In this paper, the volume fractions in the annular three-phase flow are measured based on a dual energy metering system consisting of 152Eu and 137Cs and one NaI detector, and then modeled by fuzzy logic. Since the summation of volume fractions are constant (equal to 100%), therefore the fuzzy network must predict only two volume fractions. In this study, three fuzzy networks are applied. The first network is utilized to predict the gas and water volume fractions. The next one is applied to predict the gas and oil volume fractions, and the last one to predict the water and oil volume fractions. In the next step, the numerically obtained data from MCNP-X code, must be imported to the fuzzy models. Then, the average errors of these three networks are computed and compared. The network which has the least error is selected as the best predictor model. According to the modeling results, the best fuzzy network, predicts the gas and water volume fractions with the mean relative error of less than 0.3%, which shows that the fuzzy logic can predict the results precisely
