[en] In most NPP sites of Korea including Kori site, high density storage racks were installed in the SFP (spent fuel pool) in order to expand at-reactor spent fuel storage capacity. Twelve NPPs will reach their original design life expiration year by 2029. Some NPPs will have life extension for continued operation, wile other plants will be decommissioned. As a temporary spent fuel storage option after shutdown and during decommissioning periods, the implementation of Spent Fuel Pool Island (SFPI) concept has many benefits and advantages including: reduced occupational exposure, lower cost of operations, and physical protection. In order to facilitate decommissioning of structures, systems and components that are around the SFP subsystems; some operators installed a completely new SFP subsystem, referred to as SFPI. The SFPI is functionally and operationally equivalent to the original SFP subsystems, which may include refill and drainage capability, filtration, purification, isolation, pipe, heat exchanger and instrumentation subsystems. Additionally, SFPI would reduce the requirement of spent fuel shipment during decommissioning of NPP in cases where away-from reactor storage is not available. In this paper, case studies on the regulations, operating experiences, and systems of SFPI in USA are reviewed with a view of implementing SFPI in Korea. In order to apply SFPI concept, during decommissioning, in Korea, the following steps are recommended: confirmation of design change scope of SFPI and expected final cost, submission of decommissioning plan which reflects SFPI improvement plans, assessment using Periodic, Safety Review, application of operating license change for design change, regulatory body review and approval, perform design change inspection of regulatory body, education and commissioning for SFPI operating, SFPI operation and periodic inspection, and dismantling of SFPI