1. GAMMA Code for NGNP Air Ingress Analysis Chang Oh RELAP5 Workshop November 8, 2007

2. History of GAMMA Development Air Ingress Analysis Code PCU System Analysis Analysis for H2 Production Plant (High-temperature Steam Electrolysis Process) NRL(National Research Lab) Program: 2006-2010 INERI Program: 2003-2006 INERI Program: 2007-2009 Analysis for H2 Production Plant (Thermochemical Process)

3. What is air-ingress” Why a new code? -Air-ingress is a design- based serious accident in VHTR. -Accelerating heatup of core -Mechanical degradation of bottom structural graphite -Releasing toxic gas

4. Main Characteristics of GAMMA GAMMA: GAs Multicomponent Mixture Analysis Transient multi-D fluid and solid treatment: 1D~3D Various coordinates: Rectangular & Cylindrical 1D/3D merging: some components can be treated 1D while others are treated 2D or 3D. ICE numerical scheme: matrix reduction, quick convergence, powerful for transient analysis Treatment of 6 gas species: He, O 2, N 2, CO, CO 2, H2O Chemical reaction models: homogeneous, heterogeneous Diffusion models: full multicomponent diffusion, effective diffusion, tracer diffusion models Surface-surface radiation model Porous body treatment in the core: effective thermal conductivity

5. Governing Equations of GAMMA Mass Conservation: mixture, He, N2, O2, CO, CO2, H2O Momentum Conservation Energy Conservation

6. Numerical Features of GAMMA  Semi-implicit & Donor Cell Scheme, Staggered Mesh Layout  Linearization by Newton Raphson’s Method  Matrix Reduction by ICE (Implicit Continuous Eulerian)  10N  10N  N  N Pressure Matrix

7. Numerical Tests: GAMMA and FLUENT Inverse U-tube Experiments in Binary Mixture [Takeda & Hishida (1991)] GAMMA Model FLUENT Model

8. Results Test cases Max. time stepComputation time GAMMAFLUENTGAMMAFLUENT Isothermal0.5 sec0.2 sec32 min.20 hrs Non- isothermal 0.5 sec0.2 sec36 min.22 hrs

9. Validation of GAMMA Test FacilityDNCRCPetc 1Pipe Network, NWU O 2Blowdown, NWUO O 3Buncan & Toor’s ExperimentO 4Inverse U-tube single/multiple channel testOO 5Ogawa’s circular tube testO 6Takahashi’s annular tube testO 7VENTURA pebble bed testOO 8Inverse U-tube air ingress experimentOOO 9HTTR simulated air ingress experimentOOO O 10Vertical slot experimentOO 11NACOK natural convection testOO 12SANA-1 afterheat removal testO 13HTTR RCCS mockup testOO 14SNU RCCS testOO * D : Diffusion * NC : Natural Convection * R: Radiation * C: Chemical Reaction * P: Porous Media

10. Air Ingress Analyses: PBMR 268 MWt GAMMA System Modeling input Conditions: Tin/Tout : 500/900 o C Total Coolant Flow: 129 kg/s Cavity Wall Temp. : 50 o C (ss), 80 o C (tr) water-cooled RCCS Vault Volume : 50,000 m 3

11. Air Ingress Analyses (Con’t): Results Mole Fractions of Gas Species in a Vault and Air Flow Rate Temperature Variation in Center Ring Air Volume (50,000 m 3 : German HTR-module Data in a vault) He discharge into vault Onset of natural circulation Air depletion

12. Experiments for Graphite Oxidation Type 1Type 2 Type 1Type 2 Graphite temperature Operating pressure Oxygen concentration Gas velocity Gas material Graphite material Graphite geometry Experimental Variables

13. Graphite Oxidation Models Kinetics Mass Diffusion Graphite Oxidation Models Burn-off Effect Geometrical Effect C/CO2 reaction air flow rate temperature concentration degree of burn-off size & shapeC/CO 2 reaction Moisture Effect Moisture

14. Gas Turbine Analyses

15. Main Characteristics of Throughflow Analysis Meridional plane of compressor 1.to use natural coordinates (q,m) instead of cylindrical coordinates (r, ,z): one transformed momentum equation in the q direction. 2. to produce the radial equilibrium equation combining the one transformed momentum and energy equations through eliminating pressure: radial equilibrium equation and continuity equation m: streamline tangential direction at the edges of blades q: blade-edge directions

16. Development of SANA Gas turbine analysis (SANA: Streamline curvature Analysis based on Newton-Raphson numerical Application)  Throughflow analysis based on Newton-Raphson method :  Numerically robust and efficient method  3D complex problem -> axisymmetric 2D problem (radially nonunform axial velocity distribution) Validation of SANA Coupling of SANA with GAMMA  Implementation into transient system codes

17. Performance of GTHTR300 Gas Turbine

18. Design-point Performance ParametersJAEAKAISTDeviation (%) Pressure ratio1.8701.857-0.695% Temperature ratio1.2691.258-0.867% Polytropic efficiency (%)92.8 0% Shaft Work (MW)530528-0.377% ParametersJAEAKAISTDeviation (%) Pressure ratio1.9971.977-1.002% Temperature ratio1.3591.350-0.662% Polytropic efficiency (%)90.590.70.221% Shaft Work (MW)251246-1.992%

19. Off-design Performance of Compressor

20. Work Diagram of RELAP5/GAMMA Interfacing GAMMA Dynamic Model -Component models -turbomachinery -shaft-generator -heat exchangers -valve -Controller models -bypass -inventory -reactivity RELAP5-3D Hydrogen Model -Process models: -Busen process, -HI process, -H2SO4process -Physical models: -mass transfer coeff., -pressure drop, -entrainment-weeping, -flooding,etc -Thermodynamic property models: -K-value, -activity coeff. -vapor pressure, -physical property IHX Coupling Model Interfacing Using PVMEXEC Or DLL (1st step 2006 - 2008 ) Interfacing (2nd step:2009-2011) 1st step (2006-2008) 2nd step (2009-2011) - Diffusion for multiple components - Three dimensional heat transfer capability

21. RELAP5/GAMMA Interfacing