Deformation and damage of nuclear power station fuel elements under cyclic loading

Deformation and damage of nuclear power station fuel element shells under irradiation and cyclic loading due vibrations are studied. Constitutive equations include dependencies for a creep-damage equation with a scalar damage parameter, as well as terms for thermal and irradiation creep strains, elastic, thermal, and swelling strains. The acceleration of the creep-damage process due to cyclic variation of internal pressure is considered with a dynamic creep model, for which constitutive equations are derived using the method of asymptotic expansions and averaging over a period of cyclic loading. Stress and strain states in the fuel element shell are determined by use of an in-house finite element method creep-damage code for shells of revolution. Results show the essential variation in the initially symmetric fuel element shell form, as well as the acceleration of creep-damage processes due to the cyclic pressure.