microstructural evolution of q12™ alloy irradiated … · q12™ zr-1nb0.3sn-0.1fe...

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?


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


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.


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™


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


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)


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


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


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


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™


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


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



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


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


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®


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


LOOPS MICROGRAPHS AFTER A FLUENCE OF ~13x1025 n/m2

| PAGE 20

Q12™ M5®


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


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™


● 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

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