1. UNIVERSITÀ DI PISA GRUPPO DI RICERCA NUCLEARE – SAN PIERO A GRADO (GRNSPG) Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar September 20-23, 2010 West Yellowstone, Montana September 20-23, 2010 TitleUse of RELAP5-3D at GRNSPG/UNIPI AuthorsC. Parisi, A. Kovtonyuk, C. Matteoli, M. Cherubini, A. Del Nevo, F. D'Auria Revision/Date120 09 2010

2. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 2/40 List of content A.Simulation of RIA transients by means of 3D-NK/TH model of CNA-2 B.Predictability of transients involving spatial variation of coolant proprieties in DC and LP C.Post-test analysis of LOBI TEST A1-84 by RELAP5/Mod3.3 and RELAP5-3D v2.4.2 D.Forum & Network of System Thermal-Hydraulic Codes in Nuclear Reactor Safety (FONESYS)

3. UNIVERSITÀ DI PISA GRUPPO DI RICERCA NUCLEARE – SAN PIERO A GRADO (GRNSPG) Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. A) SIMULATION OF RIA TRANSIENT BY MEANS OF 3D-NK/TH MODEL OF CNA-2

4. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 4/40 Rationale  Since 2007 San Piero a Grado Nuclear Research Group of University of Pisa (GRNSPG/UNIPI) is involved, through the Argentinean electric utility NA-SA, in the licensing activities for the Atucha-2 NPP, currently under construction in Argentina  These activities culminated in the preparation of the Chapter 15 of the FSAR being submitted to the Argentinean Safety Authority (ARN)  State-of-the-art 3D NK coupled TH computational models were set up in order to  Perform standard set of licensing & support calculations (e.g., REA, CR withdrawal, etc.)  Give answers to the LBLOCA issue (BDBA)  BEPU Approach pursued for licensing calculations

5. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 5/40 Atucha II PHWR Features  Atucha-II is a 692 MWe Siemens designed PHWR under construction in Lima, Argentina  Constructions resumed in 2005, completion scheduled for 2011  Heavy water cooled, heavy water moderated PWR  Unique features:  Primary circuit based on the Konvoi-PWR design  Circuit for moderator cooling / FW pre-heating  Natural Uranium fuel  Vertical Fuel Channels  Large RPV (7.3 meter internal diam.)

6. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 6/40 Atucha II PHWR Features  Fuel placed in 451 vertical fuel channel (FC)  37 Natural Uranium Fuel rods per each FC  On-line refueling  Active Core Height: 5.3 m  18 Oblique CRs CR layout Fuel Element RPV Layout

7. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 7/40 Rationale for simulation of RIA  Atucha-2 PHWR has a positive void coefficient  Power increase during LOCA  Fast power pulse (~1.0 sec.)  To be quenched by a fast negative reactivity insertion  injection of highly concentrated boron solution into the moderator by an active system  Jet Injection by 4 boron lances  Atucha-2 reference DBA was 0.1A CL2 LOCA (Siemens approach in the ’80s)  Argentinean Safety Authority (ARN) requested to analyze and study LOCA with breaking areas >0.1 A up to 2A  Selected Beyond Design Basis Accident

8. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 8/40 Rationale for simulation of RIA  The main chain of codes used for the transient analyses was based on the very well established and validated tools: HELIOS-RELAP5- NESTLE (HELIOS-RELAP5-3D©)  Extensive External & Internal benchmarking has been performed, e.g.:  University of Michigan (ARN consultants) developed a model based on PARCS-RELAP5 code for LOCA studies  Comparison with GRNSPG/UNIPI NESTLE-RELAP5-3D model performed with established SS & transients benchmarks  At the same time MCNP5 Monte Carlo models were set up for simulating the whole core  Support for the development of the RELAP5-3D© model  Complex Geometry  Oblique CR volumes & “correction factor” calculations  Full independent from HELIOS-RELAP5-3D© chain  assessment of neutronic calculations by coarse-mesh diffusion code NESTLE

9. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 9/40 Chain of Codes for Atucha -2 3D NK TH Analyses HELIOS Models 2 G XSec Libraries 3D MCNP5 Model ENDF/B-VI.v8 Data NJOY CODE Multi-Group Libraries (47) Continuou s Energy Libraries NESTLE RELAP5-3D 3D NK TH SS & Transient Simulation 3D SS Simulation Validation Boron Cloud Study MAIN ROUTE

10. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 10/40 3D NK – TH coupled model – Fuel Channels 280 channel  Atucha II NPP 280 channel RELAP5-3D TH model used for RIA analyses  # of TH channels modeled & coupled according to:  Hydraulic characteristics (throttled type/un-throttled)  Romboidal sub-plena belonging  Power distribution  Transient type  Code resources 451 FA simulated by 3D NK NESTLE code 280 FA simulated by RELAP5

11. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 11/40 3D NK – TH COUPLED MODEL – 3D MODERATOR TANK  Moderator Model using RELAP5-3D - 3D components  possibility to simulate with high degree of realism the boron clouds calculated by CFD  simulation of asymmetric transients  sophisticated mapping scheme resulted from the use of Cylindrical 3D TH Components coupled with Hexagonal NK cells 6 radial sectors 1+ 10 + 1 = 12 axial layers for Bottom Reflector, Core Active zone, Top reflector 1+ 10 + 1 = 12 axial layers for Bottom Reflector, Core Active zone, Top reflector 16 azimuthal sectors 16 azimuthal sectors

12. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 12/40 “280 Channels” Nodalization Resources  Number of Hydraulic Nodes: 5,744  Number of Meshes for Heat Conduction: 67,640  Number of Junctions: 6,987  Number of Materials: 9  Number of Control Variables: 950  Number of Trips: 200  Number of TMDPVOL: 13 + 94 (for boron clouds simul.)  Number of NK nodes: 6420  Number of “steps” CRs: 211  Total Number of input deck lines: ~143,000

13. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 13/40 3D NK – TH coupled model  3D NK nodes obtaining “weighted” feedback from TH model  NESTLE sending back power distribution to FA heat structures PowerNESTLE Fuel Channel TH model Moderator TH model Coolant Density Coolant Temperature Moderator Temperature Boron Concentration Fuel TemperatureRELAP5-3D

14. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 14/40 CODES INTERFACE WITH CNA-2 “280 CH.” NODALIZATION 2009 RELAP5 International User’s Seminar - Park City, Utah -August 11,12,13, 2009 CFD R5-3D CNA-2 60 Ch. CROSS SECTIONS FUEL PIN ANALYSIS

15. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 15/40 Samples from SS internal validation  Neutron Flux distribution – comparison WIMS/PUMA & MCNP5/ORIGEN vs HELIOS-RELAP5-3D© WIMS- PUMA/HELIOS- RELAP5-3D© MCNP5- ORIGEN/HELIOS- RELAP5-3D©

16. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 16/40 Samples from Transient external validation R5-3D vs. R5-PARCS 2A LBLOCA w/o boron inj. R5-PARCS vs R5-3D 2A LBLOCA w/ boron inj. @ +0.6 secs. Good found agreement between fully independent models & codes

17. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 17/40 Sample Results: CL2 DEGB LBLOCA  Main application of 3D NK TH model was the LBLOCA studies (BDBA)  Derive the power history during the first ten seconds of the transients  “Long-term” NPP dynamics studied with a reduced model (0D NK- TH)  Assess the impact on the power surge of  Break Size  Break Position  Boron system availability  Break Opening Time  Boron Injection Delay Time  CL2 2A DEGB LBLOCA resulted to satisfy DBA acceptance criteria provided full emergency system availability

18. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 18/40 Sample Results: CL2 DEGB LBLOCA  3D and 1D power profiles for LBLOCA, CL2, BIT = 0.5 s

19. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 19/40 Sample Results: Spectrum of CR Ejection  3D NK TH simulations used also for the other transients studies  Chapter 15.4 (Reactivity Initiated Accident, or RIA ) & an ATWS  3D NK TH used as support calculation where NPP control system has a relevant action  In Spectrum of Rod Ejection Accident it constitute reference calculation  Spectrum of CR Ejection Accidents, (Ch. 15.4.7)  SS @ HFP performed, CR in critical condition  Ejection of a CR of G10 bank in 0.1 seconds  SCRAM @ 1.0 sec  3 Transients calculated (G10 bank, CR #2, #8, #14)  Comparison of core dynamics with independent 0D NK model (Siemens) NESTLE-RELAP5 vs RELAP-OD NK – comparison test

20. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 20/40 Sample Results: Spectrum of CR Ejection  Advantages of 3D NK TH  Axial power shape changes  Distinguish between different CR ejection cases  do not impose inserted reactivity “a priori” Total Power – Bank G10 CR Ejection Reactor Axial Power PCT Channel Axial Power

21. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 21/40 FSAR TRANSIENTS – SAMPLE RESULTS  CR Ejection Peak Cladding Temperatures locations  CR #2, Channel 504, level 9  CR #8, Channel 272, level 8  CR #14, Channel 420, level 8

22. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 22/40 Conclusive remarks  A sophisticated TH-3D NK RELAP5-3D model was developed for performing RIA-LBLOCA studies for Atucha-II NPP  Key features: 280 channels, 3D moderator tank, 3D NK model with oblique CRs, CFD-derived boundary conditions  Extensive RELAP5-3D© model qualification was performed by internal/external benchmarks  Comparison with fully independent codes and models confirmed the quality of the RELAP5-3D© modeling  Final Results being accepted by the Argentinean Safety Authority, ARN  constitute main RIA analyses of FSAR Chapter 15  First case of FSAR integrating BE-3D NK TH code results as the reference calculation

23. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 23/40 B) PREDICTABILITY OF TRANSIENTS INVOLVING SPATIAL VARIATION OF COOLANT PROPRIETIES IN DC AND LP

24. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 24/40 NEA/CSNI PKL-2 PROJECT (2008 – 2011)

25. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 25/40 Test G3.1 Main steam line break

26. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 26/40 Test G3.1 Main steam line break Questions:  HEX from primary to secondary side during MSLB and boil-off in affected SG  Influence on NC and RPV-inlet temperature in the loops  BIC for complementary experiments in the ROCOM test facility on mixing of cold and hot water in the RPV downcomer and in the lower plenum Main objectives:  Qualification of T/H code results against:  Heat transfer in SG and influence on flowrates in the intact and affected loops  PTS and recriticality aspects

27. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 27/40 ROCOM facility modeling  Downcomer: cylindrical 3D component  Number of radial nodes = 1  Number of azimuthal nodes = 40  Number of axial nodes = 5  Lower Plenum: three concentric 3D components  Core: 193 pipes  Boundary conditions: at inlet/outlet nozzles by means of time-dependent volumes and junction  Code resources  Number of Volumes = 3246  Number of Junctions = 5471  TEST 1  Represents the minimum temperature in loop1 during the overcooling phase of MSLB  TEST 2  Represents the ECC injection phase of MSLB Loop12-4 Temperature, [ o C]153236 Mass flowrate, [kg/s]5.7431.328 Loop1-2 34 Temperature, [ o C] 227 Mass flowrate, [kg/s]0.972.60.97 ECC mass flowrate, [kg/s]- 0.52 ECC temperature, [ o C] - 25

28. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 28/40 ROCOM facility modeling  TEST 1 DC EXPDC CALC CORE EXPCORE CALC  Temperature spreading over core inlet  EXP 5 K  CALC10 K  Sharp transition region in DC between hot and cold water in experiment well predicted by calculations  Exp. & Calc. both show nearly uniform temperature distribution at core inlet plane (strong mixing in LP) loop1 loop2  TEST 2 DC EXPDC CALC CORE EXPCORE CALC  Temperature spreading over core inlet  EXP 3 K  CALC2 K loop3 loop4

29. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 29/40 C) POST-TEST ANALYSIS OF LOBI TEST A1- 84 BY RELAP5/Mod3.3 and RELAP5-3D v2.4.2

30. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 30/40 Description of LOBI-MOD2 facility  LOBI-MOD2 facility simulates the geometrical and operating configuration of KONVOI PWR  It models the entire primary system and most of the secondary system  Electrical power  5.6MW  64 rods (direct heating), 8x8 square matrix  Kv  1:712 (1:1 in elevation)  2 RCS loops (4 in the prototype reactor)  INTACT, representing 3 loops  BROKEN loop, representing one loop  ECCS can be supplied by  High Pressure Injection System (HPIS)  Accumulator injection system (AIS)

31. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 31/40 Conditions of LOBI Test A1-84  The test A1-84 (1985) is a 10% hot leg break  HPIS injection in HL intact loop  ACCU inject in  intact loop HL & CL  broken loop CL ParameterA184 Breack size10% HL Heating power [MW]5.2 Mass Flow IL [kg/s]20.2 Mass Flow BL [kg/s]6.2 Pressure in upper plenum-PRZ [Mpa]15.8 T IL vessel outlet [°C]327 T IL vessel inlet [°C]294 T BL vessel outlet [°C]328 T BL vessel inlet [°C]291 T pressurizer [°C]346 HPIS actuation pressure [Mpa]11.7+35s* Accumulators actuation pressure [MPa]2.8* LPIS actuation pressure [Mpa]NO LPIS Feed water mass flow IL [kg/s]2.07 Feed water mass flow BL [kg/s]0.61 Pressure in steam dome IL [Mpa]6.54 Pressure in steam dome BL [Mpa]6.52 T SG inlet, IL, BL [°C]209 T SG outlet, IL, BL [°C]281 Pump seal water injection IL [kg/s]0.014 Pump seal water injection BL [kg/s]0.011 scram signal pressure [MPa]13.2+0.5s cool down rate [K/h]100 Recirculation ratio IL6.2 Recirculation ratio BL4.4

32. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 32/40 Sequence of main events  The SCRAM signal activates  the heating power trip signal  the secondary side cooldown signal  the closure of the feedwater valve.  The pump coastdown set point is at primary pressure 11MPa (+ 1s of delay)  The test ends when the primary pressure reaches 1MPa. MAIN EVENTSA1-84 Break0s Scram***1.0s HPIS trip signal enabled5.0s Start of coast down of primary coolant pumps* 7.0s HPIS injection initiated40.6s Primary loops pump stop102s Temperature excursion335s Accumulator injection initiated 347-350s Accumulator injection disabled 509-520s End of test**850s

33. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 33/40 Outline of the main parameter trends PRZ pressure Max cladding temp. (top level) SG pressure Intact Loop SG pressure broken loop

34. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 34/40 Outline of the main parameter trends ACCU LVL intact loop ACCU LVL broken loop Primary mass inventory HPIS mass flow rate

35. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 35/40 Conclusive remarks  Activity performed in collaboration with prof. F. Reventos (UPC), part of MS Thesis (C. Matteoli)  UNIPI procedure for code assessment applied by means of the standard procedure  Qualification at steady state level  “On transient” qualification  Resulting Time Sequence of Events (R-TSE)  Relevant Thermal-hydraulic Aspects (RTA) – Qualitative accuracy evaluation  Time Trends of Parameters  Results of application of FFTBM (Quantitative accuracy evaluation)

36. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 36/40 D) Forum & Network of System Thermal-Hydraulic Codes in Nuclear Reactor Safety (FONESYS)

37. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 37/40 Objectives The objectives of FONESYS are:  Create a common ground for discussing envisaged improvements in various areas of SYS-TH, promoting a cooperation aimed at the improvement of the TH- SYS Codes and their application in Licensing process and Safety Analysis;  Identify area of improvement and share experience on GUI, SYS-TH code coupling with other numerical tools, such as 3-D neutron kinetic, fuel pin mechanics, CFD, etc.;  Share experience on code inadequacies and cooperate in identifying experiments and/or code to code benchmarks for resolving the deficiencies;  Share user experience on code scalability, applicability, and uncertainty studies;  Establish acceptable and recognized procedures and thresholds for V&V;  Maintain and improve user expertise and documented user guidelines for applying the code. The FONESYS strategy and the activities to be decided by top-level experts within a framework (e.g. scientific working group) consistent with standards of international Institutions

38. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 38/40  First WS was held in Pisa (13-14 May 2010)  General consensus of the participants about FONESYS 1st FONESYS Workshop #COUNTRYINSTITUTIONNAMECODE 1 -- Nusret AKSAN -- 2 FINLAND VTT Markku HANNINEN APROS 3 FRANCE AREVA-NP Jean-Luc Gandrille CATHARE2 / CATHARE3 / S-RELAP5 / MANTA 4 FRANCE CEA Dominique BESTION CATHARE2 / CATHARE3 5 FRANCE CEA Philippe EMONOT CATHARE2 / CATHARE3 6 GERMANY GRS Horst GLAESER ATHLET 7 ITALY GRNSPG/UNIPI Francesco D’AURIA -- 8 ITALY GRNSPG/UNIPI Alessandro DEL NEVO -- 9 REP. OF KOREA KAERI Kyung D. KIM SPACE 10 REP. OF KOREA En 2 t Suk K. SIM MARS 11 RUSSIAN FEDERATION GIDROPRESS Michael A. BYKOV KORSAR-GP / TECH-M 12 USA INL (USA) Phil SHARPE RELAP5-3D / RELAP 7

39. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 39/40 Next steps  31 M AY 2010. GRNSPG/UNIPI will provide to the participants and the institutions which expressed interest in FONESYS with the draft Minutes of the meeting and a new revision of the Statute. (Completed)  30 J UNE 2010. The 1 st WS participants will provide comments on the Minutes and on the technical aspects of the Statute. (Completed)  5 J ULY 2010. GRNSPG/UNIPI will circulate the final draft of the minutes and of the Statute. (Completed)  30 S EPTEMBER 2010. Comments on the legal aspects of the Statute will be collected from the Signatories Institutions.  30 N OVEMBER 2010. Statute signed and establishment of FONESYS.  24-27 J ANUARY 2011. 2 nd FONESYS Workshop hosted at CEA Headquarters in Grenoble, France

40. Gruppo Ricerca Nucleare San Piero a Grado Any reproduction, alteration, transmission to any third party or publication in whole or in part of this document and/or its content is prohibited unless the University of Pisa – San Piero a Grado Nuclear Research Group has provided its prior and written consent. This document and any information it contains shall not be used for any other purpose than the one for which they were provided. Legal action may be taken against any infringer and/or any person breaching the aforementioned obligations. Use of RELAP5-3D at GRNSPG/UNIPI 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, 2010 40/40 Conclusive remarks  The “SYS TH code development & application” constitutes a technology  FONESYS is proposed to strengthen this technology  There is not such a FORUM at the international level  An effort could be made to connect FONESYS with IAEA, OECD/NEA/CSNI, or EC Programs (FONESYS might not disappear in this case)  Draft Statute has been issued and will be finalized by end of Sept. for signature (30 Nov. 2010)  About 10 institutions expected to join the initiative  Website, currently under construction ( http://www.nrgspg.ing.unipi.it/FONESYS ) http://www.nrgspg.ing.unipi.it/FONESYS