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Positron annihilation study of neutron-irradiated nuclear reactor pressure vessel (RPV) steels
and their model alloys
Y. Nagai1, A. Kuramoto1, T. Toyama1, T. Takeuchi2, M. Hasegawa3
1The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
2Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan3Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan
PPC-10 Smolenice Castle, Slovakia
Sept. 5 - 9, 2011
2
Outline
1) Back g round
2) Fe-Cu Model Alloys: Cu Nano-Clusters (Precipitates) a) Size: 2D-ACAR Momentum Smearing
b) Number Density: AMOC
3) RPV Steel: Surveillance Test Specimen MaterialsMechnisms: Nanostructural Features
Irradiation Embrittlement & Hardening
1st & 2nd Generation A533B
Post Irradiation Annealing (PIA) Experiments
3
Origin of irradiation-induced embrittlement
Nuclear Reactor Pressure Vessel (RPV) Steel
dislocation
1) Solute Nano-Clusters
3) P Segregation at Grain Boundary
Grain boundary
2) Matrix Defects (vacancy-type defects, dislocation loops, ···)
4
Local electrode Laser
Vtotal
Vextraction
Position sensitive ion detector
Time of Flight Mass
~100nm
ZY
X
Needle sample
Laser-Assisted Local Electrode Atom Probe
4
Energy-compensated type (with “Reflectron”)
5
LEAP 3D-Atom Probe
60x60x170 nm
2x107 Atoms, 1houre+ Self-Searching:
Cu Nano-Particles in Fe
Positron Quantum-Dot Confinement in a Precipitate of 59 Cu Atoms
Density isosurface of a quantum-dot confined positron in a Cu59 in Fe matrix. The isodensity value is 0.5% of the maximum.
1nm
6
2a) Cu Nano-Precipitates (Clusters) : Size
2D-ACAR: Momentum Smearing
Z. Tang et al.:J. Phys.: Condens. Matter 20 (2008) 445203,
Size-dependent momentum smearing effect of positron annihilation radiation
in embedded nano Cu clusters
7
2b) Cu Nano-Precipitates (Clusters) : Number Density
AMOC: Time Evolution of HMCF (W-Parameter) Trapping Model
A. Inoue et al.: Phys. Rev. B83 (2011) 115459
Fig.1
0 10 20 30 40
1
1.5
2
Rati
o to
Pu
re F
e
pL [10-3 m0c]
Pure Cu 0.1h 0.2h 2h
2h
30nm
10nm
0.1h
0.2h
Fe-0.88at.%Cu: Thermal Aging @550˚C
CDB Ratio Curve 3D-AP
2h: Complete e+ Quantum-Dot Confinement
0 0.2 0.4 0.6 0.8 10.08
0.1
0.12
0.14
0.16
0.18
pure Fe pure Cu 0.1h 0.2h 2h
Time [ns]
W-p
aram
eter
Time Evolution of CDB HMCF (W-Parameter)
Pure Fe
Pure Cu
Positron Age-Momentum Correlation (AMOC)
Using digital oscilloscope : Time resolution ~170ps
Number Density (×1017 cm-3)3D-AP e+
Aging Time (h) SizeDiameter (nm)
0.10.22
0.91.12.5
0.151.21.9
0.611.41.8
Number density estimated by positron annihilation
Time dependent
HMCF ( W-parameter)
Positron trapping rate
Number density
3) RPV Steel: Surveillance Test Specimen Materials
1St & 2nd Generation A533B
11
PIA: 1st Gen A533B Kuramoto et al.: Submitted to J. Nucl. Mater.
Fluence Dependence Takeuchi et al. : J. Nucl. Mater. 402 (2010) 93.
Irradiation –Induced Embrittlement (Hardening) Mechanisms
Post Irradiation Annealing (PIA) Experiments
wt.% Chemical Composition
A533B C Si MnP S NiCrCu Mo
1st. Gen. 0.19 0.30 1.300.015 0.010 0.680.170.16 0.53
2nd. Gen. 0.19 0.19 1.430.004 0.001 0.650.130.04 0.50
12
Reactor Pressure Vessel (RPV) Steel: A533B
JMTR Irradiation
Fluence: 3.9x1019n/cm2 (0.061dpa)Flux: 1.8x1013n/cm2 ・ sec
Temperature: 2902C
Purified: Cu, P, S
Annealing Behavior of Average Positron Lifetime 1st. Gen.(0.16Cu) & 2nd. Gen.(0.04Cu) A533B, 3.9×1019 n/cm2
As-irrad.
13
200 300 400 500 600100
120
140
160
180
Annealing Temperature [℃ ]
Ave
rage
Pos
itron
Life
time
[ps] V1
Unirrad. (1st. Gen.)
Fe bulk
Unirrad. (2nd. Gen.)
