Derivation of coupling coefficient from rod drop measurements in two-point reactors

A method is proposed to determine the reactivity coupling coefficient of a zero-power coupled-core system, based on the control rod drop measurements. We derive a two-point version of the formula for a rod drop experiment. The formula is very simple and the experimental procedures are convenient as well as conventional rod drop measurements.

For experimental determination of the coupling coefficient, experiments were carried out in the UTR-KINKI reactor, a light-water-moderated and graphite-reflected reactor. The validity of the proposed method is demonstrated by close agreement in the coefficients between the present result and the previous ones from reactor-noise measurements.