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Proposal of a pool scrubbing modelling for
ASTEC:
Bubble hydrodynamic and thermalhydraulic
aspects
Safety research
Severe accidents
department
Radioelement transfer
laboratory
Marchetto Catherine
Cousin Frédéric
IRSN
2/14
Presentation outlines
1 - Pool scrubbing in ASTEC : current status and work in-progress
3 - Bubble hydrodynamic modelling
• Overview and assumptions
• Models specified in the zones
4 - Thermalhydraulic modelling
• Equations and models specified in the zones
5 - Conclusion and prospects
2 - Links between decontamination factor and parameters of bubble hydrodynamics and
thermalhydraulics
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Pool scrubbing modelling in ASTEC
• For ASTEC V2, SPARC/B 98 code is integrated for evaluating the DF
• SPARC/B 98 : some weaknesses identified in the modelling and computer structure not easily
upgradeable development of a new pool scrubbing module
Current status
New pool scrubbing module
• Roadmap
First step : proposals for the bubble hydrodynamic and thermalhydraulic models
− Based on the models in the existing codes (SPARC, BUSCA) and dedicated literature
− Only bubbly regime considered in the injection zone for the first version of the module
− Different configurations for gas injection (downcomer, one single hole sparger with different injection
directions, multi-holes sparger)
Second step : retention mechanisms models for aerosols and for volatile iodine (I2, CH3I, HOI)
Flexible computer structure for implementing, testing other/new models
Validation of the models by comparison with experimental data obtained in tests with pool
scrubbing representative conditions
• Configurations addressed: pressure suppression pools of BWR and FCVS
3/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Decontamination factor expressions
DF for volatile iodine species
DF for aerosol
vj : aerosol deposition velocity
Sgas : deposition surface
Vgas : gas volume
z : zone of the water pool
n : number of retention mechanisms
j : mass depletion rate
t : residence time
with
n
z j
j=1
DF =exp( β Δt)
• mout evaluated from mass balance equations for each species and depends on mass transfers (m) in
liquid and gaseous phases and on chemical reactions at the interface of both phases
vj , Sgas, Vgas, t, m, chemical reactions are dependent on bubble hydrodynamic
and thermalhydraulic parameters
DF=min
mout min : fission product mass entering the pool
mout : fission product mass leaving the pool
j
gas
j
gas
v Sβ =
V
4/14
min
Injection zone
Transition zone
Bubble
rise zone
Sparger with carrier gas
Water pool
Atmosphere mout
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Hydrodynamic and thermalhydraulic parameters needed for DF
db ,Ub , bubble shape, void fraction, bubble plume velocity, Tb, steam mass flow rate
are parameters from bubble hydrodynamic, thermalhydraulic and can be modeled as
follows …
Sgas, Vgas depend on bubble shape and void fraction
t evaluated for each zone
vj evaluated for each aerosol deposition mechanism
function of db (bubble size), Ub (bubble velocity),
Tb (bubble temperature), (steam mass flow rate) steamdm
dt
Chemical reactions depend on constant rates for forward and reverse reactions
function of Tb
m depends on mass transfer coefficients which are evaluated
from dimensionless numbers (Re, Sh)
function of db, Ub, Tb
5/14
min
Injection zone
Transition zone
Bubble
rise zone
Sparger with carrier gas
Water pool
Atmosphere mout
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Bubble hydrodynamics
6/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Injection zone
• Criteria for the type of the regime
• Bubbly regime : models for the bubble size
• Jet regime : experimental values for DF
•
• ; Ltrans evaluated from experimental data or correlations from existing pool scrubbing
codes, Ub given by bubble terminal velocity model
Overview and assumptions
• Possibility to mesh this zone
• ; bubble plume models for evaluating the bubble plume velocity and the void fraction
• Bubble size described by a log-normal distribution
inj gas
inj
inj
L SΔt =
V
transtrans
b
LΔt =
U
riserise
g
LΔt =
v
Linj : length of the zone
Sgas : deposition surface
: injected gas volume flow rate
Transition zone
Bubble rise zone
7/14
injV
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Injection zone
8/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Bubble size
Injector with a single orifice
downcomer, large horizontal vent for BWR, for FCVS
chosen models based on two-stage description and on basic force balance approach applied to the
bubble (considered as being spherical)
• three models found in the Kulkarni’s review [1] : for an upward vertical injection (Gaddis [2]),
for an inclined orifice (Kumar [3]) and for a downward vertical injection (Tsuge [4])
