Passive Auto-Catalytic Recombiner Operational Behavior · THAI internals neglected: • Auxiliary fan • Flanges, man holes • Bearing rings and condensate trays at inner cylinder

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Detailed Modeling of Passive Auto-Catalytic Recombiner Operational Behavior with the Coupled REKODIREKT-CFX Approach

S. Kelm, E.-A.Reinecke, *Hans-Josef Allelein

46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015

*Institute for Reactor Safety and Technology, RWTH Aachen University

Project No. 150 1407


Slide 2IEK-6 Reactor Safety,Stephan Kelm

Outline

• Background & Motivation• REKO-DIREKT model & development• RD-CFX Coupling• Validation strategy and selected results• Summary and Outlook



Task: Improved assessment of H2 mixing and mitigation

For a detailed simulation, it is essential to capture the direct interaction of flow and mitigation measure



Motivation for a detailed modeling approach

Motivation: Transfer of REKO-3 & 4 experimental database (project 1501308 / 1501394)

and detailed modeling results (CFX, SPARK) to large scale application. Unified PAR modeling approach in different TH codes

(testing of first implementation in COCOSYS ongoing) Extendable, mechanistic mode basis:

• New physics (CO conversion / poisoning, ignition, start-up behavior)• Different PAR types (e.g. AECL, NIS)

Reliable and numerically efficient modeling of PAR operational behavior Conservative and numerically stable coupling of RD and CFX Extension to a full PAR System (arbitrary number and PAR types) Validation against OECD/NEA THAI-1&2 hydrogen recombiner tests



Outline

• Background & Motivation• REKO-DIREKT model & development• RD-CFX Coupling• Validation strategy and results• Summary and Outlook



REKO-DIREKT D&V - Experimental Database

REKO-3 REKO-45m³

H2

Development

Reaction kinetics

Chimney, buoyant flow

THAI60m³

Validation

PAR atmosphere interaction



REKO-DIREKT code structure

PAR Phenomena

PAR

hou

sing

/ c

him

ney

Cat

alys

t se

ctio

n

REKO-DIREKT

Buoyancy driven flow

Thermal inertia and heat losses to the environment

Reaction kinetics(Oxygen starvation,steam impact, parallel CO recombination..)by transport approach

Heat distribution,thermal inertia ( Böhm, 2006)



Outline

• Background & Motivation• REKO-DIREKT model & development• RD-CFX Coupling• Validation strategy and selected results• Summary and Outlook



RD-CFX interface (1)

Fully parallelizable, explicit Master (CFX) – Slave (RD) coupling Data handling by means of program flow or data controlled USER

Fortran subroutines Arbitrary number and types of PARs

Input data: temperatures gas composition system pressure CFX time step

Output data: temperatures gas composition mass flow

Geometric information: box size catalyst size & numbers RD numerical grid

RD-run data: catalyst temperature field radiative view factor matrix

REKO-DIREKT

( Kelm et al., NURETH-14, 9/2011)



RD-CFX interface (2)

Direct Solution

Write Solution

End of Run

First call

Read Input File

Start of Run

Start of Time Step

End of Time Step

REKO-DIREKT

Read Input & Mesh

First call

Start of Run

Start of Coefficient Loop

Start of linear Solution

End of linear Solution

End of Coefficient Loop

End of Time Step

Linear Solution

End of Run

Write Solution

Start of Time Step

ANSYS CFX

Execute REKO-Direkt:Read Initialisation

& Input Values

Write Results on Boundary Condition

Update InputValues for REKO-

DIREKT

Memory Management System

Update REKO-DirektResults

Writing to MMSReading from MMS

(createinput.F)

(writeout.F)

(createinput.F)

Trigger RD‐exec.

