Modeling and simulation of oxygen transport in high burnup LWR fuel

Thermodynamically Informed Nuclear Fuel Codes—A Review and Perspectives

“…While this point remains speculative, this experience demonstrates how multi-physics simulations may serve as a vehicle for knowledge gap identification and gaining a greater understanding of a problem of practical interest to industry. [40]. The work described in Section 2.2 gave impetus to this work.…”

“…The work described in Section 2.2 gave impetus to this work. Instead of simulating oxygen diffusion driven by concentration gradients of oxygen via the conventional Fickian diffusion methodology, a more fundamental approach involving chemical potential gradients was used, which were calculated directly from Calphad models with multiple sublattices [40]. The conventional use of concentration gradients is typically used for sake of convenience, which also requires a correction for the Soret effect that becomes more prevalent at higher temperatures.…”

“…Moreover, there are challenges with applying concentration gradient terms to multi-component systems corresponding to fission products. Through the approach established by Simunovic et al [40], a correction is not needed for the Soret effect. Furthermore, since the approach is general, one can easily extend it to multi-component systems, which enables oxygen diffusion calculations to account for the effects of fission product chemistry [40].…”

“…As shown in Figure 3, O/M is nearly stoichiometric at the pellet periphery and reaches a maximum at the centre. One challenge reported by Simunovic et al was the marked increase in computational expense associated with performing a large number of thermodynamic equilibrium calculations within BISON [40]. Efforts were made by Poschmann et al in improving computational performance of THERMOCHIMICA when coupled with BISON [41].…”

Thermochemically-Informed Mass Transport Model for Zr in U-Zr Fuel

“…These previous efforts to perform simulations of Zr redistribution in U-Zr metallic fuels have employed a formulation of diffusion based on a term depending on the Zr concentration gradient, plus a Soret term corresponding to the temperature gradient [16,8,15]. In previous work on oxide fuels, we have developed tools that combine these terms into a generalized chemical potential formulation, in which the gradient of the chemical potential (depending on both concentration and temperature, and calculated by Thermochimica) is taken as the driving force for diffusion [41]. In this work, we extend these methods to metallic fuel systems, employing detailed thermochemical calculations to determine key parameters on the fly for our finite element diffusion calculation.…”