Injector with a multi-orifice
quencher for BWR, for FCVS
configuration rarely addressed in the literature ; one model found in the Kulkarni’s review [1] for
perforated plates (Loimer [5])
9/14
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Injection zone
Bubble rise zone
10/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Velocity and void fraction in the bubble plume
Bubble plume in a vessel : FCVS with multi-orifice injector
Bubble plume occupies the entire cross section of the pool
Described by drift flux models for large diameter pipes for bubbly flow and
churn-turbulent flow
Bubble plume in large pool : suppression pools in BWR,
FCVS with single orifice injector
Width expands with the pool elevation : plume cross sections are not known
Described by integral models for an axially symmetric plume
Two configurations are distinguished
Correlations for bubbly flow and churn turbulent flow from Schlegel [7]
Criteria for the flow regime from Shen [8]
Kubasch [6] proposed an application of this model to pool scrubbing experiments
in large water pools
11/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Bubble rise zone
Thermalhydraulic
12/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Outlines of the modelling
Assumptions
System of equations to consider
TB and msteam evolve along the water pool notably as
function of the water temperature compared to the
saturation temperature
determination of TB and msteam in each zone of the
water pool (as it is made for the bubble hydrodynamics)
TB and msteam depend on bubble size and velocity
dt : residence time
hsteam : steam specific enthalpy
hconv : convective heat transfer coefficient
Tpool : water temperature
steamdm=
dts
convection evaporation/condensation
gas
gas conv pool B steam
dH= S h T -T +h
dts
• Steam mass flux:
• Bubble enthalpy:
Two models for the steam mass flux depending on the injected
gas composition (steam and steam/non-condensable gases)
steam Bgas m steam gas
B,i
dm 1-X=S h M C Ln( )
dt 1-X
• Convection/diffusion model for steam/non-condensable gases hm: mass transfer coefficient
XB: steam mass fraction in the bubble
XiB: steam mass fraction at the
bubble/water interface
13/14
Conclusion and prospects
Work in-progress at IRSN for a new pool scrubbing module in ASTEC
Prospects
• Step for bubble hydrodynamic and thermalhydraulic model specification achieved
Pressure suppression pool and FCVS configurations addressed
Models selected in the dedicated literature and from existing pool scrubbing codes
Well-documented models and updated (since the 90's)
• Step for implementation in ASTEC and validation in-progress
Development of a flexible module
Validation by comparison with experimental data (bubble size, bubble velocity, void fraction, length of
the zones) from Lace-Espana program, PASSAM project, THAI program …
• Next step devoted to retention model specification, implementation and validation for DF
• Improvement of the models are expected in the future
As a consequence of the validation step
For the jet regime in the injection zone, for the description of transition zone …
14/14 9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
• New experimental data for bubble hydrodynamics, volatile iodine’s DF, are expected allowing thus
a wider model validation
Experimental PhD thesis on bubble hydrodynamics and CH3I retention at IRSN will be launched in October 2019
On-going IPRESCA (NUGENIA) project
[1] : Kulkarni A. and all, Bubble formation and bubble rise velocity in gas-liquid systems : a review, Ind. Eng. Chem. Res., volume 44, 5873 –
5931, 2005
[2] : E.S Gaddis and A, Vogelpohl, bubble formation in quiescent liquids under constant flow conditions, chemical engineering science,
41(1):97-105,1986
[3] : R. Kumar, N. K. Kuloor, the formation of bubbles and drops, volume 8 of advances in chemical engineering, pages 255-368, academic
press, 1970
[4] : H, Tsuge, P. Rudin, R. Kammel, bubble formation from a vertically downward facing nozzle in liquids and molten metals, journal of
chemical engineering of Japan, 19(4):326-330,1986
[5] : T. Loimer, G. Machu, U. Schlafinger, inviscid fluid formation on porous plates and sieve plates, chemical engineering science, 59:809-
818, 2004
[6] : J. H. Kubasch, Bubble hydrodynamics in large pools, DISS. ETH No. 14398, 2001
[7] : J. Schlegel, T. Hibiki, M. Ishii, Development of a comprehensive set of drift-flux constitutive models for pipes of various hydraulic
diameters, progress in nuclear energy, 52, 666-677, 2010
[8] : X. Shen, J. Schlegel, S. Chen, S. Rassame, M. J. Griffiths, T. Hibiki, M. Ishii “Flow characteristics and void fraction prediction in large
diameter pipes,” Springer International publishing, Switzerland (2014)
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Bibliography
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