Optimization of gap sizes for the high performance of annular nuclear fuels

다국어 초록 (Multilingual Abstract)

Solid-type nuclear fuels have been used for nuclear reactors for a long time. Many countries are currently developing annular fuels toimprove the efficiency of nuclear fuels. The thermoelastic-plastic-creep analyses of solid- and annular-type rods were conducted underthe same conditions. The temperature and stress of the solid- and annular-type rods were compared on the basis of gap size. In this study,we examined the advantages and disadvantages of annular-type fuel regarding the temperature and stress of the pellet and cladding. Theinner and outer gaps between the pellet and cladding play important roles in the temperature and stress distributions of fuel systems.

Therefore, the optimization of gaps in fuel systems was conducted for a low temperature under certain stress conditions. Thermoelasticplastic-creep analyses were conducted by using an in-house thermoelastic-plastic-creep finite element analysis program in VisualFORTRAN with the effective stress function algorithm. Nonlinear iterative stress analyses were conducted by nonlinear iterative temperatureanalyses; that is, a quasi-fully coupled algorithm was applied to this procedure. In this study, the thermoelastic-plastic-creepanalysis of pressurized water reactor annular fuels was conducted to determine the contacting tendency of the inner–outer gaps betweenthe annular fuel pellets and cladding, as well as to optimize the gap sizes by using the commercial package PIAnO for efficient heat transferat certain stress levels. Most analyses were conducted until the gaps disappeared. However, certain analyses lasted for 1582 days, afterwhich the fuels were replaced.

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