1.1 商业乏核燃料（SNF）总库存的一部分根据美国核管理委员会（NRC）授予的许可证存储在干桶存储系统（DCS）中。本指南的目的是提供信息，以帮助在原始许可证期限以外的期限内，安全且不将SNF从其许可限制中移除的情况下，支持这些许可证的续期。本指南提供了有关材料在条件下行为的信息，这些条件可能对延长更新期的安全评估很重要。 本指南针对包含轻水反应堆（LWR）燃料的DCSS编写，该燃料采用锆合金材料包覆，并根据《联邦法规》（CFR）在独立乏燃料贮存装置（ISFSI）中贮存。 2. 本文档中介绍的ISFSI组件包括商用SNF、容器、容器以及存储安装的所有部分，包括ISFSI垫。本指南的语言部分基于美国核管理委员会（NRC）授予的干式SNF储存许可证的要求，该许可证有效期长达20年。 虽然各国的政府法规可能不同，但此处给出的材料特性和行为指南预计具有广泛的适用性。 1.2 本指南阐述了影响ISFSI服务下材料随时间变化行为的许多因素[10 CFR第72.42部分]。这些因素被认为是在当前许可的20年期限之后，在许可证延期中对性能至关重要的因素。本指南中给出了这些因素的示例，其中包括ISFSI系统组件的材料变更或环境条件，随着时间的推移，这些因素可能对安全具有重要意义。 就本指南而言，假设许可期限为额外的20至80年。 1.3 本指南介绍了在初始20年许可期结束时，根据正常事件和条件确定乏燃料和贮存容器材料的条件。然而，本指南还论述了由于任何时期可能发生的异常和事故级事件和条件而导致的潜在乏燃料和燃料运输容器材料降解的分析。 1.4 本指南提供了有关材料行为的信息，以支持继续遵守安全标准，这是ISFSI许可存储SNF的监管基础的一部分。 本标准指南中阐述和讨论的安全功能包括热性能、辐射防护、限制、次临界和可回收性。监管依据包括10 CFR第72部分和美国核管理委员会的支持性监管指南。这些文件中规定的要求表明，原始许可决定中考虑了以下项目:材料特性、正常和非正常服务的设计考虑、操作和自然事件以及原始计算的基础。 这些项目可能需要重新考虑与安全相关的论点，以证明系统如何继续满足监管要求。此外，为了确保持续安全运行，必须根据正常和非正常服务的时间、温度、辐射场和环境条件的影响来证明材料的性能。长期性能的理由必须考虑到服务期内预期的材料变化（尤其是降解），包括初始许可证和许可证续期。 本指南仅适用于对延长储存期和检索功能（包括运输和转移操作）期间的安全至关重要的结构、系统和组件。与安全功能（包括检索功能）相关的材料信息与当前法规和许可证更新过程相关，该信息是本指南的重点。本指南无意取代现有的监管流程。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 本文件和其他参考文件中提供了信息，以帮助被许可方和许可方分析扩展存储期间SNF和DCSS组件性能的材料方面。在许可证更新过程中，审查第一个许可期的服务条件的影响。这些使用条件在 附件A1 作为影响ISFSI中材料性能的因素。重点是时间、温度、辐射和环境对SNF状况和ISFSI存储系统组件性能的影响。 5.2 根据10 CFR第50部分的规定辐照的SNF的储存受10 CFR第72部分的规定管辖。目前，《美国联邦法规》第10卷第60部分给出了该SNF后续地质处置的监管要求，而《美国联邦法规》第10卷第63部分的监管要求给出了使用尤卡山作为储存库的具体要求。在储存和处置的生命周期阶段之间，可根据10 CFR第71部分的要求运输SNF。因此，在储存过程中，必须了解生命周期的运输和处置阶段。 在这样做的过程中，要考虑对这些后续阶段很重要的材料特性，以促进SNF生命周期中这些后续阶段的成功完成。《美国联邦法规》第10卷第72.122（g）（5）部分和第10卷第72.122（l）部分规定了SNF（或高放射性废物）的可回收性。在处置之前进行的操作（例如，储存、转移和运输）中应小心，以确保SNF不会被滥用，SNF组件将可回收，包层的保护价值不会降低，并且能够在转移和运输操作期间作为放射性核素释放的主动屏障。 在干燥储存期间，覆层可能会发生变化。氢效应、包层断裂韧性和蠕变行为是生命周期干储存阶段需要评估和控制的重要参数。中讨论了这些降解机制 附件A2 和 附件A4 .

