An analytical model of radiation-induced segregation (RIS) which takes into account absorption and desorption of the point defects at grain boundaries is developed. Using this model, interrelation between the grain boundary movement and RIS is investigated. It has been shown that fast diffusing alloy atoms are depleted at the grain boundary only when the boundary velocity does not exceed some critical value (v<v c ). In the opposite case (v>v c ) the fast atoms are accumulated at the grain boundary. These analytical results are compared to those obtained in the experiments.