Multiphase CFD Applied to Steam Condensation Phenomena in the

Pressure Suppression Pool

Marco Pellegrini

STAR Japanese Conference 2016Yokohama, Japan – June 9th 2016

N U P E C

6/10/2016 STAR Japanese Conference, Yokohama, Japan

NUCLEAR PLANTS AFFECTED BY THE 3.11 EARTHQUAKE 2

Fukushima Daiichi

Fukushima Daini

Onagawa

Operating reactor

Under inspection

~ 130 kmJMA seismic intensity

March 11th 2011

6/10/2016 STAR Japanese Conference, Yokohama, Japan

STATION BLACK OUT 3

R/B

High Pressure Alternate Cooling system

Reactor Core Isolation Cooling system

Courtesy of A. Obonai, Tohoku Electric Power CO

RCIC quencherExperiment at SIET, Italy (IAE)

T-quencherExperiment at SIET, Italy (IAE)

6/10/2016 STAR Japanese Conference, Yokohama, Japan

DIRECT CONTACT CONDENSATION IN S/C 4

R/B

MAKE-UP WATER SYSTEMSDIRECT CONTACT CONDENSATION

6.E+06

6.E+06

7.E+06

7.E+06

7.E+06

7.E+06

7.E+06

8.E+06

0 500 1000 1500 2000 2500 3000 3500

RPV pressure [M

Pa(abs)]

Time(s)

Computation by A. Buccio(IAE), 2016

Injectionpoint

~ 30 m

6/10/2016 STAR Japanese Conference, Yokohama, Japan

EULERIAN TWO-PHASE FLOW 5

∙ ∙

∙ , ∙ ∙   ∙

Instantaneous representationH

eat f

lux

Source terms ∆ ∆ Energy equation

Average representation

Hea

t flu

x

6/10/2016 NURETH-16, Hyatt Regency, Chicago

HEXAHEDRAL MESH APPLIED TO A SPHERE 6

DArea Density Magnitude of Volume

Fraction Gradient

D/16 D/32 D/64 D/128

D

Volume Fraction

6/10/2016 NURETH-16, Hyatt Regency, Chicago

HEXAHEDRAL MESH APPLIED TO A SPHERE 7

0.0%2.0%4.0%6.0%8.0%

10.0%12.0%14.0%16.0%18.0%20.0%

d/8 d/16 d/32 d/64 d/128

Erro

r [%

]

~ 9% error with large refinement

D/16 D/32 D/64 D/128

Error between the computed and theoretical area

D

6/10/2016 NURETH-16, Hyatt Regency, Chicago

POLYHEDRAL MESH APPLIED TO A SPHERE 8

D/16 D/32

0.00%

0.50%

1.00%

1.50%

2.00%

2.50%

3.00%

3.50%

d/16 d/32 d/64 d/128

Erro

r [%

]

D/8Error between the computed and theoretical area

~ 2.5% error with large refinement

6/10/2016 STAR Japanese Conference, Yokohama, Japan

DOMAIN AND MESH STRATEGIES 9

Small nozzle diameterD = 2 mm

Large nozzle diameterD = 210 mm

Mesh elements: 305,067

6/10/2016 STAR Japanese Conference, Yokohama, Japan

DOMAIN AND MESH STRATEGIES 10

Mesh elements: 405,067

D/16

Small nozzle diameter Large nozzle diameter

Mesh elements: 305,067

Small nozzle diameterD = 2 mm

Large nozzle diameterD = 210 mm

6/10/2016 STAR Japanese Conference, Yokohama, Japan

MESH SENSITIVITY - 1 11

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 20 40 60 80 100 120

Inte

rfaci

al a

rea

[cm

2 ]

Time [ms]

IFA [Mesh X 0.5]IFA [Mesh X 0.75]IFA [Mesh x1.0]IFA [Mesh x1.25]

MESH x1.25 MESH x1.0 MESH x0.750 MESH x0.5

Interfacial area

6/10/2016 STAR Japanese Conference, Yokohama, Japan

DIRECT CONTACT CONDENSATION: CHUGGING 12

Single hole pipe

In recent experiment we employed transparent pipes to visualize the bubble phenomenology during direct contact condensation

