dimensional change of isotropic graphite under heavy ion-irradiation
DESCRIPTION
SEP15-18, 2013 INGSM-14 Seattle, USA. Dimensional Change of Isotropic Graphite under Heavy Ion-Irradiation. Sosuke Kondo Makoto Nonaka Tatsuya Hinoki Kyoto University. Contents. Ion-irradiation facility (DuET) at Kyoto University Development of method for dimensional change evaluation - PowerPoint PPT PresentationTRANSCRIPT
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Dimensional Change of Isotropic Graphite under Heavy Ion-Irradiation
Sosuke KondoMakoto NonakaTatsuya Hinoki
Kyoto University
SEP15-18, 2013INGSM-14Seattle, USA
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Contents
• Ion-irradiation facility (DuET) at Kyoto University
• Development of method for dimensional change evaluation
• Results
• Future work (evaluation of irradiation creep) at DuET
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Graphite for HTGR
Key Properties of Graphite Core ComponentsMaterial property changes which affect internal stress are
key to avoid the excessive deformation of the core components. For example, dimensional change, thermal conductivity, CTE change, modulus change, are essential for analyzing internal loads of core components.
Irradiation Performance of Nuclear Grade GraphiteSimply, the graphite formed by densely and randomly-
oriented small crystallite shows good dimensional stability. However, many candidates may have various “unirradiated”
properties, such as microstructure, graphitization degree, and pore structure, depending on the production method, such as starting material, heat treatment temperature, number of pitch infiltration.
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Objective
The irradiation data should be quickly accumulated for multiple candidates to ensure stable supply of the graphite.
ObjectiveDevelopment of the ion-irradiation method to evaluate the fluence- and temperature-dependent dimensional change of various graphite.
B.T. Kelly et al, IAEA-TECDOC-1154, 2000
Dim
ensio
nal c
hang
e (%
)
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Irradiation Facilities
0 500 1000 1500
Flue
nce
/ dpa
-C
0.1
1
10
100Fe-9Cr-2W V-4Cr-4Ti
SiC/SiC
Temperature / ⁰C
JOYOJNC/
OARAI
JMTRJAERI/OARAI
HFIRORNL
20dpa/year
3dpa/year
10dpa/year
DuETKyoto U.
100dpa/day
Graphite
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1.7 MV Tandetron20A 5.1 MeV Si2+
10A 6.4 MeV Fe3+
1.0 MV Singletron10A 1.0 MeV He+
DuET facility, Kyoto University
DuET: Dual-beam irradiation facility for Energy science and Technology
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Ion Irradiation Effects on Specimen Surface
10μm10μm
Non-Irradiated Irradiated
Nuclear grade graphite, Irradiated in DuET at 400⁰C
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Unirradiated
1. In-plane shrinkage (expansion) within the irradiated region was constrained by the unirradiated region.
2. If the change in crack size was absent, the in-plane tensile (compression) stress might be accumulated in the irradiated region with increasing in DPA.
3. Tensile (Compression) stress was actually released by crack opening (closing).
Reason for Crack Size ChangeBeam Direction
Irradiated Region
Unirradiated Region
Dimensional changes, both the contraction and expansion, are expressed by the change in crack size.
Change in crack size can include the bulk information because many grains, cracks, and pores are included in the irradiated plane.
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Quantification of Crack Opening Area
20μm
20μmSEM image
Binary image
𝐷𝑖𝑚𝑒𝑛𝑠𝑖𝑜𝑛𝑎𝑙 h𝑐 𝑎𝑛𝑔𝑒 , Δ 𝐿/𝐿(%)≈Δ 𝐴𝑤
❑
𝐴𝑤𝑢𝑛𝑖𝑟𝑟 ×100×
12
Binary image“after noise reduction”
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Experimental Procedure
Irradiation Holder
Ion Irradiation (DuET facility, Kyoto U.)Ions : 5.1 MeVSi2+
Irradiation Temperatures : 400, 600, 800⁰CFluence : 1.3, 2.7, 4.0 dpa (at surface)
Observation of the Irradiated SurfaceSEM (Carl Zeiss, ULTRA55)
Evaluation of the change in crack opening areaImage analysis
Estimation of the dimensional change
10mm
SamplesMaterials1. IG-1102. Candidate of nuclear graphite (CNG)
Temperature Monitor
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Comparison Unirr./Irrd. Surfaces
IG-110600⁰C, 1.3 dpa
Unirr. Irrd. Unirr. Irrd.
