Solubility Of Hydrogen In Zirconium Research Articles

INFLUENCE OF HYDROGEN SATURATION ON CHARACTERISTICS OF ZIRCONIUM

The article presents a literature review on the effect of hydrogen saturation on the properties of zirconium alloys. Zirconium alloys are an indispensable structural material for the core of nuclear reactors. During operational loads, the interaction of zirconium materials with interstitial elements (oxygen, nitrogen, hydrogen) necessarily occurs. Zirconium shows the greatest affinity for hydrogen. One of the vulnerable zirconium elements is fuel rod tubes. The safe operation of a nuclear reactor depends on their integrity. In addition, it is fuel tubes that are most exposed to hydrogen. Therefore, the systematization of knowledge about the effect of hydrogen on the properties of zirconium tubes will make it possible to better predict their operational behavior. According to scientific literature data, depending on the volume of absorbed hydrogen, either a solid solution or zirconium hydrides can form. The dependence of the absorbed hydrogen zirconium on the dilution of the hydrogen medium and temperature is shown. The chemical composition of the zirconium alloy also affects the rate and amount of absorbed hydrogen. The effect of hydrogen on the mechanical properties of zirconium alloys is presented. The differences on the fracture surface after tensile tests at room temperature are shown depending on the amount of absorbed hydrogen. Data are presented that indicate that hydrogen atoms are located in octahedral or tetrahedral interstitial voids of a hexagonal close-packed zirconium lattice. It is shown that the thermal solubility of hydrogen in α-zirconium is extremely low, its value is ~6 at. % at the eutectoid transformation temperature, and at room temperature the solubility of α-Zr hydrogen does not exceed 1·10-5 wt. %. In high-temperature β-Zr, hydrogen dissolves up to ~50 at. %. It has been established that deterioration of the properties of zirconium elements of nuclear reactors during operation due to exposure to hydrogen is likely due to a number of factors: hydrogen embrittlement, the formation of large massive accumulations of hydrides and delayed hydride cracking. It is shown that the direction of arrangement of hydrides depends on the texture of the matrix and on the stresses present in the material that act during the formation of hydrides. It has been established that hydrogen can penetrate into a metal through an oxide film, diffusing, for example, along extended defects such as dislocations and grain boundaries. It is noted that the solubility of hydrogen in zirconium depends on other penetration elements already present in the metal, for example, the solubility of hydrogen in α-zirconium depends on the soluble oxygen in the metal matrix, which is confirmed by the reduced «Zr–O–H» ternary system.

Discrete Dislocation Plasticity Modeling of Hydrides in Zirconium under Thermal Cycling

ABSTRACTUnderstanding the ratcheting effect of hydrogen and hydride accumulation in response to thermal cycling is important in establishing a failure criterion for zirconium alloy nuclear fuel cladding. We propose a simple discrete dislocation plasticity model to study the evolution of the dislocation content that arises as a micro-hydride repeatedly precipitates and dissolves over a series of thermal cycles. With each progressive thermal cycle, we find a steady growth in the residual dislocation density in the vicinity of the hydride nucleation site; this corresponds to a gradual increase in the hydrogen concentration and, consequently, the hydride population. The simulated ratcheting in the dislocation density is consistent with experimental observations concerning the hysteresis in the terminal solid solubility of hydrogen in zirconium, which can be correlated to the plastic relaxation of hydrides.

Influence of interstitial oxygen on hydrogen solubility in metals

Abstract A comparison of hydrogen solubility and enthalpy of solution of hydrogen was performed for metal–oxygen binary solid solutions. Oxygen addition into titanium, hafnium and vanadium decreased the hydrogen solubility at a fixed pressure, while the hydrogen solubility in zirconium, niobium and tantalum first increased with the oxygen content and then decreased. For the group IV metals, oxygen provided a negative effect on the enthalpy of solution of hydrogen. For the group V metals, the enthalpy of solution of hydrogen first increased with the oxygen content and then decreased. Partial thermodynamic functions of hydrogen in metal–oxygen–hydrogen ternary solid solutions were estimated using a dilute solution model. The oxygen effect on the partial molar quantities was complicated and depended on the metal. The changes in the partial molar quantities with the composition of the solution were discussed in terms of vibrational, dilatometric, and configurational contributions.

