Thermo mechanical issues of a dual cooled fuel rod

This paper deals with a dual cooled fuel for an OPR1000 reactor system. Its fuel rod of a hollow cylinder type consists of two coaxial cladding tubes in which UO2 annular pellets of a donut shape are stacked. Many problems arise due to this geometrical feature of a fuel rod. Among them, this paper especially presents some thermo mechanical tasks such as the swelling and densification behaviour of an annular pellet; the thermal and irradiation growth, the vibration characteristics and the thickness concerns of the fuel rod claddings. It was found that the deformation direction of an annular pellet would always be outward and the growth difference of the inner and outer claddings would be almost the same. It may be necessary to reduce the number of fuel rod's supports due to the increased natural frequencies. The thickness of the outer cladding needs to be increased, corresponding to the enlarged diameter