Fuel reprocessing plant is one of the most important sources of anthropogenic (14)C in the environment. A method was developed to determine the amount and chemical composition of airborne (14)C release from the Tokai reprocessing plant, Japan. Effluent monitoring using this method showed most of the (14)C is released in CO(2) form and the ratio of (14)C in hydrocarbons to the total is less than 3%, not depending on the type of fuel reprocessed. This finding would provide improved understanding on dynamical behaviour of (14)C in the environment and assessment of radioecological impact from nuclear fuel cycle.