With the continuously escalating demand for longer term interim dry storage of spent nuclear fuel from light water reactors, coupled with the increasingly high-burnup levels of that fuel, comes the need to enhance the technical basis for such storage. In 2010, the Department of Energy initiated a program whose goal is to identify and study those technical issues requiring further research and development, focusing on the degradation processes that occur during normal and off-normal dry storage conditions. The program was initiated with a review of those features, events, and processes (FEPs) that could impact the five safety functions of the structures, systems, and components (SSCs) important to safety (ITS), namely: 1) thermal performance, 2) radiation protection, 3) confinement, 4) sub-criticality, and 5) retrievability. Review articles, presentations, NRC regulations, industry standards, and NRC safety analysis reports were consulted, and a consolidated FEPs list for normal and off-normal conditions was created for each SSC of a generic dry cask storage system. The SSCs included: 1) fuel, 2) cladding, 3) fuel assembly hardware, 4) fuel baskets, 5) neutron poisons, 6) neutron shields, 7) container, 8) overpack or storage module, 9) pad, and 10) monitoring systems. The resulting FEPs lists were then refined so as to include only those degradation mechanisms that may be impacted by increasingly long storage times, higher burnup, or that had other data needs for each SSC. A summary of the key degradation mechanisms for both the storage container and the concrete overpack/storage module, along with their relative research priority is presented in Tables I and II. The research priority was defined based upon the current state of knowledge in each area, the likelihood of occurrence, ease of remediation, and potential consequences. An overview of these mechanisms and their associated research needs, will be presented.
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