L.SABOTINOV, R.FREITAS, P.DUFEIL, F.DUBOIS IRSN/PSN-RES/SEMIA CATHARE USERS’ CLUB 2013 Use of CATHARE at IRSN with focus on VVER reactors L.SABOTINOV, R.FREITAS, P.DUFEIL, F.DUBOIS IRSN/PSN-RES/SEMIA Grenoble – France October 9 – 11, 2013

Contents Use of CATHARE code at IRSN Safety assessment Studies R&D Examples of applications Focus on CATHARE use for VVERs General overview CATHARE validation based on VVER experimental facilities CATHARE validation against NPP test data, VVER- 1000 (V320) CATHARE application to VVER accident analysis Conclusions Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 2

Use of CATHARE code at IRSN JHR LOCA transient Transients with the SOFIA simulator, to reproduce some operational incidents LB LOCA – IB LOCA SGTR, FWTR, SLB Safety assessment Between one week and one year Studies More than one or two years R&D Between five and ten years LOCA analyses for French PWR PKL-ROCOM-PMK (OECD Projects) PSB Projects OECD Benchmarks (BFBT, PSBT, PREMIUM) VVER projects SFR studies Hot Rod Methodology for LOCA analyses SOFIA simulator, collaboration with AREVA : CATHARE integrated in the 900, 1300 and 1450 MWe configurations, and in the EPR one in 2012 In collaboration with AREVA : Development of the DIAGRAM module in GUITHARE for the I&C Coupled codes: HEMERA, DRACCAR/CATHARE3, ICARE/CATHARE2 Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 3

Engineering simulator at IRSN SOFIA simulator SOFIA = Simulator for Observation of Functioning during Incident and Accident Engineering simulator at IRSN Nuclear Power Plant of PWR type Developed and managed in collaboration with AREVA and L-3 COMMUNICATIONS MAPPS since 2005 Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 4

SOFIA simulator Scope of simulation An efficient tool for: CATHARE 2 v2.5_1 for primary + secondary and RHR Systems 4 configurations representative for the different types of French reactors (900 – 1300 – 1450 MWe + EPR) Simulation from FPSS to Cold shutdown states for maintenance just before reactor vessel opening Transients performed up to cladding temperature ~ 2200°F (~ 1200°C) An efficient tool for: Training (over 1000 trainees since 2000, from IRSN, ASN, CEA…) Emergency response exercises, to prepare the scenario and data used during the exercises Studies in support of safety evaluation Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 5/20

Focus on CATHARE use for VVERs 1- General overview Beginning of the IRSN activity, related to CATHARE safety analyses of VVER mid. 1991 Development of input data decks for VVER modeling CATHARE Team assistance IRSN Thermal-hydraulic Working Group on VVER calculations - WG creation : 1992 - WG objectives: to assess and adapt CATHARE to VVER analysis to allow IRSN to propose VVER safety assessment and studies. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 6/20

"Methodology" : 2 actions in parallel assessment on the basis of VVER test facilities: PACTEL, PMK, ISB, PSB, REWET, KIT etc., reactor calculations and comparison with other codes (ATHLET, APROS, RELAP, DINAMIKA, TECH) for existing calculations and plant measurements Participation in TACIS, PHARE, EC projects, bilateral activity More then 15 projects, Examples:  RUSSIA (1999-2000) TACIS RF/TS/13 « EU TSO Support to Independent Safety Related Analysis of Russian NPPs by Application of Western Codes » IRSN, GRS, SEC-NRS-Russia  UKRAINE (1998) TACIS UK/TS/04 «Support to the Transfer of Accident Analysis Codes to the Ukrainian Safety Authority and its Technical Safety Organizations and Application of these Codes», IRSN, GRS, SEC-NRS-Ukraine Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 7/20

