Voorblad presentatie

Status and Future Challenges of CFD

for Liquid Metal Cooled Reactors

IAEA Fast Reactor Conference 2013

Paris, France

5 March 2013

Ferry Roelofs

[email protected]

V.R. Gopala

K. Van Tichelen

X. Cheng

E. Merzari

W.D. Pointer

mailto:[email protected]

2 Paris • 5 March 2013

Contents

• Introduction

• Computational Fluid Dynamics

• Thermal-Hydraulics Challenges in Design and Safety

• Liquid Metal Turbulence

• Core Thermal Hydraulics

• Pool Thermal Hydraulics

• System Dynamics

• Summary

• Acknowledgement


Introduction Background

• Nuclear power plays and probably will play

important role in energy production

• Large role is attributed world-wide to fast

reactors

• Thermal-hydraulics is considered as key

issue

– Overview by Denis Tenchine in NE&D (2010)

– Overview by K. Velusamy (2010)

– Many subjects involve application of CFD


Computational Fluid Dynamics

Computational Fluid Dynamics

Paris • 5 March 2013

approximation

ph

ys

ics

co

mp

ute

r p

ow

er

DNS

LES

Hybrid

RANS/LES

(U)RANS

calculation

DNS LES Hybrid (U)RANS

System Thermal

Hydraulics

STH


Thermal-Hydraulics Challenges in

Nuclear Design and Safety

1

2 3

4 3

TH Challenges in Design and Safety


1

2

3

4

Core

Reactor Vessel

Heat Transfer System

Heat Transport System

1

TH Challenges in Design and Safety Core


1 Core

Levels:

- Complete Core

- Fuel Assembly

- Subchannel

- Molten Core

2

TH Challenges in Design and Safety Reactor Vessel / Pool


2 Reactor Vessel

- Core outlet region

- Temperature stratification &

fluctuations

- Gas entrainment

- Fission product transport

- Forced-natural convection

3 3

TH Challenges in Design and Safety Heat Transfer System


3 Heat Transfer System

- Efficiency

- Integrity

- Correlations

4

TH Challenges in Design and Safety Heat Transport System


4 Heat Transport System

- 3D effects

- Coupling STH-CFD


Liquid Metal Thermal-hydraulics

Liquid Metal Thermal-Hydraulics Heat transfer for low Prandtl number fluids


• Issue with Low Prandtl number fluids

– Existing (U)RANS engineering turbulence

models all use Reynolds analogy for

coupling temperature and velocity fields

– Not valid for fluids with low Prandtl

numbers (e.g. liquid metals)

source: R. Stieglitz (KIT)

Viscous boundary layer

Thermal boundary layer

Ratio thermal/viscous

Reynolds analogy th=

Liquid Metal Thermal-Hydraulics Heat transfer for low Prandtl number fluids


Velocity

Temperature (Pr = 1) Temperature (Pr = 0.01)

Field Scales Boundary

Layer

Velocity Small Thin

Temperature (Pr = 1) Small Thin

Temperature (Pr = 0.01) Large Thick

Liquid Metal Thermal-Hydraulics Improvement of (RANS) models


• Implemented in cooperation between CD-adapco, NRG and model developer

Sasa Kenjeres (TU Delft) in STAR-CCM+ β-version

• Challenge: Derive a model for use in all flow regimes simultaneously

2

3210 i

u

j

ij

u

j

ji

uu

i gCx

UuC

x

TuuCCu

AHFM: Kenjeres &

Hanjalic (2005)

Flow

Regime Gr(Pr, Re)

(velocity) Heat transfer

Existing

Models

AHFM

Kenjeres

2000

AHFM

Kenjeres

2005

Natural Low Conduction &

Buoyancy -

+ (air)

- (LM)

+ (air)

+ (LM)

Mixed Intermediate Mixed - - +

Forced High Convection o/+ - +

stability

Careful selection

of model constants


Core Thermal-hydraulics

Core Thermal-Hydraulics Subchannel


• 7 pin rod bundle – Code independence (STAR-CCM+ vs. OpenFOAM)

– Application of various RANS turbulence models confirms negligible influence

• 19 pin rod bundle – Grid independence (1M vs 5M vs 9M)

