Drying and residual water in spent nuclear fuel dry storage: Cladding integrity, historical evidence, and a recommended R&D direction for probabilistic evaluation

This paper gives a clear, practical summary of how vacuum drying and small amounts of residual water can influence the integrity of spent nuclear fuel (SNF) cladding in dry storage. It also proposes a practical R&D priorites and recommendations for Korea that fits licensing and routine operations. We reorganize the lessons from major U.S. efforts (CSFM, DCSC, ESCP) to show what they can and cannot answer for Korea today. We review inspection methods based on gas sampling. We explain how rupture and fracture are assessed and how data on crack sizes contribute to assessing safety margins. Rather than estimating the likelihood of various accident events, we focus on specific conservative cases regarding residual water. Within these cases, we apply probabilistic analysis to assess material integrity, considering the variability in corrosion or fracture. Historical campaigns largely validated safety empirically via sipping/gas sampling, while quantitative margins (e.g., the comparison of applied stress intensity factors against critical values under handling loads) remain under-constrained due to limited and not-fully-public post-irradiation examination (PIE) datasets.