Experimental Investigation of the Overall Residence Time of Pebbles in a Pebble Bed Reactor (PBR) using Radioactive Pebble


The granular flow of pebbles in a pebble bed reactor (PBR) under the influence of gravity is a dense granular flow with long-lasting frictional contacts. The basic governing physics is not fully understood and hence the dynamic core of a PBR and non-idealities associated with pebbles flow inside the reactor core are of non-trivial significance from the point of view of safety analyses, licensing, and thermal hydraulics. In the current study, overall and zonal pebbles residence time investigation is carried out by implementing noninvasive radioisotope-based flow visualization measurement techniques such as residence time distribution (RTD) and radioactive particle tracking (RPT). The characteristics of overall pebble residence time/transient number, zonal residence time, and the z-component of average zonal velocities at different initial seeding positions of a tracer particle have been summarized. It is found that the overall pebbles residence time/transient number increases (the z-component of average zonal velocities decreases) from the center towards the reactor wall. Also, pebbles' zonal residence time results (the whole core is divided into three zones) which provide more insight and understanding about PBR core dynamics have been reported. The benchmark data provided could be used for assessment of commercial/in-house computational methodologies related to granular flow investigations.


Chemical and Biochemical Engineering


The authors acknowledge the financial support provided by the Department of Energy (DOE) Nuclear Energy Research Initiative (NERI) project (NERI-08-043).

Keywords and Phrases

Confined Flow; Fluidized Beds; Granular Materials; Pebble Bed Reactors (PBR); Radioactivity; Computational Methodology; Core Dynamics; Dense Granular Flows; Experimental Investigations; Radioactive Particle Tracking; Radioactive Particles; Thermal Hydraulics; Visualization Measurements; Radioactive Particle Tracing (RPT); Residence Time Distribution (RTD)

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Article - Journal

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© 2016 Elsevier, All rights reserved.

Publication Date

01 Nov 2016