A SARNET Benchmark on two VULCANO Molten Core Concrete Interaction Tests

Transcription

1 A SARNET Benchmark on two VULCANO Molten Core Concrete Interaction Tests C. Journeau 1, J.F Haquet 1, B. Letexier 1, A. Greco 1, B. Spindler 2, R. Gencheva 3, P. Groudev 3, D. Dimov 4, A. Fargette 5, J. Foit 6, B. Michel 7, C. Mun 7, T. Sevon 8, C. Spengler 9, F. Polidoro 10 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)

2 Outline 1. Test presentation 2. Benchmark characteristics 3. Calculations vs. Experiment 4. Synthesis, conclusions and perspectives

3 Main Test characteristics TEST SECTION (Side View) (Cross View) Limestone rich concrete (VB-U6) - Silica rich concrete (VB-U5) Corium masses 31 kg (U6) 28 kg (U5) Net power ~ 9kW (U6) kw (U5) 1 kw

4 Concretes Concrete F- VB-U5 Concrete G VB-U6 SiO CaO Al 2 O CO H 2 O Fe 2 O Concrete ERMSAR 2012, corium Cologne pseudobinary March 21 23, 2012 phase diagrams

5 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

6 Ablation rate (cm/h) Ablation Rate VB-U6 (limestone-rich) Models consider either isotropic ablation for VB-U6 or have standard correlation for each direction 14 Axial ablation rates for VB-U6 test Time (s) 2 types of modelling: With initial transient (thermal inertia) ~constant ablation rate (TOLBIAC) Average ablation rate ~2 cm/s GRS VTT CEA_gre_base CEA_gre_case2 CEA_gre_case3 AREVA IRSN INRNE CEA_cad_9kW CEA_cad_9kW-Pcond KIT EI

7 H (cm) VB-U6 Ablation shape Crucible shapes at the end of calculations of VB-U6 test R (cm) 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 CEA Grenoble 3 (anisotropic ablation) indeed shows a too large radial ablation. VB-U6 is indeed rather isotropic. INITIAL KIT and RSE exhibit too small lateral ablation/ too large axial All the others provide a reasonably good fit.

8 H (cm) H (cm) VB-U5 Ablation (silica-rich) Crucible shapes at the end of calculations of VB-U5 test (Without anisotropy coefficients) Crucible shapes at the end of calculations of VB-U5 test (using anisotropy coefficient) ERSE -10 IRSN VTT GRS AREVA CEA_gre_base CEA_gre_case EI INRNE CEA_gre_case3 CEA_cad -25 KIT EXPERIMENT INITIAL -25 EXPERIMENT INITIAL R (cm) Various approaches -35 R (cm) 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

9 Difference from final experimental ablation volume (%) VB-U5 Ablated volumes Ablation volumes estimation for VB-U5 60% 40% 20% GRS; 14,58% CEA_gre_ case3; 41,90% AREVA; 18,62% EI; 17,17% KIT; 33,76% 0% -20% -40% -60% VTT; CEA_gre_ -12,07% CEA_gre_ case2; base_case; -7,59% -14,31% IRSN; -4,45% NRNE; -1,38% CEA_cad_ 2336K; -7,92% CEA_cad_ 2625K; -0,75% RSE; -51,90% -80% Rather good fit of results Major uncertainty lies with axial/lateral ablation anisotropy

10 Temperatures (K) Temperature (K) Corium Pool Temperatures Pool temperatures versus time for VB-U5 test Few measurements available (improved in recent tests) Uncertainty: <200 K ERSE VTT IRSN INRNE CEA_gre_case2 CEA_cad EXPERIMENT GRS AREVA EI CEA_gre_base CEA_gre_case3 KIT Time (s) RSE overestimates temperatures (linked with too, small ablation) 3000 Pool temperatures versus time for VB-U6 test Approaches with T interface =T solid underestimate the pool temperature by several 100s K ERSE VTT CEA_gre_case2 AREVA INRNE CEA_cad_9kW-Pconv EXPERIMENT GRS CEA_gre_base CEA_gre_case3 IRSN CEA_cad_9kW KIT Time (s) Models with T interface ~T liquidus provide better simulation. TOLBIAC (CEA) AREVA (U6), EI (U5) TOLBIAC with macrosegregation gives too low temperature.

11 Mass fraction (%) Pool composition UO2 wt% 60% UO2 final mass fractions for VB-U6 50% 40% GRS; 44,94% VTT; 44,60% AREVA; 42,28% IRSN; 45,57% EI; 47,29% KIT; INRNE; 48,57% 46,04% Exp. value 30% 20% 10% CEA_gre_ base_case; 19,45% CEA_gre_ case2; 19,89% CEA_gre_ case3; 17,35% CEA_cad_ 9kW; 23,88% CEA_cad_ 9kW-Pcond; 23,18% 0% 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 ERMSAR a composition 2012, Cologne close March to the 21 final 23, 2012 melt pool composition.

12 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.

13 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.

14 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.