Experimental investigation on self-leveling behavior in debris beds

An investigation on debris bed self-leveling behavior with non-spherical particles

“…In a postulated core disruptive accident (CDA) of a sodium-cooled fast reactor, core debris might settle on the core support structure and/or in the lower inlet plenum of the reactor vessel (as illustrated in Figure 1) because of rapid quenching and fragmentation of molten core materials in the subcooled sodium plenum [1,2]. Typically, the debris bed will form roughly conically shaped mounds.…”

“…Typically, the debris bed will form roughly conically shaped mounds. However, coolant boiling caused by decay heat, might lead ultimately to leveling of the debris bed [2,3]. This mechanism, as illustrated in Figure 2, defines the term 'debris bed self-leveling'.…”

“…Thus, the study on this behavior is of essential importance to the design of the tray. In addition, self-leveling behavior will greatly affect the heat removal capability of debris beds [2,3].…”

“…Overall, as illustrated in Figure 3, those experiments can be generally divided into two categories, namely the macroscopic leveling experiments and microscopic flow-regime investigations. Due to the non-transparency of particle beds, the macroscopic leveling experiments were mainly performed to clarify the overall characteristics of leveling [2,3,[8][9][10], namely the role of experimental parameters (such as particle properties and bubbling rate) on its onset and evolution. In those experiments, to simulate the coolant boiling during CDAs, various experimental methods, including depressurization boiling, bottom-heated boiling as well as gas-injection, have been employed.…”

“…the discrete element method) [14][15][16][17]. However, due to the extremely complex and uncertain nature of the three-phase flow involved in the leveling phenomenon [2,9], empirical approach is still regarded as an attractive and indispensable option at present stage because of its distinct advantage in calculation efficiency. On one hand, with an effective empirical model, experimental database can be expanded (interpolated or extrapolated) with much lower cost.…”