1.1 本指南介绍了如何使用各种测试方法和数据分析来开发模型，用于评估工程屏障系统（EBS）中所用材料的长期变化行为，以在地质处置库中处置乏核燃料（SNF）和其他高放射性核废物。废物体和EBS材料的变化行为很重要，因为它直接影响放射性核素在处置系统内的保留，如最初固定放射性核素的废物体，或间接影响放射性核素在处置系统内的保留，与EBS安全壳材料一样，EBS安全壳材料限制了地下水的进入或随着废物降解而释放的放射性核素的排出。 1.2 本指南的目的是为开发模型提供一种基于科学的策略，该模型可用于在存储库永久关闭（即，在post中）后估计材料变更行为- 关闭期）。由于地质处置涉及的时间尺度妨碍了预测的直接验证，建议基于详细数据和模型对过程进行机械理解，并考虑不确定性范围。 1.3 本指南阐述了材料行为模型中的科学基础和不确定性，以及使用这些模型对EBS设计标准和存储库性能评估的置信度的影响。这包括识别和使用保守假设，以解决材料长期性能中的不确定性。 1.3.1 评估废物体和EBS材料性能的步骤包括问题定义、实验室和现场测试、单个和耦合过程的建模以及模型确认。 1.3.2 废物体和EBS材料性能的估计基于从理论考虑、专家判断和从适当类似物的测试和分析中获得的数据解释得出的模型。 1.3.3 在本指南中，测试根据其提供的信息以及如何将其用于模型开发、支持和使用进行分类。这些测试可能包括但不限于:属性测试、特性测试、加速测试、使用条件测试和确认测试。 1.4 本指南不涉及定义或表征存储库环境所需的测试（即地下水量或化学性质、主岩性质等）。本文描述的逻辑方法和测试概念可应用于处理系统。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1. 6. 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 本指南支持开发材料行为模型，该模型可用于估计高放废物处置库关闭后的EBS材料性能，其时间比直接测试的时间长得多。本指南旨在对拟用于电子束系统的材料的降解行为进行建模，电子束系统设计用于包含数万年及以上的放射性核素。国家和国际上都认识到工程材料在地质处置库设计中的使用和长期性能的重要性。 使用按照本指南所述方法开发的模型旨在解决既定法规，例如: 5.1.1 U、 1982年的《核废料政策法案》（the Nuclear Waste Policy Act of 1982）第97–425号美国公法规定，通过多重屏障系统对高放射性废料进行深层地质处置。这些屏障包括设计用于防止放射性核素移出工程系统的工程屏障，以及在工程系统和生物圈之间提供额外运输屏障的地质宿主介质。美国核管理委员会关于地质处置的法规要求性能确认计划通过测试和分析提供数据，在可行的情况下，证明设计或假设在永久关闭后作为屏障的工程系统和组件按预期和预期运行。 5.1.2 国际原子能机构的安全要求规定，应设计工程屏障，并选择宿主环境，以容纳与废物有关的放射性核素。 5.1.3 瑞典监管局向存储库开发商提供了一般性建议，即在处置时应遵循最佳可用技术的应用，这意味着应进行存储库和附属系统组件的选址、设计、施工和操作，以防止、限制、，并尽可能延迟工程和地质屏障的释放。 5.1.4 芬兰监管机构确定需要支持安全评估，指出安全案例中使用的输入数据和模型应基于高质量的研究数据和专家判断。应尽可能验证数据和模型，并与评估期间处置场可能存在的条件相对应。 5.1.5 联合王国核管理办公室将根据《核设施法》，通过应用为所有核设施制定的安全评估原则，对运行中的地质处置库进行管理，并根据环境署的《放射性物质法》对关闭后的处置期进行管理。一份谅解备忘录概述了这两个监管机构如何合作 10 . 5.2 本指南有助于定义可接受的方法，以便从测试数据、科学理论和类似物等来源对材料的长期行为进行有用的估计。 5.3 本指南认识到，有关EBS材料实际性能的技术信息和测试数据必然基于相对于地质处置所需时间（例如，数千年或更长）较短的测试持续时间。 除了用于制定可接受的长期性能模型外，短期测试的数据还用于支持EBS设计和材料选择。例如，对一种材料的降解建模能力的置信度较低，可以证明选择具有更高置信度的替代EBS屏障材料是合理的。预计该模型将在建立设计标准、性能评估结果与安全极限的比较等预期应用中正确表示材料行为。参见第节 21 进一步讨论模型支持和置信度。 5.4 感兴趣的EBS环境是由自然条件定义的环境（例如，矿物、水分、生物群和机械应力）；随着时间的推移，在储存库建设和运行期间，以及由于放射性核素衰变（即辐射）而发生的变化- 对溶液化学的诱导损伤、加热和辐射效应；以及关闭后可能发生的变化。还应考虑与破坏性事件（例如，地震事件产生的机械应力）和过程（例如，水化学变化）相关的环境条件。

1.1 This guide addresses how various test methods and data analyses can be used to develop models for the evaluation of the long-term alteration behavior of materials used in an engineered barrier system (EBS) for the disposal of spent nuclear fuel (SNF) and other high-level nuclear waste in a geologic repository. The alteration behavior of waste forms and EBS materials is important because it affects the retention of radionuclides within the disposal system either directly, as in the case of waste forms in which the radionuclides are initially immobilized, or indirectly, as in the case of EBS containment materials that restrict the ingress of groundwater or the egress of radionuclides that are released as the waste forms degrade. 1.2 The purpose of this guide is to provide a scientifically-based strategy for developing models that can be used to estimate material alteration behavior after a repository is permanently closed (that is, in the post-closure period). Because the timescale involved with geological disposal precludes direct validation of predictions, mechanistic understanding of the processes based on detailed data and models and consideration of the range of uncertainty are recommended. 1.3 This guide addresses the scientific bases and uncertainties in material behavior models and the impact on the confidence in the EBS design criteria and repository performance assessments using those models. This includes the identification and use of conservative assumptions to address uncertainty in the long-term performance of materials. 1.3.1 Steps involved in evaluating the performance of waste forms and EBS materials include problem definition, laboratory and field testing, modeling of individual and coupled processes, and model confirmation. 1.3.2 The estimates of waste form and EBS material performance are based on models derived from theoretical considerations, expert judgments, and interpretations of data obtained from tests and analyses of appropriate analogs. 1.3.3 For the purpose of this guide, tests are categorized according to the information they provide and how it is used for model development, support, and use. These tests may include but are not limited to: attribute tests, characterization tests, accelerated tests, service condition tests, and confirmation tests. 1.4 This guide does not address testing required to define or characterize the repository environment (that is, the groundwater quantity or chemistry, host rock properties, etc.). The logical approach and testing concepts described herein can be applied to the disposal system. