1 f. onimus j.l. béchade d. gilbon1 cloué j.p. mardon ,, g ... · cea | 10 avril 2012 | page 8....

Impact of hydrogen pick‐up and applied stress on c‐component loops:

Toward a better understanding of theToward a better understanding of the radiation induced growth of recrystallized

zirconium alloys

L. Tournadre1, F. Onimus1, J.L. Béchade1, D. Gilbon1, J.M. Cloué2, J.P. Mardon2, X. Feaugas3, , , g

1 2 3

17th International Symposium on Zirconium in the Nuclear Industry

February 3-7, 2013, Hyderabad, India

INDUSTRIAL BACKGROUND & OBJECTIVES

In-reactor elongation of the

PWR fuel assembly

in Recrystallized alloysStress free growth phenomenon

grow

th stra Recrystallized alloys

Fuel assembly

Irradiation

Time in reactor (fluence n/m2 or dpa)

Breakaway growth

Time in reactor (fluence n/m or dpa)

L. Tournadre, et al. 17th International Symposium on Zirconium in the Nuclear Industry, February 3-7, 2013, Hyderabad, India 2



PWR fuel assembly a-loops


10 nm

grow


Fuel assembly

50 nm

Irradiation


Breakaway growth

<c>


VI


<a>



PWR fuel assembly a-loops


10 nm

grow


Fuel assembly

50 nm

Irradiation


Breakaway growth

<c>

V


c-component loops

VI g=0002


<a>Thin foil thickness


AREVA background: Fuel assembly growth acceleration phenomenon slightlydifferent than predicted

Two origins can be considered :

• Coupling between creep and stress free growth

Does a macroscopic stress influence the c-loop microstructure ?

• Impact of the in-service hydrogen pick-up on the c-loops ?McGrath et al. ASTM STP 1529 (2011)

Does the hydrogen content influence the c loop microstructure ?

To have a rapid answer to these two questions :

Does the hydrogen content influence the c-loop microstructure ?

Analytical study using charged particle irradiations

- Improve the understanding of growth accelerationBuild a physically based model taking into account c loops


- Build a physically based model taking into account c-loops

CHARGED PARTICLE IRRADIATIONS

Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse

Zr ion irradiations

At CSNSM

Proton irradiations

At MIBL Michigan Ion Beam Laboratory

ARAMIS – 2 MeV Tandem

IRMA –190 keV ion implantor

1,7 MeV Tandetron

2D thermal camera

Irradiation room

Proton

Samples

source and high voltage

generator

• Temperature: 300°C – 350°C

• Zr ion energies: 600 keV (ARAMIS) / 300 keV (IRMA)Aperture

• Temperature: 350°C

• Protons energy: 2 MeV

Irradiation time (1 day)

Superficial damage on 300 nm (~0,05 grain) Damage on 30 µm (~6 grains)

Irradiation time (200 h)


7 irradiations completed 6 irradiations completed

STUDIED MATERIALS

Alloying (weight ppm) Sn Nb Fe Cr O

RXA Zy-4 ~1.30 - 0.22 0.11 0.13

Two recrystallized Zr alloys studied:

• Recrystallized Zircaloy-4 (RXA Zy-4)M5TM - 1.00 0.037 - 0.14• M5TM

Intermediate product : thick tube 3 mmC-axis

<c>m

<c>

<c>

100

µ

Observed areas, thickness of ~200 nm

TEM bright field pictures with a g=0002 diffraction vector

CladdingThick Tube

RXA Zy-4

C-loop observation easier by Transmission Electron Microscopy (TEM)


Microscopy (TEM)

50 µm

ZR ION IRRADIATION &

EFFECT OF AN APPLIED STRESS

CEA | 10 AVRIL 2012

| PAGE 8

ZR ION IRRADIATION – CONTROL SAMPLES

Zr ions (300°C / 350°C)600 keV Zr ions –300°C

PWR Zy-4

L V(m

‐2)RXA Zy-4

Line

ar den

sity L

M5TM

PWR M5

M5TM

PWR (RXA Zy‐4)PWR (Low tin RXA Zy‐4)

