Low-Pressure Solubility and Diffusion of Hydrogen in Zirconium

Mallett, M. W.; Albrecht, W.M.

doi:10.1149/1.2428522

Cited by 130 publications

(14 citation statements)

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“…In the past, understanding of hydrogen diffusion in α-Zr and Zircaloy has relied mostly on experimental measurements101112131415. It has been commonly accepted that H diffuses in Zircaloy via the same mechanism as in α-Zr, with additional trapping caused by alloying elements and impurities.…”

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confidence: 99%

“…It has been commonly accepted that H diffuses in Zircaloy via the same mechanism as in α-Zr, with additional trapping caused by alloying elements and impurities. Due to the differences in the measuring methods and the preparation of samples, scattered data for H diffusivity1011121314 and contradictory results regarding the diffusion anisotropy have been reported. Due to the hexagonal symmetry of α-Zr, the diffusivity of H along <c> usually differs from that along <a> (in a plane parallel to <a> and normal to <c>), with the former suggested to be higher than the latter by Kearns et al 14…”

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confidence: 99%

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

Zhang

Jiang

Bai

2017

Sci Rep

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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...

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confidence: 99%

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

Zhang

Jiang

Bai

2017

Sci Rep

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“…The formation of the gamma solid solution between 600 and 700 C indicates that within this temperature range the solubility of hydrogen in alpha zirconium is exceeded. An unidentifiable phase, which has been designated as Unknown A, was detected in moderate intensity 10 at 700 C, This same material was observed in several samples at 700 and 800 C, and is believed to be a surface contamination resulting from a reaction with the silica container. This unknown phase remains when the sample is cooled to room temperature.…”

Section: X-ray Diffraction Studymentioning

confidence: 66%

THE REACTION OF HYDROGEN WITH ZIRCONIUM-1 AND -25 w/o URANIUM ALLOYS

Bigony¹,

Krause²,

Doig³

1959

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“…Nevertheless, the variability of the material parameters concerning the hydrogen diffusion and solubility limit is high from one study to the other. For instance, more than 50% variability in the diffusion coefficient has been reported (comparison of data in [34,35,51,52,53,54,55,56,57,58,59,60]). A calculation considering an increase by 30% of the diffusion coefficient results in a 300 µm blister in 20h (Figure 6(d)).…”

Section: Optimized Thermal Conditions For Blister Formationmentioning

confidence: 99%

Formation and characterization of hydride blisters in Zircaloy-4 cladding tubes

Ménibus

Auzoux

Dieye

et al. 2014

Journal of Nuclear Materials

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This article is focused on the formation of hydride blisters in zirconium alloys an experimental and theoritical standpoint, and their characterization in terms of morphology, hydrides crystallographic phases, hardness and hydrogen concentration. An experimental setup was developed to grow hydride blisters on pre-hydrided Zircaloy-4 cladding tubes by thermo-diffusion. The thermal conditions were optimized based on thermo-diffusion calculations, that take into account the hysteresis in the hydrogen solubility limit, to obtain a high blister growth rate. Micro X-Ray Diffraction (XRD), nano-hardness and Elastic Recoil Detection Analysis (ERDA) showed that the blisters contain a hydrogen gradient, with pure δ-hydride phase close to the external surface over one third of the blister depth. thermo-diffusion * Tel.: +33 1 69 08 39 43; e-mail: arthur.hellouin-de-menibus@cea.fr 1 calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

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Low-Pressure Solubility and Diffusion of Hydrogen in Zirconium

Cited by 130 publications

References 7 publications

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

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

THE REACTION OF HYDROGEN WITH ZIRCONIUM-1 AND -25 w/o URANIUM ALLOYS

Formation and characterization of hydride blisters in Zircaloy-4 cladding tubes

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