Institute of Nuclear Technology and Energy Systems

Transcription

1 Institute of Nuclear Technology and Energy Systems Experimental and Analytical Investigation of the Performance of Heat Pipes for Residual Heat Removal from Spent Fuel Pools J. Starflinger, C. Graß, R. Kulenovic, A. Schaffrath, M. Pöhlmann, T. Fuchs Annual Meeting on Nuclear Technology, Hamburg, May 10-12, 2016

2 Motivation Fukushima Follow-up Loss of ultimate heat sink, Station blackout, Loss of infrastructure Loss of human ability to deal with the catastrophe beyond personal experience Source: Tepco The second principle of reactor safety cooling of nuclear fuel must be assured even under severe accident conditions also for wet storage pools, preferably with passive devices! University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 2

3 Spent Fuel Pool Cooling Active vs. Passive Cooling Active Cooling Two strands of the emergency and residual heat removal system (TH) Active components (pumps, valves, etc.) Servicing, maintenance, periodic inspection Time and cost-intensive, particularly in the long-term use! Passive Cooling No active components, control system or operator intervention Based upon physical principles (buoyancy, etc.) IAEA Category B of passivity can be reached Lower failure probability, advantages in operating costs, particularly in long-term use! University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 3

4 Heat Pipes Passive Heat Removal Device Principle of Operation evaporator zone adiabatic zone condenser zone capillary structure evaporation vapour liquid condensation heat input heat output Thermosiphon (without capillary structure) Heat Pipe (with capillary structure) University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 4

5 Heat Pipe Demonstration of Operation Copper heat pipe (filled with water) and full metal copper rod tug in a glass bowl Warm water spilled into the bowl Heat transfer through the heat pipe almost instantaneously. Copper Rod Heat Pipe Glas Bowl Video: C. Graß, W. Flaig, IKE University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 5

6 Heat Pipes Passive Heat Removal System Working Fluids Hg H 2 O Li K Cs Diphenyl, Toluol CH 4 O Na Ag NH 3 Freon C 3 H 8 C 2 H 6 CH 4 N 2 H 2 Selection of working fluid results from the operational temperature range University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 6

7 Heat Pipes Application for Sensor Cooling ( 1100 C environment temperature) Sensor-cooling with heat pipes Heat Pipe Test Lab. at IKE Cooling Heat Pipe Insulation Heating University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 7

8 Heat Pipes Large-Scale Application: Heat Exchanger Hot exhaust gas Preheated combustion air Cold combustion air Cooled exhaust gas 375 Heat Pipes High redundancy! measures (estimated): 1500 x 1500 x 3000mm Heat pipe heat exchanger University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 8

9 Passive Heat Removal System for Generic Spent Fuel Pools Master-Thesis by M. Eng. C. Graß Bundles of Heat Pipes Spent Fuel Pool Air Air Passive heat removal from spent fuel pool to air driven by natural convection Heat pipes suspended from the top, no penetrations of pool walls Heat pipes will have at least two elbows University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/2016 9

10 Objectives Develop a numerical tool for steady state heat removal calculation from a wet storage pool to the air by means of heat pipes / thermosiphons Selection of the appropriate working fluid Simulation of operation performance Identify open points University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

11 Boundary Conditions Pool temperatures provided by KTA: Operation Conditions Heat Source / C Heat Sink / C Driving Force (Temperature difference) / C Normal Abnormal Accident Coarse geometrical and power data taken from spent fuel storage pool in NPP Gösgen, Switzerland Masterpiece University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

12 Numerical Iteration Scheme Steady State Heat Balance Heat balance between pool and atmosphere Chain of iteration loops for the system temperatures along the heat transfer from source to sink Equations according to VDI- Wärmeatlas, Section MI, and open literature Examination of the performance limits and the modelled performance of the heat pipe University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

13 Selection of Working Fluid - Figure of Merit Heat Pipes University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

14 Selection of Working Fluid - Figure of Merit Thermosiphons University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

15 Steady State Heat Removal Example: Results for 40mm pipe Compared to heat pipes, power transferred is higher for thermosiphons because of less friction 20% difference University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

16 Operation Limits of Heat Pipes / Thermosiphons Example: Results for 40mm pipe Counter Current Flow Limitation (CCFL) in the order of 4 6 kw Both heat pipes and thermosiphons have performance margins up to a factor of four. University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

17 Summary of Results Feasibility: Heat pipes / thermosiphons are suitable to transfer decay heat from wet storage facilities into the diverse ultimate heat sink (air) Dimensions: Length at least 12m (construction reasons) > 5 m Condenser Zone > 6 m > 1 m Adiabatic zone Evaporator zone Inclination University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

18 Summary of Results Support of Gravity: Heat pipes shall be manufactured as thermosiphons without capillary structure. Inclination of adiabatic section >5. Conservatism: With increasing temperature difference, more heat is transported through the heat pipes. Heat Transfer Limit: Air side (condensation zone of heat pipe) Measures necessary (e.g. fins, chimney effect). Open points: Long heat pipes with elbows. High pressure loss? There are no validation data available for long heat pipes. In ATHLET (or other system codes) there is no validated model available of heat pipes. University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

19 Project PALAWERO / Heat Pipes Cooperation between GRS and IKE (and AREVA) Three year project, start: Dec. 1, 2015 Funded by BMWi (FKZ and RS 1543) Scope: Experiments in laboratory and in realistic environment providing validation data Derivation of a correlation for long heat pipes, based upon experimental laboratory data Set-up and validation of a mechanistic model of heat pipes in ATHLET Benchmark of wet storage pool cooling (mechanistic model vs. correlation) University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

20 Project PALAWERO / Heat Pipes Laboratory experiment IKE laboratory hall Planned single heat pipe experiments: Pipes straight up (base case) Pipes with two elbows and different inclination Different diameters Different working fluids With and without capillary structures Validation data base with well defined boundary conditions! 4 m 8 m Roof Ground floor Basement Cooling through cryostat Water pool (heated) Water pool (heated) University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

21 Project PALAWERO / Heat Pipes Experiment under realistic environmental boundary conditions University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

22 Acknowledgements IKE and GRS like to thank the Federal Ministry of Economic Affairs and Energy for supporting the projects PALAWERO / Heat Pipes (FKZ and RS 1543) University of Stuttgart Institute of Nuclear Technology and Energy Systems 12/5/

23 Institute of Nuclear Technology and Energy Systems Thank you! Prof. Dr.-Ing. Jörg Starflinger phone +49 (0) fax +49 (0) University of Stuttgart Institute of Nuclear Technology and Energy Systems (IKE) Pfaffenwaldring Stuttgart Germany