1.1 本指南讨论了准备乏核燃料（SNF）以放置在密封干燥储存系统中的三个步骤:( 1. )评估从储水池中取出SNF后和放置于干燥储存之前干燥SNF的需要( 2. )干燥SNF，以及( 3. )证明已达到足够的干燥度。 1.1.1 SNF的范围包括从动力反应堆和研究反应堆排放的任何设计（燃料芯、包覆材料和几何结构）的核燃料及其受反应堆运行、处理和蓄水影响的状态。 1.1.2 本指南阐述了干燥方法及其在用于干燥储存在水池中的SNF时的局限性。本指南讨论了干燥过程完成后可能留在SNF、容器或两者中的水的来源和形式。 还讨论了干燥过程和任何残留水在干燥储存期间对燃料完整性和容器材料的重要和潜在影响。从机械角度讨论了残余水对容器热环境和辐射环境的影响，以指导可能需要特殊干燥方法、专门处理或其他处理的情况。 1.1.3 干燥的基本问题是:( 1. )为了确定SNF的干燥程度，以防止燃料回收性、容器加压或容器在储存、搬运和转移期间的腐蚀问题，以及( 2. )证明已达到足够的干燥度。对于完整的商用燃料来说，实现足够的干燥可能很简单，但对于任何在乏燃料池放置和储存之前或期间包壳破裂的SNF来说，实现足够的干燥可能很复杂。 污泥、积垢和任何其他含水化合物的存在也可能导致实现充分干燥的挑战。这些可以与SNF一起转移到存储容器中，并且可以保持水分和抗干燥。 1.1.4 按照行业标准，单位采用国际单位制和非国际单位制。在某些情况下，括号中给出了数学等价物。 1.2 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。 1.3 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====== 4.1 需要干燥SNF和SNF容器的燃料腔及其内部构件，以准备在储存库进行密封干燥储存、运输或永久处置。本指南提供了用于确定在选择干燥过程时需要考虑的水的形式的技术信息。本指南提供的信息有助于( 一 )选择干燥系统( b )选择干燥方法，以及( c )证明达到了足够的干燥度（见 附件A2 ). 4.2 影响干燥过程的因素包括: 4.2.1 当将商业、研究和生产反应堆用过的核燃料从湿储存中取出后，如果将其密封在干燥的储存系统或运输容器中，则可能会出现水残留问题。 移动到干燥的存储环境通常会导致燃油温度升高，这可能足以导致燃油中水分的释放。密封容器中的水释放和温度升高可能会导致容器增压、燃料或组件结构腐蚀，或两者兼而有之，从而影响燃料回收和容器腐蚀。 4.2.2 与SNF相关的水的去除可以通过多种技术来实现，包括加热、在系统上施加真空、用干气体冲洗系统以及这些和其他类似过程的组合。 4.2.3 除水过程取决于时间、温度和压力。应预测某种形式的残留水。 4.2.4 干燥过程可能不容易去除多孔材料、毛细血管、污泥、积垢、保水物理特征和薄的润湿表面膜中的水分。在破裂的SNF中截留的水可能特别难以清除。 4.2.5 干燥过程在从SNF和相关材料中去除结合水方面可能更不成功，因为只有在将打破特定水-材料键所需的阈值能量应用于系统时，才会去除结合水。对于乏核燃料，该阈值能量可能来自衰变热、外部加热或电离辐射本身的热输入组合。 4.2.6 可通过测量干燥操作完成后系统的响应来评估干燥程序的充分性。 例如，如果使用真空干燥技术去除水分，则可以向系统施加特定真空，关闭真空泵，并测量压力反弹的时间依赖性。然后，回弹响应可能与系统中的残余水，尤其是未结合水有关。 4.2.7 在干燥储存条件下，与密封包装内的SNF、积垢和污泥相关的残余水可能会与内部环境、燃料和包装材料发生反应。 4.2.8 容器内的热梯度随着时间而变化，因此水蒸气将倾向于迁移到包装的较冷部分。水可能在这些区域凝结。在重力作用下，冷凝水将倾向于迁移到物理较低的位置，如容器底部。 4.2.9 水合和其他含水化合物的辐射分解可能会向容器释放水分、氧气和氢气。 4.2.10 延长温度下的时间，再加上电离辐射的存在，可以提供必要的能量，将束缚或截留的水释放到容器中。

1.1 This guide discusses three steps in preparing spent nuclear fuel (SNF) for placement in a sealed dry storage system: ( 1 ) evaluating the needs for drying the SNF after removal from a water storage pool and prior to placement in dry storage, ( 2 ) drying the SNF, and ( 3 ) demonstrating that adequate dryness has been achieved. 1.1.1 The scope of SNF includes nuclear fuel of any design (fuel core, clad materials, and geometric configuration) discharged from power reactors and research reactors and its condition as impacted by reactor operation, handling, and water storage. 1.1.2 The guide addresses drying methods and their limitations when applied to the drying of SNF that has been stored in water pools. The guide discusses sources and forms of water that may remain in the SNF, the container, or both after the drying process has been completed. It also discusses the important and potential effects of the drying process and any residual water on fuel integrity and container materials during the dry storage period. The effects of residual water are discussed mechanistically as a function of the container thermal and radiological environment to provide guidance on situations that may require extraordinary drying methods, specialized handling, or other treatments. 1.1.3 The basic issues in drying are: ( 1 ) to determine how dry the SNF must be in order to prevent problems with fuel retrievability, container pressurization, or container corrosion during storage, handling, and transfer, and ( 2 ) to demonstrate that adequate dryness has been achieved. Achieving adequate dryness may be straightforward for intact commercial fuel but complex for any SNF where the cladding is breached prior to or during placement and storage at the spent fuel pools. Challenges in achieving adequate dryness may also result from the presence of sludge, CRUD, and any other hydrated compounds. These may be transferred with the SNF to the storage container and may hold water and resist drying. 