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MICROSTRUCTURAL
EVOLUTION OF Q12™ ALLOY
IRRADIATED IN PWR AND
COMPARISON WITH OTHER Zr
BASE ALLOYS
CEA| Sylvie Doriot
Authors: S. Doriot, B. Verhaeghe, A. Soniak,
P. Bossis, D. Gilbon, V. Chabretou,
J. P. Mardon, M. Ton-That, A. Ambard.
18th INTERNATIONAL SYMPOSIUM ON
« ZIRCONIUM IN THE NUCLEAR INDUSTRY », MAY
15-19, 2016, HILTON HEAD S.C. US
AIM OF THE STUDY
Sn Fe Cr1 Nb
M5® < 100 ppm 0.035 - 1
Zr1Nb0.3Sn0.1Fe 0.3 0.1 - 1
Zr1Nb0.3Sn0.2Fe 0.3 0.2 - 1
Q12™ 0.5 0.1 - 1
RXA Zy-4 [11] 1.35-1.4% 0.2 0.1 -
9 DÉCEMBRE 2013 | PAGE 2
Q12™ is compared to M5®
and to 2 other quaternary alloys:
If we disregard Sn content, the chemical composition of these alloys differs mainly by their iron content in the range of 350 to 2000 ppm.
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
1 Cr is an impurity element in M5® and in the three quaternary alloys
Q12™ a quaternary alloy developped by AREVA NP for structural components
| PAGE 3
AIM OF THE STUDY
In quaternary alloys Fe and Sn are added to enhance creep
strength and tensile properties of Fuel Assemblies (F.A.).Shishov V.N. ASTM STP 1529, 2012, pp. 37-66
Iron rejected out of the precipitates during irradiation is supposed to
promote the <c>-component loop nucleation responsible for growth2
phenomenon in Zy-4 alloys.
D. Gilbon et al. ASTM STP 1245,1994, pp. 521-548
What about Fe influence for Quaternary alloys?
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
2growth and creep are responsible for dimensional changes in F.A.
AIM OF THE STUDY
9 DÉCEMBRE 2013 | PAGE 4
0
1
2
3
4
5
6
7
0 10 20 30
No
rma
lize
d f
ree
gro
wth
Fluence (1025 n/m²)
M5 Zy-4
0,0
0,2
0,4
0,6
0,8
1,0
1,2
0 2 4 6 8 10 12 14 16 18 20No
rma
ilze
d f
ree
gro
wth
Fluence 1025 n/m²)
Q12™ Zr-1Nb0.3Sn-0.1Fe Zr-1Nb-0.3Sn-0.2Fe M5®
M5®
Fe 350 ppm
Q12
Fe 1000 ppm
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
It seems that iron content is not the only element governing the growth
behavior.
The aim of this study was to assess the evolution of the Zr(Fe,Nb)2 Laves
phases in correlation with the <c>-component loop linear density versus
fluence and with the growth behavior.
Zy-4
Fe 2000 ppm
200nm 200nm100nm
OUTLINE
I.- Materials of the study and irradiation conditions
II.- Experimental results
- Radiation - enhanced needle-like particles
- Zr(Fe,Nb)2 particle changes versus fast neutron fluence
- Basal irradiation-induced <c>-component loops
III.- Conclusion
| PAGE 5Microstructural evolution of Q12™. Doriot et al. | MAY 2016
I.- MATERIALS OF THE STUDY AND
IRRADIATION CONDITIONS
I.1.- MATERIALS OF THE STUDYMICROSTRUCTURE OF PRECIPITATION BEFORE IRRADIATION
| PAGE 7
Q12™ contains a homogeneous highly
refined dispersion of bNb phase precipitates
and a coarser precipitation of Zr(Fe,Nb)2
Laves Phases
M5® 350 ppm Fe homogeneous highly refined dispersion of bNb.
Zr1Nb0.3Sn0.1Fe: 1000 ppm Fe similar to Q12™.
M5®Zr1Nb0.3Sn0.2Fe: 2000 ppm Fe similar to Q12™, with more
Laves phases and some (Zr,Nb)4Fe2 FCC particles.
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
Q12™
1 mm
All the materials are in a fully recrystallized state.
I.1.- MATERIALS OF THE STUDYMICROANALYSES ON THE SECOND PHASE PARTICLES IN Q12™
| PAGE 8Microstructural evolution of Q12™. Doriot et al. | MAY 2016
0
10
20
30
40
50
60
70
80
90
20 40 60 80 100
x%
Zr %
% Nb K
% Fe K
%Cr K
% Sn L
Before irradiation : two populations of SPPs can be observed
1) contains only Zr and Nb and corresponds to bNb,
2) contains Zr, Fe, Nb and Cr and corresponds to Laves phase: Nb/Fe~2
1
1
2
2
The microanalysis results on several precipitates in the non-irradiated Q12™
alloy are plotted on this graph
(atomic percentage of iron, chromium, tin and niobium versus zirconium)
Q12™
I.1.- MATERIALS OF THE STUDYMORPHOLOGICAL ASPECT OF THE LAVES PHASES COMPARED TO bNb
| PAGE 9Microstructural evolution of Q12™. Doriot et al. | MAY 2016
The Laves phases
are larger than the
bNb precipitates
(about 150 nm in
diameter instead
of 30 nm for bNb).
