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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Materials Challenge for Clean Nuclear Fusion Energy
Development of Low Activation Structural Materials
T. MurogaNational Institute for Fusion Science, Oroshi, Toki,
Gifu 509-5292, JapanSymposium on Materials Challenges for Clean Energy
June 21-25, 2009, NIST, USA
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Roadmap of Fusion Energy Development for Japan
Operation
ITER
DEMO
IFMIF
D-T
ConstructionDesigning Operation
Fission reactors and charged particle irradiation
100-150dpa
2020 2030 2040
Plasma Performance
Materials Performance under Irradiation50dpa Power Generation
IFMIF : International Fusion Materials Test Facility
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Nuclear Fusion as a Clean Energy Source
Nuclear fusion is a clean energy source from the CO2 emission standpoints
One of the very limited candidates of major energy source in the future
From radiological standpoint, nuclear fusion is a clean energy source relative to nuclear fission
No high level radioactive waste is produced
Neutron-induced radioactivity of the components (low to middle level waste) and tritium are the only radiological issues
Neutron-Induced radioactivity is an issue for :
(1) Maintenance of in-vessel components (lifetime of maintenance tools)
(2) Waste disposal or reuse
(3) Potential hazard
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Structural Materials for Fusion Blankets
Blanket is the key component of fusion reactorsEnergy conversion (neutron to heat)Tritium production (Li + n T)
The structural materials need to have high temperature strength, resistance to neutron irradiation and compatibility with coolants.
Fusion DEMO Reactor(FFHR)
Neutrons
Reactor CoreD+T He+14.1 MeV n
Blanket
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
The Concept of Low Activation Materials
“Low Activation Materials” is defined as :
The materials in which neutron irradiation-induced radioactivity decrease to a level where economical waste disposal or recycling in the next fusion plant (possible zero emission) is feasible in <50 years of cooling.
Use of Low Activation Materials can increase largely the attractiveness of fusion system as a clean energy source
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Element Restriction for Low Activation
There is strong element restriction for low activation materialsNi, Cu, Al, Mo, Nb cannot be used as alloying elementsAl, Ag, Nb Mo should be strictly controlled to ~ppm levels
None of the commercially-established materials can be used for the low activation structural components
no limit design dependent <0.1%
Classification of the elements by the restriction for low activation
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Radioactivity of Fusion Candidate Materials
Three candidate materials are under development for fusion application as low activation materials
Reduced activation Ferritic/Martensitic steelVanadium alloysSiC/SiC composites
The candidate materials satisfy the recycling limit
Contact dose of fusion structural materials after shutdown of a reactor
10-2
10-1
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316SS�SS316LN -IG�Low activation ferritic�F82H�Vanadium alloy�NIFS -HEAT -2�SiC (no impurity�
Radioactivity (Sv/h)
Cooling Time after Shutdown (Years)
FFHR -Li BlanketFirst WallNeutron 1.5MW/m 2
30 years�foperation
Full-hands-on recycling
Full-remote recycling
10-2
10-1
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10410
-5
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-5
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10-1
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-5
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316SS�SS316LN -IG�Low activation ferritic�F82H�Vanadium alloy�NIFS -HEAT -2�SiC (no impurity�
Radioactivity (Sv/h)
Cooling Time after Shutdown (Years)
316SS�SS316LN -IG�Low activation ferritic�F82H�Vanadium alloy�NIFS -HEAT -2�SiC (no impurity�
Contact Dose (Sv/h)
Cooling Time after Shutdown (Years)
FFHR -Li BlanketFirst WallNeutron 1.5MW/m 2
30 years�foperation
Full-hands-on recycling
Full-remote recycling
V- 4Cr- 4Ti �NIFS-Heat�
Reduced Activation Ferritics �F82H)
SS -316 Pure SiC/SiC
Pure V-4Cr-4Ti
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
“Low Activation” would also be the Future Key Phrase for Nuclear Fission Systems
Disposal of Light Water Reactor in-vessel components The activity can be reduced by three orders using low activation materials
Low Activation Concrete is already investigated in nuclear fission communityReduction of Eu and Co levels for satisfying clearance level
SS316
10-410
-310
-210
-110
010
110
210
310
410
510
610-5
10-4
10-3
10-2
10-1
100
101
102
103
104
105
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10-410
-310
-210
-110
010
110
210
310
410
510
610-5
10-4
10-3
10-2
10-1
100
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Contact dose (Sv/h)
Cooling time after shut-down (years)
V-alloy
Activation by152Eu and 60Co
Cooling Time (y)
Conventional Concrete
Low Activation Concrete
