Structure and mechanics of a random pebble bed

Mechanism of forming a random pebble-bed structure of HTGR type reactor fuel elements is generally discussed. Estimation of stochastic distribution of spherical fuel elements by contact numbers is carried out random pebble-bed porosity is determined. On the basis of the analysis of spherical fuel element interaction an equation for relative deformation tensor determination in a pebble-bed is derived. Closed system of differential equations for determination of pebble-bed stressed-deformed state is formulated. A program for computation of characteristics of moving fuel element pebble-bed in a cylindrical reactor core with a central recharging port is developed. Computations verifying physical adequacy of used model are carried out. As a result of computations stagnation regions in the pebble-bed volume being characteristic of granular materials are identified. 9 refs.; 9 figs