[en] An overview is given of the achievements in the field of neutronics and nuclear data for fusion reactor applications. Much progress has been achieved in this area over the past decade, largely as result of the effort spent by the national fusion technology programmes in the EU, Japan, the RF and the US and supported by the international thermonuclear experimental reactor (ITER) project. In conjunction with the conduction of various integral benchmark experiments, this has led to the development of a well-qualified nuclear database for fusion applications, the international fusion evaluated nuclear data library (FENDL), and the assessment of safety margins derived for reactor design relevant responses. Further development work is required to enable direct uncertainty calculations for fusion reactor applications. This requires a Monte Carlo code capable for full sensitivity and uncertainty calculations along with high-quality, co-variance data as well as suitable integral benchmark experiments for qualification and validation purposes. This proceeding will allow specifying, by Monte Carlo calculations, the design relevant responses with their associated uncertainties and thus directly providing the related design safety margins