ermsar 2012, cologne march 21 – 23, 2012 a sarnet benchmark on two vulcano molten core concrete...
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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)
ERMSAR 2012, Cologne March 21 – 23, 2012
Outline
1. Test presentation
2. Benchmark characteristics
3. Calculations vs. Experiment
4. Synthesis, conclusions and perspectives
ERMSAR 2012, Cologne March 21 – 23, 2012
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)
ERMSAR 2012, Cologne March 21 – 23, 2012
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
ERMSAR 2012, Cologne March 21 – 23, 2012
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
ERMSAR 2012, Cologne March 21 – 23, 2012
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
ERMSAR 2012, Cologne March 21 – 23, 2012
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.
ERMSAR 2012, Cologne March 21 – 23, 2012
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
ERMSAR 2012, Cologne March 21 – 23, 2012
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 (%
)
ERMSAR 2012, Cologne March 21 – 23, 2012
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
ERMSAR 2012, Cologne March 21 – 23, 2012
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
ERMSAR 2012, Cologne March 21 – 23, 2012
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.
ERMSAR 2012, Cologne March 21 – 23, 2012
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.
ERMSAR 2012, Cologne March 21 – 23, 2012
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.
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