zirlotm irradiation creep stress dependence in …

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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]

2

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

3

EXPERIMENTALTest Samples

•SRA ZIRLO

•168 mm long

•Samples areeither Hepressurized oropen on both sidesto water

4

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

5

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

6

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

7

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)

8

Sample DesignSOLID CYLINDER INTERNAL MANDREL

TUBE INTERNAL MANDREL

•Solid cylinderinternal mandrelgenerates moreheat than the tubeinternal mandrel

Black = Sample

White = He Gas

Red = Internal Mandrel

9

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

10

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

11

RESULTS and DISCUSSIONIn-Reactor Creep Compliance (1 Cycle, Cycle 10) [1/3]



-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


TOTA

L D

IAM

ETER

STR

AIN

, del

taD

/Do

(%)


•Linear behavior

•In-reactor creepcompliance (slopeof the line) is thesame in tension &compression

12

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


-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


TOTA

L D

IAM

ETE

R C

REE

P ST

RA

IN, d

elta

D/D

o(%

)


•Linear behavior


•Same ΔD/Do vs.σθ(dev.) behavioras Cycle 10 data

13

In-Reactor Creep Compliance (2 Cycles, Cycles 10-11)[3/3]


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


TOTA

L D

IAM

ETER

STR

AIN

, del

taD

/Do

(%)

Tube Intenal Mandrel Solid Cylinder Internal Mandrel Open to Water Fit

•Linear behavior


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Split Total In-Reactor Strain into Growth & CreepComponentsΔD/Do(creep) = ΔD/Do(measured total) – ΔD/Do(growth)

15

Irradiation GrowthTotal Diameter Strain versus the Pressure Difference


-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

(%)


•Linear behavior

•Data includessamples open towater on both sides

•Determinedirradiation growthstrain by regressionanalysis

16

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

17

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


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

18

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


IRR

AD

IATI

ON

CR

EEP

DIA

MET

ER S

TRA

IN,

delta

D/D

o (%

)


•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

19

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


IRR

AD

IATI

ON

CR

EEP

DIA

MET

ER S

TRA

IN,

delta

D/D

o (%

)


•Linear behavior

•Data pass throughthe origin

•Deviatoric σθ isthe driving force forirradiation creep

•Tension =compression

20

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

21

Thank you for your attention

22

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

zirlotm irradiation creep stress dependence in …

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