ermsar 2012, cologne march 21 – 23, 2012 a sarnet benchmark on two vulcano molten core concrete...

ERMSAR 2012, Cologne March 21 – 23, 2012

A SARNET Benchmark on two VULCANO Molten Core Concrete Interaction Tests

C. Journeau1, J.F Haquet1, B. Letexier1, A. Greco1, B. Spindler2, R. Gencheva3, P. Groudev3, D. Dimov4, A. Fargette5, J. Foit6, B. Michel7, C. Mun7, T. Sevon8, C. Spengler9, F. Polidoro10

1 CEA, Cadarache (FR) 2 CEA, Grenoble (FR)3 INRNE, Sofia (BG) 4 Energy Inst., Sofia (BG) 5 AREVA NP, Erlangen (DE) 6 KIT, Karlsruhe (DE)7 IRSN, Cadarache (FR) 8 VTT, Espoo (FI)9 GRS, Cologne (DE) 10 RSE, Milan (IT)


Outline

1. Test presentation

2. Benchmark characteristics

3. Calculations vs. Experiment

4. Synthesis, conclusions and perspectives


Main Test characteristics

Limestone rich concrete (VB-U6) - Silica rich concrete (VB-U5)

Corium masses 31 kg (U6) – 28 kg (U5)

Net power ~ 9kW (U6) - 11.5 kW (U5) 1 kW

(Side View)

TEST SECTION

(Cross View)


Concretes

Concrete F- VB-U5

Concrete GVB-U6

SiO2 64.7 25

CaO 16.4 41

Al2O3 5.1 2

CO2 9.3 25

H2O 3.1 7

Fe2O3 1.4 0

Concrete – corium pseudobinary phase diagrams


Partners and codes

In this benchmark nine organisations from 5 different EU countries have been involved. They simulate main MCCI phenomena in VB-U5 and VB-U6 tests using different codes as it is pointed bellow:

– MEDICIS (ASTECv2) code used by IRSN, France, GRS, Germany, EI, Bulgaria and INRNE, Bulgaria;

– TOLBIAC-ICB v3.2 code used by CEA-Cadarache, France and CEA-Grenoble, France;

– CORQUENCH 3.03 code used by VTT, Finland;

– COSACO code used by AREVA, Germany;

– WECHSL code used by KIT (FZK), Germany;

– CORIUM2D code used by RSE, Italy

The purpose of these analyses is to compare code results with the results obtained by the tests, to compare the best-estimated assumptions and to synthesize conclusions


Axial ablation rates for VB-U6 test

0

2

4

6

8

10

12

14

0 1000 2000 3000 4000 5000 6000 7000 8000

Time (s)

Abl

ation

rat

e (c

m/h

)

GRSVTTCEA_gre_baseCEA_gre_case2CEA_gre_case3AREVAIRSNINRNECEA_cad_9kWCEA_cad_9kW-PcondKITEI

Ablation Rate VB-U6 (limestone-rich)

Models consider either isotropic ablation for VB-U6 or have standard correlation for each direction

2 types of modelling:•With initial transient (thermal inertia)•~constant ablation rate (TOLBIAC)Average ablation rate ~2 cm/s


Crucible shapes at the end of calculations of VB-U6 test

-35

-30

-25

-20

-15

-10

-5

00 5 10 15 20 25

R (cm)

H (c

m)

VTT

GRS

AREVA

CEA_gre_base

CEA_gre_case2

CEA_gre_case3

IRSN

INRNE

CEA_cad_9kW

CEA_cad_9kW-Pcond

KIT

EI

RSE

EXPERIMENT

INITIAL

VB-U6 Ablation shape

CEA Grenoble 3 (anisotropic ablation) indeed shows a too large radial ablation. VB-U6 is indeed rather isotropic.

KIT and RSE exhibit too small lateral ablation/ too large axial

All the others provide a reasonably good fit.


VB-U5 Ablation (silica-rich)

Crucible shapes at the end of calculations of VB-U5 test(Without anisotropy coefficients)

-35

-30

-25

-20

-15

-10

-5

0

0 5 10 15 20 25

R (cm)

H (c

m)

ERSE

VTT

GRS

AREVA

CEA_gre_base

CEA_gre_case2

KIT

EXPERIMENT

INITIAL

Crucible shapes at the end of calculations of VB-U5 test(using anisotropy coefficient)

-35

-30

-25

-20

-15

-10

-5

0

0 5 10 15 20 25

R (cm)

H (c

m)

