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On the Cu/P and Mn/Ni Interactions During Irradiation

of A533B Reactor Pressure Vessel Steels

R. Chaouadi1, W. Van Renterghem1, E. Stergar1, S. Gavrilov1, E. van Walle1 and R. Gérard2

1 SCK•CEN, Boeretang 200, 2400 Mol, Belgium2 TRACTEBEL-Engie, Avenue Ariane 7, 1200 Brussels, Belgium

rachid.chaouadi@sckcen.be

International Light Water Reactors Material Reliability Conference

Chicago, 1–4 August 2016

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Objectives and Motivation

Long term operation

Available databases

Multiple–variable experiments

Difficulty to determine the effect of a single variable but also

combined effects

Selection of key elements Cu, P, Ni and Mn

Cu/P and Ni/Mn synergies

RADAMO-13 irradiation program

Systematic single–variable experiments with Cu/P and Ni/Mn

Irradiation hardening and microstructure

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Experimental Conditions Irradiation space optimization

Transition temperature determination requires a higher number of

specimens

Tensile tests : miniature specimens (triplicated)

At least a factor of 4 in space gain

Excluding non–hardening embrittlement (often the case)

Proportionality between irradiation hardening and embrittlement

Load diagram illustration

Chemically-tailored composition

Reference : A533B Cl.1

Targeted elements : Cu, P, Ni and (Mn) ( Cu/P and Ni/Mn interaction)

Experimental evidence

Artificial Neural Networks

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Consistency between the various properties

Flow properties : strain rate and temperature dependence

Characteristic loads – SFA

Crack arrest NDT

Micro-cleavage fracture stress

TI – T0 master curve correlation

Irradiation Embrittlement due to Hardening

4

Simple tensile tests can provide

important information when baseline

condition is well characterized

Load Diagram

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Dominant Elements

5from PAMELA Workshop, Mol, 19–21/09/2011

Key elements : Cu, Ni and P (confirmed by ANN : see JNM 408 (2011) 30-39).

RP

V

em

bri

ttle

men

t

data

base

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n° C Si P S Mn Ni Cu Mo

1 0.21 0.23 0.010 0.005 0.02 0.05 0.05 0.51

2 0.21 0.24 0.010 0.006 0.82 0.00 0.05 0.53

3 0.20 0.24 0.010 0.006 1.71 0.06 0.05 0.54

4 0.20 0.24 0.009 0.005 0.04 0.74 0.05 0.51

5 0.21 0.26 0.013 0.005 0.80 0.67 0.05 0.48

6 0.20 0.24 0.011 0.007 1.73 0.69 0.04 0.51

7 0.21 0.24 0.010 0.006 0.01 1.68 0.05 0.51

8 0.20 0.24 0.010 0.007 0.80 1.72 0.05 0.49

9 0.21 0.26 0.010 0.008 1.78 1.68 0.04 0.51

10 0.21 0.25 0.008 0.008 1.48 0.69 0.01 0.51

11 0.21 0.25 0.018 0.006 1.47 0.69 0.01 0.51

12 0.21 0.25 0.029 0.006 1.46 0.69 0.01 0.50

13 0.20 0.25 0.011 0.008 1.49 0.72 0.05 0.50

14 0.20 0.25 0.020 0.008 1.46 0.69 0.05 0.50

15 0.21 0.27 0.029 0.006 1.45 0.68 0.05 0.51

16 0.20 0.26 0.010 0.007 1.50 0.68 0.14 0.51

17 0.21 0.25 0.019 0.008 1.48 0.69 0.14 0.50

18 0.20 0.25 0.027 0.007 1.47 0.68 0.14 0.51

19 0.21 0.25 0.012 0.008 1.48 0.69 0.29 0.51

20 0.20 0.25 0.020 0.007 1.47 0.68 0.29 0.51

21 0.20 0.25 0.028 0.007 1.47 0.68 0.29 0.51

22 0.21 0.25 0.002 0.008 0.04 0.00 0.01 0.48

23 0.20 0.25 0.028 0.008 1.78 1.64 0.30 0.52all ‘low’

all ‘high’

Cu P Ni Mn

very low ~0~0.010

~0.020

~0.030

0.7 1.50low ~0.05

medium ~0.14

high ~0.30

Cu/P Effects : 12 steels

Ni Mn Cu P

low ~0 ~0

0.05 0.010medium ~0.7 ~0.8

high ~1.7 ~1.8

Ni/Mn Effects : 9 steels

Materials

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Heat Treatments

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Same heat treatments for all steels

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Irradiation ProgramRADAMO–13