1.1 Part of the total inventory of commercial spent nuclear fuel (SNF) is stored in dry cask storage systems (DCSS) under licenses granted by the U.S. Nuclear Regulatory Commission (NRC). The purpose of this guide is to provide information to assist in supporting the renewal of these licenses, safely and without removal of the SNF from its licensed confinement, for periods beyond those governed by the term of the original license. This guide provides information on materials behavior under conditions that may be important to safety evaluations for the extended service of the renewal period. This guide is written for DCSS containing light water reactor (LWR) fuel that is clad in zirconium alloy material and stored in accordance with the Code of Federal Regulations (CFR), at an independent spent-fuel storage installation (ISFSI). 2 The components of an ISFSI, addressed in this document, include the commercial SNF, canister, cask, and all parts of the storage installation including the ISFSI pad. The language of this guide is based, in part, on the requirements for a dry SNF storage license that is granted, by the U.S. Nuclear Regulatory Commission (NRC), for up to 20 years. Although government regulations may differ for various nations, the guidance on materials properties and behavior given here is expected to have broad applicability. 1.2 This guide addresses many of the factors affecting the time-dependent behavior of materials under ISFSI service [10 CFR Part 72.42]. These factors are those regarded to be important to performance, in license extension, beyond the currently licensed 20-year period. Examples of these factors are given in this guide and they include materials alterations or environmental conditions for components of an ISFSI system that, over time, could have significance related to safety. For purposes of this guide, a license period of an additional 20 to 80 years is assumed. 1.3 This guide addresses the determination of the conditions of the spent fuel and storage cask materials at the end of the initial 20-year license period as the result of normal events and conditions. However, the guide also addresses the analysis of potential spent fuel and cask materials degradation as the result of off-normal, and accident-level events and conditions that may occur during any period. 1.4 This guide provides information on materials behavior to support continuing compliance with the safety criteria, which are part of the regulatory basis, for licensed storage of SNF at an ISFSI. The safety functions addressed and discussed in this standard guide include thermal performance, radiological protection, confinement, sub-criticality, and retrievability. The regulatory basis includes 10 CFR Part 72 and supporting regulatory guides of the U.S. Nuclear Regulatory Commission. The requirements set forth in these documents indicate that the following items were considered in the original licensing decisions: properties of materials, design considerations for normal and off-normal service, operational and natural events, and the bases for the original calculations. These items may require reconsideration of the safety-related arguments that demonstrate how the systems continue to satisfy the regulatory requirements. Further, to ensure continued safe operation, the performance of materials must be justified in relation to the effects of time, temperature, radiation field, and environmental conditions of normal and off-normal service. Arguments for long-term performance must account for materials alterations (especially degradations) that are expected during the service periods, which include the periods of the initial license and of the license renewal. This guide pertains only to structures, systems, and components important to safety during extended storage period and during retrieval functions, including transport and transfer operations. Materials information that pertains to safety functions, including retrieval functions, is pertinent to current regulations and to license renewal process, and this information is the focus of the guide. This guide is not intended to supplant the existing regulatory process. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Information is provided in this document and other referenced documents to assist the licensee and the licensor in analyzing the materials aspects of performance of SNF and DCSS components during extended storage. The effects of the service conditions of the first licensing period are reviewed in the license renewal process. These service conditions are highlighted and discussed in Annex A1 as factors that affect materials performance in an ISFSI. Emphasis is on the effects of time, temperature, radiation, and the environment on the condition of the SNF and the performance of components of ISFSI storage systems. 5.2 The storage of SNF that is irradiated under the regulations of 10 CFR Part 50 is governed by regulations in 10 CFR Part 72. Regulatory requirements for the subsequent geologic disposal of this SNF are presently given in 10 CFR Part 60, with specific requirements for the use of Yucca Mountain as a repository being given in the regulatory requirements of 10 CFR Part 63. Between the life-cycle phases of storage and disposal, SNF may be transported under the requirements of 10 CFR Part 71. Therefore, in storage, it is important to acknowledge the transport and disposal phases of the life cycle. In doing this, the materials properties that are important to these subsequent phases are to be considered in order to promote successful completion of these subsequent phases in the life cycle of SNF. Retrievability of SNF (or high-level radioactive waste) is set as a requirement in 10 CFR Part 72.122(g)(5) and 10 CFR Part 72.122(l). Care should be taken in operations conducted prior to disposal, for example, storage, transfer, and transport, to ensure that the SNF is not abused and that SNF assemblies will be retrievable, the protective value of the cladding is not degraded and remains capable of serving as an active barrier to radionuclide release during transfer and transport operations. It is possible that cladding could be altered during dry storage. The hydrogen effects, fracture toughness of the cladding and the creep behavior are important parameters to be evaluated and controlled during the dry storage phase of the life cycle. These degradation mechanisms are discussed in Annex A2 and Annex A4 .