Analysis of granular flow in a pebble-bed nuclear reactor

Other · Mon Apr 17 00:00:00 EDT 2006

OSTI ID:882198

Rycroft, C H; Grest, Gary S; Landry, James W; Bazant, Martin Z

Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a ma jor impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440,000 frictional, viscoelastic 6cm-diameter spheres draining in a cylindrical vessel of diameter 3.5m and height 10m with bottom funnels angled at 30° or 60° . We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: FG02-02ER25530
• OSTI ID: 882198
• Report Number(s): DOE/ER/25530-5; TRN: US200716%%199
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
22 GENERAL STUDIES OF NUCLEAR REACTORS
DESIGN
DIFFUSION
DISTRIBUTION
FRICTION
GRAPHITE
PHYSICS
POROSITY
REACTOR CORES
REACTOR PHYSICS
REACTORS
VELOCITY
pebble bed nuclear reactor
granular flow
discrete element method
simulation
diffusion
mixing
bidisperse
guide ring
Voronoi volume