Thermal Hydraulic Challenges for

Liquid Metal Fast Reactors in

Europe

F. Roelofs, A. Shams, K. van Tichelen,

A. Gerschenfeld, A. Batta, I. DiPiazza

roelofs@nrg.eu

IAEA, Vienna, Austria

15 April 2014

Contents

• Introduction

• Liquid Metal Fast Reactors in Europe

• Thermal Hydraulic Challenges

– Identification process

– Liquid Metal Turbulence Heat Transfer

– LMFR Fuel Assemblies

– LMFR Pool

– Thermal Hydraulic System Behavior

• Summary of Main Challenges for Future

Development

• Acknowledgement

2

Introduction

3

Introduction

• 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

• EU FP7 Project THINS (Thermal Hydraulics of

Innovative Nuclear Systems) and preparation of new framework progam Horizon 2020

4

Liquid Metal Fast Reactors in Europe

5

Liquid Metal Fast Reactors in EuropeSodium: ASTRID

• ASTRID = Advanced Sodium

Technological Reactor for Industrial

Demonstration

• Characteristics

– Sodium coolant

– 1500 MWth / 600 MWe

• Purpose

– Sodium Fast Reactor Technology

Demonstration

– Maintaining and rebuilding sodium fast

reactor expertise

6

Liquid Metal Fast Reactors in EuropeLead: ALFRED

• ALFRED = Advanced Lead Fast

Reactor European

Demonstrator

• Characteristics

– Lead coolant

– 300 MWth / 125 MWe

• Purpose

– Lead fast reactor demonstration

7

Liquid Metal Fast Reactors in EuropeLead: SEALER

• SEALER = Swedish Advanced Lead

Reactor

• Characteristics SEALER-3

– Lead coolant

– 8 MWth / 3 MWe

• Purpose

– Electricity production for isolated (arctic) communities

8

Liquid Metal Fast Reactors in EuropeLead-bismuth: MYRRHA

• MYRRHA = Multi-purpose hYbrid Research Reactor for

High-tech Applications

• Characteristics

– Critical and ADS mode

– Lead Bismuth Eutectic coolant

• Purpose

– Fast spectrum irradiation facility

– European technology pilot plant for LFR

9

Identification Process

10

Identification Process

11

Literature &

conferences EU Framework ProjectsInternational

Organizations

Challenges

EU System Designers

IdentificationIdentification

PrioritizationPrioritization

Liquid Metal Turbulence Heat Transfer

12

Liquid Metal Turbulence Heat Transfer

• Current practice: Reynolds analogy for heat transfer

13

Velocity

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

Field ScalesBoundary

Layer

Velocity Small Thin

Temperature (Pr = 1) Small Thin

Temperature (Pr = 0.01) Large Thick

Liquid Metal Turbulence Heat TransferStatus Model Development 2014

14

Local Temperature Dependent Prandtl Number

Reynolds Analogy

AHFM-NRG

Flow Convection Regimes

natural mixed forced

Flu

ids

(P

ran

dtl

nu

mb

er)

air

liquid

meta

ls

Look-up Tables?

AHFM-TransAt?

?

Mixed

Law-of-the-Wall?

Liquid Metal Turbulence Heat Transfer

Challenges:

• Further Assessment– Mixed convection in liquid metals

– Non wall-bounded flows (e.g. jets)

– Complex (industrial) geometries

• Model robustness evaluation by implementation and evaluation in other codes

• Further development for simultaneous application in all convection regimes

15

LMFR Fuel Assemblies

16

LMFR Fuel AssembliesWire Wraps

17

• Application: ASTRID / MYRRHA

• Status:– Hydraulic reference data available only from

high fidelity simulations by ANL

– Thermal data including blockages available in near future from EU SEARCH and MAXSIMA projects

• Challenges:– Reference data

• MIR Experiments to confirm Hydraulics

• High Fidelity CFD including heat transport in addition to thermal data from experiments which is always limited

