Analysis of granular flow in a pebble-bed nuclear reactor

@article{citeulike:2722772, abstract = {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 major 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 6-cm-diam spheres draining in a cylindrical vessel of diameter 3.5\ \ m and height 10\ \ m 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.}, author = {Rycroft, Chris H. and Grest, Gary S. and Landry, James W. and Bazant, Martin Z. }, citeulike-article-id = {2722772}, doi = {http://dx.doi.org/10.1103/PhysRevE.74.021306}, journal = {Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)}, keywords = {flow, grains, qualifier}, number = {2}, posted-at = {2008-04-27 00:15:53}, priority = {2}, publisher = {APS}, title = {Analysis of granular flow in a pebble-bed nuclear reactor}, url = {http://dx.doi.org/10.1103/PhysRevE.74.021306}, volume = {74}, year = {2006} }

TY - JOUR ID - citeulike:2722772 L3 - citeulike-article-id:2722772 TI - Analysis of granular flow in a pebble-bed nuclear reactor JF - Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) VL - 74 IS - 2 PB - APS N2 - 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 major 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 6-cm-diam spheres draining in a cylindrical vessel of diameter 3.5  m and height 10  m 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. KW - flow KW - grains KW - qualifier AU - Rycroft, Chris AU - Grest, Gary AU - Landry, James AU - Bazant, Martin PY - 2006/// UR - http://dx.doi.org/10.1103/PhysRevE.74.021306 ER -