Finite element simulation of gap opening between cladding tube and spacer grid in a fuel rod assembly using crystallographic models of irradiation growth and creep

Abstract

A physically-based crystal plasticity framework for modeling irradiation growth and creep is interfaced with the finite element code ABAQUS to study the contact forces and the gap evolution between the spacer grid and the cladding tube as a function of irradiation in a representative section of a fuel rod assembly. Deformation mechanisms governing the gap opening are identified and correlated to the texture-dependent material response. In the absence of coolant flow-induced vibrations, these simulations predict the contribution of irradiation growth and creep to the gap opening between the cladding tube and the springs and dimples on the spacer grid. The simulated contact forces on the springs and dimples are compared to available experimental and modeling data. Various combinations of external loads are applied on the springs and dimples to simulate fuel rods in the interior and at the periphery of the fuel rod assembly. It is found that loading conditions representative (to a first order approximation) of fuel rods at the periphery show higher gap opening. This is in agreement with in-reactor data, where rod leakages due to the synergistic effects of gap opening and coolant flow-induced vibrations were generally found to occur at the periphery of the fuel rod assembly.

Data-Driven Constitutive Model for the Inelastic Response of Metals: Application to 316H Steel

“…Clearly the predictiveness in these regimes will necessarily be conditioned by that of the models describing each deformation mechanism [45,46]. However, the direct use of these CP based mechanistic constitutive models within the FE solver at every integration point of a structural component [47] is computationally cost-prohibitive [48][49][50][51][52].…”

Extension of the visco-plastic self-consistent model to account for elasto-visco-plastic behavior using a perturbed visco-plastic approach

“…First, it is a stress-dependent quantity, as we show next, but we will identify it with the stress independent eigenstrain rate e*  in equation (1). Second, if the elastic interaction equation equation (22) were truly independent of the visco-plastic interaction equation equation (21), and if both of them were simply additive, e d el  would be zero. As a consequence, the term e d el  can be regarded as a measure of 'elastic consistency', and represents the degree of coupling between both regimes.…”

“…A potential advantage of the VPSC+ approach concerns the implementation of polycrystal constitutive laws in FE codes. Specifically, VPSC has been interfaced with the commercial FE software ABAQUS by several authors [18][19][20][21][22][23], which allows one to account for the evolution of local hardening and anisotropy via grain-based hardening laws and texture evolution, respectively. In the above implementations the elasticity at each integration point is treated separately from the plastic response, which requires one to iterate between elastic and plastic contributions until stress equilibrium is fulfilled [21].…”

Polycrystalline Simulations of In-Reactor Deformation of Zircaloy-4 Cladding Tubes during Nominal Operating Conditions

“…During the past several years, a renewed interest in the modelling of in-reactor deformation of zirconium alloys has arisen with the development of multiscale approaches from the single crystal to the structure component that couples a viscoplastic self-consistent model with a finite element code 15,16 . Recently, full-field simulations, based on the Fast Fourier Transform method, have also been applied to the in-reactor behavior of recrystallized Zircaloy-4 guide tubes 17 .…”