Comparison of Conventional and Advanced Nuclear Fuel Performance

事故容忍燃料（ATF）是提高核工业安全性的关键概念。2011年福岛第一核电站事故凸显了当前二氧化铀-锆系统的热局限性，因此，正在投入大量精力研究事故耐受替代品。为了被广泛采用并抵消任何研发成本，ATFs理想地应该以增加铀密度的形式提供一些经济效益，从而允许更高的燃耗或更低的燃料浓缩度。根据定义，事故耐受燃料（ATFs）是与常规UO 2-Zr系统相比，能够承受长时间的冷却剂显著损失的燃料和包壳。同时在正常操作期间保持或改善燃料性能。这种特殊的特征通常是燃料先进的热性能的结果。从燃料组件排出热能的能力可能允许在冷却剂损失事故（LOCA）的情况下延长“宽限期”，并且因此减轻氢和堆芯熔化物的产生。目前被认为是事故容忍替代燃料的两种主要竞争者是氮化铀（UN）和硅化铀（U3 Si 2），因为它们具有高导热性，高熔点和高铀密度。将使用布里斯托大学提供的直流磁控溅射设备设计每种事故容限燃料的薄膜样品。薄膜是辐射研究的理想样品。有限的样品厚度使均匀的损伤配置文件被诱导使用离子辐照，允许对热导率的影响的精确测量。该项目着眼于拟议的ATF的性能，特别侧重于比较UN和U3 Si 2对传统陶瓷氧化物化合物的热行为，并调查如何热行为的变化作为辐射的函数。

Accident Tolerant Fuels (ATF) are a key concept in the drive to improve safety in the nuclear industry. The 2011 Fukushima Daiichi accident highlighted the thermal limitations of the current UO2-Zr system and as such, significant effort is being invested in researching accident tolerant alternatives. In order to be widely adopted and offset any R&D costs, ATFs should ideally offer some economic benefit in the form of increased uranium density, allowing for either higher burn-up or lower fuel enrichment.By definitions, accident tolerant fuels (ATFs) are fuels and claddings that can withstand a significant loss of coolant for a prolonged amount of time when compared to conventional UO2-Zr system, whilst maintaining or improving fuel performance during normal operation. This particular feature is often a result of the fuels advanced thermal properties. The ability to evacuate thermal energy from the fuel assembly could potentially permit for an extended 'grace period' in the case of a loss of coolant accident (LOCA) and, as a result, mitigate against the production of hydrogen and corium. The two leading contenders currently considered as accident tolerant replacements fuel are uranium nitride (UN) and uranium silicide (U3Si2) due to their high thermal conductivity, high melting point, and high uranium density. Thin film samples of each accident tolerant fuel will be engineered using DC magnetron sputtering facilities available at the University of Bristol. Thin films make ideal samples for irradiation studies. The limited sample thickness enables homogenous damage profiles to be induced using ion irradiation, allowing for precise measurements of the effect on thermal conductivity.This project looks at the performance of the proposed ATFs, with a specific focus on comparing the thermal behaviour of UN and U3Si2 against conventional ceramic oxide compounds and investigating how the thermal behaviour changes as a function of irradiation.