Stacking faults can be noticed in Laves Phases as it is classically observed
on theses SPPs
Q12™
I.2.- IRRADIATION CONDITIONS
| PAGE 10
All the samples were irradiated in PWR conditions
The quaternary alloy samples for Transmission Electronic Microscopy microstructural observations were sections of cladding tubes irradiated in a French power plant: fluence levelup to about 13x1025 n/m2 (E>1 MeV)
Free-growth test tubes of M5® and of the quaternary alloys were launched in a European power plant in order to determine irradiation free growth behavior: fluence level up to about 18x1025 n/m2 (E>1 MeV)
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
Fluence,
1025n/m2
(E>1MeV)
Number of 18
month PWR
cycles
Dose
dpa
Zr1Nb0.3Sn0.2Fe 6.9 2 ~10
Zr1Nb0.3Sn0.1Fe 6.2 2 ~10
Q12™ 6.8 2 ~10
Q12™ 13 4 ~20
II.- EXPERIMENTAL RESULTS
II.1.- RADIATION - ENHANCED NEEDLE-LIKE PARTICLESMICROGRAPHS
| PAGE 12
Zr1Nb0.3Sn0.2Fe
~7x1025 n/m2
Zr1Nb0.3Sn0.1Fe
~7x1025 n/m2
Q12™
~7x1025 n/m2
M5®
~7x1025 n/m2
Q12™
~13x1025 n/m2
M5®
~13x1025 n/m2
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
No noticeable difference in the
size distribution and in the density
of the radiation-enhanced particles
between the different materials
and irradiation conditions
This precipitation modifies the
matrix niobium contentS. Doriot et al., ASTM STP 1543, 2015, pp. 759-799
100 nm
II.1.- RADIATION - ENHANCED NEEDLE-LIKE PARTICLESEVOLUTION OF THE LENGTH AND THE WIDTH VERSUS FAST FLUENCE
| PAGE 13Microstructural evolution of Q12™. Doriot et al. | MAY 2016
No significant difference between the quaternary alloys and M5®
despite the difference in iron content.
M5®: S. Doriot et al., ASTM STP 1543, 2015, pp. 759-799.
II.1.- RADIATION - ENHANCED NEEDLE-LIKE PARTICLES
EVOLUTION OF NUMBER DENSITY VERSUS FAST FLUENCE
| PAGE 14
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
0 2 4 6 8 10 12 14 16 18
nu
mb
er
de
ns
ity
10
22
m-3
fluence 1025 n/m2
M5®
Q12™
Zr1Nb0.3Sn0.2Fe
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
M5®: S. Doriot et al., ASTM STP 1543, 2015, pp. 759-799
●The number density of « needle-like » particles remains constant all along the
irradiation and close to 1.5x1022 m-3 for M5® and for the quaternary alloys.
● There is no impact of iron content in the range of 350 to 2000 ppm.
II.2.- Zr(Fe,Nb)2 PARTICLE CHANGES VERSUS FAST
NEUTRON FLUENCEMICROSTRUCTURAL CHANGES
| PAGE 15
7x1025 n/m2
Former Laves phases appear as micro-crystallized and highly
faulted particles in the three quaternary alloys and in M5®Microstructural evolution of Q12™. Doriot et al. | MAY 2016
After a fluence of
about 7x1025 n/m2, part
of the particles can still
be indexed as
hexagonal Zr(Fe,Nb)2
Laves phase.
After a fluence of
about 13x1025 n/m2, no
possible indexation as
hexagonal Zr(Fe,Nb)2
Laves phase.
7x1025 n/m2200 nm
100 nm
Q12™
II.2.- Zr(Fe,Nb)2 PARTICLE CHANGES VERSUS FAST
NEUTRON FLUENCEMICRO-CHEMICAL CHANGES
| PAGE 16
0102030405060708090
20 30 40 50 60 70 80 90 100
X %
Zr %
% Nb
% Fe
% Cr
% Sn
0
1
2
3
4
5
20 30 40 50 60 70 80 90 100
X %
Zr %
% Nb
% Fe
% Cr
% Sn
0102030405060708090
20 30 40 50 60 70 80 90 100
X %
Zr %
% Nb
% Fe
% Cr
% Sn
0
1
2
3
4
5
20 30 40 50 60 70 80 90 100
X %
Zr %
% Nb
% Fe
% Cr
% Sn
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
After a fluence of about 7x1025 n/m2, two populations remain in the three
quaternary alloys but the Laves phases contain only a low percentage of iron.
