Method for controlling xenone control rod in nuclear reactors

Purpose: To adequately conduct entire withdrawal or entire insertion of xenone control rods by comparing the control rod worths of the xenone control rods and the xenone amount. Method: A turbine output signal is inputted to a load variation detection circuit and, if the variation coefficient is with a predetermined setting value, it is judged that the load variation has been completed and the load is settled constant, the result of which is inputted to the control rod selection device. The reactor power signal is inputted to a control rod selection device and the number density of iodine and the number density of xenone are determined based on the neutron flux and the maximum or minimum value of the xenone at a constant load is calculated based on both of the data. Then, a function representing the variation amount of the xenone reactivity having the maximum or minimum value as the variant is determined. By comparing the function and the constant load signal, the operation for the xenone control rods is judged or selected. According to this invention, the conventional method of compensating the xenone amount variation with the adjustment of the boron concentration can be substituted with the xenone control rods. (Kawakami, Y.)