INVESTIGATION MODELING DEGRADATION ZR-BASED ......B. STEPS OF THE PROJECT 18th Symp. Zr in Nuclear Industry -15 19 / 05 / 2016 1 •Study the behavior (reaction, degradation) of Zr-based

INVESTIGATION AND MODELING OF THE

DEGRADATION OF ZR-BASED FUEL

CLADDINGS DURING CORROSION IN STEAM

AND AIR-STEAM MIXTURES AT HIGH

TEMPERATURES

FLORIAN HAURAIS, [email protected]

ÉMILIE BEUZET,

MARTIN STEINBRÜCK,

ÉRIC SIMONI,

ANTOINE AMBARD,

MOHAMED TORKHANI

18TH SYMPOSIUM ON THE ZIRCONIUM IN THE NUCLEAR INDUSTRY

15-19 / 05 / 2016

mailto:[email protected]

OUTLINE

1. INTRODUCTION

2. EXPERIMENTAL PROTOCOL AND MATRIX

3. RESULTS FROM CORROSION TESTS

4. RESULTS FROM POROSIMETRIES

5. ANALYSIS AND MODELING

6. CONCLUSIONS AND PERSPECTIVES

2 18th Symp. Zr in Nuclear Industry - 15-19 / 05 / 2016

3

1. INTRODUCTION

A. FRAMEWORK

18th Symp. Zr in Nuclear Industry - 15-19 / 05 / 2016

PhD thesis in the research project of EDF R&D about SA in PWR: MAGESTIC

Reference simulation code for overall SA sequences: MAAP

Oxidation model of Zr-based claddings: mass gain correlations

Good prediction of reaction kinetics (C-U in steam, NUREG in air)

Quid in case of gas mixtures?

No information about the cladding mechanical degradation

Quid in case of oxide cracking or air ingress or core reflooding?

Enhancement of the H2 release during reflooding for some QUENCH tests:

H2 releases (g) during QUENCH-16 Before reflood During reflood

From Zr-based claddings (by metallography) 9 81

From the shroud and rods (by metallography) 4 43

From all (by mass spectrometry) 16 128

4

1. INTRODUCTION

B. STEPS OF THE PROJECT


1

• Study the behavior (reaction, degradation) of Zr-based claddings in

SA conditions (high T°, steam, air-steam, water reflooding)

2

• Define / perform / analyze experimental tests on Zr-based claddings

in SA conditions (at KIT through a partnership with EDF)

3

• Improve the cladding corrosion model in MAAP by considering its

mechanical degradation, to better predict the H2 production

• Validate these improvements against semi-integral experiments (e.g.

QUENCH tests) and overall scenarios (e.g. TMI-2)

OUTLINE

1. INTRODUCTION







6


A. PHENOMENOLOGY

Under pure steam In air-steam mixtures

< 1300 K > 1300 K < 1300 K > 1300 K

Reaction

kinetics

Parabolic-cubic

’Breakaway’

Linear

Parabolic

Parabolic

’Breakaway’

Linear-accelerated

Parabolic-linear

Degradation

mechanisms

Stress relieving

Cracking X

Stress relieving +

Nitriding process

Massive cracking

Nitriding process

Cracking

Zirconia layers Porous Dense Highly porous Porous

This open porosity: Represents the degradation state of samples

Can be measured by experimental methods

Tests at KIT-IAM: 1) Corrosion experiments plus 2) Porosimetry measurements


1) Isothermal corrosion tests with two online measurements:

Mass gain of the sample by using a thermo-balance

Chemical composition of the outlet gas by using a mass spectrometer

2) Porosimetry by Hg intrusion with a twofold PASCAL apparatus:

PASCAL 140: up to 350 kPa ( pores down to 4 µm)

PASCAL 440: up to 400 MPa ( pores down to 4 nm)

Determination of sample volume, density and porosity (vol%)

7


B. PROTOCOL


1 Zirconium alloy: ZIRLOTM cladding samples: 1cm-long open cylinders

2 corrosive atmospheres: Pure steam

50-50mol% air-steam mixture

8 constant temperatures (K):

1100, 1150, 1200, 1250, 1300, 1350, 1450, 1500

2 or 3 specific durations:

3 in case of ‘breakaway’ 1 in the parabolic kinetics

1 right after the ‘breakaway’

1 a longer time after it

2 otherwise 1 around 5 wt%

1 around 15 wt%

2 corrosion tests per condition to assess the reproducibility of porosimetries

8


C. TEST MATRIX


OUTLINE

1. INTRODUCTION







10


A. ZIRLOTM CLADDINGS UNDER STEAM

Consequences: Material alteration + H2(g) production + Heat generation

1100, 1150, 1300, 1350, 1450, 1500 K : Dense ZrO2, parabolic oxidation (n ~ 2.2)

1200 and 1250 K : Cracked ZrO2, oxidation parab.-cub. (n ~ 2.6) linear (n ~ 1.3)

)(.2)()(.2)( 22

.600

2

1

gHsZrOgOHsZr molkJH


SMG = fct (T) * t 1/n

11


B. ZIRLOTM CLADDINGS IN AIR-STEAM MIX

In addition to steam consequences: Material alteration + Heat generation

1350, 1450, 1500 K : Cracked zirconia layers, linear oxidation (n ~ 1.1)

