Analyses of experiments for relationship between flux tilt in two-energy-group and eigenvalue separation

For a relationship between the flux tilt in two-energy-group and the first-mode eigenvalue separation, it was found that the flux tilt in two-energy-group is proportional to the perturbed reactivity and inversely proportional to the first-mode eigenvalue separation on the basis of the Modified Explicit Higher Order Perturbation method (the MHP method) with two-energy-group. To show the validity of the relationship, experiments were carried out in a coupled-core at the Kyoto University Critical Assembly (KUCA), and numerical calculations were performed for inferring the eigenvalue separation from the perturbed reactivity and the degree of flux tilt induced by a perturbation. In the coupled-core at the KUCA C-core, comparing with the results of the experiments and the numerical calculations, it was shown that the validity of the relationship is confirmed and that the flux tilt is independent on the neutron energy. (author)