A method for recognizing the step movement sequence of a control rod drive
mechanism of a nuclear reactor, which withdraws and inserts a control rod
of a nuclear reactor, includes the steps of: measuring current and
voltage flowing through an electromagnetic coil used in the control rod
drive mechanism of the nuclear reactor; calculating inductance of the
coil by using the measured current and voltage; calculating a distance
between a rotor and a stator of the control rod drive mechanism on the
basis of the calculated inductance; and recognizing the step movement
sequence of the control rod drive mechanism on the basis of the
calculated distance. This method ensures good reliability in determining
the step movement sequence, allows easy implementation using a digital
signal processor, and is hardly affected by external factors such as
noise.