Hydrogen diffusion under stress in Zircaloy: High-resolution neutron radiography and finite element modeling

Abstract

High-resolution neutron radiography (∼10 μm) was utilized to quantify hydrogen diffusion under stress in Zircaloy nuclear fuel cladding materials. A notched Zircaloy-4 plate with ∼600 wppm hydrogen underwent a thermo-mechanical test to allow hydrogen in solid solution to diffuse solely under a stress raiser. After the test, neutron radiography revealed an elevated concentration field at the notch, with a hydrogen gradient detectable over 700 μm and a maximum elevation of 130 wppm. Finite element computation was then performed by employing the Cauchy stress tensor and hydrogen-induced anisotropic transformation trains as the driving force of hydrogen diffusion.