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 RELAP5 International User’s Seminar September 20-23, 2010 West Yellowstone, Montana September 20-23, 2010 OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): comparisons among RELAP5-3D©v2.4.2, RELAP5/Mod3.3, TRACEv1 and CATHARE codes TitleOECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): comparisons among RELAP5-3D©v2.4.2, RELAP5/Mod3.3, TRACEv1 and CATHARE codes AuthorsF. Fiori, A. Petruzzi, A. Kovtonyuk, A. Del Nevo, C. Parisi, F. D'Auria Revision/Date

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 CONTENTS 1.Objective 2.PSBT benchmark 3.Thermal Hydraulics Modeling (subchannel)  Steady-state sub-channel results 4.Thermal Hydraulics Modeling (bundle)  Steady-state bundle results  Bundle transient results 5.Conclusion

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 OBJECTIVE  Assessment of TRACE5.0, RELAP5/Mod3.3, RELAP5-3D© and CATHARE2 (and 3) capabilities against PSBT data  Code-to-code comparison

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 CODE CAPABILITIES  The hydrodynamic model is a transient, two-fluid, 6 equations plus noncondensable  The two-fluid equations of motions are formulated in terms of volume and time- averaged parameters of the flow.  Phenomena such as heat transfer are formulated in term of bulk properties using empirical transfer coefficient formulations.  TRACE 5.0 code includes a 3D component (named vessel in the following of this presentation) and a CHANNEL component used to simulate BWR fuel bundle.  RELAP5-3D© code includes a multi-dimensional component which defines a one-, two-, o three-dimensional array of volumes and the internal junctions connecting the volumes.  The system model is solved numerically using a semi-implicit finite-difference technique  CATHARE2 is a fully implicit, two-fluid, 6 equations code. A non-linear system is solved using the NEWTON-RAPHTON iterative method.  CATHARE3 (planned) is based on CATHARE2, is under development and has the following advanced physical modeling three fields model, turbulence model, interfacial area transport equation

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PSBT BENCHMARK Phase 1 – Void Distribution Benchmark  Exercise 1 – Steady-state sub-channel benchmark, which can be used to improve the current models of void generation and void distribution within a subchannel.  Exercise 2 – Steady-state bundle benchmark, which can be applied to subchannel and system thermal-hydraulic codes.  Exercise 3 – Transient benchmark, to determines the capability of current codes to predict void generation during transient  Exercise 4 – Pressure drop benchmark, code-to-code comparison Phase 2 – DNB Benchmark  Exercise 1 – Steady-state fluid temperature benchmark  Exercise 2 – Steady-state DNB benchmark  Exercise 3 – Transient benchmark  Exercise 4 – Transient DNB benchmark EXERCISE

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PSBT BENCHMARK: sub-channel tests  Sub-channel S1  43 tests  Sub-channel S2  43 tests  Sub-channel S3  20 tests  Sub-channel S4  20 tests

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PSBT BENCHMARK BUNDLE TEST FACILITY BUNDLE B5: radial power distribution Heater rod cross section

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PSBT BENCHMARK BUNDLE TEST FACILITY, operating conditions BUNDLE TEST FACILITY, transient parameters

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 THERMAL HYDRAULICS MODELING SUB CHANNEL 1/2 Heated lenght: 1.555m

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 THERMAL HYDRAULICS MODELING SUB CHANNEL 2/2 Heater  Cylindrical heater  modeled by 4 slabs (following the approach used by UNIPI for the BFBT Benchmark)  The approach allows to preserve:  External Heat Exchange surface  Heat Capacity (Total Volume)

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 1/7 S1: TYPICAL SUBCHANNEL, 43 tests

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-1

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-1  Sensitivities on  Nodalization effect (axial nodes)  Effect of BIC (axial nodes)  Pressure drop

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 2/7 S2: CENTRAL SUBCHANNEL, 43 tests

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-2  Sensitivities on  Nodalization effect (axial nodes)  Effect of BIC (axial nodes)  Pressure drop

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 3/7 S3: SIDE SUBCHANNEL, 20 tests

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-3

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-3  Sensitivities on  Nodalization effect (axial nodes)  Effect of BIC (axial nodes)  Pressure drop

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 4/7 S4: CORNER SUBCHANNEL, 20 tests

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 PRELIMINARY RESULTS: sub-channel TS-3

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 5/7 OVERALL CODES PERFORMANCES 1/2 S1 S2 CATHARE2  Abs Er = St. Dev. = CATHARE2  Abs Er = St. Dev. = 0.051

