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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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 3IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 4IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 5IEK-6 Reactor Safety,Stephan Kelm
Outline
• Background & Motivation• REKO-DIREKT model & development• RD-CFX Coupling• Validation strategy and results• Summary and Outlook
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 6IEK-6 Reactor Safety,Stephan Kelm
REKO-DIREKT D&V - Experimental Database
REKO-3 REKO-45m³
H2
Development
Reaction kinetics
Chimney, buoyant flow
THAI60m³
Validation
PAR atmosphere interaction
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 7IEK-6 Reactor Safety,Stephan Kelm
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)
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 8IEK-6 Reactor Safety,Stephan Kelm
Outline
• Background & Motivation• REKO-DIREKT model & development• RD-CFX Coupling• Validation strategy and selected results• Summary and Outlook
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 9IEK-6 Reactor Safety,Stephan Kelm
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)
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 10IEK-6 Reactor Safety,Stephan Kelm
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)
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 11IEK-6 Reactor Safety,Stephan Kelm
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)
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 12IEK-6 Reactor Safety,Stephan Kelm
Outline
• Background & Motivation• REKO-DIREKT model & development• RD-CFX coupling• Validation strategy and selected results• Summary and outlook
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 13IEK-6 Reactor Safety,Stephan Kelm
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)
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 14IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 15IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 16IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 17IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 18IEK-6 Reactor Safety,Stephan Kelm
HR2 - Visualization of the PAR Operation Transient
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 19IEK-6 Reactor Safety,Stephan Kelm
HR2 - Visualization of the PAR Operation Transient
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 20IEK-6 Reactor Safety,Stephan Kelm
PAR-Atmosphere Interaction
Strong interaction between PAR operation (hot plume) and atmospheric mixing→ Hard to differentiate between single model errors!
thermal stratificationvs. H2 injection
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 21IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 22IEK-6 Reactor Safety,Stephan Kelm
HR12 PAR Behavior – Concentrations & Reaction Rate
O2 starvation O2 starvation
Consistent global balances (conversion & heat release to the vessel) Oxygen starvation captured
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 23IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 24IEK-6 Reactor Safety,Stephan Kelm
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
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 25IEK-6 Reactor Safety,Stephan Kelm
HR12 Atmospheric H2 Mixing, Temperature & Pressure
Vessel sump
Overall consistent transport and mixing processes during full transient
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 26IEK-6 Reactor Safety,Stephan Kelm
Outline
• Background & Motivation• REKO-DIREKT model & development• RD-CFX coupling• Validation strategy and results• Summary and future work
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 27IEK-6 Reactor Safety,Stephan Kelm
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)
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 28IEK-6 Reactor Safety,Stephan Kelm
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).
46th Annual Meeting on Nuclear TechnologyBerlin, Germany, May 7th 2015
Slide 29IEK-6 Reactor Safety,Stephan Kelm
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