Kinetics of Hydrogen Absorption and Release in Zirconium Alloys During Steam Oxidation

Abstract

The kinetics of hydrogen absorption during steam oxidation in Zr-Sn and Zr-Nb alloys in the temperature range of 1,000-1,400°C was investigated by neutron radiography. Hydrogen uptake can be subdivided into two steps: an initial phase and a state of equilibrium. The initial phase is controlled by the kinetics of hydrogen diffusion through the growing oxide layer. In the state of equilibrium, transport kinetics does not determine the hydrogen content of the material. An equilibrium is established between the hydrogen content of the gas environment and the metal phases. The temperature dependence of hydrogen absorption is Arrheniuslike at temperatures between 1,100 and 1,300°C.

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

“…In our model, hydrogen diffusion through the dense barrier oxide layer is taken as the rate-limiting step for H pickup [5][6][7] . The hydrogen diffusion follows the equation ) , (0 ≤ ≤ ( )) E represents the electric filed across the Zr oxide film and is calculated by…”

“…Many studies have focused on understanding the transport of hydrogen through the barrier oxide layer, as this transport is often regarded as the rate-limiting step for H pickup [5][6][7] . A number of factors, including oxide morphology, alloy additive elements and local stress, play important roles in the hydrogen transport process.…”

Hydrogen degradation of pre-oxidized zirconium alloys

“…The hydrogen dissolution in monoclinic ZrO oxide at 500-1100°C temperatures in oxygen/water vapor atmosphere ranged from 10 -5 to 10 -4 mol H/mol oxide and decreased with increasing temperature [42]. The hydrogen uptake in the initial phase controlled by hydrogen diffusion through the growing oxide layer was proportional to t 3/8 [43]. Hydrogen content in alloys oxidized at high dissolved oxygen (DO) conditions was invariably lower than that obtained at low DO conditions [44].…”

Flexible sample environment for high resolution neutron imaging at high temperatures in controlled atmosphere

“…2,3 Attenuation contrast neutron radiography and tomography allow observations of inner structures of bulk objects, e.g., differences in density, cracks, pores, water, and hydrogen concentrations and uptake. [6][7][8] By means of advanced techniques, e.g., energy resolved neutron imaging, [9][10][11][12] it is possible to gain spatially resolved information about the presence of different structural phases, texture related features or strains. 13 for corresponding observations of the kinetics of many important processes including phase transitions and changes in microstructure and crystal structure or stress fields in materials under variable conditions.…”

“…Besides the initially planned application, the presented furnace has great potential for various other studies such as, e.g., SOEC characterization and degradation; high resolution hydrogen uptake in metals (e.g., nuclear fuel claddings 7,8 ); crystal annealing, melting, recrystallization; and gas conversion and transport in catalysts and membranes. 26,27 …”