Worths and Interactions of Simulated Fast Breeder Reactor Control Rods in ZEBRA and SNEAK Assemblies

Measurements of the worths of simulated control rods for fast power reactors have been made in the ZEBRA and SNEAK critical assemblies by the modified source multiplication method (MSMM). The assemblies used were the conventional and unconventional core arrangements from the BIZET program and a compacted version of a conventional core. The control rods were mainly natural B₄C, with some study of 40% ¹⁰B-enriched B₄C and of Eu₂O₃. Correction factors for the MSMM were obtained from eigenvalue and source-mode diffusion theory calculations in XY geometry. The measured rod worths and interactions are compared with calculated values from methods and data similar to those used by the different participants in the BIZET program to predict the corresponding parameters in fast power reactors. In general, acceptable agreement is found.