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1Westinghouse Non-Proprietary Information Class 3
©2010 Westinghouse Electric Company LLC
All Rights reserved
ZIRLOTM Irradiation Creep StressDependence in Compression and Tension
16th ASTM Zirconium SymposiumChengdu, China, 9-12 May 2010
John Foster and Rita BaranwalWestinghouse Electric Company LLC
Columbia, SC, [email protected]
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INTRODUCTION● Data are from the Vogtle Unit 2 PWR Creep/Growth Program● Results for SRA ZIRLO show:
– In-reactor creep compliance is the same in tension andcompression
– If total in-reactor strain is split into growth and creepcomponents:– Deviatoric hoop stress is the driving force for irradiation
creep– Irradiation creep in tension is the same as compression
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EXPERIMENTALTest Samples
•SRA ZIRLO
•168 mm long
•Samples areeither Hepressurized oropen on both sidesto water
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Irradiation ScheduleCycle: 10 11 12 13 14 15
Fall 02 Spring 04 Fall 05 Spring 07 Fall 08 Spring 10AssemblyA1 x------------------xA2 x---------------------------------------------------------xA3 x-------------------------------------xA4 x----------------------------------------------------------------------------xA5 x--------------------xA6 x------------------x
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Test Overview● Test samples are irradiated in guide thimble positions using
segmented insert rods– Test samples do not contain fuel– Samples are placed in outer row guide thimble positions
● Six assemblies● Samples discharged for measurement are not reinserted● Disassemble samples by shearing after the refueling outage in
the pool and shipped to Hot Cell for examination– Measured by laser micrometer
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Irradiation Conditions● Data are available for 1 and 2 cycles (~17 months
irradiation/cycle)– Temperature range 300-318 oC– No axial or radial fast flux gradient
– Confirmed with retrospective dosimetry measurements– Cycle-to-cycle fast fluxes are approximately constant
– Range between 9.3-9.7x1013 n/cm2-sec E>1 MeV
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Stress Analysis● σθ, σr and σz stresses calculated with the thick-wall equations● Deviatoric hoop stress,σθ = σθ(deviatoric) + σ(hydrostatic)σ(hydrostatic) = (σθ + σr + σz)/3
– Deviatoric stress results in plastic strain (creep)– Hydrostatic stress does not result in plastic strain (creep)
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Sample DesignSOLID CYLINDER INTERNAL MANDREL
TUBE INTERNAL MANDREL
•Solid cylinderinternal mandrelgenerates moreheat than the tubeinternal mandrel
Black = Sample
White = He Gas
Red = Internal Mandrel
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RESULTS and DISCUSSIONGamma Heat Generation Rate [1/2]
Total Dia. Strain vs. Deviatoric Hoop Stress for Gamma Heat Gen. Rate of 1.60x106 Btu/h-ft3
SRA STD ZIRLO, Vogtle Unit 2 Cycle 10 (Test Assembly A1)
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-60 -40 -20 0 20 40 60 80
DEVIATORIC HOOP STRESS (MPa)
TOTA
L D
IAM
ETER
STR
AIN
, del
taD
/Do
(%)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•Calculated regressionR2 coefficient fordifferent γ-heat rates
•Fit associated withhighest R2 coefficient
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Gamma Heat Generation Rate [2/2]Regression R2 Coefficient versus the Gamma Heat Generation Rate
SRA STD ZIRLO, Vogtle 2 Cycle 10 (Test Assembly A1)
0.991
0.992
0.993
0.994
0.995
0.996
0.997
0 1 2 3 4
GAMMA HEAT GENERATION RATE (106 Btu/h-ft3)
REG
RES
SIO
N R
2 CO
EFFI
CIE
NT
1.60x106
•Determinedgamma heatgeneration rate
•Calculated internalpressures andstresses using thegamma heatgeneration rate
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RESULTS and DISCUSSIONIn-Reactor Creep Compliance (1 Cycle, Cycle 10) [1/3]
Total Dia. Strain vs. Deviatoric Hoop Stress for Gamma Heat Gen. Rate of 1.60x106 Btu/h-ft3
SRA STD ZIRLO, Vogtle Unit 2 Cycle 10 (Test Assembly A1)
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
-60 -40 -20 0 20 40 60
DEVIATORIC HOOP STRESS (MPa)
TOTA
L D
IAM
ETER
STR
AIN
, del
taD
/Do
(%)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•In-reactor creepcompliance (slopeof the line) is thesame in tension &compression
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In-Reactor Creep Compliance (1 Cycle, Cycle 11) [2/3]Total Dia. Strain vs. Deviatoric Hoop Stress for Gamma Heat Gen. Rate of 0.80x106 Btu/h-ft3
