international workshop on “influence of atomic displacement rate, neutron spectrum and irradiation...
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International Workshop on
“Influence of atomic displacement rate, neutron spectrum and irradiation temperature
on radiation-induced ageing of power reactor components”,
October 4, 2005, Ulyanovsk, Russia
M. Hasegawa1 ) , Y. Nagai1), T. Toyama1),
Zheng Tang1), Y. Nishiyama2), M. Suzuki2),
T. Ohkubo4) and K. Hono4)
1) Tohoku University, Japan
hasegawa@imr.tohoku.ac.jp
2) Japan Atomic Energy Research Institute (JAERI), Japan
3) National Institute for Materials Science (NIMS), Japan
Effects of irradiation flux on embrittlement mechanisms on reactor pressure vessel steel:
Cu nano-precipitates and defects studied by positron annihilation and 3 dimensional atom probe
Outline
RPV Surveillance Test Specimens
1) Introd. to Positron Annihilation (PA*))
2) Flux EeffctsCalder Hall Reactor vs JMTR
(PA & 3D-AP**))
* ) Positron Annihilation (PA)**) 3 Dimensional Atom Probe (3D-AP)
e+
2
1
0.511 MeV
0.511 MeV
1.27 MeV0
22Na
(a) Injection and thermalization, (b) Diffusion, (c) Trapping, (d) Annihilation.
(a)
(b)
(c)
(d)
Cu Fe
e+ annihilates with a Cu electron
e+: Self-Searching Probe22Na
Cu Nano-Precipitates
Cu Nanovoid
Cu-V Complex
1
2
Positron Quantum Dot StatePositron Density
Cu5Cu1
Cu59
Diameter ~ 1 nm
Embedded ParticlesEmbedded Particles
- Cu Precipitates in Dilute Fe-Cu Alloys -- Cu Precipitates in Dilute Fe-Cu Alloys -
Positron Density DistributionsPositron Density Distributions
Fe
Cu
Super-Cell:1024 atom sites
Positron Quantum-Dot Confinement in a Precipitate of 59 Cu Atoms Embedded in Fe Matrix
Density isosurface of a quantum-dot confined positron in a Cu59 in Fe matrix. The isodensity value is 0.5% of the maximum.
Fe
Cu
CDB CDB Ratio Spectra
γ1 γ2
Ge detector
Coincidence Doppler Broadening : CDB
e+e-
22
01LcpcmE
22
02LcpcmE
pL : Electron Momentum along the Emitted γ–ray
Ge detector
Normalize to Pure Fe
0 10 20 30 40
0.5
1
1.5
2
pL [10-3 m0c]R
atio
to
Pu
re F
e
Pure Cu
Pure Fe As-irrad.
0 10 20 30 40
102
103
104
105
106
Pure Fe Pure Cu Pure Fe As-irrad.
pL [10-3 m0c]
Cou
nts
Low High Low High
Low Momentum Region : Vacancy type defects
High Momentum Region : Cu Nano-Precipitates
Cu 3d10
Electrons
0 10 20 30 400.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Rat
io t
o pu
re F
e
PL [10-3m0c]
Fe-0.3wt%Cu
pure Cu
As irradiated
τ1 = 165ps : ~ monovacancies(V1)τ2 = 405ps (51%) nanovoids (~V30)
Vacancy & nanovoid covered with Cu atoms
0 10 20 30 400.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Rat
io t
o pu
re C
uPL [10-3m0c]
pure Fe
As irradiated
Fe-0.3wt%Cu
Fe-0.3wt%Cu: CDB Ratio Curves neutron-irrad.: 8.3×1018n/cm2, 100C
Cu 3d Peak
Almost Flat
Vac. Type Defects Vac. Type Defects
No Fe Valley
Pure Fe
Pure Cu
As-Irrad.As-Irrad.
Normalized to Fe Normalized to Cu
0 10 20 30 40 50 60
100
200
300
400 V51
V59
V27
V15
V9
V5
V2 ([100])
V2 ([111])
V1
Bulk
Pos
itron
Life
time
(ps)
Number of Vacancies
0
2
4
6
8
B
indi
ng E
nerg
y (e
V)
Positron Lifetime and Binding Energy in Vacancy Clusters in Fe
V2 [111] V2 [100]
V9V5
V15
Positron Lifetime
Positron Binding Energy
Neutron Flux Effects on the Embrittlement Mechanisms ?
Neutron Flux (n/cm2/s)
101210111010109108
MTRBWR·PWR
Calder Hall-Type Reactor
10141013
Em
brit
tlem
ent
脆化
量
照射量の平方Fluence
Total
Matrix Defects
Cu Nano Precipitates
Soneda (2003)
Embrittlement Mechanisms: Fluence Evolution
C Si Mn P S Ni Cr Cu Mo Al N
0.10 0.23 1.1 0.014 0.015 0.17 0.0960.14-0.19
0.054 0.027 0.006
Post-Weld Heat Treatment : 600ºC, 4h.
