Properties of zirconium alloys and their applications in light water reactors (LWRs) - Materials' Ageing and Degradation in Light Water Reactors - page 102

0 10 20 30 40 50 dpa

40

(a)

30

20

10

0

0 1 2 3

Fluence, F, 10 26 m − 2 ( E ≥ 1 MeV)

0 10 20 30 40 50 dpa

0.6

(b)

0.4

0.2

0.0

0 1 2 3

￿ ￿ ￿ ￿ ￿ ￿

Fluence, F, 10 26 m − 2 ( E

1 MeV)

≥

4.15 Fe content as a function of fl uence ( E > 0.1 MeV/4) at 330-350 ° C
in alloy E635, (a) SPP Zr (Nb,Fe)2 and (b) ˞ದZr solid solution. (Source:
Reprinted, with permission, from Shishov et al . (2002), copyright ASTM
International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.)

None of the SPPs become amorphous at normal reactor temperatures,
but at high burnup at 60°C (333K) the Laves phase does become at least
partially amorphous. However, all of the SPPs undergo irradiation-induced
dissolution. The Nb SPP loses Nb to the matrix, but the excess Nb then

re-precipitates as a very fi ne

β

β Nb. The Laves phase Zr(Fe,Nb) 2 transforms to

a fi ne Nb SPP, with essentially all Fe ending up in the matrix (see Fig. 4.15).

Behaviour of the T-phase (Zr,Nb) 2 Fe is more complicated, with Fe diffusing

β