Multiphase CFD Applied to Steam Condensation Phenomena in the Pressure Suppression Pool Marco Pellegrini NUPEC STAR Japanese Conference 2016 Yokohama, Japan June 9 th 2016
NUCLEAR PLANTS AFFECTED BY THE 3.11 EARTHQUAKE 2 Operating reactor March 11 th 2011 Under inspection Onagawa ~ 130 km JMA seismic intensity Fukushima Daiichi Fukushima Daini
STATION BLACK OUT 3 R/B High Pressure Alternate Cooling system Courtesy of A. Obonai, Tohoku Electric Power CO Reactor Core Isolation Cooling system T-quencher Experiment at SIET, Italy (IAE) RCIC quencher Experiment at SIET, Italy (IAE)
DIRECT CONTACT CONDENSATION IN S/C 4 MAKE-UP WATER SYSTEMS DIRECT CONTACT CONDENSATION R/B RPV pressure [MPa(abs)] 8.E+06 7.E+06 7.E+06 7.E+06 7.E+06 7.E+06 6.E+06 6.E+06 0 500 1000 1500 2000 2500 3000 3500 Time(s) Injection point Computation by A. Buccio (IAE), 2016 ~ 30 m
EULERIAN TWO-PHASE FLOW 5 Instantaneous representation Average representation Heat flux Heat flux Energy equation Source terms,
HEXAHEDRAL MESH APPLIED TO A SPHERE 6 D D/16 D/32 D/64 D/128 Volume Fraction D Area Density Magnitude of Volume Fraction Gradient 6/10/2016 NURETH-16, Hyatt Regency, Chicago
HEXAHEDRAL MESH APPLIED TO A SPHERE 7 D D/16 D/32 D/64 D/128 Error between the computed and theoretical area Error [%] 20.0% 18.0% 16.0% 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% d/8 d/16 d/32 d/64 d/128 ~ 9% error with large refinement 6/10/2016 NURETH-16, Hyatt Regency, Chicago
POLYHEDRAL MESH APPLIED TO A SPHERE 8 D/8 D/16 D/32 Error between the computed and theoretical area Error [%] 3.50% 3.00% 2.50% 2.00% 1.50% 1.00% 0.50% 0.00% d/16 d/32 d/64 d/128 ~ 2.5% error with large refinement 6/10/2016 NURETH-16, Hyatt Regency, Chicago
DOMAIN AND MESH STRATEGIES 9 Small nozzle diameter D = 2 mm Large nozzle diameter D = 210 mm Mesh elements: 305,067
DOMAIN AND MESH STRATEGIES 10 Small nozzle diameter D = 2 mm Large nozzle diameter D = 210 mm Mesh elements: 305,067 D/16 Mesh elements: 405,067
MESH SENSITIVITY - 1 11 MESH x1.25 MESH x1.0 MESH x0.750 MESH x0.5 0.7 0.6 IFA [Mesh X 0.5] IFA [Mesh X 0.75] IFA [Mesh x1.0] IFA [Mesh x1.25] Interfacial area Interfacial area [cm 2 ] 0.5 0.4 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 Time [ms]
DIRECT CONTACT CONDENSATION: CHUGGING 12 Single hole pipe Pressure sensor In recent experiment we employed transparent pipes to visualize the bubble phenomenology during direct contact condensation
EXPERIMENTAL EVIDENCE T POOL = 57-61 C water level 0.2 kg/s 13 Pool temperature [ C] 2.8 m 1.24 m Steam reaching point 0.231 m 6/10/2016 Severe Accident Mitigation and Research Collaboration
DIRECT CONTACT CONDENSATION: CHUGGING-2 14 Multi hole pipe In recent experiment we employed transparent pipes to visualize the bubble phenomenology during direct contact condensation pressure sensor
RAYLEIGH-TAYLOR INSTABILITY 15 Accelerating flow field steam steam Psteam water P steam Pwate r P water A Pstea m water Pwater P steam < P water Final terms for area growth a i n t t e t t s k 1 2 6/10/2016 NURETH-16, Hyatt Regency, Chicago
IMPLEMENTATION INTO STAR-CCM+ 16 Compressible steam flow Compressible steam flow Record amplitude length at previous time step
LARGE NOZZLE DIAMETER: POOLEX 17 pressure outlet velocity inlet T = 106 C v = 11.02 m/s adiabatic walls D/16 WATER Incompressible Constant properties k-ε standard Temperature = 62 ºC STEAM Compressible Time step = Courant number limited Stopping criteria at interfacial mass transfer (1% of inlet mass flow rate) Mesh elements: 405,067
EFFECT OF RTI MODELIZATION 18 Pressure monitor
VOLUME FRACTION 19 Minimum area model Steam flow Rayleigh-Taylor Instability Model Steam flow T pool = 62 ºC T pool = 62 ºC
Tanskanen, Ph.D. Thesis 2012 20 EXP RTI model No RTI model
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 NURETH-16, Hyatt Regency, Chicago
SMALL NOZZLE DIAMETER: CLERX ET AL. 22 D/16 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
VOLUME FRACTION FIELD 23 0.3 ms 0.6 ms 0.9 Clerx et al., 2009 1.2 ms 1.5 ms 1.8 ms Bubble implosion is less than 2 ms in the experiment at it appears immediately Minimum area model Rayleigh-Taylor Instability Model
CLERX ET AL. EXPERIMENT 24 Clerx et al., 2009 Minimum area model RTI Model Penetration Length [mm] 6.0 5.0 4.0 3.0 2.0 1.0 Clerx Experiment BL + no RTI RTI 0.0 0 2 4 6 8 10 12 Time [ms]
PREDICTION OF TEMPERATURE DISTRIBUTION 25 Minimum area model Measured temperature field RTI Model Clerx et al., 2009
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
UNIT 1 Fukushima Daiichi power plant what are the conditions at this moment? UNIT 2 UNIT 3 Courtesy of S. Mizokami, TEPCO 27