Influence of interstitial elements on hydrogen solubility in the Group IV metals

A comparison of hydrogen solubility and enthalpy of solution of hydrogen was performed for (Ti, Zr, Hf)-(O, N, C) binary solid solutions. Oxygen addition into titanium and hafnium decreased the hydrogen solubility at a fixed pressure. The hydrogen solubility in zirconium first increased with oxygen content, and then decreased at a higher oxygen content. The enthalpy of solution of hydrogen was lower for oxygen solid solutions than for pure metals. For all the metals, the presence of nitrogen and carbon increased the hydrogen solubility and provided a negative effect on the enthalpy of solution of hydrogen. Partial thermodynamic functions of hydrogen in (Ti, Zr, Hf)-(O, N, C)-H ternary solid solutions were estimated using a dilute solution model. The partial molar enthalpy and the partial molar excess entropy decreased with nitrogen and carbon contents in the solid solutions. The oxygen effect on partial molar quantities was more complex. The changes in the partial molar quantities with the composition of the solution were discussed in terms of vibrational. dilatometric, and configurational contributions.

Influence of Interstitial Impurity on Hydrogen Solubility in Zirconium

Influence of Interstitial Impurity on Hydrogen Solubility in Zirconium

Influence of interstitial impurity on hydrogen solubility in zirconium.

Hydrogen solubility in Zr-N and Zr-C alloys with various compositions has been measured at a temperature of 8731, 048 K at a pressure below 100 Pa. All the solubility data closely obeyed Sieverts' law. The presence of carbon and nitrogen in zirconium increased the hydrogen solubility at a fixed pressure and provided the negative effect on the enthalpy of solution. Partial thermodynamic functions of hydrogen in the Zr-N and Zr-C alloys were obtained by a dilute solution model and compared to those obtained previously for Zr-O alloys. Dependence of partial molar quantities of hydrogen on interstitial impurity content in zirconium was discussed in terms of dilatometric effect, configurational effect and other contributions.

Effect of Oxygen on Hydrogen solubility in Zirconium

Measurements of hydrogen solubility have been performed for pure Zr and Zr-O alloys with O/Zr atom ratios of 0.026–0.389 in the temperature range of 600–775° C. The isothermal section of the Zr-O-H ternary system at 700°C was constructed from the results for isothermal hydrogen pressure-hydrogen content curves at 700°C. The solubility data obtained at pressures below 10 2 Pa closely obeyed Sieverts' law. The solubility of hydrogen at a fixed pressure first increased with oxygen content in Zr, then decreased above a O/Zr ratio of 0.177. The enthalpy of solution showed a pronounced minimum at a O/Zr ratio of 0.111. The partial thermodynamic functions H ̄ H and S ̄ H for the Zr-O-H ternary solution were derived by applying a dilute solution model to the solubility data. The effect of solute oxygen on hydrogen solubility in Zr was discussed on the basis of the H ̄ H and S ̄ H values.

A metallographic study of the terminal solubility of hydrogen in zirconium at low hydrogen concentrations

The terminal solid solubility of hydrogen in alpha zirconium has been investigated using optical metallographic techniques. Hydrogen concentrations from 4 to 230 mg/kg were studied and good agreement found with previous determinations at concentrations above 25 mg/kg. Based on electron microscopic analysis of the hydrides, the solvus measured at hydrogen concentrations less than 25 mg/kg was determined to be that for the gamma hydride phase. From a least-squares fit of the data, the terminal solid solubility of this phase is given by the expression 3.43 × 10 4 exp(−32200/ RD) mg/kg.

An in-situ study of the dissolution of γ-zirconium hydride in zirconium

The dissolution of γ-zirconium hydride has been examined in single crystal specimens of zirconium using a hot stage in a high voltage electron microscope. It was found that a significant proportion of the dislocations generated by the hydride needles during growth were not annihilated when dissolution occurred on heating to well above the solvus temperature. This is contrary to earlier work where similar experiments were carried out with thinner specimens at conventional accelerating voltages. Electron irradiation completely prevented annihilation of the hydride dislocations during dissolution. The results are discussed in relation to (a) repeated nucleation at the same sites during thermal cycling, (b) external shape changes (growth), (c) strain steps observed during thermal cycling under creep conditions, (d) positron annihilation experiments, and (e) the terminal solid solubility of hydrogen in zirconium.

An experiment to clarify the effect of dissolved oxygen on the terminal solubility of hydrogen in zirconium

An experiment to clarify the effect of dissolved oxygen on the terminal solubility of hydrogen in zirconium

ジルコニウムの水素吸收と拡散係数の測定

The solubility of hydrogen in zirconium was determined as a function of temperature (range: 500° to 900°C) and pressure (range: 10−3 to 30 mmHg). The diffusion coefficients for H in α-Zr (range: 450° to 700°C) and in β-Zr (range: 870° to 1100°C) were calculated by diffusion-annealing method, which consisted of annealing the diffusion couples of different hydrogen contents in Pb bath, and analysing the hydrogen gradient across the diffusion zone. The calculated diffusion coefficients of H in α-and β-Zr are expressed, respectively, as:(This article is not displayable. Please see full text pdf.)

Interpretation of the solubility of hydrogen in zirconium

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The solubility of hydrogen in zirconium and zirconium-oxygen solid solutions

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