INFLUENCE OF STEAM PRESSURE ON THE HIGH …...INTRODUCTION Main objectives ofMain objectives of this study For low-tin Zircaloy-4and M5™: Influence of steam pressure (()from 1 to

INFLUENCE OF STEAM PRESSURE ON THE HIGH TEMPERATURE OXIDATION ANDTEMPERATURE OXIDATION AND POST-COOLING MECHANICAL PROPERTIES OF ZIRCALOY-4 AND M5™ CLADDING (LOCA CONDITIONS)

M. Le Saux1*, V. Vandenberghe1, P. Crébier2, J.C. Brachet1, D. Gilbon1, J.P. Mardon3, P. Jacques4, A. Cabrera4

1 CEA, DEN, 91191 Gif-sur-Yvette Cedex, France2 CEA, DEN, 38054 Grenoble Cedex 9, FranceCEA, DEN, 38054 Grenoble Cedex 9, France3 AREVA, AREVA NP SAS, Fuel Business Unit, 69546 Lyon Cedex 06, France4 EDF-SEPTEN, 69628 Villeurbanne Cedex, France*E-mail: [email protected]

17TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY, FEBRUARY 03-07, 2013, HYDERABAD, INDIA

20 FÉVRIER 2013 | PAGE 1M5™ is a trademark of AREVA NP registered in the USA and in other countries

INTRODUCTION

LOss of Coolant Accident (LOCA) in Light Water ReactorsLOss of Coolant Accident (LOCA) in Light Water Reactors

Zirconium alloys fuel claddings exposed to steam at High Temperature (HT, up to 1200°C) until quenching

Most studies focused on the Large Break LOCA conditions and thus performed at atmospheric pressure

Intermediate Break LOCA (IB-LOCA) conditions Core uncovery occurs at relativelyhigh primary pressure (several tens of bars up to ~80 bar)

Sometimes observed that steam pressure could have a significant effect on the HT oxidation of zirconium alloys

20 FÉVRIER 2013 | PAGE 217TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY, FEBRUARY 03-07, 2013, HYDERABAD

INTRODUCTION

Effect of steam pressure on the HT oxidation of Zr alloysEffect of steam pressure on the HT oxidation of Zr alloys

Scarce data and scattering and discrepancies from one study to another (e.g. Vrtilkova et al. (Nuclear Fuel Institute), Park et al. (Kyung Hee University)…)

Dependence on the oxidation temperature and the alloy (Zircaloy-4, E110, ZIRLO™…)

Oxide layer formed and hydrogen absorbed during in-service operation Potential influence on the steam pressure effect (burn-up dependence)

Origin of the steam pressure effect not clear so farOrigin of the steam pressure effect not clear so far


ZIRLO™ is a trademark of Westinghouse Electric.E110 is a trademark of A.A. Bochvar VNIINM.

INTRODUCTION

Main objectives of this studyMain objectives of this study

For low-tin Zircaloy-4 and M5™:

Influence of steam pressure (from 1 to 80 bar) on thep ( )oxidation and hydrogen pick-up at HT (between 750 and 1200°C) post-cooling mechanical properties

Impact on the steam pressure effect of representative in-servicehydriding (~ the end-of-life hydrogen contents expected for high BU cladding) oxidation (oxide layers thicknesses limited to 8 µm in this study)


OUTLINE

Materials and experimental procedureOxidation kinetics and hydrogen pick-upOxidation kinetics and hydrogen pick upOxide layer and oxygen diffusionMechanisms responsible for the steam pressure effect?ConclusionsConclusions


MATERIALS AND EXPERIMENTAL PROCEDURE

MaterialsMaterial Sn Fe Cr Nb O Zr

Nominal chemical composition (in wt.%)

Stress-Relieved Annealed low-tin Zircaloy-4 (Zy-4) and fullyrecrystallized M5™ cladding tube specimens (AREVA)

Zircaloy-4 1.3 0.2 0.1 - 0.13 Bal.

M5TM - 0.04 - 1.0 0.14 Bal.

Oxide Hydrogenspecimens (AREVA) Material State Oxidethickness

Hydrogencontent

Zircaloy-4

As-Received (AR) - -

Pre-hydrided - 500-600 wt.ppm

Pre oxidized 3 and 8 µm <100 wt ppmPre-oxidized 3 and 8 µm <100 wt.ppm

M5™



Pre-oxidized 3 and 5 µm <100 wt.ppm






Zircaloy-4 1.3 0.2 0.1 - 0.13 Bal.

