the cladding of fuel rods in nuclear reactors for their excellent corrosion resistance and very low absorption cross-section of thermal neutrons. During their service time, these alloys operate in extremely harsh environments, combining high temperatures and corrosive coolants such as water. In light water reactors, Zircaloy claddings directly contact coolant water, with a local temperature at the interface of about 400 °C. Consequently, Zircaloy react with water, producing an oxide layer at the interface and hydrogen (H), of which a substantial fraction infiltrates into the cladding interior 3 . Due to the low solubility of H in α -Zr, which is the main component of claddings, hydrides precipitate in the cladding matrix 4-6 . Hydride formation can detrimentally affect the cladding integrity primarily in two ways. First, the formation of hydrides reduces the fracture toughness of the cladding matrix 7,8 , increasing the probability of fuel failure when fuel-cladding mechanical interaction (PCMI) occurs during fuel operation. Second, upon cyclic thermal and mechanical loadings, hydrides can dissolve and reorient. During used-fuel storage, fracture may propagate via the so-called delayed-hydride-cracking (DHC) mechanism, which is induced by the dissolving of matrix hydrides and their subsequent re-formation at crack tips 3,9 . To mitigate thes...

show abstract

“…Here  is the electrical resistivity of the oxide (in Mcm) and j is the oxidation current density (in A/cm 2 only from the added oxygen and the oxide has a uniform thickness, the time-dependent oxide thickness L(t) (including the protective barrier oxide layer L b (t) and the nonprotective porous layer) can be calculated by…”

Section: Methodsmentioning

confidence: 99%

Continuum model for hydrogen pickup in zirconium alloys of LWR fuel cladding

Wang

Zheng

Szlufarska

et al. 2017

Journal of Applied Physics

View full text Add to dashboard Cite

A continuum model for calculating the time-dependent hydrogen pickup fractions in various Zirconium alloys under steam and pressured water oxidation has been developed in this study. Using only one fitting parameter, the effective hydrogen gas partial pressure at the oxide surface, a qualitative agreement is obtained between the predicted and previously measured hydrogen pickup fractions. The calculation results therefore demonstrate that H diffusion through the dense oxide layer plays an important role in the hydrogen pickup process. The limitations and possible improvement of the model are also discussed.

show abstract

Hydride Formation in Zirconium Alloys

Cited by 85 publications

References 46 publications

Observations on the Zirconium Hydride Precipitation and Distribution in Zircaloy-4

Observations on the Zirconium Hydride Precipitation and Distribution in Zircaloy-4

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

Continuum model for hydrogen pickup in zirconium alloys of LWR fuel cladding

Contact Info

Product

Resources

About