SRA STD ZIRLO, Vogtle Unit 2 Cycle 11 (Test Assembly A5)
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
-60 -40 -20 0 20 40 60
DEVIATORIC HOOP STRESS (MPa)
TOTA
L D
IAM
ETE
R C
REE
P ST
RA
IN, d
elta
D/D
o(%
)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•In-reactor creepcompliance (slopeof the line) is thesame in tension &compression
•Same ΔD/Do vs.σθ(dev.) behavioras Cycle 10 data
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In-Reactor Creep Compliance (2 Cycles, Cycles 10-11)[3/3]
Total Dia. Strain vs. Deviatoric Hoop Stress for Gamma Heat Gen. Rate of 1.20x106 Btu/h-ft3
SRA STD ZIRLO, Vogtle Unit 2 Cycles 10 & 11 (Test Assembly A3)
-1.0
-0.5
0.0
0.5
1.0
1.5
-40 -20 0 20 40 60
DEVIATORIC HOOP STRESS (MPa)
TOTA
L D
IAM
ETER
STR
AIN
, del
taD
/Do
(%)
Tube Intenal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•In-reactor creepcompliance (slopeof the line) is thesame in tension &compression
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Split Total In-Reactor Strain into Growth & CreepComponentsΔD/Do(creep) = ΔD/Do(measured total) – ΔD/Do(growth)
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Irradiation GrowthTotal Diameter Strain versus the Pressure Difference
SRA STD ZIRLO, Vogtle Unit 2 Cycle 10 (Test Assembly A1)
-0.8
-0.4
0.0
0.4
0.8
-15 -10 -5 0 5 10 15
PRESSURE DIFFERENCE, Pi-Po (MPa)
TOTA
L D
IAM
ETER
STR
AIN
, del
taD
/Do
(%)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•Data includessamples open towater on both sides
•Determinedirradiation growthstrain by regressionanalysis
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Irradiation Creep Hoop Stress CorrelationIrradiation Creep Diameter Strain versus Thick-Wall Hoop Stress (Total)
SRA STD ZIRLO, Vogtle 2 Cycle 10 (Test Assembly A1)
-0.8
-0.4
0.0
0.4
0.8
-100 -50 0 50 100
HOOP STRESS (TOTAL) (MPa)
IRR
AD
IATI
ON
CR
EEP
DIA
MET
ER S
TRA
IN,
delta
D/D
o (%
)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit Fit
•Linear behavior
•Between -16 and 0MPa, σθ is negative& ΔD/Do is positive(the red line) –physically unrealistic
•σθ is not the correctdriving force forirradiation creep
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Irradiation Creep Deviatoric Hoop StressCorrelation (1 Cycle/Cycle 10)
Irradiation Creep Diameter Strain versus Deviatoric Hoop StressSRA STD ZIRLO, Vogtle Unit 2 Cycle 10
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
-60 -40 -20 0 20 40 60
DEVIATORIC HOOP STRESS (MPa)
IRR
AD
IATI
ON
CR
EEP
DIA
MET
ER S
TRA
IN,
delta
D/D
o (%
)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Regression Fit
•Linear behavior
•Data pass throughthe origin
•Deviatoric σθ is thedriving force forirradiation creep
•Tension =compression
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Irradiation Creep Deviatoric Hoop StressCorrelation (1 Cycle/Cycle 11)
Irradiation Creep versus Deviatoric Hoop StressSRA STD ZIRLO (Test Assembly A5), Vogtle Unit 2 Cycle 11
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
-60 -40 -20 0 20 40 60
DEVIATORIC HOOP STRESS (MPa)
IRR
AD
IATI
ON
CR
EEP
DIA
MET
ER S
TRA
IN,
delta
D/D
o (%
)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•Data pass through theorigin
•Deviatoric σθ is thedriving force forirradiation creep
•Tension = comp.
•ΔD/Do vs. σθ(dev.)same as Cycle 10 data
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Irradiation Creep Deviatoric Hoop StressCorrelation (2 Cycle/Cycles 10-11)
Irradiation Creep versus Deviatoric Hoop StressSRA STD ZIRLO, Vogtle Unit 2 Cycles 10 & 11
-1.0
-0.5
0.0
0.5
1.0
1.5
-30 -20 -10 0 10 20 30 40 50
DEVIATORIC HOOP STRESS (MPa)
IRR
AD
IATI
ON
CR
EEP
DIA
MET
ER S
TRA
IN,
delta
D/D
o (%
)
Tube Internal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit
•Linear behavior
•Data pass throughthe origin
•Deviatoric σθ isthe driving force forirradiation creep
•Tension =compression
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CONCLUSIONS● For SRA ZIRLO,
– In-reactor creep compliance is the same in tension andcompression
– If total in-reactor strain is split into growth and creepcomponents:– Deviatoric hoop stress is the driving force for irradiation
creep– Irradiation creep in tension is the same as compression
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Thank you for your attention
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PUBLICATIONS● Initial 1 cycle results were reported in 15th International
Symposium of Zirconium in the Nuclear Industry● Initial 1 cycle dosimetry results were reported in Proceedings
of the 13th International Symposium on Reactor Dosimetry