Poly(N-vinyl 2-pyrrolidone-g-citric acid) (PVP-g-CA) hydrogels with varying compositions were prepared from ternary mixtures of N-vinyl 2-pyrrolidone-citric acid-water by using Co-60 gamma-rays. The effect of gel composition on the uranyl ions adsorption capacity of PVP-g-CA hydrogels was investigated. Uranyl adsorption capacity of these hydrogels were found to be in the range of 18-144 mg [UO22+]/g dry gel from the aqueous solution of uranyl nitrate and 22-156 mg [UO22+]/g dry gel from the aqueous solution of uranyl acetate, depending on the content of citric acid in the hydrogel, while poly(N-vinyl 2-pyrrolidone) hydrogel did not sorb any uranyl ion. The swelling of PVP-g-CA hydrogel containing 2.7 mol % CA was observed in water (1620%), in uranyl acetate solution (1450%) and in uranyl nitrate solution (1360%), as compared to 700% swelling of pure PVP hydrogels. The diffusion coefficients were varied from 12.57 up to 4.04 . 10(-8) m(2) s(-1). (C) 2000 John Wiley & Sons, Inc.