1. ERMSAR 2012, Cologne March 21 – 23, 2012 Pascal PILUSO (CEA) Seong-Wan HONG (KAERI) Matjaz LESKOVAR (JSI) Presentation by François BOUSSARD (CEA) On behalf of SERENA members 2011 CSARP/MCAP Sep. 20-23, 2011 pascal.piluso@cea.fr. swhong@kaeri.re.kr, matjaz.leskovar@ijs.simatjaz.leskovar@ijs.si Status of SERENA-2

2. ERMSAR 2012, Cologne March 21 – 23, 2012  Scope of SERENA Project  Status of the SERENA Project  Experimental Program  Analytical program  Concluding Remarks Outline

3. ERMSAR 2012, Cologne March 21 – 23, 2012 Scope of SERENA Project  Phase 1 (started October 2003, 4 years)  Mainly calculations evidencing some discrepancy between the different codes but remaining under the max stress level design of a reactor vessel  The same exercise applied to ex-vessel concrete led to insufficient safety margins for the containment.  Phase 2 (started October 2007, 4 years)  Carry out confirmatory research required to reduce uncertainties on these phenomena and thus to an acceptable level for risk assessment.

4. ERMSAR 2012, Cologne March 21 – 23, 2012 Scope of SERENA Project- Partners in Phase 2  Started from Oct., 2007 and will be continued for four years.  KAERI and CEA: Operation agents  18 Orgs. from 11 countries are participating:  Belgium (Tractebel-Engineering SUEZ)  Canada (AECL)  Finland (VTT)  France (CEA, IRSN, EDF)  Germany (GRS, IKE)  Japan (JNES)  Korea (KAERI, KINS, KMU)  Slovenia (JSI)  Sweden (SSM, KTH)  Switzerland (PSI)  USA (US NRC, UWM)

5. ERMSAR 2012, Cologne March 21 – 23, 2012 Scope of SERENA Project-Main Objective of Phase 2 (1) To reduce the scatter of the predictions for Steam Explosion in order to be able to increase the confidence in the calculated containment safety margins for ex-vessel reactor case conditions.  Experimental tests (TROI and KROTOS facilities) by:  Providing the missing experimental data on one key FCI phenomena: the prototypical corium composition (“material effect”) using a large spectrum of corium melts representative of accident scenarios.  Providing innovative experimental data : spatial and size distribution of corium melts and void fraction during premixing and at the time of explosion and its dynamics.

6. ERMSAR 2012, Cologne March 21 – 23, 2012 Scope of SERENA Project-Main Objective of Phase 2 (2)  Experimental tests (TROI and KROTOS facilities) by:  Improving modelling on the basis of the new data to obtain consistent predictions of cavity loading by ex-vessel steam explosion.  Doing work oriented for elaboration on the major effects which are related to the explosion strength.  Analytical work by:  Improving of FCI models/codes for use in reactor analyses by complementing the work performed in Phase-1 through integrating the results of the Phase-2 Experimental program.  Doing work oriented for safety analysis and quantification of the major effects which reduce the explosion strength.

7. ERMSAR 2012, Cologne March 21 – 23, 2012 5 kg of melt 1-D geometry New release device Fast X-ray camera External trigger 20 kg of melt 2-D geometry Intermediate catcher Tomography External trigger Prototypical corium compositions Status of SERENA Project-Experimental Program (1) KROTOS Facility (CEA) TROI Facility (KAERI)

8. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Experimental program (2) The complementary and innovative features of KROTOS (CEA) and TROI (KAERI) facilities are used  KROTOS for investigating the FCI characteristics of prototypical corium melts in one-dimensional geometry and fine characterization of the premixing thanks to X-Ray fast radioscopy able to distinguish corium, water and void.  Essential for computer code model improvement  TROI for investigating the FCI behaviour in reactor-like conditions by having more mass and multi-dimensional melt water interaction geometry.  Suitable for validating the capability of the computer codes in reactor-like situations.

9. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of KROTOS : experimental Program (3) KROTOS TROI 1Challenging conditions High melt superheat High system pressure (0.4 MPa, Room water temp.) High system pressure (0.4 MPa) Reduced free fall (Melt jet velocity) and thick melt jet (Room water T.) Mat 1: 70%UO 2 -30%ZrO 2 2Geometry effect Effect of geometry by comparison between KROTOS and TROI Standard conditions: jet of diameter 3 cm Large jet at penetration (5 cm) Mat 1: 70%UO 2 -30%ZrO 2 3Reproducibility tests Idem Test 2 4Material effect Oxidic composition Standard conditions: jet of diameter 3 cm Large jet at penetration (5 cm) Mat 2: 80%UO 2 -20%ZrO 2 5Material effect Oxidation/composition Standard conditions: jet of diameter 3 cm Large jet at penetration (5 cm) Mat 3: 70%UO 2 -15%ZrO 2 + 15%Zr 6Material effect Large solidus/liquidus  T Standard conditions. Effect of fission product: higher melt superheat Large jet at penetration (5 cm). Mat 4: 70%UO 2 -30%ZrO 2 +FP+iron oxide Performed Performed ( KS March 14 th ) Performed Status Performed

