Numerical study of fuel-clad mechanical interaction during long-term burnup of WWER1000

Thermo-mechanical behavior of fuel rod is of great importance for safety assessment of nuclear reactors. This paper deals essentially with the mechanical description of pressurized water reactor (PWR) fuel rods under long-term burnups. The main goal of the work is generation of a numerical code for study of pellet-cladding interaction (PCI) as long-term phenomena in Bushehr nuclear power plant (BNPP). In this way, a basic modeling hypothesis with particular attention being paid to the numerical treatment of stress relaxation and interaction of fuel swelling and clad creep down have been implemented. In this model, the mechanical equilibrium equations are integrated on principle of virtual work with generalized plane strain assumption and the numerical algorithm is based on finite element method. Afterward, the generated code, IR-FRA (Iranian Fuel Rod Analysis), is developed for long-term behavior study of fuel rods. For validating the IR-FRA code, the pellet-cladding interaction results in some test cases are compared with the FROBA, BISON codes and experimental data. These comparisons demonstrated the accuracy and capability of the presented code for prediction of fuel rods thermo-mechanical behavior. Eventually, the fuel and cladding mechanical interaction during long-term burnup of WWER1000 for the BNPP is simulated and results show good agreement with experimental and published data.