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 6/7 OVERALL CODES PERFORMANCES 2/2 S3 S4 CATHARE2  Abs Er = St. Dev. = CATHARE2  Abs Er = St. Dev. = 0.033

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 SUB CHANNEL RESULTS 7/7  US CODES SUMMARY:  The results of the US codes are very close one to another and are in good agreement with the experimental results.  For all the test sections the TRACE5.0 results have a smaller standard deviation.  All the three codes show better agreement with the experimental data for the S4 test section.  CATHARE SUMMARY:  Tendency to underestimate the experimental results  Errors in the order of magnitude of 5% (void fraction)  Error increases with the void fraction and the pressure  CATHARE-3 calculations are still in progress

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 THERMAL HYDRAULICS MODELING BUNDLE 1/2 TRACE 5.0, RELAP5/mod3.3 and RELAP5-3D©:  36 pipes connected with cross flow junctions  22 axial cells (16 cells for the heated section)  Heater rods modeled with four heat structures  Flow channel walls are modeled (external insulated)  No K-factors adopted for cross flow junctions The RELAP models have been modified: the cross flow junction are not used in the following result since in some connections a cross mass flow comparable, or even higher, than the axial mass flow was predicted. Moreover in certain subchannel a negative mass flow was calculated

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 THERMAL HYDRAULICS MODELING BUNDLE 2/2: vessel component A second TRACE 5.0 model has been set-up using the 3D VESSEL component, (using Cartesian Coordinate)  22 axial level (16 cells for the heated section)  6 x 6 arrays  1 lower plenum  1 upper plenum  Heater rods modeled with four heat structures  Flow channel walls are modeled (external insulated)  No K-factors adopted for cross flow junctions

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 THERMAL HYDRAULICS MODELING Heater BUNDLE 3/3: heater rod  Cylindrical heater  modeled by 4 slabs (following the approach used by UNIPI for the BFBT Benchmark)  The approach allows to preserve:  External Heat Exchange surface  Heat Capacity (Total Volume)

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 1/8 BUNDLE B5: uniform axial power shape NO CROSS JUNCTIONS MODELED IN RELAP

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 2/8 BUNDLE B5: uniform axial power shape NO CROSS JUNCTIONS MODELED IN RELAP

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 3/8 BUNDLE B5: uniform axial power shape NO CROSS JUNCTIONS MODELED IN RELAP

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 4/8  Avg. Error < all elevations  Improvement with 3-D model (?) BUNDLE B5: uniform axial power shape: CATHARE-2  CATHARE-2 preliminary results  1-D model applied (Avg. on bundle section)  Only benchmark cases

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 5/8  Avg. on bundle section  Sensitivity analyses appear less dispersed than in case of sub- channel BUNDLE B5: uniform axial power shape: CATHARE2

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 6/8 BUNDLE B5: uniform axial power shape UPPER LEVEL NO CROSS JUNCTIONS MODELED IN RELAP

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 STEADY STATE BUNDLE RESULTS 8/8 OVERALL CODES PERFORMANCE RELAP5-3D© crashes in 10 cases CATHARE2 *  * preliminary 1D results

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 TRANSIENT BUNDLE RESULTS 1/2 BUNDLE B5: Power increase transient

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 TRANSIENT BUNDLE RESULTS 2/2 BUNDLE B5: Flow reduction transient

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. OECD/NRC Benchmark based on NUPEC PWR Subchannel and Bundle Tests (PSBT): Codes Results Analyses 2010 RELAP5 International User’s Seminar West Yellowstone, Montana – September 20-23, /37 CONCLUSIONS BUNDLE CALCULATION RESULTS  For all the four sets of calculation the TRACE5.0 results are closer to the experimental data than the other two codes.  Results of RELAP5/Mod3.3 and RELAP5-3D© models are in well agreement with the TRACE5.0 results until a value of around 0.5 of the void fraction, above this the results over-predict both the experimental and TRACE5.0 results.  The TRACE5.0 code with the VESSEL COMPONENT is the closest to the experimental data, both in steady state and transient calculations.  A RELAP5-3D© model using MULTI-D components will be set up and the results compared with the TRACE5.0, VESSEL component performances.  CATHARE-2 results are based on a simplified 1D model. Nevertheless, the results are acceptable and comparable with the other codes. General underestimation to be confirmed by the 3D model, which is more representative for the comparisons with the experimental data