PWR (M5TM)


C-loops observed after Zr ion irradiations

CEA STRESS DEVICE FOR ZR ION IRRADIATION

Irradiated surface.St di tl li k d t

Original 4-point bending device developed at CEA

Stress directly linked to the applied deformation

Irradiation up to 4 1 dpa without stress- Irradiation up to 4.1 dpa without stress- Stress applied after 4.1 dpa irradiation (when c-loops are already created), up to 7 dpa- Rapid relaxation of the stress in the irradiated layer (due to irradiation creep)Rem : high applied stress (close to yield stress) not representative of in-reactor loading


Effect of stress on c-loops ?

STRESS APPLIED ON C-LOOPS – ZR ION IRRADIATION

Pre-irradiated Zy-4 (4.1 dpa) – applied stress (≈yield stress) during 2.9 dpa. Total dose : 7 dpa

σ

σ

<c><c>

Stress applied perpendicular to the c-axisc axis

High c-loop densities




σ

σ

<c><c>

Stress applied perpendicular to the c-axis

σ σ<c><c>

c axis





σ

σ

<c><c>

Stress applied perpendicular to the c-axis

σ σ<c><c>

c axis

Applied stress closer to the c-axis


C-loop density decreases if the stress is applied

C-loop density decreases


if the stress is applied along the c-axis

EXPERIMENTAL RESULTS VS. SIPA MECHANISM

RXA Zy-4 after Zr ion irradiations :

C-loop densities vs.

d70

80

90Mean diameter (nm)

2 (max)

1E+14

1,2E+14

Linear density ( )

Counted loops : 5240

VdNLv

σ

<c><c>20

30

40

50

60

6E+13

8E+13

1E+14Thickness measured by EELS

σ 0

10

‐ 1/3 0 1/3 2/3

Stress deviatoric component along the c‐axis (fraction of )

3E+21Number of c‐loops per unit volume (m‐3)

2E+13

4E+13

6E+13σ σ<c><c>

1,5E+21

2E+21

2,5E+21

10 (max)controlsample

0

2E+13

‐ 1/3 ‐0 1/3 2/3

Stress deviatoric component along the c‐axis (fraction of )0

5E+20

1E+21

‐ 1/3 0 1/3 2/3



Stress deviatoric component along the c axis (fraction of )

Results in good agreement with the SIPA mechanism (Garner et al., 1979)


STRESS INDUCED PREFERENTIAL ABSORPTION (SIPA)

Absorption bias of point defects by loops ( ) is modified by the deviatoric stress :

Influence on the(Garner et al., 1979)

Stress applied perpendicular to c-axis :

σ

Absorption of SIA

Net vacancy absorption

<c><c>


σ






σ

Absorption of SIA


<c><c>


σC-loop growth






σ

Absorption of SIA


<c><c>


σC-loop growth

σ<c><c>σ






σ

Absorption of SIA


<c><c>


σC-loop growth

Absorption of SIA

Stress applied along the c-axis : σ<c><c>σ



Absorption of SIA

C-loop shrinking

PROTON IRRADIATION &

EFFECT OF HYDROGEN CONTENT

CEA | 10 AVRIL 2012

| PAGE 19

PROTON IRRADIATIONS – CONTROL SAMPLES2 MeV protons – 350°C2 MeV protons – 350°C

VdNLv

2 MeV protons 350 C

Counted loops : 6566

p

PWR Zy-4RXA Zy-4

PWR M5

M5TM

PWR M5

( )

C-loops observed after proton irradiations

PWR (RXA Zy‐4)PWR (Low tin RXA Zy‐4)

PWR (M5TM)


Effect of the Zr alloy chemical composition in agreement with neutron irradiationStudy of the effect of H mainly conducted on the M5TM + avoid H desorption

C loops observed after proton irradiations

IMPACT OF HYDROGEN IN THE “MATRIX”

