Thermal Hydraulic Studies for PFBR using PHOENICS

1. Thermal Hydraulic Studies for PFBR using PHOENICS U. PARTHA SARATHY Indira Gandhi Centre for Atomic Research Kalpakkam May 3-5 th 2004

2. PROTOTYPE FAST BREEDER REACTOR(PFBR) • Power - 500 MWe, 1250 MWth • Fuel – Mixture of UO2 (79 %) and PuO2 (21 %) • Coolant – Sodium (liquid metal) in Pry and Secy Circuits – Water in Tertiary Circuit • High Temperatures • High Velocities • Problems – • High temperatures leading to creep, fatigue damage • Flow induced vibrations • Thermal striping • Gas entrainment

3. PFBR Primary Circuit Inner Vessel PUMP IHX Hot Pool Nuclear heat CORE Cold Pool Grid Plate

4. Schematic PFBR Flow Sheet • Primary Circuit • Secondary Circuit • Steam/Water circuit

5. HYDRAULIC ANALYSIS OFGRID PLATE- e Page HYDRAULIC ANALYSIS OF GRID PLATE

6. HYDRAULIC ANALYSIS OF GRID PLATE • Consists of 1758 sleeves • Receives flow from four pipes • Distributes flow to various subassemblies Objectives • Flow and pressure distribution • Pressure drop in GP • Velocity over sleeves

7. HYDRAULIC ANALYSIS OF GRID PLATE Modelling • 2-D model in cylindrical co-ordinates (r- θ) • Sleeves modeled through porosity in radial and circumferential directions (Porous body formulation) • Inlet as Velocity BC • Outlets as mass sinks • Pressure drop due to sleeves modeled through Zukauskas correlation • Addition of resistance terms in the momentum equation using ‘ground’ subroutine. • K-E Turbulence model Schematic of Grid Plate

8. Results of Grid Plate Analysis Results • Predicted ΔP is 4.6 m of sodium • Similar to that extrapolated from 1:3 scale air experiments. • Pressure contours are concentric – uniform flow through fuel SA • Maximum cross flow velocity is 8.5 m/s Flow Distribution in Grid Plate

9. Thermal Analysis of Hot and Cold Pools- Title Page Thermal Analysis of Hot and Cold Pools

10. Thermal Analysis of Hot and Cold Pools Objectives • Inner Vessel temperature distribution • Stratification In sodium pools • Hot pool free surface velocity & temperature CORE

11. CFD Model and Boundary Conditions Modelling • 2-D model in cylindrical co-ordinates (r-z) • Core is modeled as a block • Porous body approximation for immersed components – IHX, Pump • Mass sink at IHX & PUMP inlets • Velocity BC at IHX and Core outlets • Conjugate thermal hydraulic analysis of hot & cold pools including IV • K-E Turbulence model

12. Flow Distribution in Hot and Cold Pools • Good mixing in hot and cold pools

13. Temperature Distribution in Inner Vessel Hot Pool Free Surface Temperature Distribution Results • Tmax in IV is 534 OC • ΔT across thickness is 64 K • Max hot pool free surface temperature is 572 OC

14. Flow Distribution in SG Inlet Plenum- Title Page FLOW DISTRIBUTION IN STEAM GENERATOR INLET PLENUM

15. Objective:To identify flow distribution devices and reduce maximum radial velocity over tubes from FIV considerations. Schematic of PFBR SG 3/5 scale model of SG Inlet Plenum

16. Modelling • 3/5 scale model • 3-D cylindrical coordinates • 180 O symmetric model • K-E turbulence model • Inlet as velocity BC 3/5 scale model of SG Inlet Plenum

17. Flow distribution in Inlet window region at 1430 mm from inlet Flow distribution in SG Inlet Plenum – Basic Configuration Radial Velocity Profile along the Window with Basic Configuration =0 1430 mm

18. Axial Velocity in the Annulus at 575 mm – Basic Configuration

19. Porous plate used as a Flow distribution devices 3/5 scale model of SG Inlet plenum with Flow distribution devices Porous plate • Porous body formulation for porous plate and porous shell

20. Axial Velocity in the Annulus at 575 mm from Inlet with Different Porous Plates

22. Flow distribution in Inlet window region at 1430 mm from inlet (= 0) 3/5 scale model of SG Inlet plenum with Flow distribution devices 1430 mm Flow distribution in SG Inlet plenum with Flow distribution devices

24. RESULTS • Combination of graded porous plate and porous shell render as uniform flow both axially and circumferentially. • The distributions of porosity in the plate and shell have been identified. • Maximum radial velocity is 0.75 m/s (average is 0.45 m/s) whereas the same is 3 m/s in basic configuration

25. Inter-Wrapper flow Studies-Title Page Inter-Wrapper flow Studies

26. Inter-Wrapper flow Studies - Steady State Inter Wrapper flow Sub-Assembly Steel hexagonal Wrapper Objectives • Effect of IWF on SA clad hotspot • Flow distribution in IWS • To develop a model for studying various design basis events which will give detailed temperature distribution in hot and cold pools

27. Sodium Flow in Primary Circuit DHX CORE

28. CFD model for IWS and Hot and Cold Pools Modeling • 2-D cylindrical coordinates (r-z) • Inlets as velocity BC • Outlets as mass sink • Porous body formulation for core and other immersed structures • Coupling with 1-D model for neutronics, heat transfer calculations in core, IHX, DHX etc.

29. Schematic of the SA Computational Model Schematic of Fuel SA

30. Exchange of Results between 1-D and 2-D PHOENICS Models for Boundary Conditions

31. 1-D 2-D Flow Chart for Coupled 1D Code – PHOENICS code Calculations

32. m/s m/s Temperature Contours in Hot and Cold pools Flow Distribution in Hot and Cold pools

33. 425 415 555 405 395 OC m/s m/s Temperature and Velocity Distribution in Inter-Wrapper Space

34. Results • SSA outlet temperature increases by about 2 K • Total heat transferred to IWS is 370 kW • Axial temperature gradient of hot/cold interface is 150 K/m Temperature Distribution in IV Temperature Distribution in MV

35. Inter-Wrapper flow Studies - Transient Analysis (under progress) • Station blackout incident • All pumps trip • Primary circuit flow coasts down • Secondary circuits not available • Reactor trips only at 2.5 s • Temperature inside SA goes up • Good amount of heat is taken away by the IWF

36. Results Transient Evolution of Temperatures in Hot and Cold Pools

37. Thank You