Thermal conductivity of UO2 fuel: Predicting fuel performance from simulation

Abstract

How would you……describe the overall significance of this paper? Atomistic level simulations have not traditionally contributed to nuclear fuel performance simulations. However, recent advances in methodologies and computer power are now enabling atomic level simulations to provide mechanistic insights and parameters that can help in the development of performance codes.…describe this work to a materials science and engineering professional with no experience in your technical specialty? Predicting the thermal and mechanical properties of nuclear fuel is a difficult task due to the many length and time scales involved. In this paper we discuss how the results obtained at the atomistic scale contribute to the continuum models of the standard nuclear fuel performance codes.…describe this work to a layperson? Nuclear reactor performance depends crucially on the ability of the nuclear fuel to transport energy generated by the nuclear reaction to the electricity generating station. This ability is influenced greatly by the structure of the fuel at the very fine scale: down to the position of the individual atoms. In this paper we discuss how computer simulations are able to penetrate to this scale and help to predict energy transport characteristics of the nuclear fuel.Recent progress in understanding the thermal-transport properties of UO 2 for fission reactors is reviewed from the perspective of computer simulations. A path to incorporating more accurate materials models into fuel performance codes is outlined. In particular, it is argued that a judiciously integrated program of atomic-level simulations and mesoscale simulations offers the possibility of both better predicting the thermal-transport properties of UO 2 in light-water reactors and enabling the assessment of the thermal performances of novel fuel systems for which extensive experimental databases are not available.

Thermal conductivity and energetic recoils in UO2using a many-body potential model

“…Thus, thermal conductivity is a key performance parameter for fuel. There have been many experimental studies and simulations of UO 2 thermal conductivity [20]. As the fuel operates under severe radiation environments, its thermal transport properties under radiation damage must be understood.…”

Thermal Energy Transport in Oxide Nuclear Fuel

“…The impact of grain boundaries on UO2 thermal conductivity has also been estimated and extrapolated from MD simulations, revealing only a small impact for micrometer-sized grains (as are typically present in fresh fuel) [638,639,640,641]. However, because grain boundaries serve as sinks for point defects, it is expected that the impediment to thermal transport caused by grain boundaries will increase under irradiation [407,552].…”

“…For example, the reduction in thermal conductivity of UO 2 for several concentrations of edge dislocations has been predicted to develop an analytical form suitable for use in a fuel performance code . The impact of grain boundaries on UO 2 thermal conductivity has also been estimated and extrapolated from MD simulations, revealing only a small impact for micrometer-sized grains (as are typically present in fresh fuel). − However, because grain boundaries serve as sinks for point defects, it is expected that the impediment to thermal transport caused by grain boundaries will increase under irradiation. , MD simulations have been used to investigate the degradation of thermal conductivity due to porosity and the accumulation of fission gas (Xe) or decay gas (He) into bubbles. As expected, increased porosity reduces the thermal conductivity; however, Chen et al and Lee et al both showed a decrease in thermal conductivity as the voids were filled with Xe and He, respectively.…”

Thermal conductivity variation in uranium dioxide with gadolinia additions

“…The thermal conductivity of UO 2 is a key property to understand, for the safe and efficient operation of nuclear fuel [8,9,10]. Each fission event produces heat, which is transported through the fuel into the cooling fluid of the power reactor.…”