2μm 2μm 2μm 2μm
IG-110600⁰C, 2.7 dpa
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Unirr. Irrd.
2μm 2μm
Unirr. Irrd.
2μm 2μm
Candidate of nuclear grade graphite(CNG)600⁰C, 1.3 dpa
Candidate of nuclear grade graphite(CNG)600⁰C, 2.7 dpa
Comparison Unirr./Irrd. Surfaces
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Num
ber o
f Cra
cks D
etec
ted,
/0.
2mm
2
Size Distribution of the Surface Crack
IG-110, 4000C
Unirradiated
4dpa
2.7dpa
1.3dpa
Unirradiated
4dpa
2.7dpa
1.3dpa
4dpa
2.7dpa
1.3dpa
IG-110, 6000C IG-110, 8000C
Opening Area, mm2 Opening Area, mm2 Opening Area, mm2
Unirradiated
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Num
ber o
f Cra
cks D
etec
ted,
/0.
2mm
2
Size Distribution of the Surface Crack
CNG, 4000C
CNG, 6000C CNG, 8000C
Opening Area, mm2 Opening Area, mm2 Opening Area, mm2
Unirradiated
4dpa2.7dpa
1.3dpa
Unirradiated
4dpa
2.7dpa
1.3dpa
Unirradiated
4dpa
2.7dpa1.3dpa
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CNG, 6000C
Unirradiated
4dpa
2.7dpa
1.3dpa
Unirradiated
4dpa
2.7dpa
1.3dpa
IG-110, 6000C
Num
ber o
f Cra
cks D
etec
ted,
/0.
2mm
2
Opening Area, mm2
Num
ber o
f Cra
cks D
etec
ted,
/0.
2mm
2
Opening Area, mm2
Comparison at 600 °C
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0 1 2 3 4 5 6-1
-0.8
-0.6
-0.4
-0.2
0400°C600°C800°C
DPA
Dim
ensi
onal
Cha
nge,
%
0 1 2 3 4 5 6-1
-0.8
-0.6
-0.4
-0.2
0400°C600°C800°C
DPA
Dim
ensi
onal
Cha
nge,
%
IG-110
800⁰C
600⁰C
400⁰C
800⁰C
600⁰C
400⁰C
CNG
Dimensional Change of Ion-irradiated Regions
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20μm20μm
1μm1μm
Microstructure of Unirradiated Surface
CNGIG110
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graphite
Ion beam Ion beamInitial stress: 14.8MPa
Development on going
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Unilateral support intended to release of irradiation induced residual stress in the thin irradiated region.
SamplesIon beam
Development on going
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3D laser scanning microscope(KEYENCE, VK-X200)
Measurement of the Irradiated Curvature
Laser monochrome image
2D height profile
Averaged height profile
1 mm
1 mm
5 μm
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Preliminary Results
Compression (fixed)
Straight (fixed)
Straight (unfixed)
After released from fixtures
After released from fixtures
After released from fixtures
After ion-irradiation at 800°C
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Summary & Conclusions
We tried to evaluate the dimensional stability of graphite using ion-irradiation.
Results- Ion irradiation modified the surface-crack size due to the constraint by the
unirradiated region.- The T and DPA dependence of the dimensional change estimated appear
to be reliable considering the neutron irradiation data.Conclusions- Ion-irradiation method can be a quick tool for evaluating the dimensional
stability of the nuclear grade graphite.- Further tests for various graphite are essential because all the nuclear
graphite may not show the same dimensional stability.Future work- Modify the method (if necessary,) and extend data beyond TA.- Develop the ion-irradiation-creep testing method.