M5TM - 0.04 - 1.0 0.14 Bal.

Oxide Hydrogenspecimens (AREVA)

Hydrogen charging in an argon/hydrogen mixture at 400°C (AREVA/CEZUS Paimboeuf)

Material State Oxidethickness

Hydrogencontent

Zircaloy-4



Pre oxidized 3 and 8 µm <100 wt ppm( ) Pre-oxidized 3 and 8 µm <100 wt.ppm

M5™









Zircaloy-4 1.3 0.2 0.1 - 0.13 Bal.

M5TM - 0.04 - 1.0 0.14 Bal.

Oxide Hydrogenspecimens (AREVA)

Hydrogen charging in an argon/hydrogen mixture at 400°C (AREVA/CEZUS Paimboeuf)

Material State Oxidethickness

Hydrogencontent

Zircaloy-4



Pre oxidized 3 and 8 µm <100 wt ppm( )

Two-side pre-oxidation in staticautoclave at 360°C with typicalPWR primary water chemistry


M5™




(1000 ppm B, 2.2 ppm Li and 30 cc/kg H2) (EDF R&D)

Pre-transient oxide layers homogeneouslysmooth and black/dark grey



High temperature oxidation and coolingcooling

Double-side oxidation in a flowing steam environment in the CINOG HP facility (CEA)

Steam inlet

Oxidation temperatures (T): 750, 850, 900, 1000, 1100 and 1200°CSteam pressures (P): 1, 10, 20, 40, 60 and 80 barOxidation times (t): 200, 400, 600, 1800, 3600, Condenser

Sample and quartz tube

( ) , , , , ,7200, 9000 and 18000s

Cooling, quite fast (~100-150°C/s down to 500°C) but slower than during a direct water quenchingg q g


OUTLINE



OXIDATION KINETICS AND HYDROGEN PICK-UP

At atmospheric pressureResults in good agreement with data previously 10

15

cm2 )

Zy-4, 1 bar1100 C

1000 C

1200 C

g g p yobtained in other CEA facilities

Oxidation kinetics sub-parabolic (n≈2.6) between 700 and 900°C and nearly parabolic (n≈2) b t 1000 d 1400°C

5

10

Wei

ght g

ain

(mg/

c

900 C

1000 C

― CINOG BP- - DEZIROX 1Symbols: This study

between 1000 and 1400°C

Oxidation kinetics faster for fresh Zy-4 than for fresh M5™ for T below 1100°C, nearly the same f b th t i l t hi h T

nKtWg 1

00 1000 2000 3000 4000

W

Oxidation time (s)

850 C750 C

15M5™, 1 bar1100 Cfor both materials at higher T

For both materials, Wg lower than those predicted by the Baker-Just (BJ) correlation whatever T, not far from the Cathcart-Pawel (CP) correlation

10

ain

(mg/

cm2 )

1000 C

1200 C ― CINOG BP- - DEZIROX 1Symbols: This study

far from the Cathcart Pawel (CP) correlation beyond 1000-1100°C and lower below

No hydrogen uptake at HT (pre-breakaway oxidation regime)

0

5

Wei

ght g

a850 C750 C

900 C

1000 C


00 1000 2000 3000 4000

Oxidation time (s)


Effect of P on fresh Zy-4 (1/3)

6

g/cm

2 )

Zy-4, 850 C

600BJ 1800s

BJ 3600s 1800s

3600s

750-1000°C: Oxidation kinetics enhanced under high P, since the early stages of oxidation (≤200s)

Wei

ght g

ain

(mg

200s

600s

BJ 200s

BJ 600s

P

oxidation (≤200s) Wg under high P (>60 bar) slightly greater thanthose predicted by the BJ correlation

1100 and 1200°C: Effect of P quite low or

0.60 20 40 60 80

Steam pressure (bar)20Zy-4, 1100 C

1100 and 1200°C: Effect of P quite low or negligible

No significant effect of P on the exponent n of th l id ti ki ti d l ga

in (m

g/cm

2 )

200s

400s

BJ 200s

BJ 400s

P

the general oxidation kinetics model

2W

eigh

t g

200s


20 20 40 60 80

Steam pressure (bar)


Effect of P on fresh Zy-4 (2/3) 1exp,, PtTPtTWg

Park et al.