(rekodirekt.F)

(rekodirekt.F)

Loop

over

each PAR

( Kelm et al., NURETH-14, 9/2011)



RD Application in CFX

m

q

m

small scale application (e.g. resolving the plume @ THAI )

q

m

m

large scale application, coarse mesh (e.g. PWR)



Outline

• Background & Motivation• REKO-DIREKT model & development• RD-CFX coupling• Validation strategy and selected results• Summary and outlook



Separation of Errors: RD-CFX Validation strategy

Scenarios of systematically increasing complexity• HR2 / HR3 / HR5 Effect of pressure• HR12 Effect of humid atmosphere• HR35 Effect of oxygen starvation

TestPressure

[bar]Temperature

[°C]

Steam Concentration

[vol.-%]

Oxygen Concentration

[vol.%]

HR2 1.0 25 0 20

HR3 1.5 25 0 20

HR5 3.0 25 0 20

HR12 3.0 120 60 < 8

HR35 3.0 120 60 < 2

( Freitag & Sonnenkalb, HR35 comparison report, 12/2013)

( Kanzleiter et al., QLR, 2/2009)

( Kanzleiter et al., QLR, 9/2009)



Separation of Errors: RD-CFX Validation strategy

Scenarios of systematically increasing complexity Three step validation approach

RD stand-alone

Fundamental validation [7]

RD-CFX 3D THAI

Integral validation of H2 mixing and mitigation

RD-CFX 2D test

Verify coupling Reference for

3D simulation

CFX

Project No. 1501394



HR Experimental Setup and CFD Geometry

Geometric model simplifications [2]:

Injection lines: • H2: 2D Inlet boundary condition

PAR box:• Zero thickness (in CFD model)• Only ‚active‘ half considered• Inlet and Outlet section conserved

THAI internals neglected:• Auxiliary fan• Flanges, man holes• Bearing rings and condensate

trays at inner cylinderH2 feed line

Measurementchannel

0.5* AREVA FR90/380T

Kelm et al, CFD4NRS-4, Korea, 2012



HR Physical Model

CFD (ANSYS CFX15) Model [2]: U-RANS equations Ideal gas equation of state Temperature dependent properties k--SST model incl.

buoyancy prod. & dissipation Sct=Prt=0.9 Conjugate heat transfer Thermal radiation:

Monte Carlo, 200.000 histories, participating media, steam=1.0, w=0.6

Gas sampling: 15 sink points Wall & bulk condensation Automatic wall treatment at inner walls

REKODIREKT (RD) Model: H2 & O2 start concentration: 0.1vol.% PAR Startup time: according to experiment Kelm et al, CFD4NRS-4, Korea, Sept. 2012



HR Numerics

Numerical Model: High resolution advection scheme 2nd order Euler-backward t ~0.2 s, ave CFL~2, max CFL<20 Max residual < 1E-3 (RMS<1E-5) 3..6 coefficient loops per time step Grid independent solution

Computational Effort: 5000s ~ 10 days on 8 CPU’s RD runtime < 70ms / time step

~ 0.5 h / total transient



HR2 - Visualization of the PAR Operation Transient



HR2 - Visualization of the PAR Operation Transient



PAR-Atmosphere Interaction

Strong interaction between PAR operation (hot plume) and atmospheric mixing→ Hard to differentiate between single model errors!

thermal stratificationvs. H2 injection



HR Validation Strategy

(1) Detailed assessment of PAR performance: Prove consistent prediction of the conversion rate /

heat source compared to experiment

Prove consistent thermal representation of the• In-/outlet conditions• Catalyst Temperature• Inlet velocity (throughput)• Rate & Efficiency

(2) Comparison of atmospheric mixing: Analyse effect of PAR operation on

• H2 distribution• Pressure and gas temperature

, , , ∙∙ ∙ ∙

∙

Aim: Avoid elimination of errors



HR12 PAR Behavior – Concentrations & Reaction Rate

O2 starvation O2 starvation

Consistent global balances (conversion & heat release to the vessel) Oxygen starvation captured



Gas temperature@ PAR inlet

HR12 PAR Behavior – Thermal Aspects

Reaction heat distribution is qualitatively and quantitatively well predicted PAR thermal inertia is a key issue for predicting the exhaust gas temperature



HR12 PAR Behavior – Buoyant Flow Rate

Qualitatively well predicted, but visible scattering among the different experiments / TH conditions