After a fluence of 13x1025 n/m2 (Q12™), only one population still
exists, with only Zr and Nb.
| PAGE 17
a)
0
0,02
0,04
0,06
0,08
0,1
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0 50 100 150 200 250
Cr/
Zr, F
e/Z
r
Nb
/Zr
nm
Nb/Zr
Fe/Zr
Cr/Zr
core
periphery
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
II.2.- Zr(Fe,Nb)2 PARTICLE CHANGES VERSUS FAST
NEUTRON FLUENCECONCENTRATION PROFILE AFTER A FLUENCE OF ~7x1025 n/m2
Homogeneous
profile in the
core of the
Laves phase
with a very low
content of Fe
(Nb/Fe~10) and
the same
content of Cr
than before
irradiation
The core probably
produces the
hexagonal diffraction
diagram seen just
before.
No Fe nor Cr at
the periphery
and a higher
Nb content
The periphery is probably
transformed into CC bNb
particles as said in the
literature(Shishov V.N
ASTM STP 1529, 2012, pp. 37-66)
Zr1Nb0.3Sn0.Fe
II.2.- Zr(Fe,Nb)2 PARTICLE CHANGES VERSUS FAST
NEUTRON FLUENCELAVES PHASES AND <c>-COMPONENT LOOPS
| PAGE 18
1. c)
Zr(Fe,Nb)2 Zr(Fe,Nb)2
Zr(Fe,Nb)2
Zr(Fe,Nb)2
Zr(Fe,Nb)2
Zr(Fe,Nb)2
Zr(Fe,Nb)2
Q12™ ~7x1025 n/m2
M5® 14x1025 n/m2
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
In the quaternary alloys, the correlation between the
Laves phases and the <c>-component loops is
expressed by a higher density of <c>-component loops
at the vicinity of the Laves phases.
bNb
bNb
bNb
bNb
bNb
In M5®, no correlation
between Laves phases
and <c>-component
loops
Zr1Nb0.3Sn0.2Fe
~7x1025 n/m2Zr1Nb0.3Sn0.1Fe
~7x1025 n/m2
Q12™ ~13x1025 n/m2
100 nm
100 nm
II.3.- BASAL IRRADIATION-INDUCED <C>-COMPONENT
LOOPS MICROGRAPHS AFTER A FLUENCE OF ~7x1025 n/m2
| PAGE 19
Zr1Nb0.3Sn0.2Fe
Q12™ 2 cycles
M5®
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
Zr1Nb0.3Sn0.1Fe Q12™
<c>-component loops seem less numerous in the quaternary alloys than in
M5® for the same fluence level (~7x1025 n/m2)
Particularly limited in
numbers and can be
seen only at the
vicinity of Laves
phases
Correlated to Laves
phases but can be
observed at few 100 nm
from the precipitates.
Evenly spread in the
material 200 nm
200 nm200 nm
II.3.- BASAL IRRADIATION-INDUCED <C>-COMPONENT
LOOPS MICROGRAPHS AFTER A FLUENCE OF ~13x1025 n/m2
| PAGE 20
Q12™ M5®
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
This tendency is confirmed here at higher fluence ~13x1025 n/m2
<c> component loops correlated to Laves phases in Q12™ and evenly
dispersed in M5®.
200 nm200 nm
II.3.- BASAL IRRADIATION-INDUCED <C>-COMPONENT
LOOPS <C>-COMPONENT LOOP DENSITY VERSUS FLUENCE
| PAGE 21
0
5
10
15
20
0 2 4 6 8 10 12 14 16 18 20 22
lin
ear
den
sity
10
13
m/m
3
fluence 1025 n/m2
M5®RXA Zy-4Zr1Nb0.3Sn0.2FeZr1Nb0.3Sn0.1FeQ12™
Microstructural evolution of Q12™. Doriot et al. | MAY 2016
● For RXA Zy-4 alloys irradiated in PWR conditions (at~320°C) a fluence level of
about 10x1025 n/m2 appeared to correspond already to the growth breakaway regime
(S. Doriot et al., ASTM STP 1467, pp 175-201). For this fluence the <c>-component loop linear
density was measured as high as 10x1013 m/m3 (S. Doriot et al., ASTM STP 1543, pp 759-799).
● <c>-component loop linear density is much lower than 5x1013 m/m3 for M5®
cladding tubes for a very high dose in PWRs. The curve slope for <c>-component
loops versus fluence of Q12™ alloy is similar to that of M5®. This is consistent with
the similar free growth behavior of the two alloys.
CONCLUSION
- The influence of iron on the <c>-component loops and on the
growth behavior seems more complex than expected.
- This influence is expressed locally by a higher density of
<c>-component loops at the vicinity of the Laves phases.
- But globally the total iron content seems to have little
influence on the <c>-component loop linear density in the
alloys studied here, in the range 0.2 % to 350 ppm.
- This is consistent with a similar free growth behavior of M5®
and of the quaternary alloys and with no growth breakaway
on M5® and on quaternary fuel rod elongations in the usual
fuel assembly fluence irradiation range, despite their different
iron content (S. Doriot et al., ASTM STP 1467, pp 175-201, V. Chabretou et al., ASTM STP
1529).| PAGE 22Microstructural evolution of Q12™. Doriot et al. | MAY 2016
DANS
DMN
SRMA
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