Mathematical modeling and analysis of fuel rods

On the analogy between thermally and irradiation induced creep

“…result differs from tha t given in (10] in two respects : ( 1 ) Two physically different reduced time scales are present rather than one , and ( 2 ) The nonlinear stress dependence is obtained by generalizing stress to -4 -U--functions of stress rather than by introducing stress into the compliance.…”

“…the material parameters depending on both T and ~~~. For th is case , Rashid [10] proposed a single memory integral with a modified reduced time containing functions of T and •. In this paper we use an alternate approach whereby we superpose memory integrals with two distinct reduced times , where both times contain functions of T and $ with one dominated by the thermal dependence and the other by the flux dependence.…”

Elastic and viscoplastic pellets fragmentation modeling using an axisymmetrical 1D finite element code

“…The relocation of fragments can be treated only on an empirical way (Oguma, 1983;Walton and Matheson, 1984;Ito et al, 1983). The relaxation of stresses and strains can be treated through the mechanical laws by considering the fragmentation using a material approach (Ito et al, 1983;Jankus and Weeks, 1972;Rashid, 1974;Williford et al, 1982;Riktzhaupt-Kleissl and Heck, 1993;Garcia et al, 2002) or an inelastic strain approach (Jernkvist, 1997;Marino et al, 1996;Harriague et al, 1980;Lassmann and Moreno, 1977). The first solution, consisting in the modification of material characteristics, seems to be the most used method.…”

Application of the BISON Fuel Performance Code to the FUMEX-III Coordinated Research Project

“…The relocation model is from ESCORE 10 and prescribes the increase in fuel diameter as a function of the linear heating rate and burnup. The smeared cracking model follows the approach outlined by Rashid 11 , where cracking is simulated by adjusting the elastic constants at material points. This is in contrast to a discrete cracking model, where topographic changes are made to the finite element mesh.…”