Clearance ZoneR
elat
ive
Rad
ioac
tivity
Radioactivity after 60 y operation of PWR
Radioactivity of concrete after 20 y operation
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Operation Temperature and Efficiency
High operation temperature is essential for high conversion efficiencyPlant efficiency is influenced also by other factors (e.g. net working rate)
20
30
40
50
200 300 400 500 600 700 800 900 1000
Con
vers
ion
effic
ienc
y / %
Coolant temperature / oC
PWR
BWR
SSTR*
FBR
ARIES-1*
AGR
HTGR
DREAM*
RAF steel
V alloy
SiC ceramicFFHR*
WaterFlibe, Li, Li-Pb
He
*Fusion
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
History of Vanadium Alloys for Fusion Reactors
Vanadium alloys were once candidates of FBR core materials in 1970sV-Nb-Cr, V-Nb-Mo, V-Cr-Zr (JP-NIMS) , V-Ti-Cr, V-Cr-Fe (US), V-Ti-Si (Germany)The programs were concluded because of insufficient compatibility with NaVanadium alloys attracted attention for fusion reactors from 1980sLow activation property -- potentiality for recyclingHigh temperature strength, high thermal stress factor
950� 1hr
V-XCr-YTi
The effects of Cr+Ti (wt%) on Ductile-Brittle Transition Temperature of V-Cr-Ti alloys
Fusion materials programs identified V-4Cr-4Ti as the leading candidate
Industrial infrastructure of vanadium alloys are still quite limited
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Impurity Reduction is the Key Issue for V-Alloys
Vanadium is a reactive metal, whose properties are influenced heavily by C, N, O impurities
C, N, O impurities need to be controlled
Contamination from the environment may be an issue
Vanadium alloys must satisfy low activation criteria
Nb, Mo, Al, Ag need to be controlled to 1~10 ppm
Cross contamination by sharing facilities for other purposes may be an issue
Elon
gatio
n (%
)
The effect of O, N and C levels on Elongation
NIFS has promoted a program for development of high purity V-4Cr-4Ti
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Commercial Production Process of Metal Vanadium
C N Nb, Mo (Cross Contamination)
OAl
Ores
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Improvement of the Process
Intermediates Conventional process Improved processC N O C N O
Ammonium Vanadate 12 41 12 41
(Calcination)
V2O5 100-150 20-90 44 10 10-20 44
Al 20-80 10 10-20 10
(Themic reduction)
V-Al-O 180 300-400 800-5000 60 60-120 800-5000
(EB refining)
Metal V 300 400-710 50-150 100 60-160 40-100
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Production of Purified Metal Vanadium
Metal Vanadium with <100wppm O and <200ppm N were produced by improving the production process
0
100
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300
400
500
0 100 200 300 400 500 600
Laboratory ScaleUS-DOE Program (900, 2200 kg)Conventional (50 kg)Improved (25 kg)
Oxy
gen
/ wpp
m
Nitrogen / wppm
This study
Conventional largeingots ofcommercial vanadium in Japan
Large ingotsby US-DOE
0
O and N levels of metal V produced 125 kg ingots of purified V
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Alloying Technology
Alloying to V-4Cr-4Ti was carried out by EB and VAR methods
Special cares were taken to avoid contamination with O and N from atmosphere and with Nb and Mo by cross-contamination
EB-weldingEB melting from V, Ti, Cr flakes 1st VAR Ingot scaling
2nd VAR Ingot160 kg ingotcanningHot Forging
N and O Nb, Mo (Cross Contamination)
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Resulting Purity of the Alloys
ID C O N B Na Mg Al Si V Cr Mn Fe Ni Cu
NIFS-HEAT-1 56 181 103 7 17 <1 119 280 Bal. 4.12 <1 80 13 4
NIFS-HEAT-2 69 148 122 5 <1 <1 59 270 Bal. 4.02 <1 49 7 2
US832665 170 330 100 3.7 0.01 0.17 355 785 Bal. 3.25 0.21 205 9.6 0.84
US832864 37 357 130 <2 <1 193 273 Bal. 3.8 228 <50
Purification of metal vanadium resulted in low O level relative to US alloys.
US alloy had high Nb level because the infrastructure was common to Nbproduction system
This is a valuable lesson for future manufacturing of low activation V-alloys
ID As Zr Nb P S Ca Co Ag Sn Sb Ti W Mo Ta
NIFS-HEAT-1 1 <10 1.4 16 9 3 2 <0.05 <1 <1 4.13 <1 23 58
NIFS-HEAT-2 <1 2.5 0.8 7 3 12 0.7 <0.05 <1 <1 3.98 <1 24 13
US832665 1.4 <46 60 33 16.5 <0.26 0.30 0.078 0.24 0.17 4.05 25 315 <19
US832864 106 <30 4 3.8 <50
Chemical compositions of V-4Cr-4Ti ingots produced by NIFS and USDOE Programs
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
V-4Cr-4Ti Products
Various high purity products were manufactured
26t 6.6t 4.0t1.9t 1.0t 0.5t 0.25t
2d
8d
(mm)
Plates, Sheets, Wires and Rods
Laser weld joint
Thin pipes
W coating by plasma spraying
Creep tubes
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
V-4Cr-4Ti Tubing by Drawing
Quality of tubes increased by reducing O levels
O impurity before fabrication ~400 ppm
O impurity before fabrication ~130 ppm
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Welding – Impurity Control is the Key Issue
Welding can results in contamination with C, N, O by two ways(a) Contamination of the weld joints with C, N, O from atmosphere during
the welding(b) In V-4Cr-4Ti, large fraction of C, N, O are stored in Ti-CON precipitates.
