This publication is a revision by amendment of IAEA Safety Standards Series No. SSG-15 and provides recommendations and guidance on the storage of spent nuclear fuel. It covers all types of storage facility and all types of spent fuel from nuclear power plants and research reactors. It takes into consideration the longer storage periods beyond the original design lifetime of the storage facility that have become necessary owing to delays in the development of disposal facilities and the reduction in reprocessing activities. It also considers developments associated with nuclear fuel, such as higher enrichment, mixed oxide fuels and higher burnup. Guidance is provided on all stages in the lifetime of a spent fuel storage facility, from planning through siting and design to operation and decommissioning. The revision was undertaken by amending, adding and/or deleting specific paragraphs addressing recommendations and findings from studying the accident at the Fukushima Daiichi nuclear power plant in Japan.