Dependency of Wg on P nearly exponential

P effect increases with increasing t

1,exp1,,

PtTtTWg

Steam pressure effectparameter

P effect increases with increasing t, significantly at the beginning of oxidation and slower after (kind of saturation as the oxidegrowths) 0.6

0.8

1

essu

re e

ffect

α

(-) 900 C

850 CZy-4

1000 C

P effect maximal at 850°C but does not change so much between 750 and 1000°C

0

0.2

0.4

0 1000 2000 3000 4000mal

ized

stea

m p

repa

ram

eter

, α

750 C

1100 C1200 C

t

-0.4

-0.2

Nor

mOxidation time (s)



Effect of P on fresh Zy-4 (3/3)

300

350

pm)

Zy-4Increase of Wg with increasing P associated witha significant but limited hydrogen pick-up

150

200

250

en co

nten

t (w

t.pp

80 bar

The higher the P, the greater the hydrogenuptake (no hydrogen uptake at 1 bar)

Hydrogen uptake increases during oxidationP

t

0

50

100

0 10 20 30 40 50 60 70

Hyd

rog

1 bar

40 barHydrogen pick-up fraction relatively low (ratio of hydrogen absorbed by the material and hydrogenreleased during oxidation <10%)

P

0 10 20 30 40 50 60 70(Oxidation time (s))1/2



6

g/cm

2 )

M5™, 850 C

BJ 1800s

BJ 3600s

3600s

7200sEffect of P on fresh M5™

Wei

ght g

ain

(mg

600s

BJ 200s

BJ 600s

1800s

3600s

750-1200°C: P effect quite low or negligible Wg lower than those predicted by the BJ correlation P

0.60 20 40 60 80


200s

BJ 200s

20M5™, 1100 C

correlation

No significant effect of P on the exponent nof the general oxidation kinetics model

gain

(mg/

cm2 )

400sBJ 200s

BJ 400s

No significant hydrogen uptake whateverthe oxidation conditions P

2W

eigh

t g

200s

20 20 40 60 80




Effect of pre-hydriding at 850 and 1000°C

10

g/cm

2 )

FreshPre-H. 600 wt.ppm

Zy-4

1000 Cand 1000°C

For both Zy-4 and M5™, no significant impact of pre transient hydriding ( h i ) up

Wei

ght g

ain

(mg

1000 C200s

400s

of pre-transient hydriding (gaseous charging) up to end-of-life hydrogen contents on the

oxidation kineticshydrogen uptaket ff t

10 20 40 60 80


850 C600s

10FreshPre-H 150 wt ppm

M5™steam pressure effect

P effect important for Zy-4 and much less significant for M5™, whether the material is pre-hydrided or not ga

in (m

g/cm

2 )

Pre-H. 150 wt.ppm

1000 C400spre-hydrided or not

1W

eigh

t g

850 C600s

1000 C200s


10 20 40 60 80



Effect of a thin pre-oxide layer at 850 and 1000°C (1/2)

Pre-ox β (+α )t

10

g/cm

2 )

FreshPre-ox. ~3 µmPre-ox. ~8 µmBJCP

Zy-4, 1000 C, 400s

FreshBJCP

For both materials, for the same ox. conditions under 1 or 80 bar, Wg lower for the pre-oxidized samples (the

Pre-ox.

O2

Stea

m

βZr (+αZr)t0

Wei

ght g

ain

(mg

Pre-ox. ~3 µm

P

CP

pre oxidized samples (the thicker the pre-ox. layer, the greater the decrease in Wg), at least for short t St

eam OO2

αZr(O)Pre-ox. βZr (+αZr)HT ox.t1>t0

10 20 40 60 80


Pre-ox. ~8 µm

P

10FreshPre-ox. ~3 µm

M5™, 1000 C, 400s

Wg of pre-ox. materials substantially lower than those predicted by the CP and BJ correlations, even for P as high as 80 bar

gain

(mg/

cm2 )

Pre ox. 3 µmPre-ox. ~5 µmBJCP

Fresh

BJCP

In the case of pre-ox. materials, for a given pre-oxide layer thickness, Wg of M5™ close to those of Zy-4, whereas lower in the case of non pre-ox. materials (decrease in Wg due to pre-ox. lower for M5™ 1

