The Long-Range Migration of Hydrogen Through Zircaloy in Response to Tensile and Compressive Stress Gradients

Abstract

Zircaloy-4, which is used widely as a core structural material in pressurized water reactors (PWRs), picks up hydrogen during service. Hydrogen solubility in Zircaloy-4 is low and zirconium hydride phases precipitate after the Zircaloy-4 lattice becomes supersaturated with hydrogen. These hydrides embrittle the Zircaloy-4, degrading its mechanical performance as a structural material. Because hydrogen can move rapidly through the Zircaloy-4 lattice, the potential exists for large concentrations of hydride to accumulate in local regions of a Zircaloy component remote from its point of entry into the component. Much has been reported in the literature regarding the long-range migration of hydrogen through Zircaloy under concentration gradients and temperature gradients. Relatively little has been reported, however, regarding the long-range migration of hydrogen under stress gradients. This paper presents experimental results regarding the long-range migration of hydrogen through Zircaloy in response to both tensile and compressive stress gradients. The importance of this driving force for hydrogen migration relative to concentration and thermal gradients is discussed.

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

“…Stress gradients induce hydrogen diffusion was observed in various studies about hydrogen induced delayed hydride cracking [81] and in a study of Kammenzind et al [82]. Hydrogen diffusion in a thermal, a hydrogen concentration gradient and a stress gradient can be modelled in the framework of the thermodynamic of the irreversible processes by the equation 2 plus a term for the stress gradient contribution [81]:…”

Glow Discharge Optical Emission Spectrometer Calibration Using Hydrogenated Zr-2.5Nb Alloy Standard Samples

“…Many macroscopic properties of metals and their alloys depend on hydrogen, which is a common impurity found in structural materials after their usage [3][4][5][6][7][8]. Hydrogen can cause phase transformations leading to hydride formation [9][10][11][12][13][14][15][16], interactions with structural defects modifying the plastic activity of materials [17], the interplay with point defects provoking swelling [18][19][20][21], or so-called hydrogen embrittlement. It makes the development of methods for the protection of zirconium alloys from penetration of hydrogen significant.…”

Mechanical Property Testing of Hydrogenated Zirconium Irradiated with Electrons

“…In the presence of a solid thin oxide film on the surface, zirconium alloys slightly absorb hydrogen even at high temperatures [16]. The stress distribution in the plastic deformation zone was studied in [17]. Diffusion of hydrogen in zirconium as a function of temperature was described in [18].…”

“…The influence of external stress was studied in [25]. In the absence of external stresses, the hydrogen concentration in the α-phase of hydrogenated zirconium was determined in [17]. A delayed hydride cracking calculation model was proposed for the stationary model [25,26].…”

“…A delayed hydride cracking calculation model was proposed for the stationary model [25,26]. The effect of temperature on strength characteristics was studied in a number of other papers [17,[27][28][29][30][31], including the effect of isotopic composition [32].…”