10. ERMSAR 2012, Cologne March 21 – 23, 2012 KAERI and CEA performed all 6 TS and KS tests  Triggered steam explosions in five tests out of 6 tests were observed (KS and TS).  The repeatable tests (TS-2 and TS-3) showed that many parameters including dynamic pressure almost agree with each other.  KS4 and TS-4 tests (80%UO 2 -20%ZrO 2 ) both show larger explosion load than other TS or KS tests respectively, except TS-6 and possibly KS6 (under analysis).  TS-5 test with added metallic Zr produced steam spike before triggering and no explosion was observed. KS-5 produced a triggered explosion (X-Ray confirmed).  TS-6 which has the lowest liquidus temperature and the largest solidification range shows the largest explosion of TS tests. KS6 is still under analysis (last week performed) and an energetic explosion has been observed. Status of the SERENA Project- Experimental Program (5)

11. ERMSAR 2012, Cologne March 21 – 23, 2012  KROTOS: test section instrumentation Status of the SERENA Project - Experimental tools (1)

12. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project - Experimental tools (2)  KROTOS : X-Ray radioscopy: fine characterization of premixing  Quantitative data Corium 3D Void 3D Corium volume Corium surface area Void volume Void surface area

13. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project - Experimental tools (3) Rayleigh-Taylor instability formation and stripping Premixing and droplet formation mechanism  KROTOS : X-Ray radioscopy: fine characterization of premixing

14. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project - Experimental tool (4)  KROTOS: post-test characterization of corium exploded and non exploded debris

15. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project - Experimental Outcomes (1)  TS and KS-4: inverse material effect: strongest explosion for composition with solidification interval  KS and TS4: strongest explosion never observed with protoypical materials FCI and material effects Before SERENA : After SERENA Pure compound (alumina, corium azeotrope) =>Strong steam explosion Corium composition with solidification interval =>Weak steam explosion FCI and material effects Before SERENA: After SERENA: KS-5 and TS-5 weak explosion Oxidation effect: different reaction according to the nature of the material (oxide/”metallic”) Simulant material #prototypical material => impact on strength of the steam explosion

16. ERMSAR 2012, Cologne March 21 – 23, 2012  One of objectives : To reduce the scatter of the predictions in order to be able to put safety margins to containment failure  Have completed data base on the key phenomena for codes  Have provided more accurate experimental data  Melt front location  Mixing information  jet break-up length (Krotos X-Ray system)  Melt temperature  Volume average void fraction  Dynamic pressure and load Status of the SERENA Project- Experimental Outcomes (2)

17. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (1)  The main tasks of the Analytical Working Group (AWG) are:  Performing pre- and post-test calculations in support of test specification and analysis.  Improving analytical models and understanding of those key phenomena that are believed to have a major influence on the FCI process.  Addressing the scaling effect and application to the reactor case.  Demonstrating the progress made in SERENA Phase-2 as compared with Phase-1 (in particular on reducing the scatter of the predictions) by repeating the “ex-vessel reactor exercise”.

18. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (2)  Applied FCI computer codes and organizations using them:  MC3D ; AECL, CEA+Tractebel, IKE, IRSN, JSI, KAERI, KINS, VTT.  TEXAS-V ; UWM, VTT.  JASMINE ; JNES.  JEMI (IKEMIX/IKEJET) + IDEMO ; IKE  TRACER-II ; KMU  Codes JEMI+IDEMO and MC3D are being ongoing improved based on AWG findings

19. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (3)  Calculation of Experiments  Performed pre- and post-test calculations with accompanying sensitivity studies for performed experiments.  Pre-test calculations for defining optimal test conditions.  Post-test calculations and sensitivity studies for code validation, modeling improvements and as support for interpretation of experiments.  The observed differences of the simulation results between the codes and different modeling approaches, and the differences between the simulation results and experimental measurements have been analyzed and discussed.

20. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (4)  Calculation of Experiments  Performed pre- and post-test calculations with accompanying sensitivity studies for performed experiments;  The calculations are focusing on the understanding and modeling of key phenomena influencing FCI, with reactor applications in mind.  Post-test calculations of last experiments are underway.

21. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (5)  Reactor Case  PWR: Bottom (2D) and Side Vessel Failure (3D)  BWR: Bottom Vessel Failure (2D) PWR (Bottom Failure) BWR (Bottom Failure)

22. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (6)  Reactor Case : Representative Initial conditions

23. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (7)  Reactor Exercise : Time Schedule  June – October 2011: Calculations performed by AWG members according to Reactor exercise specifications  End of October 2011: Calculation results provided to CEA coordinator  November – December 2011: Preparation of draft synthesis of calculations  End of December 2011: Draft synthesis of calculations submitted to Partners  January – February 2012: Iteration of Draft synthesis  March 2012: Final synthesis report submitted to partners

24. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project-Analytical Program (8)  AWG Outcome document  Reflects the elaboration process and progress in the specific tasks, focusing on key phenomena influencing the FCI, with reactor applications in mind.  Jet-breakup, Melt mass and void in mixture, Melt solidification, Explosion phase, FCI modeling in integral codes.