1.1.4 Units are given in both SI and non-SI units as is industry standard. In some cases, mathematical equivalents are given in parentheses. 1.2 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. 1.3 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 ====== 4.1 Drying of the SNF and fuel cavity of the SNF container and its internals is needed to prepare for sealed dry storage, transportation, or permanent disposal at a repository. This guide provides technical information for use in determining the forms of water that need to be considered when choosing a drying process. This guide provides information to aid in ( a ) selecting a drying system, ( b ) selecting a drying method, and ( c ) demonstrating that adequate dryness was achieved (see Annex A2 ). 4.2 The considerations affecting drying processes include: 4.2.1 Water remaining on and in commercial, research, and production reactor spent nuclear fuels after removal from wet storage may become an issue when the fuel is sealed in a dry storage system or transport cask. The movement to a dry storage environment typically results in an increase in fuel temperature, which may be sufficient to cause the release of water from the fuel. The water release coupled with the temperature increase in a sealed container may result in container pressurization, corrosion of fuel or assembly structures, or both, that could affect retrieval of the fuel, and container corrosion. 4.2.2 Removal of the water associated with the SNF may be accomplished by a variety of technologies including heating, imposing a vacuum over the system, flushing the system with dry gases, and combinations of these and other similar processes. 4.2.3 Water removal processes are time, temperature, and pressure-dependent. Residual water in some form(s) should be anticipated. 4.2.4 Drying processes may not readily remove the water that was retained in porous materials, capillaries, sludge, CRUD, physical features that retain water and as thin wetted surface films. Water trapped within breached SNF may be especially difficult to remove. 4.2.5 Drying processes may be even less successful in removing bound water from the SNF and associated materials because removal of bound water will only occur when the threshold energy required to break the specific water-material bonds is applied to the system. For spent nuclear fuel this threshold energy may come from the combination of thermal input from decay heat, externally applied heat, or from the ionizing radiation itself. 4.2.6 The adequacy of a drying procedure may be evaluated by measuring the response of the system after the drying operation is completed. For example, if a vacuum drying technology is used for water removal, a specific vacuum could be applied to the system, the vacuum pumps turned off, and the time dependence of pressure rebound measured. The rebound response could then be associated with the residual water, especially unbound water, in the system. 4.2.7 Residual water associated with the SNF, CRUD, and sludge inside a sealed package may become available to react with the internal environment, the fuel, and the package materials under dry storage conditions. 4.2.8 Thermal gradients within the container evolve with time, and as a result water vapor will tend to migrate to the cooler portions of the package. Water may condense in these areas. Condensed water will tend to migrate to the physically lower positions under gravity such as the container bottom. 4.2.9 Radiolytic decomposition of hydrated and other water-containing compounds may release moisture, oxygen and hydrogen to the container. 4.2.10 Extended time at temperature, coupled with the presence of ionizing radiation, may provide the energy necessary to release bound or trapped water to the container.