The transport of radioactivity in the primary circuits of water-cooled reactors is an important problem in the nuclear power industry. It is generally believed that active species (particularly Co-60 and Co-58) are transported via particulates or in solution and may be incorporated into the oxide films on Inconel, which accounts for 15% of the total surface area exposed to the primary coolant in modern PWRs. This thesis describes investigation of the oxidation of the Inconel alloy in aqueous media at 473 K and 573 K, and its interaction with cobalt ion. The X-ray photoelectron spectroscopy in conjunction with argon-ion etching has been utilised in achieving this objective. By this technique the compositional depth distribution and the chemical state information of the elements in the oxide film on Inconel can be obtained. Being aware of the damage that may be induced by the ion beam, an alternative has been sought in order to have more information on the way the elements are orderly distributed in the film. Cr 2p spectra have been analysed thoroughly by the method of 'peak fitting' with the use of constant intensity energy loss backgrounds. It has been shown that this method is useful in determining the chemical states of the elements in the oxide film and the presence of cobalt on top of the chromium oxide at the base of the film. The proportion of cobalt incorporated was observed to be dependent on the concentration of cobalt in the solution but apparently unchanged when the water chemistry was modified to simulate reactor coolant. Cobalt was shown to be incorporated in the divalent state; at a higher proportion in the oxide/solution interface and decreases towards deeper depth in the oxide film.