Exposed to the high radiation environment, the PWR fuel rod will be swelling. The deformation is quite different azimuthally which caused by the different subchannels coolant temperature and some manufacture issues. And the asymmetry deformation will have a great effect on fuel rod safety for the increasing pellet center temperature and FCMI due to the change of gas gap. An accurate prediction on fuel strain which is associated with the temperature distribution closely should be done to assure the safety of the fuel rod. The conventional finite difference method has deficiency on treating with the deformation and the finite element method (FEM) could satisfy the requirement.

Based on the principle of FEM, the model of thermal conduction, stress-strain analysis is established. The two dimensional model is chosen considering the characteristic of fuel. The analysis code SSTFEM is developed and verified using the experimental data from the opening literature and results of authorized code. After that the code is used to analyze the effect of the asymmetry deformation which is caused by the asymmetry coolant temperature distribution in adjacent subchannels and the manufacture eccentricity between the fuel rod and the cladding. The effect law of deformation and the stress is obtained after a systematic analysis.

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