Properties of zirconium alloys and their applications in light water reactors (LWRs) - Materials' Ageing and Degradation in Light Water Reactors - page 99

Before Grain boundary Precipitates Matrix

Zr 2 (Fe,Ni) type

Sn

Fe

Ni

Zr(Fe,Cr) 2 type

After (schematic illustrating change as result of irradiation)

Sn (segregation to GB)

Sn

Fe & Ni (slight loss
from dissolution) Ni & Fe

Fe +

Zr 2 (Fe,Ni) type

Fe

Fe (large loss from SPP due to
amorphization and dissolution)
· evenly distributed in matrix
· some trapped at dislocations

Ni +

Zr(Fe,Cr) 2 type
Cr-rich zone within
20 nm of original SPP

Fe

4.12 Schematic illustrating SPP dissolution and solute redistribution
for small SPP Zircaloy-2 irradiated near 300 ° C. (Source: Reprinted, with
permission, from Mahmood et al . (2000), copyright ASTM International,
100 Barr Harbor Drive, West Conshohocken, PA 19428.)

0.1 μ m 0.1 μ m 0.1 μ m 0.1 μ m

￿ ￿ ￿ ￿ ￿ ￿

Crystalline
Amorphous

Fe, Cr Fe, Cr Fe, Cr Fe, Cr

Fe
Cr
(Before irradiation)

Fe
Cr

Fe
Cr

Fe

Cr

(1) Amorphization/
Fe depletion proceeding
towards the centre
(low fluences)

(2) Amorphization/
Fe depletion completed,
Cr dispersion ongoing
(high influences)

(3) Completely vanished
due to irradiation-
induced dissolution
(very high fluences)

4.13 Evolution of a Zr-Fe-Cr particle under BWR irradiation. Upper
fi gures: TEM micrographs; middle diagrams: schematic illustration of
amorphization; lower fi gures: schematic illustrations of the chemical
compositions. (Source: Reprinted, with permission, from Takagawa
et al . (2004), copyright ASTM International, 100 Barr Harbor Drive, West
Conshohocken, PA 19428.)