M5TM : irradiated up to 4.9 dpa – 2 MeV protons – 350°C

<c+a> dislocation

Control sample

200 nm 350 wppm

200 nm

No c-loop at 4 9 dpa C-loops observed at 4 9 dpa

Pre-hydrided at 350 ppm

No c loop at 4.9 dpa C loops observed at 4.9 dpa

Incubation dose higher than 4.9 dpa Incubation dose lower than 4.9 dpa


Hydrogen reduces the incubation dose for c-loop nucleation


M5TM : effect of H in the “matrix” (far from precipitated hydrides) At 19 dpa – 350°C

Control 80 ppm – 19 dpa

In pre-hydrided samples :

Density slightly higher

Control sample

80 ppm 19 dpa

C-loop microstructures more homogeneous

Density slightly higher


Also observed at 8.1 dpa and 12.5 dpa350 ppm – 19 dpa


M5TM – 19 dpa – 350°C Thickness measured by Energy Electron Loss Spectroscopy

M l

dens

ity

Mean value5 grains2215 loops Mean value

4 grains3453 loops

Line

ar

Mean value6 grains2158 loops

Mean value5 grains2285 loops

19 dpa

Hydrogen content (wppm)

19 dpa


Hydrogen content (wppm)

Hydrogen atoms in solid solution enhances the nucleation / growth of c-loops

EFFECT OF HYDROGEN ON C-LOOPS

Hydrogen atoms in solid solution (~100 wppm at 350°C) :

Trapped on the stacking fault diskReduce the c-loop basal stacking fault energy

Domain and al. ab initio calculations

+ experimental results (Vizcaino, McMinn and al.)

Trapped in the stress field of c-loop dislocation linesReduce the elastic energy Girardin, PhD (2010), Oudriss et al. OCAS (2011)

T l l

Emission of vacancy C-Loop growth

Total c-loop energy

B








T l l


Total c-loop energy

B








T l l


Total c-loop energy

B


Hydrogen atoms trapped could enhance c-loops nucleation and growth

EXPERIMENTAL RESULTS : C-LOOP BUNDLESFormation of c-loop bundles: example of the 350 wppm M5TMFormation of c-loop bundles: example of the 350 wppm M5

At 19 dpa – 350°C

OR2

Locally high c-loop densitiesIn some specific areas, c-loops gathered as “bundles”

Former δ hydrides now partially or completely dissolved (<c+a> dislocations)


Former δ-hydrides now partially or completely dissolved (<c+a> dislocations)

Also observed at lower irradiation doses and for lower hydrogen content (80 ppm)


At 19 dpa – 350°C

OR2

200 nm







Dissolved hydrides :Hydride dissolution: a source of hydrogen atoms enhance loop growth

<c+a> remaining accommodation dislocations after dissolution: c-loops nucleation site ?

g=0002Helical climb of <c+a> dislocation and/or dissociation in the basal plane of the <c+a> dislocation + climb of the partial dislocation

b<c+a> B

the partial dislocation

B

b<c>1

b<c>2

π

π

b<c+a>

π


50 nm- Hydride : source of hydrogen- <c+a> dislocations as a nucleation site for c-loops

CONCLUSION

• Macroscopic stress :

• C-loops observed after Zr ion and proton irradiations

• Macroscopic stress :

SIPA mechanism observed on RXA Zy-4,

(for high stress not representative of PWR conditions)( g p )

• Hydrogen impact :

Clearly observed on M5TM with 350 ppm hydrogenClearly observed on M5TM with 350 ppm hydrogen

Impact of H in solid solution (effect on the basal stacking fault energy)Impact of H in solid solution (effect on the basal stacking fault energy)

Impact of dissolved hydrides (c-loop bundles) (source of hydrogen, c+a dislocation as nucleation site for c-loops)


p )

Thank you for your attention !


1 f. onimus j.l. béchade d. gilbon1 cloué j.p. mardon ,, g ... · cea | 10 avril 2012 | page 8....

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