0

1

2

3

4

5

6

7

8

-500 -300 -100 100 300 500n

eu

tro

n f

lue

nce

(1

01

9n

/cm

², E

>1M

eV

)

position (mm)

dosimeter

tensile

µstructure

RADAMO-13Tirrad = 290°C

6 7 89 10 11

14 1516

17 18 19

22 2324

25 26 27

30 31 32

33 34 35

28 29

20 21

12 13

Irradiated tensile (4.5 mm) Irradiated µstructure (8.5 mm)

6 810

15

17 19

22 24

26

31

33 35

28

21

12

n° 6 + 8 + 10 : medium low fluence

n° 31 + 33 + 35 : low fluence

n° 15 + 17 + 19 : medium high fluence

n° 22 + 24 + 26 : high fluence

unirradiated tensile (4.5 mm)

Unrradiated µstructure (8.5 mm)

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Cu/P Effects

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Role of Cu/P in Irradiation Hardening and Embrittlement

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Question : how does Cu interact with P ?

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Combined Cu/P Effect on Irradiation Hardening

-50

0

50

100

150

200

250

0 2 4 6 8 10

yie

ld s

tre

ngt

h in

cre

ase

, Ds

y(M

Pa)

neutron fluence (1019 n/cm², E>1MeV)

0.012%P

0.020%P

0.028%P

Cu/P-Synergestic EffectsCu=0.29%Ni=0.7%Mn=1.5%

The effect of Cu-content significantly larger than P-content effect

0.29%Cu

same range

Reference

0.01%Cu/0.008-0.029%P

Dsy0before

irradiation

13 – 40 MPa

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Cu/P-Effects on Irradiation Hardening

Constant slope at all Cu-levels No synergy between P and Cu

(at 290°C PWR-relevant) [ ! Might not hold for other Tirrad]12

same slope(~1750 MPa/%P)

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Ni/Mn Effects

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Objective and Motivation The role of Mn was reported by many authors to significantly affect irradiation

hardening and embrittlement in particular in presence of high Ni-content (e.g.

Ringhals welds)

Modeling supported by microstructural data suggest also that Mn should play

some role as it is found in the solute clusters

Experimental data on model alloys were also suggesting an important effect of

Mn (Yabuuchi data)

Objective : how Ni and Mn interact

Individual effect of Ni versus individual effect of Mn-content

Interaction Ni/Mn

Does the amount of Mn affects directly or indirectly irradiation hardening

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Motivation : Mn effectModel alloys

0

50

100

150

200

0 5 10 15 20

adju

ste

d y

ield

str

en

gth

incr

eas

e, Ds

y(M

Pa)

neutron fluence (1019 n/cm², E>1MeV)

0.69%Mn

0.82%Mn

1.40%Mn

2.10%Mn

Commercial

alloys

From K. Yabuuchi, JNM 414 (2011) 498–502 From K. Yabuuchi, Mat Sci For 654-656 (2010) 2911–2914

adjusted to account

for Cu, P and Ni

differences

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Mn-effect

From LONGLIFE, R-5089 (2010)

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No Effect of Mn-content on Low Ni Steels

-50

0

50

100

150

0 2 4 6 8 10

yie

ld s

tre

ngt

h in

cre

ase

, Ds

y(M

Pa)

neutron fluence (1019 n/cm², E>1MeV)

0.02%Mn

0.82%Mn

1.71%Mn

Ni/Mn-Synergestic EffectsCu=0.05%P=0.010%Ni=0.05%

±25MPa

0.05%Ni

Dsy0before

irradiation

17 – 33 MPa

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No Effect of Mn-content on Medium Ni Steels

-50

0

50

100

150

0 2 4 6 8 10

yie

ld s

tre

ngt

h in

cre

ase

, Ds

y(M

Pa)

neutron fluence (1019 n/cm², E>1MeV)

0.04%Mn

0.80%Mn

1.73%Mn

Ni/Mn-Synergestic EffectsCu=0.05%P=0.010%Ni=0.70%

±25MPaDsy0

before

irradiation

10 – 47 MPa

17

0.70%Ni

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Significant Effect of High Mn-content of High Ni Steels

-50

0

50

100

150

0 2 4 6 8 10

yie

ld s

tre

ngt

h in

cre

ase

, Ds

y(M

Pa)

neutron fluence (1019 n/cm², E>1MeV)

0.01%Mn

0.80%Mn

1.78%Mn

Ni/Mn-Synergestic EffectsCu=0.05%P=0.010%Ni=1.70%

Ni/Mn-Synergestic EffectsCu=0.05%P=0.010%Ni=1.70%

±25MPa

1.70%Ni

Dsy0before

irradiation

22 – 41 MPa

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Clear Mn-content Effect at High Mn-content (~1.7%)

