Thermo-mechanical behavior simulation coupled with the hydrostatic-pressure-dependent grain-scale fission gas swelling calculation for a monolithic UMo fuel plate under heterogeneous neutron irradiation

Abstract

Monolithic UMo fuels have a higher uranium density than previously developed fuels. They have become the most promising fuels to be used in high-flux research and test reactors after the US Office of Material Management and Minimization Reactor Conversion Program (formerly Reduced Enrichment Research and Test Reactor (RERTR) program). In this study, a computational method is established to couple the macro-scale irradiation-induced thermo-mechanical behavior simulation with the hydrostatic-pressure-dependent fission gas swelling calculation in the UMo grain. The stress update algorithms and consistent stiffness moduli are respectively presented for UMo fuel, in which both the hydrostatic-pressure-dependent irradiation swelling and deviatoric-stress-directed irradiation creep are taken into account. Accordingly, the user subroutines to define the thermo-mechanical non-homogeneous constitutive relations for the UMo fuel meat and Al cladding are developed and validated. The in-pile behavior in a monolithic UMo fuel plate under a location-dependent irradiation condition is calculated and discussed.

Effects of U-Mo Irradiation Creep Performance on the Thermo-Mechanical Coupling Behavior in U-Mo/Al Monolithic Fuel Assemblies

“…For the numerical implementation of the thermal-mechanical theoretical models on the commercial software ABAQUS, it is necessary to define the location-irradiation time-temperature dependent thermal-mechanical constitutive relations. The solution techniques in this study are similar to those in our previous works Gong et al, 2013;Gong et al, 2014;Zhao et al, 2014;Cui et al, 2015;Kong et al, 2018). Here, the threedimensional mechanical constitutive relation in an incremental form is briefly introduced as follows.…”

“…One should develop stress update algorithms and consistent stiffness modulus, with the other strain increment contributions involved, and then the subroutines of UMAT can be programmed to define the irradiation-induced complex mechanical constitutive relations. For the U-Mo fuel foil and Al alloy, the similar solution strategy as those in our previous works Gong et al, 2013;Gong et al, 2014;Zhao et al, 2014;Cui et al, 2015;Zhao et al, 2015;Kong et al, 2018) is adopted in this study, and the developed models, algorithms and user-defined subroutines have been verified. Especially, with the mechanistic gaseous swelling model and irradiation creep model used for U-Mo fuels, the fuel foil thickness increments in a mini plate were calculated to match well with the experimental results (Jian et al, 2019a).…”

Macro-Mesoscale In-Pile Thermal-Mechanical Behavior Simulation of a UMo/Zr Monolithic Fuel Plate

“…Firstly, the heat generation of the UMo fuel meat will cause non-uniform temperature field in the fuel plate, which causes certain temperature gradients and thermal stress in the fuel element (Yan et al, 2019a). In addition, the solid and gas fission products lead to the volume growth of the UMo fuel meat (Kong et al, 2018). The fission gas swelling is dependent on the nucleation and growth of fission gas bubbles and affected by stress state, fission rate, temperature and recrystallization effect (Kong et al, 2016;Yan et al, 2019a;Kong et al, 2018), etc.…”

“…In addition, the solid and gas fission products lead to the volume growth of the UMo fuel meat (Kong et al, 2018). The fission gas swelling is dependent on the nucleation and growth of fission gas bubbles and affected by stress state, fission rate, temperature and recrystallization effect (Kong et al, 2016;Yan et al, 2019a;Kong et al, 2018), etc. As shown in Figure 1, the fission gas bubbles make the UMo fuel meat a porous structure, which will continue to evolve with the development of burn-up (Meyer et al, 2014).…”

Coupled Thermomechanical Responses of Zirconium Alloy System Claddings under Neutron Irradiation

“…The three-dimensional deformation of a typical 17 × 17 fuel assembly was determined by numerical simulation [10]. The thermomechanical behavior simulation, coupled with the hydrostatic-pressure-dependent, grain-scale fission gas swelling calculation for a monolithic UMo fuel plate, was studied under heterogeneous neutron irradiation [11]. The thermomechanical behavior of a Zr-4 fuel rod was studied by experiments and a simulation.…”