Advanced nuclear reactors use a large pool of water inventory with an immersed heat exchanger to remove decay heat especially in the case of Station Black Out (SBO). The isolation condenser (IC) immersed in Gravity Driven Water Pool (GDWP) of Advanced Heavy Water Reactor (AHWR) is an example of such systems. Heat rejected by the IC is absorbed in the pool. As a result water density decreases and moves towards the free surface of the pool causing layers of hot water to pile up over colder one giving rise to stratified water inventory. It causes negligible heat transfer and coolant circulation in the pool. The pool at the free surface starts boiling before the grace period (7 days) of AHWR, and structural components such as GDWP walls are subjected to high temperature, which is detrimental in nature. These conditions are undesirable for the integrity of the concrete wall.

  
In the present paper, thermal stratification has been modeled using scaled model of the prototype. Based on power to volume scaling philosophy, a scaled experimental facility has been designed as a part of this work and the use of three shrouds around the IC has been proposed. Shrouds induce strong circulation and mixing of water in the pool, enabling participation of the whole pool inventory in the heat transfer process. This results in a lower temperature of the pool, which in turn increases the efficiency of the passive safety system, and suppresses thermal stratification. Experiments using particle image velocimetry (PIV) technique for the scaled system has been performed for the pool without shrouds and for the pool with the application of three shrouds. PIV allows visualization of flow patterns generated in different sections of the scaled pool, which helps in assessing the efficiency of heat removal system and optimization of the pool. Thermal stratification found to be effectively more suppressed for the inclined heater orientation in the pool for both the cases of with and without shroud configurations.


Experimental Investigations on Thermal Stratification in a Large Pool of Water With Immersed Isolation Condenser

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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