Pressure sensor

0.231 m

6/10/2016 Severe Accident Mitigation and Research Collaboration

EXPERIMENTAL EVIDENCEPo

ol te

mpe

ratu

re [°

C]

TPOOL = 57-61 °C

Steam reaching point

0.2 kg/s

water level

2.8

m

1.24

m

13

6/10/2016 STAR Japanese Conference, Yokohama, Japan

DIRECT CONTACT CONDENSATION: CHUGGING-2 14

pressure sensorMulti hole pipe

In recent experiment we employed transparent pipes to visualize the bubble phenomenology during direct contact condensation

NURETH-16, Hyatt Regency, Chicago

RAYLEIGH-TAYLOR INSTABILITY

6/10/2016

15

Psteam < Pwater

2

1i ska

Final terms for area growth

A

steam

water

Psteam

PwaterPsteam Pwater

steam

water

Accelerating flow field

Psteam

Pwater

n tt t te

6/10/2016 STAR Japanese Conference, Yokohama, Japan

IMPLEMENTATION INTO STAR-CCM+ 16Compressible steam flow Compressible steam flow

Record amplitude length at previous time step

6/10/2016 STAR Japanese Conference, Yokohama, Japan

LARGE NOZZLE DIAMETER: POOLEX 17

WATER• Incompressible – Constant properties• k-ε standard• Temperature = 62 ºCSTEAM• Compressible

velocity inletpressure outlet

adiabaticwalls

T = 106 °Cv = 11.02 m/s

Time step = Courant number limitedStopping criteria at interfacial mass transfer (1% of inlet mass flow rate)

Mesh elements: 405,067

D/16

6/10/2016 STAR Japanese Conference, Yokohama, Japan

EFFECT OF RTI MODELIZATION 18

Pressuremonitor

6/10/2016 STAR Japanese Conference, Yokohama, Japan

VOLUME FRACTION 19

Tpool = 62 ºCTpool = 62 ºC

Minimum area model Rayleigh-Taylor Instability Model

Steam flow Steam flow

6/10/2016 STAR Japanese Conference, Yokohama, Japan

20

EXP

RTI model

Tanskanen, Ph.D. Thesis 2012

No RTI model

6/10/2016 NURETH-16, Hyatt Regency, Chicago

EFFECT OF MISPREDICTION OF CHUGGING 21

Prediction of oscillating bubble creates thermal stratification in the pool

Chugging is responsible for very large mixing in the pool

6/10/2016 STAR Japanese Conference, Yokohama, Japan

SMALL NOZZLE DIAMETER: CLERX ET AL. 22

WATER• Incompressible – Constant properties• k-ε standard• Temperature = 25 ºCSTEAM• Compressible

Time step = Courant number limitedStopping criteria at interfacial mass transfer (1% of inlet mass flow rate)

Mesh elements: 405,067

D/16

6/10/2016 STAR Japanese Conference, Yokohama, Japan

VOLUME FRACTION FIELD 23

Minimum area model Rayleigh-Taylor Instability Model

Clerx et al., 20090.3 ms 0.6 ms

1.2 ms

0.9

1.5 ms 1.8 ms

Bubble implosion is less than 2 ms in the experiment at it appears immediately

6/10/2016 STAR Japanese Conference, Yokohama, Japan

CLERX ET AL. EXPERIMENT 24

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 2 4 6 8 10 12

Pene

tratio

n Le

ngth

[mm

]

Time [ms]

Clerx ExperimentBL + no RTIRTI

Minimum area model RTI ModelClerx et al., 2009

6/10/2016 STAR Japanese Conference, Yokohama, Japan

PREDICTION OF TEMPERATURE DISTRIBUTION 25

RTI Model

Clerx et al., 2009

Measured temperature field

Minimum area model

6/10/2016 STAR Japanese Conference, Yokohama, Japan

THE CHALLENGE OF ACCIDENT COMPUTATION 26

R/B R/B R/B

accident time scale [days]

Unit 1 vent pipes Unit 2 RCIC Unit 3 RCIC

6/10/2016 STAR Japanese Conference, Yokohama, Japan 27

UNIT 3UNIT 2

UNIT 1

Courtesy of S. Mizokami, TEPCO

Fukushima Daiichi power plantwhat are the conditions at this moment?