– Blockage formation by accumulation of small particles

217 pin sodium bundle LES (ANL)

solid

transparent

LMFR Fuel AssembliesGrid Spacers

18

• Application: ALFRED

• Status:

– Numerical approaches with little validation

• Challenges:

– Reference data for validation of numerical

approaches

• Hydraulics experiments

• Thermal hydraulics experiments

• High Fidelity simulations

– Evaluation of influence of blockages ALFRED spacer design (ANS)and CFD assessment (NRG)

LMFR Fuel AssembliesInter-wrapper flow

19

• Status:

– Limited reference data (PLANDTL

experiments)

• Challenges:

– Reference data for validation of numerical

approaches

PLANDTL Inter-wrapper flow experiments (Kamide et al., 2001)

LMFR Fuel AssembliesComplete Core Simulation

20

• Status:

– Subchannel or system thermal hydraulics codes

• Challenges:

– Improvement of existing approaches

– Development of new approaches to obtain more

details or improved accuracy

AP-CGCFD (Viellieber & Class, 2012)

LMFR Pool

21

LMFR Pool

• Status:– Designs specific experiments and

simulations

– No validation

• Challenges:– Generic validation for numerical

approaches

– Link hydraulics with thermal hydraulics

– Transition from forced to natural convection cooling

– Evaluation of stratifications

– Numerical modelling of integrated complex components (core, HEX, pumps, fuel handling systemsF)

22

RAMONA facility (KIT)

JESSICA facility (CEA)

LMFR Pool

• Development:

23

MYRRHAbelle water mock-up (VKI)MYRRHA design (SCK-CEN) ESCAPE LBE mock-up (SCK-CEN)

LMFR Pool

• CIRCE experiments– Transition forced to natural

convection

• Qualification of heat transfer and stratification modeling in CFD

• Prediction of convection patterns in CFD

• Validation of system codes

24

heated section

Argon injection

riser

gas separator

heat exchanger

CIRCE facility (ENEA)

LMFR Pool

• Numerical Modelling:

25

MYRRHA numerical model (VKI)

- Conjugate heat transfer

- 10-30 million computational volumes

MYRRHA numerical model (CRS4)

- Conjugate heat transfer

- Five fluid regions to describe the core

- Explicit free surface modelling

Thermal Hydraulic System Behavior

26

Thermal Hydraulic System BehaviorSystem Code

27

Core :

axial

modules

Hot pool

Cold pool

IHX

diagrid

Primary

pumps

Hot pool

Primary

pumps

IHX

Cold

pool

core

CATHARE input deck (CEA)

Thermal Hydraulic System BehaviorMulti Scale

• 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

28

CATHARE – TRIO_U (CEA)

Thermal Hydraulic System BehaviorSystem Code vs. Multi Scale

• System Code– limited stratification

prediction

– stratification prediction linked to discretization

– limited prediction 3D phenomena in complex geometry

• Multi Scale– Domain selection

(domain decomposition or overlapping, iterative method)

– Allows to predict properly local 3D behavior

– CPU intensive (esp. for long transients)

– Validation

29

experimentsystem code

coupled

Main Challenges for Future Development

30

Main Challenges for Future Development

• Status of LMFR thermal-hydraulics developments & future challenges:

– Liquid Metal Turbulence Heat Transfer

• Further validation of the promising approaches using:

– Geometrically more complex cases

– Flows not bounded by walls

• Development of approaches allowing application in all flow regimes simultaneously

