Advanced Methods for BWR Transient and Stability Analysis. F.Wehle,S.Opel,R.Velten Framatome ANP GmbH P.O. BOX Erlangen Germany

Transcription

1 Advanced Methods for BWR Transient and Stability Analysis F.Wehle,S.Opel,R.Velten Framatome ANP GmbH P.O. BOX Erlangen Germany

2 Advanced Methods for BWR Transient and Stability Analysis > Background and Overview of Framatome ANP s BWR Methodology > Application of the Advanced Transient Analysis > OECD/NRC Boiling Water Reactor Turbine Trip Benchmark > KATHY-Loop Stability Measurements 2

3 Challenges for Design and Operation of Modern BWR Fuel Assemblies and Cores >Customer Optimal fuel utilization for safe, reliable and highly flexible reactor operation > Framatome ANP Advanced fuel design Modern core loading concepts High operational flexibility > Design Tools Comprehensive physical modelling Qualified single codes and code systems 3

4 Overview of Framatome ANP s BWR Methodology MCNP Monte-Carlo CASMO-4 Neutronics Lattice THRP 2-Phase Thermal Hydraulics RINGS Subchannel Analysis CARO Thermo- Mechanical Fuel Assembly MICROBURN-B2 Core Simulator PRIMO-B Loading Pattern Optimization 3D Core Steady State POWERPLEX/FNR-K Online Core Monitoring RAMONA-3 3D-Space-Time Kinetics COBRA-TF Transient Subchannel Thermal Hydraulics Core Transients STAIF Stability in Frequency Domain VERENA(RELCOS)/COSBWR/FRANCESCA Plant Analysis Plant Transients 4

5 Overview of Framatome ANP s BWR Methodology MCNP Monte-Carlo CASMO-4 Neutronics Lattice THRP 2-Phase Thermal Hydraulics RINGS Subchannel Analysis CARO Thermo- Mechanical Fuel Assembly MICROBURN-B2 Core Simulator PRIMO-B Loading Pattern Optimization 3D Core Steady State POWERPLEX/FNR-K Online Core Monitoring RAMONA-5 3D-Space-Time Kinetics COBRA-TF Transient Subchannel Thermal Hydraulics Core Transients STAIF Stability in Frequency Domain S-RELAP/RAMONA-5 Best Estimate Plant Analysis, 3D Core Representation Plant Transients 5

6 3D Transient Code RAMONA 3 - Neutronics: 1 1 / 2 -Group Diffusion Model - Thermal Hydraulics: 4-Equation Drift Flux Model - BWR System Components: Pumps, Separators, Steam Line, Reactor Protection System Validation: - Peach Bottom Turbine Trip - Spert Reactivity Insertion Experiments - Ringhals Stability Benchmark - Validation against Plant Stability Measurements and Operational Transients - GUN C Cycle 12 and 13 (global and regional instabilities) 6

7 RAMONA Hydraulic Model Components Steam Dome MSIV Turbine-Valve Steam Separator S/R-Valves Bypass Feedwater Stand Pipes Downcomer 1 Upper Plenum Core Parallel Channels Bypass Downcomer 2 Lower Plenum 2 Lower Plenum 1 7

8 BOC - Core Averaged Axial Power 8

9 BOC Radial Power Factors 9

10 EOC - Core Averaged Axial Power 10

11 Comparison of the Fission Powers 11

12 Limiting Case Radial Factor of Hot & Cold Channel 12

13 Limiting Case MCPR of the Hot Channel 13

14 BWR Turbine Trip Benchmark > Exercise 1 Power vs. Time plant system simulation with fixed axial power profile table is given => thermal-hydraulic system response > Exercise 2 Coupled 3D and/or 1D kinetics/core thermal-hydraulic BC model > Exercise 3 Hot zero power. Hot full power and transient using the provided core BC. Best-estimate coupled 3D core/thermal-hydraulic system modeling 14

15 Plant Code S-RELAP5 > S-RELAP5 is based on RELAP5/MOD2 and incorporates elements of RELAP5/MOD3 and RELAP5-3D > Special Features: - 2-dimensional component model - improved formulations for energy and momentum equations - modified heat transfer and hydrodynamic constitutive models - special fuel modeling - suited for best-estimate licensing methods 15

16 Exercise 3: Fission Rate 16

17 Exercise 3: Dome Pressure 17

18 Advanced Transient Methodology - Summary > Advanced method reduces OLMCPR by app compared to the conservative 1D methodology > The method allows more operational flexibility. > The advanced transient method has already been approved by TÜV NORD. > Based on the OECD/NRC BWR Turbine Trip Benchmark the transient applicability of the code system S-RELAP5/RAMONA5 has been proven successfully. 18

19 Feedback Mechanisms of BWR Stability Exit Flow Rate Neutronics Feedback Heat Flux Thermal Hydraulics δ pii Rod Temperature (Core and External Loop) δ pii =- δ pi δα Void Fraction δα Thermal Power Neutron Flux δ pi Reactivity Void Reactivity Coefficient Inlet Flow Rate 19

20 Most Sensitive Stability Parameters Fuel Assembly Parameters Effect on Stability Flow Area + Hydraulic Diameter + Loss Coefficient LTP + Loss Coefficient UTP - Loss Coefficient Spacer - Fuel Time Constant + Void Coefficient + Operating Parameters Axial Peaking Factor - Radial Peaking Factor - Reactor Power - Reactor Mass Flow + Inlet Subcooling - 20

21 Multifunction Thermal Hydraulic Test Loop KATHY Direct contact condenser Pressurizer Water steam seperator To conenser High pressure coolers 5MW Circulation pump 10 MW Void Fraction Measurement Device Feed water Pel. 9,5MW PWR Test Vessel p 185 bar P el. 15 MW Control valve BWR Test Vessel p 110 bar Control valve Downcomer Natural Circulation Loop 21

22 KATHY Stability Test Loop Steam Separator + Expansion Chamber Riser ζ exit Downcomer ζ spacer ζ spacer ζ spacer ζ spacer ζ spacer Test Section ζ spacer ζ spacer ζ inlet Axial Power Profile 22

23 Steady State Flow Rate Flow Rate (kg/s) ζ exit =1.5 DR = 1 CPR = 1 DR = 1 CPR = 1 ζ exit =7.5 Inlet Subcooling: 124 kj/kg Inlet Subcooling: 144 kj/kg Bundle Power (MW) 23

24 KATHY Stability Test Data DR:

25 Transient Dryout During Instability 25

26 Comparison of STAIF Results with Karlstein Stability Tests 26

27 Transient Dryout Tests Simulating Typical Limiting Transients System data during turbine trip Standardized values Power System pressure Massflow Time Temperature Rod temperature response during turbine trip Time

28 Conclusions > Safe, reliable, and flexible BWR operation requires fuel assembly and core designs optimized for all reactor operating conditions. > The comprehensive methodology of Framatome ANP meets the challenges to analyze and predict steady-state and transient BWR operation. - The methodology is based on state-of-the-art physical modeling. - It has been thoroughly qualified, using a large database including recent, sophisticated, and highly accurate measurements. - The code system is further developed and qualified continuously. 28