Tensile properties and microstructure of austenitic steels irradiated in different reactors

DEN - Saclay – Nuclear Material departement

"Influence of atomic displacement rate… " Workshop - Ulyanovsk - October 5, 2005 Ph. Dubuisson - 1

DMN / SRMA

Tensile properties and microstructure Tensile properties and microstructure of austenitic steels irradiated in of austenitic steels irradiated in

different reactorsdifferent reactors

Ph. DubuissonX. Averty

M. Žamboch

V.K. ShamardinV.I. Prokhorov

J.P. MassoudC. Pokor

Influence of Atomic Displacement Rate onInfluence of Atomic Displacement Rate onRadiation-induced Aging of Power ReactorRadiation-induced Aging of Power Reactor

Ulianovsk, Russia - October 2 - 8, 2005Ulianovsk, Russia - October 2 - 8, 2005

Y. Bréchet



DMN / SRMA

Reach "rapidly" the end-of-life doses FBRFBR• Mechanical properties

• SCC

• Microstructure

• Modelling

Objective Objective : Evaluate the effects of neutron irradiation on mechanical properties and resistance to SCC

Irradiations in Experimental Reactors

Temperature

370°C

300°C

320°C Bor-60 BORISBORIS

EBR-II/Phénix

30 dpa

Dose

PWR40 years

95 dpa

360°C

Materials Representative of Core Internals of the PWRs

SA 304L Baffle plates, Former, Core barrel

CW 316 Baffle bolts

C Cr Ni Mn Mo Si Cu

SA 304L 0.022 18.6 9.9 1.8 0.06 0.36 0.25

CW 316 0.054 16.6 10.6 1.1 2.25 0.68 0.24

Tensile specimens



DMN / SRMA

Irradiations in Experimental Reactors

Irradiations in FBR Irradiations in FBR Spectrum effect ? Spectrum effect ?

He effect• Mechanical properties

• SCC tests

BOR-60 / Osiris Tensile 10 dpa

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E-04 1.E-01 1.E+02 1.E+05 1.E+08Energie en eV

E.F(E).Flux

(cm-2s-1)

PWROsirisSMBOR-60

Area without shieldFast & thermal Fast & thermal

neutronsneutrons

2 irradiation areas

Tensile

Area with Hf shieldFast neutronsFast neutrons

Steel

Temperature

370°C

300°C

320°C Bor-60 BORISBORIS

EBR-II/Phénix

30 dpa

Dose

PWR40 years

95 dpa

360°C

SM

Osiris

Flux, GazFlux, Gaz He, H He, H

Modelling

SAMARASAMARA



DMN / SRMA

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120 140

Dose (dpa)

U.E. (%)

0

1

0 20 60 100 140

Tensile propertiesFast Breeder Reactor BOR 60

Te = 330°C3 10-4 s-1

320°C

BOR 60BOR 60

0

200

400

600

800

1000

1200

0 20 40 60 80 100 120 140

Dose (dpa)

YS (MPa)0.2%

SA 304L

CW 316

SA 304L

CW 316

Saturation

Total Elongation5 – 10%

U.T.S. YS0.2%

CW 316 > SA 304L - 125 dpa

SA 304L > 5 dpaCW 316 10 dpa



DMN / SRMA

0

200

400

600

800

0 2 4 6 8 10 12

Elongation (%)

Stress (MPa)

BOR 60BOR 60

0

200

400

600

800

0 2 4 6 8 10 12

Elongation (%)

Stress (MPa)

Tensile propertiesBOR 60 - Osiris

Osiris

0

200

400

600

800

0 2 4 6 8 10 12

Elongation (%)

Stress (MPa)

5 dpa5 dpa

0

200

400

600

800

0 2 4 6 8 10 12

Elongation (%)

Stress (MPa)

Osiris

10 dpa10 dpa

No difference between Osiris and BOR 60 No effect of neutron spectrum

Saturation of mechanical properties > 5 dpa

Te = 330°C3 10-4 s-1

SA 304LSA 304L



DMN / SRMA

0

5

10

15

20

25

30

35

40

0 10 20 30

Dose (dpa)

U.E. (%)

0

200

400

600

800

1000

1200

0 10 20 30

Dose (dpa)

