Controller for reactor control rod drive

Control rods can be driven by a signal greater than a minimum control rod drive signal with no degradation of controllability in the device according to the present invention. That is, when an input signal is greater than the minimum control rod drive signal, the input signal is applied to a first control circuit as a control rod drive signal. On the other hand, when the input signal is smaller than the minimum control rod drive signal, the input signal is integrated into a predetermined control rod drive signal and inputted to a second control circuit. Then, the first control circuit containing a filter does not output a signal if the input signal is smaller than the minimum control rod drive signal. On the other hand, the filter of the second control circuit filtrates the input signal if it is greater than the minimum control rod drive signal, and integrates the input signal if it is smaller and otuputs it at a predetermined value during a predetermined period of time. Accordingly, fine operation can be conducted with an equivalent operation signal per unit time without cutting off even signals smaller than the minimum control rod drive signal (I.S.)