Static analysis of a dual-cooled fuel with different elongations of an inner and outer cladding tube

Innovative water reactor fuel center of the Korea Atomic Energy Research Institute (KAERI) recently started a new project for developing a dual-cooled fuel technology through a National R and D Program by the Ministry of Science and Technology. The key feature of the dual-cooled fuel is its annular cross-section of a fuel rod. The fuel rod has an internal coolant passage in addition to an external one so that a fuel rod consists of coaxial inner and outer cladding tubes in which donut shaped pellets are stacked. An intrinsic purpose of this shape is to increase the surface area of heat transfer which results in a reduction of the fuel temperature. The important effects of this idea are to enhance the fuel safety and to achieve a power uprating. A cladding tube is elongated by heat and neutron irradiation. The inner and outer cladding tubes of a dual-cooled fuel rod can be extended differently by incore environmental factors. If these two tubes are lengthened differently, a dual-cooled fuel rod and the assembly could be tilted. The tilted fuel assembly will interact with a neighboring fuel assembly, which is one of the critical issues for a dual-cooled fuel development. So it is necessary to investigate the length behavior of the inner and outer tubes. It is also important to know how to reduce this phenomenon if it actually happens. In this paper, static analyses are performed to predict the elongation behavior of these two tubes