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300

400

500

600

700

800

0 1 2 3 4

stre

ngt

h, s

yan

d s

u(M

Pa)

Ni+Mn content (%)

yield strength

sy

0.05Ni0.02Mn

0.74Ni0.04Mn

0.00Ni0.82Mn

0.67Ni0.80Mn

1.68Ni0.01Mn

0.06Ni1.71Mn

0.69Ni1.73Mn

1.72Ni0.80Mn

1.68Ni1.78Mn

tensile strength

su

Effect of Ni– and Mn– Content on the Initial Tensile Properties

Ni% Mn% S(i)-Fe sy su su–sy

0.05 0.02 1.14 392 513 121

0.74 0.04 1.93 420 542 122

1.68 0.01 2.88 476 593 117

0.00 0.82 1.81 450 592 142

0.67 0.80 2.52 486 604 118

1.72 0.80 3.54 537 654 117

0.06 1.71 2.84 521 647 126

0.69 1.73 3.63 536 647 111

1.68 1.78 4.61 492 792 300

all other alloying (excl. Ni and Mn)

and trace elements <~1%

The high NI/high Mn steel has definitely another behavior than other

steels including RPV materials in both unirradiated and irradiated conditions

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400

500

600

700

800

900

1000

1100

300 400 500 600 700 800 900 1000

ten

sile

str

en

gth

(M

Pa)

yield strength (MPa)

0.05%Cu/0.010%P/1.68%Ni/1.78%Mn unirrad0.05%Cu/0.01%P/1.68%Ni/1.78%Mn irrad0.30%Cu/0.028%P/1.64%Ni/1.78%Mn unirrad0.30%Cu/0.028%P/1.64%Ni/1.78%Mn irradother RADAMO-13 steelsRPV materials

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Effect of Ni/Mn on the Flow Curve

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Distinct strain hardening behavior of the high Ni/High Mn steel

400

450

500

550

600

650

700

750

0 0.01 0.02 0.03 0.04 0.05

stre

ss (

MP

a)

strain (--)

high Ni/high Mn

high Ni/medium Mn

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TEM Examination

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Enriched phase: 3.4 Mn / 2.6 Ni (wt%)

Complex structure (mainly bcc)

Bainite: 1.7 Mn / 1.8 Ni (wt%),

with (Fe,Mn)3C and Mo2C carbides

Before deformation :

Enriched phase is partially twinned

from martensite transformation

After deformation (~12%) :

Progressive martensite tranformation

( cfr. TRIP steel)

Unirradiated Condition

twins

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TEM Examination

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Undeformed

Similar phases as in unirradiated

No visible radiation damage

Deformed (~11%)

No progressive martensite

transformation

Irradiated Condition

Work in progress …

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Confirmation by Pre-straining/Annealing

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0

250

500

750

0 0.05 0.1 0.15 0.2 0.25

stre

ss (

MP

a)

strain (--)

as-received (n°34)

pre-straining (n°36)

pre-strained+annealed (n°36)

medium Ni/high Mn Steel

0

300

600

900

0.00 0.05 0.10 0.15 0.20 0.25

stre

ss (

MP

a)

strain (--)

as-received (n°25)

pre-straining (n°36)

pre-strained+annealed (n°36)

high Ni/high Mn Steel

Pre-straining+Annealing removes deformation-induced

martensitic transformation of the high Ni/high Mn steel

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ConclusionsWithin the limits of the present experimental data (composition variables, irradiation

conditions)

On the Cu/P effects

Cu is clearly and by far the most radiation-sensitive element

The effect of P is relatively small

No synergy between these Cu and P (at this Tirrad)

On the Ni/Mn effects

Ni and Mn effects are significantly lower in comparison to Cu-effect

No synergy between Ni and Mn is observed except for the high Ni/high Mn

steel (1.7%Ni/1.8%Mn)

TEM examination revealed the presence of a second phase (NiMn-rich phase)

1.7%Ni/1.8%Mn steel significantly higher work hardening capacity

Behavior attributed to martensitic transformation during deformation (twins)

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Closing Remarks The conclusions on Cu/P synergistic effects drawn from this work should be

confirmed

at lower irradiation temperature (260°C or lower) where P-contribution is

expected to significantly increase

eventually new batch of steel with higher P-content (>0.05%)

The conclusions on Ni/Mn synergistic effects drawn from this work should be

confirmed

at higher fluence levels (> 1 1020 n/cm²)

at lower irradiation temperature (260°C or lower)

Performing experiments on a new batch of 1.7%Ni/1.8%Mn with adapted heat

treatment avoiding the formation of the unwanted secondary phase and

leading to moderate work hardening (long term)

TEM examination (in progress) + additional microstructural analysis (APT)

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