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ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012 COLIMA Experiment : Transport of the aerosol through the concrete crack sample Aerosol: prototypic aerosol (COLIMA) Thermite mixture Concrete degradation products Elements simulating the fission products Concrete crack (RSE) ΔP: 1 bar 0.3 m-piece of a crack 1.5 meter-length (assuming then a total pressure drop of 5 bars along a whole real crack)
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ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Aerosol Retention in Containment Leak Paths: Indications for a Code Model
in the Light of COLIMA Experimental Results
Sonia Morandi, Flavio Parozzi, Emilio Salina (RSE) Christophe Journeau, Pascal Piluso (CEA)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
COLIMA Experiment : Transport of the aerosol through the concrete crack sample
In the framework of SARNET of FP6
CEA and RSE managed an ad-hoc experiment, with prototypic aerosol generated from the facility COLIMA and a sample of cracked concrete with defined geometry
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
COLIMA Experiment : Transport of the aerosol through the concrete crack sample
Aerosol: prototypic aerosol (COLIMA)
Thermite mixture Concrete degradation productsElements simulating the fission products
Concrete crack (RSE)
ΔP: 1 bar 0.3 m-piece of a crack 1.5 meter-length (assuming then a total pressure drop of 5 bars along a whole real crack)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
COLIMA Results
Zone Collected mass
Mass fraction
0-5 cm 210 mg 70%5-10 cm 68 mg 23%10-20 cm 21 mg 7%
In the 5-20 cm range, some preferred flow path traces are visible
Intense aerosol deposition in the first 5 cm of the crack
Almost no deposit after 20 cm
Total of about 270-300 mg of aerosols directed to the sample
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Eulerian approach – Deposition Model
Gravitational settling Inertial deposition from turbulent flow Centrifugal deposition from bent pipes
and curved pathways Diffusional deposition from turbulent flow Diffusional deposition from laminar flow Thermophoretic deposition Diffusiophoretic deposition Pool scrubbing
VMA
dtdM
d
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Eulerian approach – Resuspension Model
dtdM
M1
ΔtA0MAΔM
0ΔtlimΛ
bFa F Resultant force acting on the particle
a, b Constant based on experimental data
Aerodynamic Forces
Fcoh Cohesive ForceFfric Frictional Adhesive ForceFcen Centrifugal Force
Adhesive Forces
Fgra Gravitational Force Aerodynamic/Adhesive Force
Fdrag Drag ForceFburst Bursting Force
graFcenFfricFcohFburstFdragFF
Faero < Fadhe → Deposition
Faero > Fadhe → Resuspension
Deposition inhibited
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Analysis of the Experiment with Eulerian Approach
AMMD 0.97 µm
σg 2.05
Aerosol mass flow 5·10-7 kg/s
Density 7350 kg/m3
Porosity 20–80 %
Crk1 Crk2 Crk3 Crk4 Crk5 Crk6Inlet Outlet
Crack Length 0.30 m
ΔP 1 bar
Gas flow 400 Nlit/min
Temperature 383.15 K
Curvature radius 0.01-0.02 m
Concrete crack
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Comparison with the experimental results
The adhesive forces strongly prevail over the lift forces
Main mechanism of deposition: Centrifugal sedimentation because of the crack tortuosity
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Comparison with the experimental results
0
50
100
150
200
250
300
Aer
osol
dep
osite
d m
ass
[mg]
EXPPorosity 80%Porosity 60%Porosity 40%Porosity 20%
rbend 0.01 m
rbend 0.01 mrbend 0.01 m
rbend 0.01 m
rbend 0.02 m
rbend 0.02 mrbend 0.02 m
rbend 0.02 m
0 - 5 cm 5 - 10 cm 10 - 20 cm 20 - 30 cm
Best Fit:Curvature Radius: 0.02 mPorosity: 60-40%
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Lagrangian Approach
Lagrangian approach: Fast-running and numerically stable Performed only when the boundary conditions change significantly
(i.e. crack geometry, carrier gas and aerosol properties) Mechanistic approach congruent with the other aerosol deposition
models in Source Term Codes
Eulerian approach : heavy calculation when coupled to a containment analysis under accident conditions
Very short time steps required to analyze the crack (~ 10-4 s)
Time step required for containment volumes related to nodalizations and model stability (~ s )
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Lagrangian Approach - Aerosol
Decontamination factor
)k(rjDFjkrTOTDF Removal mechanisms Particle size Local gas flow conditions.