– Fuel Assemblies

• Validation of the flow hydraulics in a wire wrapped rod bundle using high fidelity

numerical reference data or experimental data

• Further development of complete core approaches

– Pool Thermal Hydraulics

• Validation: Flow and heat transfer

• Include heat transport through inner structures in the pool

– Thermal Hydraulic System Behavior

• Include 3D effects from experiments or CFD simulations in STH codes

• Couple system thermal hydraulic codes with CFD codes

• Validation of the coupling methodologies and application

• Transition from forced to natural convection

31

National Program on Thermal

Hydraulics Modelling and

Simulation for Fast Reactors

F. Roelofs

roelofs@nrg.eu

IAEA, Vienna, Austria

14 April 2014

Dutch National Program

• Dutch National Program– Four policy targets of Dutch government

– NRG budget 2014 ~ 8 M€

– ‘Optimization of Solutions for Nuclear Waste’

• Characterization of nuclear waste and final disposal

• Minimization of nuclear waste and fast reactors

– Largely Integrated in EU framework

33

System Thermal HydraulicsCodes

• RELAP

• MELCOR

• TRACE

• SPECTRA

34

Mainly LWR Applications

Flexible Applications

System Thermal HydraulicsSPECTRA

35

• Sophisticated Plant Evaluation Code for Thermal-hydraulic Response Assessment.– Fully integrated system analysis

code

– Thermal Hydraulics• Cooling systems

• Emergency & control systems

• Containment

• Reactor building

– Flexible input module for physical properties and correlations enabling application of different coolants

– Flexible in applications: PWR, BWR, HTR, LFR, SFR...

– V&V analysis covering code to code, theoretical as well as experimental and operation cases

System Thermal HydraulicsSPECTRA

• Coolant Selection– Flexible input module for

physical properties and correlations

• Water

• Helium

• Sodium / Lead

• Main code for fast reactor applications– Sodium (ESFR / EBR-II)

– Lead (ELSY / ALFRED)

• Fast Reactor Developments– Mainly further V&V

– ‘Customer’ request

36

SPECTRA EBR-II Model

Computational Fluid DynamicsCodes

• STAR-CCM+

• FLUENT

• CFX

• NEK5000

• OpenFOAM

• Code selection on case by case basis, driven

by code competences, user preferences, and

license availability

37

NEK5000

Computational Fluid DynamicsFuel Assembly & Core Modelling

38

Sub-channel LevelFuel Assembly LevelFull Core Level

CFD

Multiscale

• Validate CFD at sub-channel level

• Scale up (reduced resolution) to fuel assembly level

• Scale up (low resolution) to full core level

Computational Fluid DynamicsFuel Assembly & Core Modelling

• Heat transport (AHFM-NRG)– increasing accuracy and predictability

• Single Subchannel– spacer assessment

– validation

• Down scaled fuel assembly– 7 & 19 pins (validation)

– Experimental blockages (validation)

• Fuel assembly– 127 pin MYRRHA including inlet and

outlet headers

– Partial blockage

• Multiple fuel assemblies– Complete and partial blockages

– Inter wrapper flow

• Complete core– Inter wrapper flow

– Blockages

– Primary system modelling

39

Computational Fluid DynamicsPool Modelling

• Scaling Analyses

– MYRRHA - ESCAPE

• Gas Entrainment

– ESFR

• Sloshing

– ELSY

• Development

– Modelling complete fast

reactor primary system

• Stratification

• Transients

• Transition forced-

natural

40

Scaling simulations

Full scale – velocity scale – Froude scale

Computational Fluid DynamicsSodium Fire Modelling

• Model Implementation Check– Pool

• Evaporation and combustion of sodium

• Validation– Spray

• Validation to combustion of single falling sodium droplet

• Application– Combined sodium spray and pool fire in

closed environment

• Status– Developed method suitable for scoping

analyses

– Further validation required for safety analyses

41

Multi Scale Thermal Hydraulics

• Development of coupling 3D CFD to 1D STH

– Coupling mechanisms tested by coupling STH-STH

(time and space) and CFD-CFD (space)

– Proof of Principle (STH-CFD)

• Heat diffusion in 1D pipe

• Domain overlap

• Treatment of boundary conditions

42

T & Q

STH

CFD

Questions?

43