An exact closed-form solution for the stresses and strains in an idealized nuclear reactor fuel pin under operational conditions is presented. The fuel is considered as a single region, either solid or annular, which may or may not interact with the surrounding cladding, depending on initial fuel-claddinggap and subsequent reactor operating parameters. Temperature-dependent thermal conductivity and irradiation swelling and temperature-independent creep in both fuel and cladding are allowed. Although the model is considerably simplified from those used in the more detailed numerical simulations, design parameters of interest can be easily and readily studied, and the important mechanisms contributing to cladding deformation can be identified. More importantly, however, the exact solutions can be used as a benchmark to check the accuracy of the more detailed but necessarily approximate numerical techniques. Example calculations are presented for a fuel pin operating under typical liquid-metal fast breeder reactor conditions for cases with and without fuel-cladding interaction occurring over the lifetime of the pin.