HOME AND DRY | SPECIAL REPORT
Orano’s NUHOMS MATRIX concrete overpack design is one of many different dry storage designs in use worldwide. Source: Orano
canisters or bare fuel may be held in a storage building (or vault), with additional equipment like cranes. Storage units may have the fuel in either vertical (single or multiple units) or horizontal orientation and may be above or below ground. The first step in the AMP approach is to identify materials and the environment (e.g., humidity, temperature, salt content) for each in-scope structure, system or component (SSC), referring to the information on which safety assessment and licensing was based. Environments named in the report include: outdoor air, demineralised water, helium, groundwater/soil, sheltered, fully encased or lined, and embedded in concrete, metal or neutron shielding. For each, the AMP should identify credible ageing effects and plans for managing them for various components: concrete overpacks and support pads; materials for spent fuel assemblies; and materials for various components in dry cask storage systems. A programme based exclusively on detecting SSC failures is not regarded as an effective AMP. Effective inspection, testing and monitoring methods are needed to detect ageing effects before a structure or system suffers any loss of function or fails. It is important to know when, where, and how programme
data are collected and to justify, the method or technique (such as visual, volumetric, or surface inspection) and frequency with codes and standards referenced. In an effective performance monitoring programme, the
‘detection of ageing effects’ programme element discusses and establishes the monitoring methods that will be used for performance monitoring. In addition, the ‘detection of ageing effects’ programme element also establishes and justifies the frequency with which these performance monitoring activities will be implemented;
What is ‘important to safety’? These ‘Important to Safety’ SSCs (and associated subcomponents) ensure that the following safety functions are fulfilled: criticality, shielding, confinement, heat transfer, structural integrity and retrievability. Another way of
defining these functions is as: ● Confinement Boundary: Retaining radioactive material under normal, abnormal and accident conditions
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● Criticality Control: Maintaining a subcritical configuration under normal, abnormal and accident conditions
● Radiation Shielding: Reducing radiation emitted by the contents under normal, off normal and accident conditions
● Heat Transfer: Removing decay heat under normal conditions and protecting temperature sensitive components such as lead shielding and seals under abnormal and accident conditions
● Structural Support: To maintain the contents in a safe condition during normal, off normal and accident conditions
● Fuel Retrievability: For operations support for example loading, unloading, maintenance, monitoring, or transporting, which if it fails could preclude removing individual or canned fuel assemblies from wet or dry storage or removing a canister loaded with assemblies from a storage cask or overpack or from the storage location.
Operating experience In the USA alone, there are over 50 different types of dry stores approved by the US NRC for general use. The wide range of canister sizes and concrete overpack designs, mean
In the USA alone, there are over 50 different types of dry stores approved by the US NRC for general use. Source: US DOE
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