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Simulation of an inherently-safe system for a nuclear reactor energy source

Simulation of an inherently-safe system for a nuclear reactor energy source. Stellenbosch University NRF - primary funder Presented by Karl Loubser Supervised by Mr RT Dobson. Energy Postgraduate Conference 2013. Overview. Background Objectives Theoretical model

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Simulation of an inherently-safe system for a nuclear reactor energy source

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  1. Simulation of an inherently-safe system for a nuclear reactor energy source Stellenbosch University NRF - primary funder Presented by Karl Loubser Supervised by Mr RT Dobson Energy Postgraduate Conference 2013

  2. Overview • Background • Objectives • Theoretical model • Experimental Setup – Primary loop • Experimental Setup – Secondary loop • Results – Convective mixing • Results – Bubble trouble • Conclusion

  3. Background • Importance of safety • Inherently safe • Containment layers x4 • Natural circulation benefits • System • Primary loop • Secondary loop • Encasement • Air-cooled Natural circulating emergency condenser • Concrete shell natural cooling 4 3 2 1

  4. Objectives • Develop theoretical model with computer simulation of primary loop • Design and build experimental model of primary and secondary loops • Validated theoretical model using experiment • Derive empirical model of secondary loop • Recommendations ?

  5. Theoretical model • Fully explicit transient simulation • Developed and written in Fortran • 1-D, homogeneous flow model • Boussinesqapproximation • Equations derived from mass, momentum and energy conservation laws • Dimensions equivalent to experiment

  6. Primary Loop Experimental Setup • Water working fluid • Total height 5 m • Max temp. 120˚C • 12 Thermocouples • Full length windows • Pressuriser connection • Orifice flow meter [10Hz] • Reactor [9 kW] • Riser [3m] 4 3 2 1

  7. Secondary loop Experimental Setup • Methanol working fluid • Compact • 2 separate loops • Condenser-water cooled • Constant head water supply • Condensate return • Remove 7.2 kW each (ΔT=95˚C)

  8. Convective mixing Results • Single directional flow • Large vs. small diameter • Experimental plumes • Mixing function by volume • Results • Experiment • Without • With • Importance of • correlation Test results Without convective mixing With convective mixing

  9. Bubble trouble Results • Sub-cooled boiling • Nucleation points • Pulsations • Geysering • Heat-pipe mode • Return flow • Orifice restriction Boiling Begins 1 2 3 4 5 6 7 8

  10. Conclusion • 1D theory positives/negatives • Experimental validation and observations • Fluctuating flow rates effects • Natural circulation flow rate variables • Heat-pipe performance • Future recommendations • Thanks

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