Validation of FLACS CFD Model for Helium Distribution in H-type Chamber

Transcription

1 Validation of FLACS CFD Model for Helium Distribution in H-type Chamber Speaker:Hung-Pei Chen Authors:Wen-Sheng Hsu, Chang Lin Zhong, Hui Chen Lin 23, May, 2013

2 Agenda Introduction Experimental facility Simulation by FLACS Results and Discussions Conclusions 2

3 Introduction Fukushima Daiichi nuclear disaster in 2011 was a series of nuclear meltdowns, hydrogen explosions, and radioactive releases During a severe accident in a nuclear power plant, large amount of hydrogen is generated due to core degradation Accurate calculation of hydrogen concentration distribution and the pressure distribution following hydrogen explosion are important for devising accident management procedures 3

4 Background FLACS (FLame ACceleration Simulator) CFD-tool for gas dispersion and explosion modeling has developed since FLACS uses a 3D Cartesian implicit Navier-Stokes solver based on the SIMPLE method Flow equations are closed with κ-ɛ model for turbulence 4

5 Software Architecture FLACS contains 3 main programs: The preprocessor CASD The CFD simulator Flacs The postprocessor Flowvis Build Geometry CASD Configure Grid Define Scenario FLACS Simulator Monitoring Simulations Flowvis Visualize Results 5

6 Experimental Facility Helium was substituted for Hydrogen because Helium has stable property and similar molar weight as Hydrogen The experimental equipment contains the following 2 parts: H-type Chamber Measuring Instruments Oxygen sensors C (He) = C (O2) 6

7 Experimental facility S3 S5 S2 S4 S6 S1 S7 7

8 Simulation by FLACS Define parameters based on the experiment conditions LEAKAGE CONDITION Type JET Mass flow rate E-5 (kg sec -1 ) Time 600 (sec) Direction +Z Turbulence intensity 0.05 Turbulence length scale (m) GRID STATUS Grid size 4*4*4 (cm) Total number of cells 10,920 8

9 Case 1 Results (1/7) Helium flow patterns in H-type chamber 9

10 Case 1 Results (1/7) Helium flow patterns in H-type chamber 9

11 Case 1 Results (2/7) % difference

12 Case 1 Results (3/7) 0 ~ 300 sec 300~600 sec S2 S S1 S1 Position of experiment oxygen sensor Position of simulated monitor point Direction of He flow 11

13 Case 2 Results (4/7) % difference

14 Case 2 Results (5/7) ~ 300 sec S S1 Position of experiment oxygen sensor Position of simulated monitor point Direction of He flow 13

15 Case 3 Results (6/7)

16 Case 3 Results (7/7) ~ 300 sec S2 S S1 S1 Position of experiment oxygen sensor Position of simulated monitor point Direction of He flow 15

17 Conclusions Successfully obtained snapshots of the He concentration distributions without interfering the flow field. Simulation results by FLACS code show good agreement with H-type chamber experimental data. 16

18 Future work The effect of vapor environment instead of air on He distribution will be studied in future works Simulations with finer meshes by taking advantages of FLACS multi-core version will be conducted. Use FLACS code to simulate Hydrogen distributions in nuclear power plants 17

19 18

20 China Where is Taiwan? Nuclear Safety & Disaster Prevention Lab 7,500 miles Taiwan

21 Core Degradation Nuclear fuel rods are sheathed in zircalloy If sufficient cooling water for fuel rods is lost and the temperature gets higher than 1500, a chemical reaction will occur rapidly then. The formula of zirconium-water reaction : Zr + 2 H 2 O ZrO 2 + 2H BTU/lb GRAPHIC: Wilson Andrews, Alberto Cuadra, Bonnie Berkowitz, Patterson Clark, Laris Karklis, Nathaniel Vaughn Kelso, Todd Lindeman, Alicia Parlapiano, Jason Samenow, Laura Stanton, Gene Thorp, Bill Webster, Karen Yourish - The Washington Post. Updated March 25, 2011.

22 Experimental Conditions Assume N 2 =79%, O 2 =21% 0.21 X 0.79 Y = Y 3.762X C He =1- X - Y = C O 2 22

23 Results Sensitivity analysis for key parameters Turbulence Length Scale Turbulence Intensity Grid size 23

24 Results Turbulence Length Scale Sensitivity Analysis 1% jet diameter ( m) 10% jet diameter (0.004 m) 100% jet diameter (0.04 m) No difference 24

25 Results Turbulence Intensity Sensitivity Analysis Low (0.005) Medium (0.05) High (0.5) No difference 25

26 Results Grid Sensitivity Analysis Fine mesh (2 cm) Coarse mesh (4 cm)

27 Monitor points 27

28 The sensitivity of the O2 sensors QEL CTS-M5 Maximum Display Range Default Range Response Time Sensor Type Sensor Life Signal Output Applicable Temperature 0-25% v/v 0-25% v/v < 60 秒 Electrochemistry 2~3Years Analogy 4~20mA -20oc~40oc Tolerance ±