Engineered Zircaloy Cladding Modifications for Improved Accident Tolerance of LWR Fuel

工程锆合金包壳改进可提高轻水堆燃料的事故耐受性

• 批准号: EP/K034650/1
• 负责人: Michael Preuss
• 金额: $ 126.18万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FK034650%2F1
• 关键词: Engineered; Zircaloy; Cladding; Modifications; Improved; Engineered; Zircaloy; Cladding; Modifications; Improved

This integrated research project aims to evaluate the modified Zircaloy LWR cladding performance under normal BWR/PWR operation and off-normal events. A combination of computational and experimental protocols will be employed to design and evaluate modified Zircaloy cladding with respect to corrosion and accelerated oxide growth, the former associated with normal operation, the latter associated with steam exposure during loss of coolant accidents (LOCAs) and low-pressure core refloods. Urania pellet modifications to improve thermal conductivity will be investigated as well, with the goal of reducing pellet temperature gradients, associated pellet swelling and pellet-cladding interaction (PCI), and fission product release. In addition, Pb-Bi eutectic liquid metal gap fillers will be investigated to promote pellet-cladding heat transfer. Both the cladding and pellet performance evaluations will be incorporated into a reactor system modelling effort of neutronics and thermal hydraulics, thereby providing a holistic approach to accident tolerant nuclear fuel. The proposed project brings together personnel, facilities, and capabilities across a wide range of technical areas relevant to the study of modified nuclear fuel and LWR performance during normal operation and off-normal scenarios. The proposed project leverages existing DOE NEUP support and extends collaborative activities from U.S. academia to U.S. industry, U.S. national laboratories, and to UK academia. Anticipated deliverables will be i) an experimental data base of modified cladding and pellet performance under normal BWR and PWR operational conditions and under off-normal LOCA conditions, ii) improved predictive capability of fuel performance codes, and iii) improved predictive capability of neutronics and thermal hydraulics performance codes. Two pathways toward accident tolerant LWR fuel are envisioned, both based on the modification of existing Zircaloy cladding. The first is the modification of the cladding surface by the application of a coating layer designed to shift the M+O to MO reaction away from oxide growth during steam exposure at elevated temperature. The second is the modification of the bulk cladding composition to promote precipitation of minor phase(s) during fabrication. These precipitates will be stable under normal operation, but dissolve during the temperature excursions; the migration of solute elements to the free surface would then shift the reaction away from oxide formation. Improved pellet thermal conductivity will act to limit cladding hoop stress via reduced fission gas gap pressure and PCI. A synergistic response of the fuel rod is anticipated in which the combined mitigation of brittle exothermic oxide formation, reduced cladding temperature, and reduced cladding stress lead to accident tolerance with respect to cladding failure.

该集成的研究项目旨在评估正常BWR/PWR操作和正常事件的修改后的LWR覆层性能。将使用计算和实验方案的组合来设计和评估改良的锆石覆盖层相对于腐蚀和加速氧化物的生长，前者与正常运行相关，后者与冷却液事故损失（LOCAS）和低压核心倒流有关。还将研究Urania颗粒改性以提高热导率，目的是降低颗粒温度梯度，相关的颗粒肿胀和固定固定层的相互作用（PCI）以及裂变产物释放。此外，将研究PB-BI共晶液体金属间隙填充剂，以促进固定颗粒的传热。覆层和颗粒性能评估都将纳入中子和热液压的反应堆系统建模工作中，从而提供了一种全面的耐心核燃料方法。拟议的项目汇集了与在正常运行和正常情况下进行修改的核燃料和LWR性能有关的广泛技术领域的人员，设施和能力。拟议的项目利用现有的DOE NEUP支持，并将合作活动从美国学术界，美国工业，美国国家实验室和英国学术界扩展。预期的可交付成果将是i）在正常的BWR和PWR操作条件下以及在正常的LOCA条件下，ii）提高燃料性能代码的预测能力，iii）提高了中性源和热液压性能代码的预测能力。设想了两种通向意外LWR燃料的途径，这都是基于现有锆石覆层的修改。首先是通过涂层层的涂层层修饰覆层表面，该涂层旨在将M+O转移到MO反应时，在蒸汽暴露于升高的温度下，远离氧化物的生长。第二个是散装覆层组成的修饰，以促进制造过程中次要相的降水。这些沉淀物在正常运行下将是稳定的，但在温度偏移期间溶解。然后，溶质元素向自由表面的迁移将使反应从氧化物形成中转移。改善的颗粒导热率将起作用，可通过降低裂变气体间隙压力和PCI来限制甲板应力。预计燃油棒的协同反应将在脆性放热氧化物形成，覆层温度降低和覆层应力降低导致意外耐受性方面的脆性响应。