Neutronic Decoupling and Space-Dependent Nuclear Characteristics for Large Liquid-Metal Fast Breeder Reactor Cores

Eigenvalue separation, which is used as a criterion to determine the degree of neutronic decoupling of the core, is measured by a static flux-tilt method on Zero-Power Physics Reactor assemblies. Space-dependent nuclear characteristics, such as the radial distributions of the reaction rates and the control rod worths, are also measured for the same assemblies. The calculation/experiment (C/E) values vary with core radius depending on the assemblies. The relationship between decoupling and C/E radial dependence is investigated, and a quantitative relation is found between the eigenvalue separation of the first radial mode and the C/E radial dependence.