Extension of fuel cycle periods

The consequences of extended fuel residence time and higher burnup with regard to reactor safety are outlined (impact concerning the safety limits put down in the safety analysis report, and resulting consequences for licensing requirements). The article discusses the results of a study. The first part deals with the consequences of extended cycle periods of the fuel and hence higher burnup, with regard to the nuclear data forming part of the accident analyses data. The second part discusses the required recurrent safety analyses and the impact of the various fuel management techniques on the shutdown margins. System modifications that may be necessary are given. The examples discussed include the safety analyses made for French CP-1 plants with 3-loop systems, and for the Tihange plants in Belgium. (orig./GL)