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

Abstract

Studies on debris bed self-leveling behavior with non-spherical particles are crucial in the assessment of actual leveling behavior that could occur in core disruptive accident of sodium-cooled fast reactors. Although in our previous publications, a simple empirical model (based model), with its wide applicability confirmed over various experimental conditions, has been successfully advanced to predict the transient leveling behavior, up until now this model is restricted to calculations of debris bed of spherical particles. Focusing on this aspect, in this study a series of experiments using non-spherical particles was performed within a recently developed comparatively larger scale experimental facility. Based on the knowledge and data obtained, an extension scheme was suggested with the intention to extend the base model to cover the particle-shape influence. The proposed scheme principally consists of two parts -with one part for correcting the terminal velocity of a single non-spherical particle, which is the key parameter in our base model, and the other for representing the additional particle-particle interactions caused by the shaperelated parameters. Through detailed analyses, it is found that by coupling this scheme, good agreement between experimental and predicted results can be achieved for both spherical and non-spherical particles given current range of experimental conditions.

A new empirical model for self-leveling behavior of cylindrical particle beds

“…In these comprehensive studies, it was successfully demonstrated that the proposed empirical model has wide applicability over various conditions for predicting the transient leveling development observed in experiments using spherical particles. In addition, the above model was recently extended to consider the particle-shape effect by correcting u t for non-spherical particles and introducing shaperelated parameters into Equations (5) and (6) to represent particle-particle interactions [16]. The extended model also provides good agreement with the available experimental data for non-spherical particles.…”

“…This is because the gas was injected into the bed through porous metallic plates, which have a relatively large flow resistance. A detailed description of the selfleveling experiments is presented in our previous studies [13,16].…”

“…According to this method, particle sphericity can be determined by the well-known Ergun correlation [21]. The pressure drop measurement experiment is explained in detail in our recent papers [16,17].…”

“…To further clarify the mechanisms underlying selfleveling behavior, we conducted several series of experiments using simulant materials in collaboration with the Japan Atomic Energy Agency (JAEA) and Kyushu University in Japan [11][12][13][14][15][16][17]. In these experiments, depressurization boiling, conventional pool boiling and gas injection were used to simulate sodium boiling.…”

SIMMER-III Analyses of Local Fuel-Coolant Interactions in a Simulated Molten Fuel Pool: Effect of Coolant Quantity

“…The disaster in March 2011 at the Fukushima Daiichi Nuclear Power Plant in Japan has caused many people to realize that severe accidents might occur, even if their probability is extremely low [1][2][3]. For sodium-cooled fast reactors (SFR), since the core is not generally designed at the most reactive configurations, in the past, the sequences and consequences of hypothetic severe accidents have been extensively investigated [4][5][6][7].…”