The design study for the KALIMER upper internal structure (UIS) and reactor refueling system has been described. Two distinct features are plug-in UIS and extended refueling outage. For the UIS system, the functional, structural and material requirements have been determined and the accommodation approaches to meet these functional requirements described. For the refueling system, the functional, structural, process and I and C (Instrument and Control) requirements have been established and the accommodation approaches for the functional and process requirements described. The impact on plant availability due to extension of the refueling outage has also been investigated. The accommodation approaches for UIS system show that the design concept of the system will satisfy the functional requirements with a few design issues to be resolved, such as UIS plug in/out handling system and cask design. It is also shown that the functional and process requirements of the refueling system are achievable with the design of the IVTM cask and related transfer system and the extended refueling outage has little effect (within 1%) on the plant availability if extra refueling time do not exceed 1 week. 1 refs. (Author).