25. ERMSAR 2012, Cologne March 21 – 23, 2012 Concluding Remarks (1)  Steam explosion is one of major unresolved issues in severe accidents after TMI-2.  TROI and KROTOS FCI tests: new accurate data and observation thanks to experimental tests using prototypical compositions  Experimental specific features and advanced measurement techniques on KROTOS and TROI facilities  Analyses of the full experimental results must be achieved in the next 6 months  The calculations are focusing on the understanding and modeling of key phenomena influencing FCI, with reactor applications in mind.  Application to reactor case to evaluate and decrease the scatter of results

26. ERMSAR 2012, Cologne March 21 – 23, 2012 Concluding Remarks (2)  OECD/NEA SERENA project  A concluding seminar will be organised on 13-15 Nov. 2012 Thank you for your attention

27. ERMSAR 2012, Cologne March 21 – 23, 2012 TS Plan (Actual)Features 1Challenging conditions0.4 MPa, 301K, Mat 1: 70%UO 2 -30%ZrO 2 (73.4:26.6 ) Trigger : ~0.85 s S/E Max. C MPa 2Geometry effect Effect of geometry by comparison between KROTOS and TROI 0.2 MPa, 334K Mat 1: 70%UO 2 -30%ZrO 2 ( 68:32) Trigger : ~0.85 sec S/E Max. D2 Mpa 3Reproducibility tests0.2 MPa, 331K Mat 1: 70%UO 2 -30%ZrO 2 ( 71:29), Trigger : ~0.85 sec S/E Max. D1 Mpa 4Material effect Oxidic composition 0.2 MPa, 333K Mat 2: 80%UO 2 -20%ZrO ( 81:19 ), Trigger:~1.05 s S/E Max. B Mpa 5Material effect Oxidation/composition 0.2 MPa, 337K Mat 3: 70%UO 2 -15%ZrO 2 + 15%Zr Steam Spike 6Material effect Large solidus/liquidus  T 0.2 MPa, 338K, Mat 4: 70%UO 2 -30%ZrO 2 +FP+iron oxide; 73. : 20.4 : 4.1 : 1.3 0.3 :0.8 :0.2 8.5 (UO2 : ZrO2 : Fe2O3 : Cr2O3: BaO:La2O3:SrO) 73.32: 18.45 : 4.885 : 1.74 : 0.385 : 0.975 : 0.24 ; Trigger : ~1.05s S/E Max A Mpa Status of the SERENA Project- Experimental Program (4) TROI facility

28. ERMSAR 2012, Cologne March 21 – 23, 2012 Status of the SERENA Project - Experimental Program (7) KROTOS (Actual)Features 0KF-C Calibration test 0.4 MPa, 302K, Tmelt=2930K, free fall: 0.570m Mat 1: 70%UO 2 -30%ZrO 2 S/E 1KS-1 Challenging conditions 0.4 MPa, 302K, Tmelt=2970K, free fall: 0.570m Mat 1: 70%UO 2 -30%ZrO 2 S/E 2KS-2 Geometry effect 0.2 MPa, 334K, Tmelt=3010K, free fall: 0.630m Mat 1: 70%UO 2 -30%ZrO 2 S/E 3KS-3 Reproducibility tests 0.2 MPa, 331K, Tmelt=3013K, free fall: 0.492m Mat 1: 70%UO 2 -30%ZrO 2 No S/E 4KS-4 Material effect Oxidic composition 0.2 MPa, 333K, Tmelt=2970K, free fall: 0.492m Mat 2: 80%UO 2 -20%ZrO 2 S/E Max. value for SE 5KS-5 Material effect Oxidation/composition 0.2 MPa, 337K, Tmelt=2970K, free fall: 0.492m Mat 3: 70%UO 2 -15%ZrO 2 + 15%Zr “Explosion” KROTOS facility

29. ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012 Background Investigation of accident scenarios from core degradation to melt formation and relocation in the vessel, melt dispersion to the reactor cavity, MCCI and hydrogen related phenomena in severe accidents The phenomena addressed in the studies are extremely complex and generally demand the development of specific research The research field is too wide to allow investigation of all phenomena by any national programme Existing experimental platforms should be opened for the transnational access to optimise the use of the resources at both national and international levels 29

30. ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012 Acknowledgements The authors gratefully acknowledge funding by Euratom and CAEA to support the work within ALISA project 30

31. ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012 … and finally Thank you for your attention! 31