Summary: Numerical simulation of ceramic breeder pebble bed
thermal creep behavior
Alice Ying *, Hulin Huang, Mohamed Abdou
Mechanical and Aerospace Engineering Department, UCLA, Los Angeles, CA 90095-1597, USA
The evolution of ceramic breeder pebble bed thermal creep deformation subjected to an external load and a dif-
ferential thermal stress was studied using a modified discrete numerical code previously developed for the pebble bed
thermomechanical evaluation. The rate change of creep deformation was modeled at the particle contact based on a
diffusion creep mechanism. Numerical results of strain histories have shown lower values as compared to those of
experimentally observed data at 740 °C using an activation energy of 180 kJ/mol. Calculations also show that, at this
activation energy level, a particle bed at an elevated temperature of 800 °C may cause too much particle overlapping
with a contact radius growth beyond 0.65 radius at a later time, when it is subjected to an external load of 6.3 MPa.
Thus, by tracking the stress histories inside a breeder pebble bed the numerical simulation provides an indication of
whether the bed may encounter an undesired condition under a typical operating condition.
Ó 2002 Elsevier Science B.V. All rights reserved.
Characterization of the elastic and creep properties
of ceramic breeder pebble beds under thermomechanical
loads is necessary to ensure that the integrity of beds
does not become the blanket lifetime limiting factor.