Assumptions :No variations:
Crack geometric characteristicsThermodynamic conditions Particle size, shape and density
Condensation/evaporation of radionuclide species is neglected
No resuspension of particles
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03rp [m]
Faer
odyn
amic
/ F ad
hesiv
e
0.05 m
0.02 m
Straight path
Tortuous path0.005 m0.01 m
0.001 m
0.03 m
Deposition inhibited
Deposition allowed
CURVATURE RADIUS
Lagrangian Approach - Aerosol
No resuspension of particles
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Lagrangian Approach - Aerosol
Airborne concentration decay because of deposition mechanisms along a path
Assumption:All the particles of a given size class have equal deposition velocityThe thermal-fluid dynamic conditions are homogeneous (well-mixed conditions)Only tranverse mixing occursNo interactions among the particles
)x(ndxxdn
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Lagrangian Approach - Aerosol
dAdvncAv0ncAvn
cAvdAdvexp)k(rjDF
bendACvfloorASvtotADvTHvLvTDvTlvdAdv
Deposition velocity of particles vd is calculated as the combination of the different removal mechanisms
Deposition Mechanisms:•Turbulent flow•Diffusional deposition •Thermophoresis •Diffusiophoresis•Gravitational settling•Centrifugal deposition
Balance inside a generic spatial step
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Lagrangian Approach – Thermal Hydraulic
0.E+00
2.E+05
4.E+05
6.E+05
8.E+05
1.E+06
1.E+06
0 0.5 1 1.5 2Crack abscissa [m]
Pres
sure
[Pa]
ECART Eulerian calculationsimplifying correlation
pressure inside containment
pressure outside containment
Assumptions: Constant pressure and temperature along the crack pathway
during the considered time interval
Estimate ofPressure profile = f (PCont, PEnv)
Darcy–Weisbach Blasius Equation
2
xL4A20p0pxp
L
2cp0pcpA
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Comparison between Lagrangian and Eulerian predictions
0
50
100
150
200
250
300
Aer
osol
dep
osite
d m
ass
[mg]
EXP
Eulerian model (with resuspension)
Eulerian model (without resuspension)
Lagrangian model (without resuspension)
rbend : 0.015 mPorosity: 60 %
0 - 5 cm 5 - 10 cm 10 - 20 cm 20 - 30 cm
Eulerian vs Lagrangian:ComparableRetention efficiency :
Lagrangian >Eulerian
Eulerian no-res vs Lagrangian:Similar distribution deposited mass
Note: Eulerian Model : 6 Control Volume Lagrangian Model : 4800 Spatial Steps
Aerosol transported throughout the crack: the smallest particles are less influenced by the centrifugal force
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Conclusions Typical Eulerian approach: good agreement with the experimental data
Lagrangian approch: – Fast running, numerically stable, including typical retention mechanism of Source Term Codes– Can be performed only when boundary conditions change significantly
Discrepancies between experimental results and simulation:– Simulation : aerosol parameters were assumed as constant with time– Experiment: aerosol parameters deduced from integral measurements made after the
experiment (i.e. particle concentrations and size distributions), or affected by uncertainties (i.e. particle shape and density).
The simulations underline that resuspension conditions are likely to occur along the crack, probably in terms of inhibition of deposition, involving the smallest aerosol particles.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
Thank you!
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