• Validation (Challenge) – JAEA experiments (large uncertainties → limited

validation)

– ANL reference 7 pin LES benchmark (ANL-SCK-NRG cooperation starting 2013)

– NRG reference 1 pin LES (under preparation)

– Experiments in NACIE and KALLA loops (2013-2014)

7 pin bundle LES (ANL)

Single pin LES preparation (NRG)

19 pin RANS (NRG)

Core Thermal-Hydraulics Fuel Assembly

• Numerical evaluation of performance of

spacer designs

– Pressure drop

– Clad temperatures

– Local velocities

– Cross flow


ALFRED FA (SRS)

Evaluation of spacer performance (NRG)


• LES reference data (ANL)

– 7 Pin Bundle

– 19 Pin Bundle

– 37 Pin Bundle

– 217 Pin Bundle

• Validation of RANS and low

resolution approaches

– Pressure drop

• Improvement of correlations

• Extending applicability range of

correlations

– Velocity and it’s fluctuations


217 pin sodium bundle LES (ANL)



Approach Traditional CFD LRGR CFD

Mesh

Solve All (Flow, bulk turbulence,

boundary layers,

secondary flows)

Main flow

characteristicts

Bulk turbulence

Sub Grid Model To consider

Core Thermal-Hydraulics Complete Core


Complete geometry

Identify representative

block within complete

geometry

Section of geometry

Setup of numerical grid for

representative block

Detailed CFD-simulation

of representative block

Extraction of CG-Forces

employing CFD results

Complete geometry

Setup coarse mesh for

complete geometry

Simulation of complete

geometry

employing CGCFD

Parameterization

of CG-Forces


Pool Thermal-hydraulics

Pool Thermal-Hydraulics Fundamental Validation

• Triple Jet (Nam & Kim, 2004)

– LES & RANS

• Double Jet: MAX facility (ANL)

– Design support by LES

– Validate LES and RANS with

experimental results

23

LES of Triple parallel jet

experiments by Nam & Kim (2004)

MAX facility and design support (ANL)

Pool Thermal-Hydraulics Integral Simulation


Democritos Water Mock-up

(VKI)

MYRRHA Design

(SCK)

ESCAPE LBE Mock-up

(SCK) Scaling simulations

Full scale – velocity scale – Froude scale

• Simulation of integral pool system

– Challenge: Validation with experimental campaign (water and

liquid metal)

Pool Thermal-Hydraulics Gas Entrainment

• Determination of flow patterns in SFR upper

plenum to analyse gas entrainment risk

• From URANS to LES modeling approaches

• From single phase to multiphase

• Modeling core outlet and large components


Multiphase LES in TRIO-U (Tenchine, 2010)

URANS (NRG)


System Dynamics

System Dynamics

• Code Coupling

– ATHLET – OpenFOAM (KIT)

– Phenix natural convection test

– Pool in OpenFOAM


ATHLET nodalization and 3D pool snapshot from OpenFOAM (KIT)

System Dynamics

• Code Coupling

– CATHARE – TRIO_U (CEA)

– Phenix natural convection test

– Dedicated post-processing tools enabling 3D visualization

(using 3D glasses) of sodium flow patterns in reactor pool



Summary


Summary & Conclusions

• Status of CFD developments and future challenges:

– Liquid metal turbulence

• Heat transport modelling for RANS and LES

• Thermal fluctuation prediction for thermal fatigue evaluation

• Flow induced vibrations of e.g. a fuel pin

– Core thermal hydraulics

• Wire wrap fuel assembly simulation and validation

• Low resolution CFD modelling of a fuel assembly to assess blockage scenarios

• Coarse Grid CFD development to allow modelling a complete core

– Pool thermal hydraulics

• Fundamental validation using separate effect facilities, e.g. multiple jets

• Pool modelling validation using prototypical scaled down facilities

• Gas entrainment modelling and validation

• Seismic evaluations including liquid metal sloshing

– System dynamics.

• Coupling of STH and CFD

Acknowledgements

• Colleagues at

– NRG

– SCK•CEN

– KIT

– ANL

• Denis Tenchine and his colleagues at CEA!


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