A set of initiating events are identified and the associated accident sequences are developed for impurity control systems in tokamak fusion reactors. The master logic diagram concept used in risk analysis is developed for a tokamak. The notion of the fusion island is used as the central power producing element in fusion power plants. Differences in the severity of initiating events and/or accident sequences that are associated with the two leading candidate impurity control concepts, the pump limiter and the poloidal divertor, are identified. They reflect both safety-related and/or financial consequences.