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Void Fraction Prediction by the French Thermal-Hydraulic Code CATHARE 2 in single channels of Light Water Reactors

Void Fraction Prediction by the French Thermal-Hydraulic Code CATHARE 2 in single channels of Light Water Reactors. Luben Sabotinov, IRSN-France. BgNS International Conference “ NUCLEAR POWER FOR THE PEOPLE” 26 – 29 September 2010, Nesebar , Bulgaria. CONTENTS ► Context of the analysis

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Void Fraction Prediction by the French Thermal-Hydraulic Code CATHARE 2 in single channels of Light Water Reactors

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  1. Void Fraction Prediction by the French Thermal-Hydraulic Code CATHARE 2 in single channels of Light Water Reactors Luben Sabotinov, IRSN-France BgNS International Conference “NUCLEAR POWER FOR THE PEOPLE” 26 – 29 September 2010, Nesebar, Bulgaria

  2. CONTENTS • ► Context of the analysis • ► Test subchannels of PSBT • ► CATHARE modeling of the subchannels • ► Steady state subchannel results • ► Conclusions and perspectives

  3. ► Context of the analysis • Code strategy of qualification is based on: • Verification procedure • Validation on separate effect tests • Validation on integral tests. • IRSN participates in NUPEC OECD/NRC PWR Subchannel and Bundle Tests (PSBT) Benchmark, which is an appropriate exercise for CATHARE qualification, based on void fraction and critical heat flux predictions on the level of full-scale fuel assembly with a typical reactor power and fluid conditions.

  4. The OECD/NRC PSBT benchmark activities are performed as an International project with the coordination and sponsoring organisations: • PSU (Pennsylvania State University) • OECD/NEA • NRC-USA • METI (Ministry of Economy, Trade, and Industry, Japan) • NUPEC (Nuclear Power Engineering Corporation, Japan) • JNES (Japan Nuclear Energy Safety organization)

  5. The First PSBT meeting took place 12-13 of April 2010 in Pisa, hosted by the Research Group of Pisa University (UNIPI) The workshop was attended by 48 participants from 28 organizations in 13 countries (Canada, France, Germany, Hungary, Italy, Japan, Korea, Russia, Spain, Switzerland, Sweden, United Kingdom, USA). The interest in this benchmark is very large as shown by the participation from research institutions, universities and industry with system thermal-hydraulic codes, sub-channel codes and CFD codes: • CATHARE2, CATHARE3, RELAP5.33, RELAP5 3D, TRACE5.0, • FLICA-OVAP, F-COBRA-TF, ASSERT-PV, MATRA, SUBCHANFLOW, THYC-COEUR • CFX, NEPTUNE-CFD, STAR-CD

  6. ►Two parts (phases) of PSBT Benchmark The NUPEC PSBT benchmark consists of two parts (phases), each part considering different exercises: ►Phase I – Void Distribution Benchmark ►Phase II – DNB Benchmark The CATHARE 2 calculations have been carried out for Void Distribution Benchmark, Exercise 1: Steady-state Single Subchannel Benchmark

  7. Test Section for Subchannel Void Distribution Measurement

  8. Four single subchannels for void fraction tests: S1, S2, S3 and S4

  9. Fig. 4 Cross Sectional View of Subchannel Test Assembly

  10. CATHARE modeling and results • Single subchannels: • The subchannels S1, S2, S3, and S4 are modeled in CATHARE with axial elements, inlet and outletboundary conditions and connected with junctions. The axial element (1.555m) is of the type tube channel geometry with 24 axial segments, which correspond to the axial meshes of the power distribution if a cosine profile has to be used. • Parametric analysis is performed for S1 also with RODBUNDL option. • Inlet boundary conditions: • BC3A (for steady void distribution calculations: Tin, Hvsat, ALFA, Vl, Vg) can be used. • BC5YY (for transient void distribution- imposed functions:TL,TG,ALFA,GAMMA,Qt) • Outlet boundary conditions:BC5A (outlet pressure P)

  11. CATHARE fuel model In CATHARE the heat structures (fuel simulators) are represented also with 24 axial segments as the hydraulic channel. In radial direction the fuel rod is divided in 2 parts: heater and insulator, where the volumetric power is calculated over the annular volume, based on the external and internal heater diameter respectively, Dext=9.5 mm and Dint=7.8 mm Heater Rod Structure for Subchannel Test Assembly

  12. CATHARE subchannel void fraction results (S1, S2, S3, S4) 42 cases calculated Test subchannel S1, Central (Typical) S1T1- tube option S1B1- rod bundle option

  13. S1, Run No 1.4312 (P= 100.2kg/cm2, MF=5.106 kg/m2.h, Pow=79.8kW, Tin=248.9°C) Void fraction

  14. S1, Run No 1.4312 (P= 100.2 kg/cm2, MF=5.106 kg/m2.h, Pow=79.8kW, Tin=248.9°C) Density

  15. S1, Run No 1.4312 (P= 100.2 kg/cm2, MF=5.106 kg/m2.h, Pow=79.8kW, Tin=248.9°C) Liquid temperature Velocity

  16. CATHARE results, Test subchannel S2, Central (Thimble)

  17. CATHARE results, Test subchannel S3, Side

  18. CATHARE results, Test subchannel S4, Corner

  19. Conclusions and perspectives ►In 4 types of subchannel tests the void fraction is well predicted by CATHARE 2 code ► The impact of the operational parameters (pressure, flow rate, power, inlet subcooling) on void fraction distribution needs further analysis ► The tests with subchannel steady state void distribution of Phase I could be used for further validation of the code ► CATHARE 2,3 calculations of the bundle benchmarks (steady state and transient) are foreseen (1D et 3D) ► Comparison with CFD calculations

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