 IMPAM-VVER project (EC FIS5-2001-00117, 2001-2004)  BULGARIA (2009-2011) Projects BNRA-RA-07-01, BNRA-RA-07-02, Review and assessment of the ISAR of BELENE NPP Task 2: Performance of additional research oriented activities and generic oriented in-depth studies: LARGE BREAK LOSS OF COOLANT ACCIDENT ANALYSIS OF BELENE NUCLEAR POWER PLANT IRSN, GRS, BNRA  IMPAM-VVER project (EC FIS5-2001-00117, 2001-2004) (Improved Accident Management of VVER) IRSN, VTT Energy, LUT, Fortum, KFKI, Paks, FZR + NRI Rez, VUJE, IVS, INRNE Objectives: - Effective means and criteria for primary depressurization in SB LOCA - Evaluation of system code capabilities to predict phenomena Work plan: WP1: Experimental investigation: PACTEL and PMK-2 WP2: Computer analyses of the experiments + NPP Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 8/20

2- CATHARE validation, based on VVER experimental facilities PACTEL : International Standard Problem ISP-33, OECD/NEA, natural circulation (1/305 by volume, 3 loops, 1:1 elevation scaling factor) PACTEL : EC IMPAM-VVER (7.4% break, F&B) PMK : Standard Problem Exercises SPE1,2,4, IAEA ISB (EREC-Russia) PSB (EREC-Russia), OECD, Czech republic (11% break, PRISE) (1/300 VVER-1000 model) REWET (Reflooding) IVO CCFL (Counter-currant flow limitation) KIT (subcooled boiling) Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 9/20

CATHARE PSB-VVER analysis 11% UP Break Good prediction of the basic physical phenomena and parameters such as: primary and secondary pressures, temperatures, void fractions, levels, flow rates etc. Faster ACCU discharge at the beginning, which leads to higher condensation rate and slight pressure underprediction Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 10/20

Tmax (CATHARE) Tmax measurement The experimental and calculation results are very sensitive regarding the fuel cladding temperatures, which have periodical nature with strong correlation with the ACCU discharge The core heat up has been reasonably predicted; this can provide bounding values regarding the safety analysis criteria with appropriate methodology, including uncertainty analysis. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 11/20

CATHARE PSB-VVER analysis Large Primary to Secondary Leakage (PRISE), De=100mm UP pressure SG-4 pressure Due to the leak, the primary pressure is decreasing, which leads to the actuation of the scram signal at 21.8 s (UP pressure < 13.7 MPa). At 25.3 s, the pressure in the broken steam generator (SG #4) reaches 7.16 MPa, then opening and seizure of BRU-A in open position occurs. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 12/20

primary and secondary pressures, temperatures, flows etc. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 Good prediction of the basic physical phenomena and parameters such as: primary and secondary pressures, temperatures, flows etc. The final core heatup is in good agreement with the experiment. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 13/20

CATHARE Assessment of PACTEL LOCA Experiments with Accident Management (EC IMPAM-VVER) Test T2.1 Cathare vs. experiment PACTEL facility The basic thermal-hydraulic parameters are correctly predicted by Cathare. Timing and amplitude of the key parameter Tclad are also in good agreement with the experiment. Delayed ACCU injection (reduced pressure set-point) has favorable effect on core cooling . Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 14/20

3- CATHARE modeling and validation against NPP test data, VVER-1000 (V320) Modeling of primary circuit and steam generator Information (specification of the VVER-1000 reference plant, more than 50 NPP drawings) Primary circuit (axial elements, volumes, T-elements) 4 loops modeled separately (or single loop with PRZ + triple loop) reactor vessel (downcomer, core,bypass, upper plenum) hot and cold legs, pumps etc. Steam generator modeling point SG once-through SG recirculation SG model Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 15/20

► Modeling (Primary circuit) Nodalization scheme of VVER-1000 reactor pressure vessel in CATHARE (for LB LOCA ) Core: 163 hexagonal fuel assemblies, 312 fuel rods in each fuel assembly arranged in a triangular lattice. Fuel pellets have central co-axial hole. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 16

