Understanding the In-Reactor Performance of Advanced Ceramic Cladding Materials

事故容忍燃料(ATF)是通常用于轻水反应堆(LWR)的燃料设计，轻水反应堆约占世界核能发电能力的90%。由于采用了新型覆层材料，尤其是陶瓷覆层，它们提供了显著改善的高温能力。国际燃料供应商有兴趣将现有和新的轻水反应堆的ATF商业化，但前提是技术准备方面的差距已经得到解决。因此，研究的目的是建立先进的陶瓷覆层材料的令人满意的性能，这些覆层材料能够承受严重事故条件下的典型温度-通常在1700℃左右-这是通过用能够承受更高温度的复合陶瓷覆层来取代传统的锆合金燃料覆层来实现的。与现有燃料相比，这将显著提高安全性，从而为英国燃料制造商提供竞争优势。这项工作将集中在具有代表性的核反应堆堆芯条件下的连接和结合的碳化硅复合覆层的性能。碳化硅已经被证明在辐照下是稳定的，并且具有非常高的温度能力，但它有两个主要的困难。包层必须提供能够容纳燃料颗粒并保留气态裂变产物的气密管。这需要用高度完整的接头密封管子的两端。然而，碳化硅不能焊接，以前生产机械和胶接接头的尝试都失败了。2.作为一种陶瓷，碳化硅的断裂韧性很低，必须保持压缩状态才能提供足够的机械强度。这可以通过用碳化硅纤维缠绕中空的碳化硅管子来实现，使管子保持压缩状态。然而，必须找到一种合适的方法将纤维粘合到下面的管子上。曼彻斯特最近的工作已经确定了两种有希望的解决方案：使用激光诱导陶瓷钎焊来产生气密密封；使用选择性区域激光沉积(SALD)来产生碳化硅沉积，从而在碳化硅纤维和下面的管之间起到粘结的作用。这些技术已经在实验室规模上得到了演示，但在代表反应堆内运行的条件下，还没有证明这种钎焊和粘结材料。因此，这项工作的主要目标是证明焊接接头和粘合纤维能够在反应堆内的条件下存活。

Accident Tolerant Fuels (ATF) are fuel designs typically intended for use in Light Water Reactors (LWRs), which comprise around 90% of the world's nuclear generating capacity. They offer significantly improved high temperature capability, due largely to the adoption of novel cladding materials, notably ceramic cladding. International fuel vendors are interested in commercialising ATF for both existing and new LWRs, but only after the gaps in technology readiness have been addressed. The aim of the research is therefore to establish the satisfactory performance of advanced ceramic cladding materials that are capable of surviving to temperatures typical of those encountered during severe accident conditions - typically around 1700 deg C. This is achieved by replacing the traditional zirconium-alloy fuel cladding with a composite ceramic cladding that is capable of surviving much higher temperatures. This would provide a very significant increase in safety compared with existing fuels, and hence provide a competitive advantage to UK fuel manufacturers. The work will focus on the performance of joined and bonded SiC-SiC composite cladding under conditions representative of those found in nuclear reactor cores.Silicon carbide has been shown to be stable under irradiation, and has very high temperature capabilities, but it has two major difficulties.1. The cladding must provide a gas-tight tube capable of accommodating the fuel pellets and retaining the gaseous fission products. This requires the sealing of the ends of the tube with a high-integrity joint. However, SiC cannot be welded, and previous attempts to produce mechanical and glued joints have failed. 2. Being a ceramic, SiC has very low fracture toughness, and it must be maintained in compression to provide sufficient mechanical strength. This can be achieved by winding the hollow SiC tube with SiC fibres that keep the tube in compression. However, a suitable means must be found of bonding the fibres to the underlying tube.Recent work at Manchester has identified two promising solutions to these difficulties: the use of laser-induced ceramic brazing to produce a gas-tight seal; and the use of Selective Area Laser Deposition (SALD) to produce a deposit of SiC that can act as a bond between SiC fibres and the underlying tube. These techniques have been demonstrated at laboratory scales, but the braze and bond materials have not been demonstrated under conditions representative of in-reactor service. The principal objectives of the work are therefore to demonstrate that the brazed joints and bonded fibres are capable of surviving under in-reactor conditions.