Properties of zirconium alloys and their applications in light water reactors (LWRs) - Materials' Ageing and Degradation in Light Water Reactors - page 129

Table 4.8 Types of corrosion observed for Zircaloy in-reactor and out-of-reactor

Type of corrosion Comment Observed Irradiation effect in

oxygenated coolant (BWR)

Irradiation effect in
hydrogenated coolant PWR

Uniform Normal mode Out-of-pile, in-BWR and

in-PWR

5-10 × increased from
beginning, low fl ux
dependency

2-4 × increased after 1st
corrosion rate transition,
low fl ux dependency

Nodular Local breakdown of

oxide protectiveness

In-BWR and out-of-pile
>500 ° C, Zry with
large SPP

Increases almost linearly
with fast fl ux, little temp.
dependency

Not observed

Shadow corrosion Probably driven by

potential differences

Only under irradiation
and oxidative coolant
conditions (BWR)

Increases probably almost
linearly with fast fl ux

Not observed

Crevice corrosion Change of environment

in small gaps

Out-of-pile, in-BWR and
in-PWR

Observed Observed

Increased corrosion
with fi ne SPP

Reduction of protectivity Out-of-pile, in-BWR and

in-PWR

Increases almost linear
with fast fl ux

Increases almost linearly
with fast fl ux, little
temp. dependency

Increased corrosion
at high fl uences

Reduction of protectivity In-PWR ? Increases with increasing

fl uence above a critical
threshold

Increased corrosion
at high hydride
concentrations

Lower corrosion
resistance of hydride

Out-of-pile, in-BWR and
in-PWR

Observed Flux dependent but less

temperature dependent

Source: A.N.T. International (2011) and Garzarolli in ZIRAT7 STR 'Corrosion in Zirconium Alloys', Adamson et al . (2002).