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 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 This guide supports the development of material behavior models that can be used to estimate performance of the EBS materials during the post-closure period of a high-level nuclear waste repository for times much longer than can be tested directly. This guide is intended for modeling the degradation behaviors of materials proposed for use in an EBS designed to contain radionuclides over tens of thousands of years and more. There is both national and international recognition of the importance of the use and long-term performance of engineered materials in geologic repository design. Use of the models developed following the approaches described in this guide is intended to address established regulations, such as: 5.1.1 U.S. Public Law 97–425, the Nuclear Waste Policy Act of 1982, provides for the deep geologic disposal of high-level radioactive waste through a system of multiple barriers. These barriers include engineered barriers designed to prevent the migration of radionuclides out of the engineered system, and the geologic host medium that provides an additional transport barrier between the engineered system and biosphere. The regulations of the U.S. Nuclear Regulatory Commission for geologic disposal require a performance confirmation program to provide data through tests and analyses, where practicable, that demonstrate engineered systems and components that are designed or assumed to act as barriers after permanent closure are functioning as intended and anticipated. 5.1.2 IAEA Safety Requirements specify that engineered barriers shall be designed and the host environment shall be selected to provide containment of the radionuclides associated with the wastes. 5.1.3 The Swedish Regulatory Authority has provided general advice to the repository developer that the application of best available technique be followed in connection with disposal, which means that the siting, design, construction, and operation of the repository and appurtenant system components should be carried out so as to prevent, limit, and delay releases from both engineered and geological barriers as far as is reasonably possible. 5.1.4 The Regulatory Authority in Finland identified the need to support the safety assessment stating that the input data and models utilized in the safety case shall be based on high-quality research data and expert judgement. Data and models shall be validated as far as possible and correspond to the conditions likely to prevail at the disposal site during the assessment period. 5.1.5 The Office of Nuclear Regulation in the United Kingdom will regulate an operating geological repository under the Nuclear Installations Act through application of the Safety Assessment Principles developed for all nuclear facilities and the post-closure disposal period will be regulated under the Radioactive Substances Act by the Environmental Agency. A Memorandum of Understanding outlines how the two regulators work together 10 . 5.2 This guide aids in defining acceptable methods for making useful estimations of long-term behavior of materials from such sources as test data, scientific theory, and analogs. 5.3 This guide recognizes that technical information and test data regarding the actual behavior of EBS materials will by necessity be based on test durations that are short relative to the time periods required for geologic disposal (for example, thousands of years and longer). In addition to use in formulating acceptable long-term performance models, data from short-term tests are used to support EBS design and the selection of materials. For example, low confidence in the ability to model the degradation of one material may justify the selection of alternative EBS barrier materials that can be modelled with higher confidence. It is expected that the model will correctly represent material behavior in the intended applications of establishing design criteria, comparison of performance assessment results with safety limits, and so forth. See Section 21 for further discussion on model support and confidence. 5.4 The EBS environment of interest is that defined by the natural conditions (for example, minerals, moisture, biota, and mechanical stresses); changes that occur over time, during repository construction and operation, and as a consequence of radionuclide decay, namely, radiation, radiation-induced damage, heating, and radiolytic effects on the solution chemistry; and changes that may occur over the post-closure period. Environmental conditions associated with disruptive events (for example, mechanical stress from seismic events) and processes (for example, changes in water chemistry) should also be considered.