Structure and Thermodynamical Properties of Zirconium hydrides from first-principle

TL;DR

This paper uses first-principles calculations to determine the structural and thermodynamic properties of zirconium hydrides, providing essential parameters for modeling hydride precipitation in nuclear cladding materials.

Contribution

It presents DFT-based calculations of the crystal structures and latent heats of fusion for three zirconium hydride polymorphs, aiding phase-field modeling of hydride formation.

Findings

Determined crystal structures of elta-, b3-, and psilon-ZrH phases.

Calculated latent heats of fusion for the hydrides.

Provided parameters crucial for phase-field modeling of hydride precipitation.

Abstract

Zirconium alloys are used as nuclear fuel cladding material due to their mechanical and corrosion resistant properties together with their favorable cross-section for neutron scattering. At running conditions, however, there will be an increase of hydrogen in the vicinity of the cladding surface at the water side of the fuel. The hydrogen will diffuse into the cladding material and at certain conditions, such as lower temperatures and external load, hydrides will precipitate out in the material and cause well known embrittlement, blistering and other unwanted effects. Using phase-field methods it is now possible to model precipitation build-up in metals, for example as a function of hydrogen concentration, temperature and external load, but the technique relies on input of parameters, such as the formation energy of the hydrides and matrix. To that end, we have computed, using the density functional theory (DFT) code GPAW, the latent heat of fusion as well as solved the crystal structure for three zirconium hydride polymorphs: \delta-ZrH1.6, \gamma-ZrH, and \epsilon-ZrH2.