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Multiphase CFD Applied to Steam Condensation Phenomena in the Pressure Suppression Pool Marco Pellegrini N U P E C STAR Japanese Conference 2016 Yokohama, Japan June 9 th 2016 NUCLEAR PLANTS AFFECTED BY THE 3.11 EARTHQUAKE 2 March 11 th

SLIDE 1

Multiphase CFD Applied to Steam Condensation Phenomena in the Pressure Suppression Pool

Marco Pellegrini

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

N U P E C

SLIDE 2

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 km

JMA seismic intensity

March 11th 2011

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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 quencher Experiment at SIET, Italy (IAE) T-quencher Experiment at SIET, Italy (IAE)

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

DIRECT CONTACT CONDENSATION IN S/C

4

R/B

MAKE-UP WATER SYSTEMS DIRECT 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+06 500 1000 1500 2000 2500 3000 3500

RPV pressure [MPa(abs)] Time(s)

Computation by A. Buccio (IAE), 2016

Injection point ~ 30 m

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

EULERIAN TWO-PHASE FLOW 5

∙ ∙ , ∙ ∙

∙

Instantaneous representation Heat flux Source terms ∆∆

Energy equation

Average representation Heat flux

SLIDE 6

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

HEXAHEDRAL MESH APPLIED TO A SPHERE

6

D

Area Density

Magnitude of Volume Fraction Gradient

D/16

D/32 D/64 D/128

D

Volume Fraction

SLIDE 7

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

Error [%] ~ 9% error with large refinement

D/16 D/32 D/64 D/128 Error between the computed and theoretical area

D

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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 Error [%]

D/8

Error between the computed and theoretical area

~ 2.5% error with large refinement

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

DOMAIN AND MESH STRATEGIES

9

Small nozzle diameter D = 2 mm Large nozzle diameter D = 210 mm

Mesh elements: 305,067

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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 diameter D = 2 mm Large nozzle diameter D = 210 mm

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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 20 40 60 80 100 120

Interfacial area [cm2]

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

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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

SLIDE 13

0.231 m

6/10/2016 Severe Accident Mitigation and Research Collaboration

EXPERIMENTAL EVIDENCE

Pool temperature [°C]

TPOOL = 57-61 °C

Steam reaching point

0.2 kg/s water level 2.8 m 1.24 m

13

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

DIRECT CONTACT CONDENSATION: CHUGGING-2

14 pressure sensor Multi hole pipe In recent experiment we employed transparent pipes to visualize the bubble phenomenology during direct contact condensation

SLIDE 15

NURETH-16, Hyatt Regency, Chicago

RAYLEIGH-TAYLOR INSTABILITY

6/10/2016

15

Psteam < Pwater

1

i s

k a            

Final terms for area growth A

steam water Psteam Pwate

r

Psteam Pwater steam water

Accelerating flow field

Pstea

m

Pwater

n t t t te

 

 



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

IMPLEMENTATION INTO STAR-CCM+

16 Compressible steam flow Compressible steam flow Record amplitude length at previous time step

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

LARGE NOZZLE DIAMETER: POOLEX

17 WATER

Incompressible – Constant properties
k-ε standard
Temperature = 62 ºC

STEAM

Compressible

velocity inlet pressure

utlet

adiabatic walls

T = 106 °C v = 11.02 m/s

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

Mesh elements: 405,067

D/16

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

EFFECT OF RTI MODELIZATION

18 Pressure monitor

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

VOLUME FRACTION

19 Tpool = 62 ºC Tpool = 62 ºC Minimum area model Rayleigh-Taylor Instability Model

Steam flow Steam flow

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

20 EXP RTI model

Tanskanen, Ph.D. Thesis 2012

No RTI model

SLIDE 21

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

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

SMALL NOZZLE DIAMETER: CLERX ET AL.

22 WATER

Incompressible – Constant properties
k-ε standard
Temperature = 25 ºC

STEAM

Compressible

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

Mesh elements: 405,067

D/16

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

VOLUME FRACTION FIELD

23 Minimum area model Rayleigh-Taylor Instability Model

Clerx et al., 2009

0.3 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

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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 2 4 6 8 10 12 Penetration Length [mm] Time [ms] Clerx Experiment BL + no RTI RTI

Minimum area model RTI Model

Clerx et al., 2009

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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

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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

SLIDE 27

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

UNIT 3 UNIT 2 UNIT 1

Courtesy of S. Mizokami, TEPCO