Numerical Simulation of the Solid Particle Sedimentation and Bed Formation Behaviors Using a Hybrid Method

Abstract

In the safety analysis of sodium-cooled fast reactors, numerical simulations of various thermal-hydraulic phenomena with multicomponent and multiphase flows in core disruptive accidents (CDAs) are regarded as particularly difficult. In the material relocation phase of CDAs, core debris settle down on a core support structure and/or an in-vessel retention device and form a debris bed. The bed’s shape is crucial for the subsequent relocation of the molten core and heat removal capability as well as re-criticality. In this study, a hybrid numerical simulation method, coupling the multi-fluid model of the three-dimensional fast reactor safety analysis code SIMMER-IV with the discrete element method (DEM), was applied to analyze the sedimentation and bed formation behaviors of core debris. Three-dimensional simulations were performed and compared with results obtained in a series of particle sedimentation experiments. The present simulation predicts the sedimentation behavior of mixed particles with different properties as well as homogeneous particles. The simulation results on bed shapes and particle distribution in the bed agree well with experimental measurements. They demonstrate the practicality of the present hybrid method to solid particle sedimentation and bed formation behaviors of mixed as well as homogeneous particles.

Experimental and numerical investigations into molten-pool sloshing motion for severe accident analysis of sodium-cooled fast reactors: A review

“…For sloshing motion with solid particles, taking into account the past numerical investigations into particle-related phenomena for the assessment of severe accidents in SFRs (Shamsuzzaman et al, 2014;Tagami and Tobita, 2014;Guo et al, 2017;Tagami et al, 2018;Sheikh et al, 2020), in which solid particles played a major role in the multiphase behaviors, microscopic models for inter-particle collisions and contacts or the discrete element method (DEM) may additionally be considered in the simulations to provide appropriate estimates of particle-particle interactions. 6) Further investigations into the effect of coupling between nuclear power deposition as well as recriticality and pool sloshing motion based on the knowledge obtained from thermal-hydraulics studies.…”

Characteristics and Mechanisms of Debris Bed Formation Behavior in Severe Accidents of Sodium-Cooled Fast Reactors: Experimental and Modeling Studies

“…In IGCAR, experiments were conducted with high-density lead particles to develop an empirical model for predicting the repose angle of the formed debris bed [65]. At Kyushu University and JAEA, by employing single (i.e., single-sized and single-shaped) solid particles and mixed solid particles, some typical experimental parametric impacts on the overall accumulated-bed characteristics (e.g., bed height and shape) were clarified [23,28,29,[62][63][64]. From their experiments, it was confirmed that under different experimental parameters, the debris bed's geometrical shape would generally be convex or concave.…”

“…Therefore, to elucidate the characteristics and mechanisms of DBF behavior in the case of an SFR, in the past decade, extensive experimental and modeling studies were performed separately at Kyushu University, the Japan Atomic Energy Agency (JAEA) [23,28,29,[62][63][64], Indira Gandhi Centre for Atomic Research (IGCAR) [65], and Sun Yat-Sen University (SYSU) [24,[66][67][68][69][70][71][72]. Figure 2 summarizes these investigations, which can be divided according to their different focal points: (1) investigations focusing on the overall accumulated-bed characteristics; and (2) investigations focusing on the flow regime characteristics.…”

“…Solid particles were discharged into the water pool from the top by gravitation through a nozzle and accumulated at the bottom to form the particle bed. In the investigations focusing on the overall accumulated-bed characteristics [24,29,30,[63][64][65][66], single-sized particles and mixed-sized solid particles in a range of 1.1~6.0 mm were employed, and some key parameters (e.g., particle type, nozzle height, and nozzle diameter) were quantitatively studied based on inter-particle interactions. It was found that concave or conical accumulated beds may be formed during DBF, dependent on the experimental conditions.…”

“…Based on the different formation mechanisms of these flow regimes, an empirical model was developed to predict the DBF flow regime transitions, and its predictability was further extended owing to the knowledge accumulated from the experiments under more realistic conditions (e.g., mixed-sized particles and sodium boiling situations). [23,[28][29][30]41,[61][62][63][64][65]73] and flow-regime characteristics [24,[67][68][69][70][71][72].…”