Experimental Investigation On Heat Transfer Behavior Of The Spent Fuel Bundle Under The Pool-Boiling Condition

Fukushima nuclear accident causes the attention of researchers to the safety of the spent fuel pool in the nuclear power plant,especially the heat transfer behavior of spent fuel bundle on the background of the cooling system failure of the spent fuel pool.Because the impact of special rod bundles is special,the heat transfer characteristics are very complex for the two-phase boiling heat transfer of the spent fuel.So far,the research on the pool boiling heat transfer of spent fuel pool is not enough,and the two-phase boiling behavior,flow characteristics and heat transfer mechanism need further research.As a result,the boiling heat transfer characteristics of the two-phase flow in rod bundle channel are studied in this paperA rod bundle channel pool boiling experimental test rig was built with 9×9 stainless steel vertical tube bundle to simulate the spent fuel assemblies,for which the diameter is 9.6mm and the length is 4800mm.And a series of experiments were carried out in different power and initial water levels.The heat transfer coefficients along the channel height direction were obtained in the pool boiling experiment.Meanwhile,the bubble flow patterns in the rod bundle channel were identified and classified by using the high-speed imaging technology,and also we have studied and analyzed all kinds of flow patterns combined with the heat transfer coefficient.Furthermore,the effects on the heat transfer coefficient of different heat fluxes and different initial water temperature of the spent fuel assemblies were analyzed and studied according to the experimental data.And we have analyzed and evaluated the safety of the pool boiling in spent fuel pool according to the experimental phenomena and data.The result reports that DNB won't appear inside the spent fuel assembly during the boiling stage,which reprensents there is few possibility for the rod to burn out.even with partial exposion to the air.