Delayed hydride cracking in Zircaloy-2 with and without liner at various temperatures investigated by high-resolution neutron radiography

Aaron W Colldeweih,Francesco Fagnoni,Pavel Trtik,Robert Zubler,Manuel A Pouchon,Johannes Bertsch

doi:10.1016/j.jnucmat.2022.153549

Aaron W Colldeweih, Francesco Fagnoni + Show 4 more

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https://doi.org/10.1016/j.jnucmat.2022.153549

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Journal: Journal of Nuclear Materials	Publication Date: Jan 20, 2022
Citations: 11	License type: cc-by

Affiliation: Paul Scherrer Institute

Abstract

Delayed hydride cracking (DHC) remains an important phenomenon when considering cladding mechanical integrity during transport and storage of spent nuclear fuel. This work studies the hydrogen diffusion and precipitation patterns during DHC as a function of temperature via high-resolution neutron imaging. Zircaloy-2 cladding tubes with and without an inner liner were radially cracked from the outside-in direction within a temperature range of 210–360 °C. A quantitative analysis was performed on the neutron radiographs showing the average radial concentration of hydrogen around the crack tip. The results show the trend of an increase in local concentration of hydrogen precipitated around the crack tip with an increase in cracking temperature. The elevated local concentrations correlate with the amount of hydrogen in solid solution available to diffuse towards the crack tip as well as the tensile stresses at the crack tip.

Highlights

Zirconium alloys have been the nuclear fuel cladding material of choice for light and heavy water reactors
This study focuses on delayed hydride cracking (DHC) and its novelty lies within the approach to fuel cladding testing in a realistic cracking direction and visualization with neutron imaging
The only variation in DHC test conditions was the test temperature that resulted in a change in total testing time

Summary

Introduction

Zirconium alloys have been the nuclear fuel cladding material of choice for light and heavy water reactors. These alloys have been developed for high corrosion resistance while maintaining sufficient mechanical properties, and an economical neutron absorption cross-section [1]. Many effects of hydrogen in zirconium have already been studied, some of which include the embrittlement of the cladding, and delayed hydride cracking (DHC) [2,3,4,5]. The embrittlement of claddings due to hydrogen acts on a macroscopic scale while DHC acts locally at a stress concentration [5,6,7]

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