Importance of transactinide nuclear data for the physics of fast and thermal reactor cores

The importance of transactinium isotope nuclear data in the physics of fast and thermal reactors relating directly to core parameters and to fuel composition calculations is reviewed. The influence of transactinides on reactivity loss and internal breeding gain and power in fast reactors is analysed. The accuracies required in transactinide nuclear data for core parameter calculations, and the sensitivity of the isotopic compositions of fast reactor fuel due to variations in transactinide cross sections are evaluated. Specific nuclear data accuracies are recommended. (author)