Wei

ght g Pre-ox. ~3 µm

Pre-ox. ~5 µm

P


a e a s ( g pthan for Zy-4 for the conditions investigated)

10 20 40 60 80



Effect of a thin pre-oxide layer at 850 and 1000°C (2/2)

0.6

0.8

1

essu

re e

ffect

(-)

Zy-4

--- 850 C 600s― 1000 C 400s

P effect on the oxidation of Zy-4 reduced in the presence of a thin pre-oxide layer

Differences between sensitivities of Zy-4 and0

0.2

0.4

0 2 4 6 8rmal

ized

stea

m p

repa

ram

eter

, α

Differences between sensitivities of Zy-4 and M5™ to P significantly smaller after pre-oxidation

For the same oxidation conditions, hydrogen pick-up of pre-oxidized Zy-4 under 80 bar (no hydrogen

-0.4

-0.2Nor

Pre-oxide thickness (µm)

M5™

180

2001 barZy-4up o p e o d ed y u de 80 ba ( o yd oge

uptake at 1 bar) lower than those of the fresh or pre-hydrided material, in correlation with the lower Wg

100

120

140

160

180

ck-u

p (w

t.ppm

) 80 barZy 4

850 C80 bar

No significant hydrogen uptake at HT in the case of pre-oxidized M5™

20

40

60

80

Hyd

roge

n pi

c

1000 C80 bar

1 b

FreshPre-ox.~3µm


00 2 4 6 8 10

Weight gain (mg/cm2)

1 bar

OUTLINE



OXIDE LAYER AND OXYGEN DIFFUSION

Oxide and metallic layersthicknesses

1 bar 80 bar

FreshM5™

Oxidelayer

Oxidelayer

Measured oxide layers thicknesses in accordance with Wg:

not significantly modified by the increase

M5™

Oxidelayer

Oxidelayer

1

not significantly modified by the increase in P at 850, 1000 or 1200°C for M5™ increase with increasing P at 850 and 1000°C but not at 1200°C for Zy-4 25 µm

FreshZy-4

0.6

0.7

0.8

0.9

1

conc

entra

tion

(-)

1 bar80 bar

Zy-4850 C 3600s

Enhanced oxidation kinetics of Zy-4 under high Pat 850 and 1000°C not associated with additional oxygen diffusion through the metallic substrate

0.1

0.2

0.3

0.4

0.5

Nor

mal

ized

oxy

gen

1 bar 80 bar

metallic substrate

00 50 100 150 200 250 300

N

Distance from the initial outer surface (µm)20 FÉVRIER 2013 | PAGE 2017TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY, FEBRUARY 03-07, 2013, HYDERABAD

OXIDE LAYER AND OXYGEN DIFFUSION

Morphology of the oxide layers

For both materials whatever T and PFor both materials, whatever T and P, columnar structure of the oxide

M5™: No significant effect of P on the morphology, porosity or damage of oxide

1 bar 80 bar

FreshM5™morphology, porosity or damage of oxide

layers formed between 750 and 1200°C

Zy-4: Oxides formed under high Pbetween 750 and 1000°C

M5™

are more “stratified” and exhibitmore pores and cracks show crystallites smaller and more disorganized and disoriented with

FreshZy-4

2 µm

Observations performed aftercooling and mechanical testing Additional pores and cracks

disorganized and disoriented with grain boundaries not defined as well as in the oxides formed at 1 bar

2 µm


OUTLINE



MECHANISMS RESPONSIBLE FOR THE STEAM PRESSURE EFFECT?

Mechanisms inherent to the P effect take place at the early stage of oxidationMechanisms inherent to the P effect take place at the early stage of oxidation

Oxidation mechanisms not fundamentally ≠ under high P and atmospheric P

Influence of P on the reaction at the outer oxide/steam interface and/or on the oxygen transport through the existing oxide but not on the reaction at the inner M/Ooxygen transport through the existing oxide but not on the reaction at the inner M/O interface and the oxygen diffusion beneath it

Alloy dependent influence of P on the microstructure of the oxide formed at HT (and thus on the oxygen diffusion through it) but not really on the oxygen transport rate yg g ) y yg pthrough the pre-existing scale (rate limiting process until complete reduction of the pre-oxide)

Oxide layer formed under high P still partially protective



Oxide morphology, porosity and cracking

P effect associated with a faster development within the oxides formed under high P of porosities and micro-cracks Easier access of oxygen and hydrogen atoms to the metallic substrate

