Experimental study of fast power-reactor control rods in the Masurca critical assembly

The paper discusses (1) the features of the experimental programme, during which a study was made of the neutron properties of the rods in relation either to their cross-section or to their composition (the rods were inserted into the centre of a zone whose enrichment in equivalent plutonium was similar to that of the external zone of Super-Phenix 1), (2) the characteristics of the calculation method used for analysing the experiments and for project calculations, and (3) the main conclusions drawn from the analysis of this programme, which were concerned with: (a) the effect of rod cross-section on the discrepancies between theoretical and experimental results obtained for negative reactivities or power perturbations (on the basis of all the results now available, it is possible to derive a variational law describing the differences between theory and experiment when the rod cross-section varies between 28 and 280 cm2); (b) the effect of the composition of diluting rods (steel-sodium) on the differences between theory and experiment characterizing the negative reactivities, the case of rods with a low steel content (approximately 8 vol.%) corresponding to the followers of Super-Phenix being analysed in detail; (c) the effect of the enrichment in 10B (20 to 90%) of the B4C absorber rods on the differences between theory and experiment observed in the case of negative reactivities and power distribution perturbations; and (d) the degree of approximation in the method used to describe the rods of the Super-Phenix type by a single homogeneous medium in carrying out project calculations. (author)