An experimental study has been made on FCA Assembly VIII-2 to test the validity of the calculational method for the reactivity effect due to axial displacement of fuel and cladding. The emphasis was placed on the systematic measurement of reactivity change and flux distribution in simple configurations rather than the simulation of a possible accident sequence. The analysis was made using the Japan Atomic Energy Research Institute Fast Set Version II. The transport calculation with an S4P0 approximation predicts both the reactivity change and the fission rates of 235U and 238U fairly well, although there still remains the trend of underestimation of reactivity effect, which increases with expansion of the fuel slumping to the core edge.