Measurement of Eigenvalue Separation in Coupled-Core Systems using Optical Fiber with Scintillator

摘要

The first-harmonic eigenvalue separation of loosely coupled cores constructed at the light-water moderated/reflected core in the Kyoto University Critical Assembly (KUCA) have been measured using optical fiber with Scintillator. The method is based on the measurement of flux tilt introduced by the asymmetric insertion of control rod in the two coupled core halves. The use of the optical fiber detector enabled the rapid flux tilt measurement compared to the conventional activation wire method. The measured eigenvalue separation showed excellent agreement with the results of the rod drop and Feynman-α measurements. The flux tilt method gave the smallest experimental error, and is applicable to a less loosely coupled system with a larger eigenvalue separation, where the conventional Feynman-a method is hardly applicable.