Oxide grains morphology and orientation modified under high P Steam diffusion and pores formation at grain boundaries and inter-granular cracking facilitatedfacilitated



Oxide phases and stoichiometry and metallic substrate

Potential influence of P on the stability of the tetragonal phase of zirconia (metastable below 1000°C) and/or on the tetragonal to monoclinic phase transformation Additional stresses and formation of pores or even cracks

Eff t f P th id t i hi t ( i ) M i fl tEffect of P on the oxide stoichiometry (oxygen vacancies) May influence atoms diffusion through the oxide, stability of zirconia tetragonal phase and/or oxide plasticity (sometimes, whitish color of the outer surface of the oxide layers formed on Zy-4 under high P)

P effect potentially related to the evolution of the characteristics and the resultingP effect potentially related to the evolution of the characteristics and the resultingproperties of the metallic substrate, in particular at the beginning of the ox. process(750-1000°C: metallic substrate in αZr phase or two-phases (αZr+βZr) + dissolution of someintermetallic precipitates in Zy-4 and apparition of Nb-enriched βZr phase in M5™)


OUTLINE



CONCLUSIONS

Oxidation kinetics and hydrogen pick-up

U d hi h P b t 750 d 1000°C id ti ki ti f f b i t d lUnder high P between 750 and 1000°C, oxidation kinetics of as-fabricated low-tin Zy-4 enhanced and combined with a significant but limited hydrogen uptake since the early stages of oxidation

P effect quite low or negligible between 750 and 1000°C for as-fabricatedP effect quite low or negligible between 750 and 1000 C for as-fabricated M5™, and at 1100 and 1200°C for both alloys

P has potentially an effect on the oxidation rate but does not really modify the (sub-) parabolic oxidation kineticsp

Oxidation kinetics, hydrogen uptake and effect of P not significantly modified by in-service pre-hydriding (gaseous charging) up to the end-of-life hydrogen contents expected for Zy-4 and M5™

Weight gains at 850 and 1000°C lower for materials with thin pre-oxide layers (3 to 8 µm thick, formed in autoclave at 360°C with typical PWR primary water chemistry) and ≠ between sensitivities of Zy-4 and M5™ to P significantly reduced after pre-ox. i th thi k i ti t d


in the thickness range investigated

CONCLUSIONS

Oxide layer, oxygen diffusion and mechanismspotentially responsible for the P effect

Enhanced oxidation kinetics of Zy-4 under high P correlated with a thickening of the oxide layers formed at HT but not associated with additional oxygen diffusion through the metallic substratediffusion through the metallic substrate

P has an influence on the microstructure (crystallites morphology, porosity and cracks) of the oxide formed within the 750-1000°C T range on Zy-4, but not on M5™

Assumptions: Changes in oxide microstructure, probably responsible for a faster oxygen (and hydrogen) transport through the oxide layer, potentially induced by a destabilization promoted under high P of the tetragonal phase of zirconia?


CONCLUSIONS

Post-cooling mechanical properties and P effect consequences during in-reactor transients

Effect of P on the post-cooling mechanical properties (ring compression tests at 20 and 135°C) of fresh, pre-hydrided and pre-oxidized Zy-4 and M5™ oxidized at HT

ll li it d f th diti i ti t dgenerally limited for the conditions investigated

According to calculations, impact of the P effect for Zy-4 very low or negligible on the ECR actually achieved during typical in-reactor transientsy g yp No consequence on LOCA related criteria verification


Thank you for your attention

Direction de l’Energie NucléaireCommissariat à l’énergie atomique et aux énergies alternatives

| PAGE 30

17TH INTERNATIONAL SYMPOSIUM ON Direction de l Energie NucléaireDépartement des Matériaux pour le NucléaireService de Recherches Métallurgiques Appliquées

Commissariat à l énergie atomique et aux énergies alternativesCentre de Saclay | 91191 Gif-sur-Yvette CedexT. +33 (0)1 69 08 12 28 | F. +33 (0)1 69 08 71 67

Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 01920 FÉVRIER 2013

17TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY, FEBRUARY 03-07, 2013, HYDERABAD

Documents

INFLUENCE OF STEAM PRESSURE ON THE HIGH …...INTRODUCTION Main objectives ofMain objectives of this study For low-tin Zircaloy-4and M5™: Influence of steam pressure (()from 1 to