Nuclear Safety Research Unit Vienna (Austria), 31.05-4.06.2010 IAEA meeting Evaluation of creep...

Nuclear Safety Research Unit Vienna (Austria), 31.05-4.06.2010

IAEA meeting

Evaluation of creep during dry storage Evaluation of creep during dry storage

in low and high burnup fuelsin low and high burnup fuels

F. Feria, L.E. Herranz

CONTENTS

1.1. Motivation and objectiveMotivation and objective

2.2. Extension of FRAPCON-3.3 creep lawExtension of FRAPCON-3.3 creep law

3.3. Creep assessmentCreep assessment

4.4. Final remarksFinal remarks


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1. 1. MOTIVATION AND OBJECTIVEMOTIVATION AND OBJECTIVE

Safety objectives: - Radiation dose

- Subcriticality

- Confinement

- Retrievability

Degrading mechanisms

SCC Creep DHC

Cladding integrity

Evaluation in low and high burnup


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dtd cp

In-FRAPCON modelling

r,z,id Ti

pi

pi

eii

2. 2. EXTENSION OF FRAPCON-3.3 CREEP LAWEXTENSION OF FRAPCON-3.3 CREEP LAW

2321

cc ))(f)·T(f)·(f(

4

)4.967·10exp(725.2)(f -81

)RT/10000exp()T(f 2

-293 5.129·10)(f

Creep law:


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Creep law validity range

Restricted to in-reactor conditions

Extension of the creep law is needed to apply the code to dry storage conditions


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Zircaloy-4 database (EDF)

cs

cp

c

s,pi)t(f)·t(f)·T(f)·(f i4i3i2i1ci


Generic correlation


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CIEMAT creep law

5.0321 t)·t(f)·T(f)·(f

b1 2

a)(f

273T

cexp)T(f 2

)t·dexp()t(f3



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CIEMAT creep law

0.0

0.1

0.2

0.3

0 100 200 300 400 500 600

t(h)

(%

)

CIEMAT

EDF

0

0.1

0.2

0 200 400 600 800 1000

t(h)

(%

)

CIEMAT

EDF



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Implementation

≥ 121 MPa → Creep law parameters derived from irradiated claddings data

≤ 121 MPa → Creep law parameters derived from non-irradiated claddings data


Together with a suitable logic that allows choosing between the “in-reactor” equation and the dry storage equation, according to the prevailing conditions at the calculation time

The extension splits in two hoop stress ranges:

No experimental data is available with irradiated material under low hoop stress


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0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500

t(days)

Ave

rag

e lin

ear

po

wer

(kW

/m)

0

5

10

15

20

25

30

35

40

0 500 1000 1500 2000 2500

t(days)

Av

era

ge

lin

ea

r p

ow

er

(KW

/m)

0.0

0.2

0.4

0.6

0.8

1.0

0 200 400 600 800

t(days)

T

3. 3. CREEP ASSESMENTCREEP ASSESMENT

a) Zircaloy-445 GWd/tU

1º) In-reactor irradiation

2º) Pool storage (1 year)

3º) Dry out (1 day)

4º) Dry storage (2 years)

Phasesb)

Zircaloy-463 GWd/tU

Postulated scenarios


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Resultsa)

Zircaloy-4 45 GWd/tU

b) Zircaloy-463 GWd/tU

-0.8-0.7

-0.6-0.5

-0.4-0.3

-0.2-0.1

00.1

0.2

0 400 800 1200 1600 2000 2400

t(days)

(%

)

Trillo

Dry storageIn-pool cooling

-1

-0.5

0

0.5

1

1.5

0 400 800 1200 1600 2000 2400

t(days)

(%

)

Trillo2

Dry storageIn-pool cooling

Once dry storage starts hoop stress causes a creep-out situation


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The creep main impact would take place during the first months


Results

In no case creep reaches 1 % strain limit

Nearly 4 times higher hoop strain as burn-up is increased by 40 % 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 100 200 300 400 500 600 700 800

t(days)

D

(%)

45 GWd/tU

63 GWd/tU


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4. 4. FINAL REMARKSFINAL REMARKS

High burn-up effect seems substantial and causes major differences in the nuclear fuel response in terms of creep

Further work:

• Extend CIEMAT creep law to irradiated fuel rods submitted to low stresses

• Extend the study up to 100 years to estimate the final creep asymptotic value

The results would have a conservative nature because the irradiation hardening effect is not considered at low stresses


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ACKNOWLEDGMENTSACKNOWLEDGMENTS

The authors are indebted to ENRESA for their financial support and the technical discussions held and to the FRAPCON-3 developers for their technical support during this work


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THANK YOU FOR YOUR ATTENTION

Nuclear Safety Research Unit Vienna (Austria), 31.05-4.06.2010 IAEA meeting Evaluation of creep...

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