YS (MPa)0.2%

Tensile propertiesBOR 60 - Osiris

BOR 60BOR 60 SA 304L

CW 316

SA 304L

CW 316

OsirisOsiris

No difference between Osiris and BOR 60 No effect of neutron spectrum

Saturation of mechanical properties SA 304LSA 304L 5 dpa5 dpaCW 316CW 316 10 dpa10 dpa

Te = 330°C3 10-4 s-1

0

200

400

600

800

1000

1200

0 10 20 30

Dose (dpa)

YS (MPa)0.2%

0

5

10

15

20

25

30

35

40

0 10 20 30

Dose (dpa)

U.E. (%)

0

1

0 10 20 300

1

0 10 20 30

320°C



DMN / SRMA

0

200

400

600

800

0 2 4 6 8 10

Elongation (%)

Stress (MPa)

Tensile propertiesHelium effect SM 2

0

200

400

600

800

0 2 4 6 8 10

Elongation (%)

Stress (MPa)

SM 2SM 2

6 dpa6 dpa 17 dpa17 dpaSame FluxSame Flux

10 appm10 appmHeHe

300 appm300 appmHeHe

No obvious effect of Helium (H2) contentSaturation of mechanical properties < 6 dpa

Te = 330°C3 10-4 s-1

300°C

14 appm14 appmHeHe

600 appm600 appmHeHe

SA 304LSA 304L



DMN / SRMA

0

5

10

15

20

25

30

35

40

0 10 20 30

Dose (dpa)

U.E. (%)

0

5

10

15

20

25

30

35

40

0 10 20 30

Dose (dpa)

U.E. (%)

0

5

10

15

20

25

30

35

40

0 10 20 30

Dose (dpa)

U.E. (%)

0

200

400

600

800

1000

1200

0 10 20 30

Dose (dpa)

YS (MPa)0.2%

0

200

400

600

800

1000

1200

0 10 20 30

Dose (dpa)

YS (MPa)0.2%

Tensile propertiesBOR 60 – Osiris – SM 2

BOR 60BOR 60SA 304L

CW 316

SA 304L

CW 316

OsirisOsiris

Te = 330°C3 10-4 s-1

No obvious effect of helium (H2) on tensile characteristics

Tensile characteristics similar to those measured after irradiationin Bor-60 (FBR) at 320°C both for CW 316 and SA 304L

0

200

400

600

800

1000

1200

0 10 20 30

Dose (dpa)

YS (MPa)0.2%

0

1

0 10 20 300

1

0 10 20 300

1

0 10 20 30SM 2SM 2

No flux effect



DMN / SRMA

Tensile properties

Saturation dose at 5 dpa for SA 304L10 dpa for CW 316

No evolution between 10 and 125 dpa for both SA 304L - CW 316

CW 316 > SA 304L hardness – residual ductility

No neutron spectrum effect on tensile charactericticsGaz content and flux



DMN / SRMA

Hardening Model

Evolution of the Yield Stress after irradiationTemperature, fluence, neutron spectrum

Model of the population of point defects clusters

(dislocation loops)

Model of hardeningby a cluster population

proportional , L

Microstructural data ofneutron irradiated materials

TEM

Yield Strength of neutron irradiated materials

Tensile tests

PWR InternalsPWR InternalsEBR II, Osiris, BOR 60



DMN / SRMA

Microstructure

Frank Loops

No precipitationNo more dislocation lines

Saturation for dose about 5 - 10 dpasize SA 304L 316density SA 304L > CW 316

0

10

20

0 10 20 30 40 50

dose dpa

diameternm

1.E+22

1.E+23

1.E+24

0 10 20 30 40 50

dose dpa

density

m-3

375°C

330°C

375°C

330°C

SA 304L

Main featureFrank loops formation

Black dots

Voids

SA 304L CW 316

EBR II375°C - 10 dpa

EBR IIOsiris

BOR 60



DMN / SRMA

Microstructure ModellingFrank loop

Chemical kinetic Model"Cluster Dynamics"

Dislocation network evolution

Loops

dt

dC iv,

Evolution of the concentration of point defects

Production - Recombination (v-i) - Loss of v and i at sinks- Agglomeration

Evolution of the concentration of interstitial or vacancy cluster containing n defects

dC

dtn ( )