Sensible parameter to reaction rate (mass transfer approach)

Ongoing detailed CFD simulations of measurement channel / flow resistances

vave~0.8 m/s

vane wheel



HR12 Atmospheric H2 Mixing, Temperature & Pressure

Vessel sump

Overall consistent transport and mixing processes during full transient



Outline

• Background & Motivation• REKO-DIREKT model & development• RD-CFX coupling• Validation strategy and results• Summary and future work



Summary & Future Work

Detailed mechanistic PAR model REKO-DIREKT, developed from small scale separate effect tests REKO-3 and REKO- 4, was implemented in CFX

Systematic validation performed by means of technical scale OECD/NEA THAI hydrogen recombiner tests

Validation results in overall consistent and plausible results• Conversion rate and global heat and species mass balances• Importance of PAR thermal inertia for prediction of the gas temperatures and

resulting buoyant mass flow rate• Significant impact of thermal radiation heat transfer on gas temperatures, pressure,

thermal stratification and gas mixing Extension of the interface to parallel CO conversion Development of a model to predict PAR start-up Extension to other PAR types (AECL, NIS) Detailed CFD application to determine measurement uncertainties and

model coefficients (e.g. flow resistances of chimney internals)



Acknowledgements

The continued development of CFD models for prediction of H2 mixing and mitigation is performed in close cooperation with RWTH Aachen University and funded by German Federal Ministry of Economic Affairs and Energy (Project No. 150 1407)

Parts of REKO-3 / 4 experimental programme and REKODIREKTcode development are performed in close cooperation with RWTHAachen University and funded by German Federal Ministry ofEconomic Affairs and Energy (Project No. 150 1308 / 150 1394)

The PAR performance test have been performed within theOECD/NEA THAI and THAI2 project. We acknowledge the supportof all the countries and the international organizations participating inthe projects and the staff of Becker Technologies for their effort forpreparing, performing and documenting the experiments.

Analytical investigations on PAR operational behaviour areperformed in collaboration with the Institut de Radioprotection et deSûreté Nucléaire (IRSN).



References

(1) Böhm, J.: Modelling of processes in catalytic recombiners, Forschungszentrum Jülich, Energy Technologies Vol 61 (2007).

(2) Kelm et al.: Simulation of hydrogen mixing and mitigation by means of passive auto-catalytic recombinersProc. 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), Toronto, Ontario, Canada, September 25-29, 2011.

(3) Kelm et al.: Passive auto-catalytic recombiner operation - Validation of a CFD approach against OECD-THAI HR2-test, Proc. OECD/NEA & IAEA Workshop on Experiments and CFD Codes Application to Nuclear Reactor Safety(CFD4NRS), Deajon, South Korea, September 9-13, 2012

(4) Kanzleiter, T. et al.:Quick Look Report Hydrogen Recombiner Tests - HR-1 to HR-5, HR-27 and HR-28 (Tests without steam, using an Areva PAR), Report No. 150 1326–HR-QLR-1, OECD-NEA THAI Project, February 2009

(5) Kanzleiter, T. et al.:Quick Look Report Hydrogen Recombiner Tests HR-6 to HR-13, HR-29 and HR-30 (Tests with steam, using an Areva PAR), Report No. 150 1326–HR-QLR-2, OECD-NEA THAI Project, August 2009

(6) Freitag, M., Sonnenkalb, M.: Comparison Report for Blind and Open Simulations of HR 35 - “Onset of PAR operation in case of extremely low oxygen concentration”, Report No. 150 1420 – HR35 – AWG (VB), OECD-NEA THAI2 Project, 17. December 2013

(7) Reinecke et al.: Validation of the PAR code REKO-DIREKT against large scale experiments performed in the frame of the OECD/NEA-THAI project, Proc. 7th European Review Meeting on Severe Accident Research (ERMSAR-2015), Marseille, France, 24-26 March 2015, Paper No. 060

Documents

Passive Auto-Catalytic Recombiner Operational Behavior · THAI internals neglected: • Auxiliary fan • Flanges, man holes • Bearing rings and condensate trays at inner cylinder