Welding results in contamination of matrix with C, N, O
(a) is avoidable by highly controlling the welding atmosphere(b) can be avoided only by reducing the original level of C, N, O in the
material
Base Metal Weld Metal
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
TIG Welding with Ultra-High Purity Wire
Weld joint
0 50 100 150 200 250 300 350 4000
100
200
300
Oxygen in weld metal / wppm
NH1 / HP
US / HPNH1 / NH1
0
US / US
DBTT = +60 K / 100 wppm oxygen0
5
10
15
-100-200 0 100Test temperature (C)
US / US47 C
NH1 / NH1-85 C
US / HP-90 C
-145 CNH1/HP
Abs
orbe
d En
ergy
(J)
Plate / WireDBTT
0
5
10
15
0
5
10
15
-100-200 0 100Test temperature (C)
US / US47 C
NH1 / NH1-85 C
US / HP-90 C
-145 CNH1/HP
Abs
orbe
d En
ergy
(J)
Plate / WireDBTT
Alloy Name O level (appm)
US-Large Heat (US) 310NIFS-HEAT-1 (NH1) 180High Purity Wire (HP) 36
Alloy Name O level (appm)
US-Large Heat (US) 310NIFS-HEAT-1 (NH1) 180High Purity Wire (HP) 36
Ultra-high purity wires were used for TIG welding for the purpose of reducing impurity level of weld jointsWith the decrease in the oxygen level in the weld joint, DBTT decreased
Absorbed energy of Charpytests for weld joints
DBTT of weld joints as a function of oxygen level
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Radiation Effects at Low Temperature
Irradiated Vanadium alloys showed plastic instability
Interaction of dislocations with radiation-induced defect clusters (black dot images by TEM) is thought to be the key process
Atom Probe Elemental Mapping showed the black dots are decorated with Ti, O and TiO.
35nm
Ti
O
TiO
11nm
10nm
(Rice 1998)
(Nita 2003)
Elemental mapping of radiation-induced defect clusters by Atom Probe
Change of tensile property and typical microstructure after deformation in V-4Cr-4Ti irradiated at low temperature
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Enhanced Uniform Elongation in V-Cr-Ti-Si,Al,Y
Uniform elongation after irradiation decreased to ~ 0 after irradiation at <400ºC
However, the uniform elongation recovered by addition of Si, Al, Y
Si, Al and Y can scavenge impurity O in V-4Cr-4Ti matrix and suppress the formation of the “decorated” defect clusters
Uniform elongation of V-4Cr-4Ti after neutron irradiation
(Abe, Satou 2003)
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Nano oxide dispersion strengthened (ODS) materials are under development for fusion as advanced options :
Enhanced high temperature strengthImproved radiation damage resistance because of high density of defect sinks
ODS low activation steel : Fe-9Cr-WCollaboration with FBR and SCWR
ODS vanadium alloysODS Cu alloys : Heat sink materials
400nm
Nano Structural Materials for Fusion
0
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400
600
800
1000
1200
1400
300 500 700 900 1100
Tens
ile S
tres
s (M
Pa)
Temperature (K)
Ferritic steel
9CrODS steel
0
2
4
6
8
10
12
Uni
form
Elo
ngat
ion
(%)
0
200
400
600
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1000
1200
1400
0
200
400
600
800
1000
1200
1400
300 500 700 900 1100
Tens
ile S
tres
s (M
Pa)
Temperature (K)
Ferritic steel
9CrODS steel
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2
4
6
8
10
12
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2
4
6
8
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12
Uni
form
Elo
ngat
ion
(%)
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Stre
ss (M
Pa)
TTest = 298 K
TTest = 1073 K
0
200
400
600
800V - 1.0 vol% Y 2O3 - 0.7 vol% YN
V - 4.4 wt% Cr - 4.1 wt% Ti
20%
NIFS-HEAT-1
Strain (%)
Stre
ss (M
Pa)
TTest = 298 K
TTest = 1073 K
0
200
400
600
800V - 1.0 vol% Y 2O3 - 0.7 vol% YN
V - 4.4 wt% Cr - 4.1 wt% Ti
20%
NIFS-HEAT-1
ODS V-alloys
9Cr Ferritic Steel vs. 9Cr ODS steel
W, Be, C
CuCrZr to ODS-Cu
Steels
ITER First Wall
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Development of Low Activation Vanadium Alloys for Nuclear Fusion Reactors
Summary
Materials development is the key to successful development of fusion energy.
Use of “low activation” structural materials can largely increase the attractiveness of fusion reactors as a clean energy source.
High temperature operation is essential for high efficiency energy conversion
Vanadium alloys are attractive candidate low activation structural materials for fusion reactors because of low activation and high temperature strength.
Control of both potentially-radioactive impurities (Nb, Mo, Al, Ag) and interstitial impurities (C, N, O) is essential for vanadium alloy development.
Nano Structural Materials are longer-term advanced options to enhance the operation temperature window and radiation resistance of structural components.