C-Mn base Ferritic Steel wt.%
CHR Surveillance JMTR*
Flux (n/cm2-s) 4.2×108 2.2×1012
Fluence (n/cm2) 2.7×1017 2.2×1018
Irradiation Period 20 years 7 days
Irradiation Temperature (ºC) 240 224*Japan Materials Testing Reactor
Low flux High flux
Irradiation Conditions
Calder Hall Reactor (CHR) in Tokai*, Japan: Surveillance Test Specimen
* In –Service (1966 – 1998)
CHRSurveillance
4.2x108n/cm2·s
JMTR3.6x1012n/cm2·s
Irradiated at 240ºC
Strengthening by IrradiationCHR vs. JMTR
0.5 0.55 0.6
0.004
0.006
0.008
0.01
0.012
Low Momentum Fraction
Hig
h M
omen
tum
Fra
ctio
n
CDB (Low, High) Momentum Correlation
Thermal Ageing:Cu Nano Precipitates
Vacancy-Type Defects
Pure Cu
Pure Fe
Unirrad.
Pure Fe irrad.
JMTR
aged at 300ºC, 70,000h
CHR Surveillance
aged at 400ºC, 70,000h
0
100
200
Posi
tron
Lif
etim
e [p
s]
0
20
40
60
80
100
I 2 [
%]
Positron Lifetime
CHR Surveillance
JMTR
Unirrad.
300ºC, 70,000h
400ºC, 70,000h
V1
bulk Fe
V1τ2
τav
τ1
I2
10nm
10n
m
30nm
Cu
Mn
Ni
Si
CHR Surveillance
10nm
10n
m
30nm
JMTR
3D-AP Mapping : As-irrad.
200 300 400 500 600 700
100
120
140
160
Hv
Unirrad.
surveillance JMTR
As-irrad.
Annealing Temperature [°C]
Isochronal Annealing: CDB & Hardness200~700ºC, 30 min.
Vickers Microhardness
0.9 1 1.1 1.20.5
1
1.5
2
Low Momentum Fraction
Hig
h M
omen
tum
Fra
ctio
n
As-irrad.
300°C
400°C
As-irrad.
400°C
Surveillance JMTR
500°C
500°C
Pure Fe
Pure Cu
Unirrad.
300°C
600°C
600°C
650°C
Pure Fe( As-irrad.)
CDB Low/High Momentum Correlation
Recovery of Vacancy-Type Defects
Recovery of Cu Nano- Precipitates
0.9 1 1.1 1.20.5
1
1.5
2
Low Momentum Fraction
Hig
h M
omen
tum
Fra
ctio
n
As-irrad.
300°C
400°C
As-irrad.
400°C
Surveillance JMTR
500°C
500°C
Pure Fe
Pure Cu
Unirrad.
300°C
600°C
600°C
650°C
CHR SurveillanceJMTR
0.9 1 1.1 1.20.5
1
1.5
2
Low Momentum Fraction
Hig
h M
omen
tum
Fra
ctio
n
As-irrad.
300°C
400°C
As-irrad.
400°C
Surveillance JMTR
500°C
500°C
Pure Fe
Pure Cu
Unirrad.
300°C
600°C
600°C
650°C
CHR SurveillanceJMTR
3D-AP Mapping : Annealed at 450ºC for 0.5h
10nm
10n
m
30nm
Cu
Mn
Ni
Si
CHR Surveillance
10nm
10n
m
30nm
JMTR
As-irradiated State
CHR-Surveillance : Cu nano-precipitates
JMTR : Almost no Cu precipitates but vacancy-type defects
Post-Irradiation Annealing
CHR-Surveillance : The Cu nano-precipitates anneal out and Hv recovers at 650ºC.
JMTR : The vacancy-type defects recover at 450ºC. The Cu precipitation is not significant.
CHR-Surveillance : Low Flux JMTR : High Flux
Positron Annihilation and 3D-AP Analysis for RPV SteelsSummary : CHR vs. JMTR
Marked Flux Effects Low flux irradiation in CHR :
Strengthning is caused by enhanced Cu precipitation at very low doses.
High flux irradiation in JMTR : Almost the same strengthening is due to matrix defects but not to Cu precipitates.
LEAP in Hasegawa Lab. (Oarai Center)( Local Electrode Atom Probe: LEAP By IMAGO )
Specimen
Local Electrode
Position SensitiveDetector
High Field Region
Conventional Atom Probe(Energy-Compensating Type)
LEAP Atom Probe
10x10x60 nm
3x105 Atoms, 6 hours
60x60x170 nm
2x107 Atoms, 1hour
Cu Precipitates: Fe-1.0wt%Cu Aged at 475C for 10h
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