IRSN

EI

INRNE

CEA_gre_case3

CEA_cad

EXPERIMENT

INITIAL

Various approaches

– No coefficient to model anisotropy: Too large axial ablation

– No coefficient but different h : VTT/CORQUENCH: good shape

– Empirical coefficient added: leads to rather good fit of curves

Predictive nature of the empirical coefficients to be assessed


VB-U5 Ablated volumes

Rather good fit of results

Major uncertainty lies with axial/lateral ablation anisotropy

Ablation volumes estimation for VB-U5

RSE; -51,90%

KIT; 33,76%

CEA_cad_2625K; -0,75%

CEA_cad_2336K; -7,92%

NRNE; -1,38%

IRSN; -4,45%

GRS; 14,58%

CEA_gre_case3; 41,90%

AREVA; 18,62% EI;

17,17%

VTT; -12,07% CEA_gre_

base_case; -14,31%

CEA_gre_case2; -7,59%

-80%

-60%

-40%

-20%

0%

20%

40%

60%

Dif

fere

nce

fro

m f

inal

exp

erim

enta

l ab

lati

on

vo

lum

e (%

)


Corium Pool Temperatures

Few measurements available (improved in recent tests)

Uncertainty: <200 K

RSE overestimates temperatures (linked with too, small ablation)

Approaches with Tinterface=Tsolid

underestimate the pool temperature by several 100s K.

Models with Tinterface~Tliquidus provide better simulation.

– TOLBIAC (CEA)

– AREVA (U6), EI (U5)

– TOLBIAC with macrosegregation gives too low temperature.

Pool temperatures versus time for VB-U5 test

0

500

1000

1500

2000

2500

3000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000Time (s)

Tem

pera

ture

(K)

ERSE GRSVTT AREVAIRSN EIINRNE CEA_gre_baseCEA_gre_case2 CEA_gre_case3CEA_cad KITEXPERIMENT

Pool temperatures versus time for VB-U6 test

0

500

1000

1500

2000

2500

3000

0 1000 2000 3000 4000 5000 6000 7000 8000Time (s)

Tem

pera

ture

s (K

)

ERSE GRSVTT CEA_gre_baseCEA_gre_case2 CEA_gre_case3AREVA IRSNINRNE CEA_cad_9kWCEA_cad_9kW-Pconv KITEXPERIMENT


Pool composition UO2 wt%

Analyses: 40-53wt% UO2 in central part of pool

TOLBIAC do not model well final composition

– CEA_gre: Macrosegregation: crusts enriched in UO2-ZrO2

– CEA_cad: crust at pool composition at the time of deposit

Even if there are crusts, they must be remelted when ablation progresses and be at a composition close to the final melt pool composition.

UO2 final mass fractions for VB-U6

EI; 47,29% KIT;

48,57%

CEA_cad_9kW;

23,88%

CEA_cad_9kW-Pcond;

23,18%CEA_gre_case3; 17,35%

CEA_gre_case2; 19,89%

CEA_gre_base_case;

19,45%

INRNE; 46,04%

IRSN; 45,57%

AREVA; 42,28%VTT;

44,60%

GRS; 44,94%

0%

10%

20%

30%

40%

50%

60%M

ass

frac

tio

n (

%) Exp. value


Synthesis

10 partners – 6 code benchmark was a key point in EU networking on MCCI.

Cavity volume and shape are roughly well predicted

– VB-U5 needs to take into account anisotropy, either explicitly or implicitly (CORQUENCH).

– Axial ablation is generally overestimated

Assuming an interface temperature around liquidus provides better estimates of the pool temperature

Crusts, if they exist, shall have a composition close to the current pool composition.


Conclusions

Up to now, it is still not possible to propose a comprehensive modelling of MCCI that could predict the observed anisotropy and all the parameters of the experiment.

No single calculation has been able to compute all the parameters of the experiments.

But we are using multi 0D quasi-steady state modelling to model an intermittent ablation process

– complex geometry both at the interface

– complex convection pattern in the pool because of combined effects of gas bubbling and solutal convection.

Nevertheless, reasonably good estimates of ablation volume and profile.


Conclusions - Perspectives

VB-U5 and VB-U6 were within the first VULCANO MCCI experiments

They used typical Gen 2 plant concretes and prototypical corium

Latest VULCANO tests have better measurements

– Better estimation of radiated and ablated powers

– Valid measurement of temperature every ~10 min

Coming SARNET-VULCANO tests shall eliminate initial transient crusts (by introduction of Zr)

SARNET is in parallel writing a State of the Art report.

ermsar 2012, cologne march 21 – 23, 2012 a sarnet benchmark on two vulcano molten core concrete...

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