Study on Radial Temperature Distribution of Aluminum Dispersed Nuclear Fuels: U3O8-Al, U3Si2-Al, and UN-Al

Abstract

The understanding of the radial distribution of temperature in a fuel pellet, under normal operation and accident conditions, is important for a safe operation of a nuclear reactor. Therefore, in this study, we have solved the steady-state heat conduction equation, to analyze the temperature profiles of a 12 mm diameter cylindrical dispersed nuclear fuels of U3O8-Al, U3Si2-Al, and UN-Al operating at 597 °C. Moreover, we have also derived the thermal conductivity correlations as a function of temperature for U3Si2, uranium mononitride (UN), and Al. To evaluate the thermal conductivity correlations of U3Si2, UN, and Al, we have used density functional theory (DFT) as incorporated in the Quantum ESPRESSO (QE) along with other codes such as Phonopy, ShengBTE, EPW (electron-phonon coupling adopting Wannier functions), and BoltzTraP (Boltzmann transport properties). However, for U3O8, we utilized the thermal conductivity correlation proposed by Pillai et al. Furthermore, the effective thermal conductivity of dispersed fuels with 5, 10, 15, 30, and 50 vol %, respectively of dispersed fuel particle densities over the temperature range of 27–627 °C was evaluated by Bruggman model. Additionally, the temperature profiles and temperature gradient profiles of the dispersed fuels were evaluated by solving the steady-state heat conduction equation by using Maple code. This study not only predicts a reduction in the centerline temperature and temperature gradient in dispersed fuels but also reveals the maximum concentration of fissile material (U3O8, U3Si2, and UN) that can be incorporated in the Al matrix without the centerline melting. Furthermore, these predictions enable the experimental scientists in selecting an appropriate dispersion fuel with a lower risk of fuel melting and fuel cracking.

High Pressure and Temperature Dependence of the Structural, Electronic, Thermal and Transport Properties of U3Si2: Computational Insights

“…In Figure 9b, we illustrate the variation of the thermal conductivity as a function of temperature and chemical potential, and the behavior is changed of the maximum value of thermal conductivity and it shifted to 2 eV; we also note that electronic part of thermal conductivity increases with increasing of temperature from 300 to 1500 K. Figure 9c shows our calculated electronic thermal conductivity as a function of temperature plotted together with literature values, experimental data, [10] and theoretical data. [9,14,40,44,50] Our calculated value for thermal conductivity agrees well with experimental and theoretical data from 0 to 300 K, while the calculated k e is significantly overestimated at high temperature. The reasons for this disagreement are the type of code these groups use, as reported by T. P. Kaloni et al [40] The BoltzTraP code also permits the calculation of the electrical conductivity (σ/τ) where τ is the constant electronic relaxation time.…”

Electronic Transport of Uranium Mononitride

“…We also calculated the electronic thermal conductivity of UN, using Equation It can be noted that the derived thermal conductivity for the assumed constant number of mobility electrons is almost independent of temperature and behaves similarly to that studied by us for Al [6]. Therefore, to reproduce the experimentally observed strong temperature dependence (indicated by black, solid line) of Figure 5.…”

“…In these metallic fuels, thermal conductivity does not deteriorate with increasing temperature like the lattice-governed thermal conductivity in insulators (e.g. urania [6]). This is due to the increasing presence of electronic carriers with mobility as temperature rises.…”

Влияние облучения тяжелыми ионами Ni 12+ на радиационное дефектообразование в керамиках BeO1

“…Смещение максимума дифракционной линии в область малых углов свидетельствует об увеличении межплоскостных расстояний, которое обусловлено миграцией и внедрением выбитых из узлов решетки атомов в междоузлие, а также увеличением концентрации дефектов и локальных областей разупорядоченности в структуре. Изменение формы дифракционной линии может быть следствием двух факторов: размерного эффекта и искажений и деформаций кристаллической решетки [13]. Анализ формы и ширины дифракционных линий методом Вильямса-Холла показал, что для облученных образцов оба фактора имеют равновероятностный характер влияния на изменение структурных свойств.…”