Below 1350 K : Cracked zirconia layers, oxidation parab. (n ~ 2.3) linear (n ~ 0.8)

)()()( 2

.1100

2

1

sZrOgOsZr molkJ

)()()(1.370

221 sZrNgNsZr molkJ

)()()()( 221

2

.730

2

1

gNsZrOgOsZrN molkJ

1350 K 1350 K

Pure steam

50-50mol% air-steam mix


1150 K 1150 K

OUTLINE

1. INTRODUCTION







Air-steam mix: Significant porosity (> 4 vol%) for all T°

Pure steam: Significant porosity (> 4 vol%) at 1200 and 1250 K, with ‘breakaway’

Negligible porosity (< 2 vol%) at other T°, without ‘breakaway’

13


A. INFLUENCE OF OXIDIZING CONDITIONS

The variability of porosity

results is due to:

- Measurement uncertainties

(~1 vol% absolutely)

- Variability of corrosion tests,

especially in case of ‘breakaway’


‘breakaway’

no ‘breakaway’

Pure steam: porosity higher after (~ 5 vol%) than before (~ 2 vol%) the ‘breakaway’

Air-steam mix: porosity increases (> +2 vol%) during the ‘breakaway’

especially at 1250 K: +7 vol%

14


B. IMPACT OF ‘BREAKAWAY’ (1/2)


AFTER ‘breakaway’

BEFORE ‘breakaway’

BEFORE: pores > 4 μm = only a few macrocracks (~ 2 mm3/g)

AFTER: pores > 4 μm = macrocracks (~ 2 mm3/g, formed before ‘breakaway’)

+ pores < 4 μm = microcracks (~ 7 mm3/g, formed during ‘breakaway’)

15


B. IMPACT OF ‘BREAKAWAY’ (2/2)

air-steam - 1200 K

BEFORE ‘breakaway’

air-steam - 1200 K

AFTER ‘breakaway’


Higher porosity after ‘breakaway’ than before and in air-steam than in pure steam

Porosity evolution similar at 1200 and 1250 K

16


C. EVOLUTION OVER TIME


AFTER

‘breakaway’

BEFORE

‘breakaway’

OUTLINE

1. INTRODUCTION







18


A. POROSITY INCREASE RATES (1/2)

Under pure steam:


Only the 2 temperatures with ‘breakaway’ and significant porosity data, 1200 and 1250 K,

will be considered as inducing porosity.

Linear regressions Coefficient ~ 0.024 (vol% / (g.m-2)) between 1175 and 1275 K

T (K) 0 ↑

Steam dP/dt = 0

dP/dt =

0.024 *

dM/dt

dP/dt = 0

Air-steam dP/dt = 0.032 * dM/dt

dP/dt =

0.019 *

dM/dt

dP/dt =

0.019 *

dM/dt

dP/dt =

0.042 *

dM/dt

19

dP/dt (vol%.s-1) = Coefficient * dM/dt (g.m-2s.-1)

Caption:

Darker areas: ‘breakaway’ phenomena occur

Hatched areas: zirconia cracking occur

1175 1275 1325 1400



A. POROSITY INCREASE RATES (2/2)

20


B. TRANSIENT TESTS FOR COMPARISON


Zirconium alloy: ZIRLOTM cladding samples: 1cm-long open cylinders

Corrosive atmospheres: Pure steam and 50-50mol% air-steam mixture

Temperature range: 1100 K 1500 K

Heating rates (K.min-1): 50, 20, 10 Corrosion durations (min): 8, 20, 40

2 tests per condition to assess the reproducibility

Porosity (vol%) vs. heating rate (K.min-1)

(Triangles: simulations – Dashes: measurements)

Steam:

good qualitative agreement but negligible values (< 2 vol%)

Air-steam:

50-20 K.min-1: negligible measurements (< 2 vol%)

10 K.min-1: measurements (6 vol%) < simulations (10 vol%)

OUTLINE

1. INTRODUCTION







The ‘breakaway’ process and its consequences occur:

At 1200 and 1250 K under pure steam

At 1100, 1150, 1200, 1250 and 1300 K in the air-steam mix

The porosity of oxidized ZIRLOTM cladding samples:

Is higher when ‘breakaway’ occurred (especially at 1200 and 1250 K)

Becomes significantly higher if the atmosphere contains air (O2 + N2)

Seems to be proportional to the SMG, in all conditions

These porosity values (from porosimetry by Hg intrusion) are used to:

Define and implement porosity increase rates into the MAAP code

Simulate the cladding mechanical degradation during detrimental phenomena

Improve the prediction of the H2 production, especially during core reflooding

22


A. CONCLUSIONS


23


B. PERSPECTIVES

Experimental aspects

Additional oxidation tests and porosity measurements to extend conclusions

•Other Zr alloys (Zry-4 and/or M5)

•Other air-steam mixtures

•Several gas flow rates

•Higher temperatures (up to almost 1900 K)

Modeling aspects

Consideration of the temperature variation rate

Validation against semi-integral experiments (e.g. QUENCH tests)

Validation against overall scenarios (e.g. TMI-2)


Documents

INVESTIGATION MODELING DEGRADATION ZR-BASED ......B. STEPS OF THE PROJECT 18th Symp. Zr in Nuclear Industry -15 19 / 05 / 2016 1 •Study the behavior (reaction, degradation) of Zr-based