1st.Gen. (0.16Cu)2nd.Gen. (0.04Cu)
1 1.02 1.04 1.06
1
1.2
1.4
1.6H
igh
Mom
entu
m C
ompo
nent
Fra
ctio
n
Low Momentum Component Fraction
Pure Fe
Pure Cu
Pure Fe as-irrad.
1st.Gen. (0.16Cu)2nd.Gen. (0.04Cu)
CDB HMCF-LMCF Correlations 1st. Gen. (0.16Cu) & 2nd. Gen. (0.04Cu) A533B, 3.9×1019 n/cm2
As-irrad. (1st. Gen. )
400 °C
450 °C
600 °C
300 °C
300 °C
As-irrad.(2nd. Gen. )
600 °C
Unirrad.(1st. Gen. )
550 °C
Unirrad.(2nd. Gen. ) 450 °C
14
0.5 0.55 0.6 0.650.004
0.006
0.008
0.01
0.012
0.014
LMCF
HMCF
As-irrad.
As-irrad.
Unirrad.
500Pure Cu
Pure Fe
500
Unirrad.
Neutron Irradiation: 8.3×1018n/cm2 (1.2×10-2dpa, ~100ºC)Fe-Cu Model Alloys ( 0.3wt.%Cu, 0.05wt.%Cu )
0.3Cu
0.05Cu
As-irrad. 350 °C 400 °C
10nm
Si
Mn
P
Ni
Cu
Atom Maps of the Solutes: Annealing Behavior (As-irrad.~400℃)1st. Gen. (0.16Cu) A533B, 3.9×1019 n/cm2
16
Atom Maps of the Solutes: Annealing Behavior (As-irrad.~350 ℃)2nd. Gen. (0.04Cu) A533B, 3.9×1019 n/cm2
300 ℃ 350 ℃As-irrad.
Si
Mn
P
Ni
Cu
10nm17
As-ir-
rad.
350 400 450 50075
80
85
90
95
100
Annealing Temperature [°C]
Co
mp
osi
tion
[%]
Co
mp
osi
tion
[%]
Average Chemical Compositions of Solute Clusters3.9×1019 n/cm2
Annealing Temperature [°C]
As-irrad. 300 350 40075
80
85
90
95
100
Cu,Mn,Si,NiothersFe,
18
1st. Gen. (0.16Cu) A533B 2nd. Gen. (0.04Cu) A533B
Cu
Mn
SiNi
Fe
200 300 400 500 6000
1
2
Rad
ius
of G
yrat
ion
[nm
]
200 300 400 500 60002468
10
Num
ber
Den
sity
[1023
/m3 ]
200 300 400 500 6000
2
4
6
8
10
Vol
ume
Fra
ctio
n [×
10-3
]
Annealing Temperature [℃]
Radius of Gyration (rg), Number Density (Nd) & Volume Fraction (Vf)A533B, 3.9×1019 n/cm2
19
rg
Nd
Vf
Radius of Gyration
Number Density
Volume Fraction
1st. Gen.
2nd. Gen.
1st. Gen. (0.16Cu)
CuMnSiNi Clusters
2nd. Gen. (0.04Cu)
MnSiNi Clusters
Hardening
Russell-Brown Model
200 300 400 500 600
0
20
40
60
80Δ
Hv
Annealing Temperature [℃]
ExperimentalEstimated Hardening from SCs
Annealing Behavior of Irradiation Hardening (∆Hv)1st. Gen. (0.16Cu) A533B, 3.9×1019 n/cm2
As-irrad.20
e+ : Vac-Defects
3D-AP: CuMnSiNi Clusters
0.8
1
1.2
1.4
Hig
h M
omen
tum
C
ompo
nent
Fra
ctio
n
Unirrad. (1st., 0.16Cu)Pure Fe
Unirrad. (2nd., 0.04Cu)
200 300 400 500 600
0
20
40
60
80
ΔH
v
100
120
140
160
180
Ave
rage
P
ositr
on L
ifetim
e [p
s]
Unirrad. (1st., 0.16Cu)
Fe Bulk
V1
Unirrad. (2nd., 0.04Cu)
1st., 0.16Cu2nd., 0.04Cu
1
1.02
1.04
1.06
Low
Mom
entu
m
Com
pone
nt F
ract
ion
Unirrad. (1st., 0.16Cu)
Pure Fe
Unirrad. (2nd, 0.04Cu)
As-irrad.Annealing Temperature [°C]
1st. Gen. (0.16Cu)2nd. Gen. (0.04Cu)3.9×1019n/cm2
Av
LMCF
HMCF
Hv
What & How Positron Annihilation Can Say on RPV-Embrittlement Mechnisms ?
Unique Nano-Features 1) Cu-Rich Nano-Clusters Evolution, Recovery: Clear-Cut Info. Size, Number Density: Not Easy 2) Vacancy-Related Defects
Correlation: Mech. Properties Integration: Other Methods, such as 3D-AP, SANS,TEM
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Quantative !!