A study on evaluation of pebble flow velocity with modification of the kinematic model for pebble bed reactor

A review on numerical models for granular flow inside hoppers and its applications in PBR

“…However, the improper values of the contact parameters can lead to subsequent unexpected simulation problems [34], especially the stiffness k n in soft sphere model which can not be measured directly was considered to be relevant to k t and it is now usually given with an empirical value with no agreed applied rules [6]. Additionally a number of assumptions and constants determined from experimental data will be difficult given the large parameter space [26]. Besides the soft sphere model is somehow simplified which induces deviation from the real contact force, which may lead to some theoretical and conceptual problems [10], so further study and applications of the classical nearexact contact mechanism are required.…”

“…It was found that B increased with the local velocity as well as the conical angle, so a nonlinear constitutive law was proposed and modifications on boundary conditions and spot dynamics were suggested to better describe the general field [8,17]. In addition, some researchers [26] considered that the wall friction related with particle properties was not pertinently included in Equation (5) and it was difficult to analyze pebble velocity in conical hoppers and PBRs having annular core and defuel chutes with an application of this model, therefore in the study, with frictional terms added in Equation (5) and assumptions made upon the flow, a modified kinematic equation without changing B is given as follows. The horizontal view of the pebble reactor with an upper cylindrical region, a conical funnel and a bottom discharge tube is given as Figure 2 ∂…”

“…with kinematic and DEM methods [8]. Kim et al proposed a modified kinematic model with experimentally determined coefficients to simulate the pebble velocity for reactors with annular core [26]. Li et al investigated the trajectories and velocities as well as the particle diffusion at the interface of the "double zones" in PBR during monosized glass beads discharging using the DEM simulation code Granule developed by Thornton's group [37].…”

“…On solving the boundaryvalue problem above, the implicit Crank-Nicholson integration scheme [8,17] has been used to generate numerical solutions to the partial differential equation in Equation (5). A range of parameter B values have been measured experimentally by various groups [17,25,26], and the experimental flow field qualitatively predicted by kinematic model with a single fitting parameter B for steady flows of noncohesive materials in simple geometries were viewed as successes of the model. However, the problem with simple kinematic "continuum" method is that, in the main, it ignores the effects of microstructure of the bulk and relies on an assumed (often over-simplistic) constitutive equation.…”

Neutronic Analysis of LBE-Uranium Spallation Target Accelerator Driven System Loaded with Uranium Dioxide in TRISO Particles

“…The UO 2 fuels prepared in the form of tristructuralisotropic (TRISO)-coated microspherical fuel particles are buried in carbon matrix pebbles with the TRISO packing fraction PF t = 29% and the pebble packing fraction PF p = 60%. TRISO particles are formed as fuel kernel in the center, coated with four layers made of three isotropic materials, (1) porous carbon buffer, (2) inner pyrolytic carbon (IPyC), (3) silicon carbide (SiC) and (4) outer pyrolytic (OPyC) [10]. As is apparent from Fig.…”