► Secondary circuit and SG SG secondary side is represented with a recirculation model with a volume element GVVOL1 and an axial element GVDOWN1 with a downcomer and riser parts of the recirculation circuit. The thermal connection with the primary circuit is modeled in the riser part with three heat exchanging tube bundles. The steam lines to the turbine are modeled with axial elements and volumes for connection of the steam dump device BRU-A, safety valves and BRU-K. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 17

Validation against NPP test data Pressure losses in the primary circuit Nominal steady state Natural circulation tests (3.3%, 7.9%,10.9% and 12.5% NP) Coastdown of the MCP (20% NP) Turbine load reduction OECD/V1000-CT Benchmark (Kozloduy-6 pump start-up experiment and vessel mixing experiments) Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 18

Example : Coastdown of the RCP (20% NP) Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 19

4. Reactor applications to VVER-1000 Performed calculations CL LOCA (70 mm, 109 mm, 180 mm, Sensitivity study on MCP trip delay after SI signal, on break modeling etc.) SGTR (Improvements to the break modeling of horizontal tube bundles (VVER), Sensitivity studies) SGCB (De=100 mm, Approach to the break modeling of VVER) AB sequence (HA line break D=279 mm, no active ECCS) Total Loss of SG Feed Water (TLFW) Without operator intervention Operator action : Gas Blow-off System (after 30 min) Operator action : Opening of PRZ safety valve (after 30 min) Primary LOCA by pressurizer PORV failure Large Break LOCA (DBA, BDBA) (Guillotine break 2A, D=850 mm) Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 20

Illustration of BDBA LB LOCA ANALYSIS WITH FAILURE OF ACTIVE ECCS VVER-1000 Belene NPP (V466B) Guillotine 2A LB LOCA (D=850 mm) Specific features of BNPP of increased passive systems are taken into account and modelled. - Hydroaccumulators second stage (HA-2), (8x120 m3) - Secondary Passive Heat Removal System PHRS (SPOT) Two scenarios with realistic and atmospheric (0.1MPa) containment counter pressure were calculated. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 21

Maximal fuel cladding temperatures (realistic containment counter pressure) The cool-down of the reactor core is achieved and maximal fuel cladding temperature for the time span of 24 hours remains below the limiting temperature of 1200°C, applying realistic boundary conditions regarding the containment counter pressure.  Confirmation of TECH-M results fuel cladding temperatures (Zoom) fuel cladding temperatures Hot core Average core Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 22

Counter pressure realist Counter pressure 0.1MPa More conservative containment conditions (0.1MPa counter pressure) lead to core heat up after 13 hours and fuel melting after 16 hours.. Void fractions (t=16 h) Counter pressure realist Counter pressure 0.1MPa Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 23

Conclusions : Important IRSN contribution : ~20 IRSN engineers use CATHARE code: To performed studies in the frame of expertise To develop engineering simulators To develop IRSN methodology and specific tools for safety assessment To identify the lacks of knowledge and the need of research Conclusion on VVER applications: ☺► The CATHARE code is able to predict correctly the thermal-hydraulic phenomena in VVER reactors and can be applied for safety studies ☺► Important validation work on CATHARE has been carried out on Separate Effect Tests Facilities and Integral Test Facilities regarding VVERs Collaboration with different organisms on CATHARE code: INR(Czech Republic), INRNE(Bulgaria), KI(Russia), BARC(India), Bel- V(Belgium), JNRC(Jordan), VARANS(Vietnam) etc. Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 24

Continuation of currents applications and developments Numerous journal publications and presentations at international conferences Perspectives: Continuation of currents applications and developments New applications/developments for new type of reactors Experimental reactors like the JHR Gas cooled reactor Sodium cooled fast reactor Advanced reactors (EPR, VVER …) Important involvement on NEPTUNE project, in particular CATHARE3 evaluation Use of CATHARE at IRSN with focus on VVER reactors - CATHARE USERS’ CLUB 2013 25