Parametric Studies on Heterogeneous Cores for Fast Breeder Reactors: The Pre-Racine and Racine Experimental Programs
Résumé
ritical assembly at Cadarache since 1976, were designed for the study of the neutron physics
characteristics of heterogeneous fast reactor cores. Geometrically simple configurations were chosen
in which parameters, being typical for heterogeneous cores, were varied in a systematic manner while
the basic fissile composition was kept the same.
Measurements were made especially of the critical mass, the distributions of reaction rates and
the spectral indices, the reactivity of sodium voiding, and control rod worths. Analyses were made
independently by Commissariat a VEnergie Atomique (CEA) and DEBENE using their own calculational
techniques and cross sections. No bias for core heterogeneity was found on critical mass predictions.
The CEA calculations for void reactivities are consistent in heterogeneous and homogeneous
configurations.
For the calculation of local parameters, e.g., reaction rates and spectral indices, more
sophisticated methods must be applied in heterogeneous cores, as transport effects also become more
important in fissile zones with increasing fertile volume fraction.
It was found at CEA that the ratio of the calculated reactivity of a central control rod to the experimental
value does not change with the core size or with the presence of internal breeder zones.