Proposal of a pool scrubbing modelling for ASTEC: Bubble ... 2019... · Presentation outlines 1 - Pool scrubbing in ASTEC : current status and work in-progress 3 - Bubble hydrodynamic

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,


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



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



Bubble hydrodynamics



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



Injection zone



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



Injection zone

Bubble rise zone



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



Bubble rise zone

Thermalhydraulic



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 …



• 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)



Bibliography

Documents

Proposal of a pool scrubbing modelling for ASTEC: Bubble ... 2019... · Presentation outlines 1 - Pool scrubbing in ASTEC : current status and work in-progress 3 - Bubble hydrodynamic