( ) ( ) ( )t

a C t b C t c C tn n n n n n 1 1 1 1

External source of irradiation

defects

Interstitial or .

vacancy

Interstitial vacancycluster

Interstitial or vacancy

sinks : clusters dislocation lines grain boundaries /

free surfaces

Neutrons

Homogeneous medium

Neutron spectrum Flux - EPKA



DMN / SRMA

Microstructure ModellingFrank loop

Chemical kinetic Model"Cluster Dynamics"

External source of irradiation

defects

Interstitial or .

vacancy

Interstitial vacancycluster

Interstitial or vacancy

sinks : clusters dislocations grain boundaries /

free surfaces

Neutrons

Homogeneous medium

1020

1021

1022

1023

0

10

20

30

40

50

0 20 40 60

Dosedpa

Densitym-3

Diameternm

0

5 1020

1 1021

1,5 1021

2 1021

2,5 1021

0 5 10 15 20 25

Density

Diameternm

m-3

0,1 dpa

1 dpa

10 dpa

30 dpa50 dpa

Loops



DMN / SRMA

Microstructure ModellingFrank loops

1. Adjust material parameters of the model on low dose data EBR II - Osiris2. Predict the behavior at higher doses EBR II – Osiris –

BOR 603. Comparison with experimental data – BOR 604. Comparison with future results high doses BOR 60 (90 dpa) and Osiris (10 dpa)

Chemical kinetic Model"Cluster Dynamic"

0

10

20

30

0 10 20 30 40 50

0

10

20

30

0 10 20 30 40 50

0

10

20

30

0 10 20 30 40 501,E+20

1,E+21

1,E+22

1,E+23

1,E+24

0 10 20 30 40 50

dose dpa

density

m-3

1,E+20

1,E+21

1,E+22

1,E+23

1,E+24

0 10 20 30 40 50

1,E+20

1,E+21

1,E+22

1,E+23

1,E+24

0 10 20 30 40 50

1,E+20

1,E+21

1,E+22

1,E+23

1,E+24

0 10 20 30 40 50

0

10

20

30

0 10 20 30 40 50

dose dpa

diameternm SA 304LSA 304L

375°C

330°C

Emv 1.35

eV

Emi 0.45

eV

Eb2i 0.6

eV

0 1010 cm-2



DMN / SRMA

Experimental Simulation Material

Temperature (°C)

dose (dpa) i (nm) i (m

-3) v (nm) v (m-3) i (nm) i (m

-3)

320 10 11,5 25 10 21 / / 11,2 27 10 21

CW 316 320 19 7 92 10 21 2 < 10 20 12,8 32 10 21

333 24 10 12 10 21 / / 18,7 18 10 21

SA 304 310 35 10 15 10 21 1 1 10 21 10,2 80 10 21

In terms of interstitial loops size and density,the results of the model are in relatively good agreementwith the results obtained from field experience in PWRs.

Microstructure of expertised components

In agreement with results from experimental reactors



DMN / SRMA

Hardening - Orowan Model

Dislocations networkevolution

Good agreement at low dose

Data / Model

Cluster DynamicsModel

Model of defect clusters no diameter and density saturationOrowan hardening no hardening saturation

loops 0,4

loopsloopsloopsb M + l ( ) -di

do

- -di

do

-

?

Same for CW 316

SA 304L

330°C

0

400

800

1200

0 20 40 60 80 100

dose dpa

Mpa

Osiris

BOR 60

0

400

800

1200

0 20 40 60 80 100



DMN / SRMA

Hardening due to Frank Loops

Defaulting of the Frank loops Transformation in perfect loop under a applied stress

Critical shear stress for defaulting a Frank loop of diameter One relation between and

and increase with dose Perfect loop glide and annihilate Saturation at the critical stress

Critical dose for the mechanism of hardening

Modified Orowan Model

dcMain parameters : Stacking Fault Energy, d

One adjustable parameterNumber of dislocations in the pile-up

loopsloopsloopsb M

loopsloopsloopsb M

No Defaulting

Defaulting

No Defaulting

Defaulting

dose

DefaultingNo

Defaulting



DMN / SRMA

Modified "Orowan" model Hardening model permitting defaulting of Frank Loops

Saturation of Hardening

Well description of experimental data by the model

330°C Good description of experimental data375°C Need data at high dose to verify Voids data / Model in SA 304

