Hydrogen redistribution in Zr-base cladding under gradients in temperature and stress

TL;DR

This paper uses computational models to simulate hydrogen redistribution in zirconium-based nuclear fuel cladding under temperature and stress gradients, highlighting its role in local embrittlement during reactor operation.

Contribution

It introduces specific models for axial and radial hydrogen diffusion in zirconium cladding, providing insights into hydrogen localization and its effects.

Findings

Hydrogen tends to localize near interpellet gaps, causing zirconium hydride precipitation.

Radial diffusion leads to a hydrided rim beneath the oxide layer.

Hydrogen redistribution significantly influences cladding embrittlement.

Abstract

Computational models are used here for simulating diffusion-controlled redistribution of hydrogen that is picked up by zirconium-base nuclear fuel cladding during light water reactor operation. Axial localization of hydrogen, leading to localized precipitation of zirconium hydrides at lower-temperature regions near interpellet gaps, is studied with a bespoke model, while radial diffusion, leading to formation of a densely hydrided rim subjacent to the waterside oxide layer, is studied with a more general model. The calculated results are compared with experimental observations and similar computational studies reported in the literature. The results underline the importance of hydrogen redistribution with regard to local embrittlement of the cladding tubes.