ERMSAR 2010, Bologna 11-12 May 2010

Two EU-funded tests in VULCANO to assess the effects of concrete nature on

its ablation by molten corium

Christophe Journeau, Lionel Ferry, Pascal Piluso, José Monerris, Michel Breton, Gérald Fritz,

CEA Cadarache (France)

Tuomo Sevón

VTT Espoo (Finland)

ERMSAR 2010, May 11-12, 2010, Bologna 2

Outline

The VULCANO Facility

Description of the 2 MCCI tests– VB U7 Test with EPR Olkiluoto 3 sacrificial concrete– VB ES U2 : Separate Effect (ES) Test with “concrete

clinker” concrete

Synthesis on concrete nature and ablation anisotropy

ERMSAR 2010, May 11-12, 2010, Bologna 3

The VULCANO Facility Plasma Arc Furnace

Plasma arc furnace for oxidic corium melting

~150 kW maximum power

25- 50 kg maximum oxidic corium pour

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The VULCANOFacility Test section: induction heating

Inducteur : 14 barres de 25 mm espacées de 5 mm

BETON

INDUCTEUR

SIPOREX

700 mm

BETON

150

mm

25

0 m

m

450

mm

300 mm15050 mm

Clarinette

Sole

Induction heating in the bulk of the melt to simulate decay heat

Hemicylindrical cavity (+ refractory ceramic wall)

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The VULCANO Facility Test sections instrumentation

Concrete test section with 100+ thermocouple to monitor ablation

10 W thermocouples to measure bulk oxide temperature

2 Pyrometers to measure surface oxides temperature

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VULCANO Experiments : Concrete Compositions

Tests had up to now been performed with two concrete types.

– Concrete F is rich in Silica

– Concrete G is rich in Limestone

Two new concretes studied in 2009– Concrete C is made with ciment

clinker (calcinated calcareous ore)

Same liquid phase composition as Concrete G

Large aggregates and no decarbonation as concrete F

– Concrete E (EPR) with ferro- siliceous agregates, low gas content.

wt% CaO CO2 SiO2 Al2 O3 Fe2 O3 Mg O

H2 O

“Concrete C”

49.2 - 29.6 3.9 2.1 0.9 10.7

“Concrete E”

12.7 1.4 45.5 3.3 32.9 0.3 3.7

“Concrete F”

16 9 63 5 - - 3

“Concrete G”

42 25 26 2 - - 4

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VB-U7 (EPR Concrete)

~54 kg of corium poured

80 minutes of simulated decay heat

– Average net power 17 kW

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VB-U7 Temperature evolution

Melt Initial Temperature ~2250°C

After 80 minutes: ~1550°C

0

500

1000

1500

2000

2500

11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00

Tem

péra

ture

(°C

)

TCW1 TCW2 TCW3 TCW4

TCW5 TCW6 TCW7 TCW8

TCW9 TCW10

1890°C

2250°C

1550°C 1550°C

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Ablation front progression in concrete

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Post Test Examinations

A leak occurred

Corium spread (relatively low viscosity)

Possibility to observe the crusts

Material Analyses underway

Channels between lateral concrete

and pool

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VB-ES-U2

Transfer of about 45 kg of corium to the test section

3 hours simulated decay heat

More intense gas sparging than VB-U7

800

1000

1200

1400

1600

1800

2000

2200

2400

11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30

Tem

pera

ture

(°C

)

Surface renewal (Figure 4)

Fine crust Fine crust

Surface activity Surface

activity

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Melt Pool Temperature evolution

0

500

1000

1500

2000

2500

11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30

Tem

pera

ture

(°C

)

2250°C

1450-1500°C

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Final Cavity shapes

Cavity ablation is significantly anisotropic (ratio > 2)

Both tests lead to very close cavity shapes– Corium Concrete Interaction is not a stochastic phenomenon!

-450

-400

-350

-300

-250

-200

-150

-100

-50

00 50 100 150 200 250 300 350 400 450

VB-U7 45° VB-U7 135°

VB-ES-U2 45° VB-ES-U2 135°

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Rationale

A few « typical Gen 2 reactor » concrete compositions had been subjected to interaction with corium.

No consensus exists on a predictive model that can explain the anisotropic behaviour of silica-richconcretes and the isotropic behaviour of the limestone-rich concretes.

– (An)isotropic heat transfer coefficients (h)

– Different boundary conditions (Tinterf )

– Different flux history (∫φdt)

– Other causes….

Current codes must use an a-posteriori fixed partition coefficient to recalculate the anisotropicablations.

Need to:

– Understand the phenomena controlling the ablation (an)isotropy

– Determine thresholds and model the ablation ratio between vertical and horizontal walls.

Separate Effect Tests to be performed with prototypic corium.

– Before the leading phenomenon(a) is (are) known, it is impossible to derive scaling relationships !

Use of « Artificial concretes » design so that just 1 (or 2) of the characteristics of the concretechange(s) between two tests.

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Differences between concretes

Property Concrete F

VB-U4, U5, CCI 3

63% SiO2

Concrete G

VB-U6

67% CaCO3

Concrete C

VB-ES-U1,2

Cement clinker

Concrete E

VB-U7

Fe2 O3 , SiO2

Ablation Anisotropic ~isotropic Anisotropic Anisotropic

Gas 8 mol/ L of concrete

18 mol/ L of concrete

14 mol/L of concrete

6 mol/ L of concrete

Concrete melting Liquidus 2000 K Liquidus 2300 K

Eutectic valley

~ Concrete G Low liquidus

Gravel degradation Quartz at 2000 K

Mortar at lower temp.

Limestone destroyed at 1100 K

Clinker not destroyed by decarbonation

Aggregates are not destroyed at low temp

Concrete shrinkage Molten concrete ~same volume than cold concrete

30 % shrinkage due to decarbonation

Molten concrete ~same volume than cold concrete

Molten concrete ~same volume than cold concrete

Moletn concrete transport properties

Viscous

Low diffusion

Fluid

Higher Diffusion

Fluid

Higher Diffusion

Intermediate

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Conclusions

Two EU-funded VULCANO experiments have been realized in 2009.– Thanks to PLINIUS FP6 and SARNET 2 grants.

Two new concrete compositions have been tested including the EPRsacrificial reactor-pit concrete

Both tests presented similar anisotropic behaviour and important pool temperature drop(to 1450-1550°C)

Gas superficial velocity does not seem to be causing the shift from isotropic to anisotropic ablation regimes.

Decarbonation (destruction of large agregates/ volume shrinkage) seems to be the cause of isotropic ablation

– Next VULCANO Separate Effect Test with a siliceous mortar shall provide more clues on the parameters controlling isotropy.

When the cause of anisotropy is found, improved modelling will be required.