2 steels : 0

Voids

0 1010 cm-2

26 Jm-2

0 1014 cm-2

42 Jm-2

0

200

400

600

800

0 20 40 60 80 100

dose dpa

MPa

330°C

375°C

CW 316CW 316

330°C

375°C

0

200

400

600

800

0 20 40 60 80 100

dose dpa

MPa 330°C

375°C

SA 304L

330°C

375°C

SA 304L



DMN / SRMA Slow Strain Rate Tests (SSRT)PWR environment

0

100

200

300

400

500

600

700

800

900

1000

0 0,02 0,04 0,06 0,08 0,1

(%)

B65: 5,2 dpa, 10 appm He, Tensile test in airB71: 5.0 dpa, 298 appm He, Tensile test in airB68: 5.6 dpa, 15 appm He, SSRT in PWRB70: 5.4 dpa, 297 appm He, SSRT in PWR

(MPa)

B71

B70

B68

B65

0

100

200

300

400

500

600

700

800

900

1000

0 0,02 0,04 0,06 0,08 0,1

(%)

A53: 4.5 dpa, 9 appm He, Tensile test in airA59: 4.3 dpa, 294 appm He, Tensile test in airA60: 4.6 dpa, 9 appm He, SSRT in PWRA54: 4.5 dpa, 294 appm He, SSRT in PWR

(MPa)

A60

A54A59

A53

Te = 320°C5 10-8 s-1

300°C

13 MPaO2 ~ 0 ppb H2 29 – 30 ml/kg

<10 ppb

5 dpa5 dpa

SA 304LSA 304LCW 316CW 316

T.E. of SSRT specimens strongly reduced (compared to tensile tests in air)lower for the specimens with “low helium”

Hardening lower for SA 304 after tests in PWR No significant difference in susceptibility between SA304L and CW 316

Flow rate2 autoclave vol./h

SA 304LSA 304LCW 316CW 316

MPa MPa

AirAirPWRPWRAirAir

PWRPWR

Slight effectof He content



DMN / SRMA

Fracture surfacesductile

fracture

IGfracture

ductile fracture

TG / IGfracture

He (appm) 294 9 297 15

% brittle fracture 33,3 71,1 38,0 50,8

facet initiation TGTG IGIG TG»IGTG»IG IGIG

fracture in facets TG»IGTG»IG IG>TGIG>TG TG=IGTG=IG IG>TGIG>TG

5 facets

3 facets

TransgranularTransgranularIntergranularIntergranular

SA 304LSA 304L CW 316CW 316

high Hehigh He

Low HeLow He



DMN / SRMA

Conclusions - Perspectives Tensile properties

Saturation dose at 5 dpa for SA 304L10 dpa for CW 316

CW 316 > SA 304L hardness – residual ductility No neutron spectrum effect on tensile characterictics

Gaz content and flux

Microstructure High density of small Frank loops + Voids at high temperature in SA 304L Disappearance of the initial dislocations network No precipitation Reproduce Microstructure observed on PWR components

Hardening Model Cluster Dynamic Model

Good agreement with TEM quantification – Frank loopsNo real saturation of loop number density

and diameter Hardening Model

● Orowan Model No saturation of hardening● Modified Orowan Model permitting the defaulting of Frank loops

Saturation of Hardening

No evolution between10 and 125 dpa



DMN / SRMA

Conclusions - Perspectives

In simulated PWR water Total Elongation of the SSRT specimens strongly reduced Fracture surface partly intergranular T.E. lower - Fracture surfaces more intergranular “low helium” content

Further examinations and SCC tests will be performed on more highly irradiated materials

Mechanical properties saturate He content increases

Intergranular fracture SM 2 > BOR 60Flux effect ? Medium ?Flux effect ? Medium ?



DMN / SRMA

This work was performed through a collaboration betweenEDF, CEA and RIAR partly sponsored by EPRI

Authors are grateful to:

HT Tang (EPRI),

V. Golovanov and G. Shimansky (RIAR),

P. Brabec and A. Brožova (NRI)

F. Rozenblum, J.C. Brachet and A. Barbu (CEA).

Tensile properties and microstructure of austenitic steels irradiated in different reactors

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Transcript of Tensile properties and microstructure of austenitic steels irradiated in different reactors