Properties of zirconium alloys and their applications in light water reactors (LWRs) - Materials' Ageing and Degradation in Light Water Reactors - page 151

0.8%

Zircaloy-4

ZIRLO

Guide tube length
Guide tube diameter
Long. strip (thin)
Tran. strip (thin)
Long. strip (thick)
Tran. strip (thick)
Linear fit

Guide tube length
Guide tube diameter
Long. strip (thin)
Tran. strip (thin)
Long. strip (thick)
Tran. strip (thick)
Theoretical

0.7%

0.6%

0.5%

0.4%

0.3%

0.2%

0.1%

0.0%

0 500 1000 1500 2000

Hydrogen content (ppm)

4.60 Dimensional changes in unirradiated ZIRLO and Zircaloy-4
tubing and strip for different sample orientations as a function of
hydrogen content. (Source: Reprinted, with permission, from King
et al . (2002), copyright ASTM International, 100 Barr Harbor Drive, West
Conshohocken, PA 19428.)

heavily cold worked material, it has been reported that some shrinkage
may occur. In a non-textured material such as SS, creep down of the
cladding would only result in an increase in cladding thickness, with no
change in length.
Creep due to PCMI after hard contact between the cladding and fuel. ￿

This occurs in mid-life, depending on the cladding creep properties and
the stability of the fuel.
Hydriding of the cladding due to corrosion.

￿ ￿ ￿ ￿ ￿ ￿

￿

Bow of a component such as a BWR channel or PWR control rod assembly
can occur if one side of the component changes length more than the other
side. Such differential length changes occur due to differential stress and
creep, to relaxation of differential residual stresses or to differential growth
due to differences in fl ux-induced fl uence, texture, material cold work and
hydrogen content (and, although not usually present, differences in temper-
ature or alloying content). This is described more in the ZIRAT 10 Special
Topics Report on Structural Behaviour of Fuel and Fuel Components (Cox
et al ., 2005 ).
The next section discusses the effect of irradiation on dimensional
stability.