Method of power-up operation for nuclear reactors

Purpose: To increase the reactor power upto an aimed high power level by at first increasing the reactor power from low to medium level by the position control of control rods and then switching to the reactor power control. Method: The present invention concerns a method of reactor operation capable of obtaining an optional high power upto about 10 MW in a trigger type pulsed reactor having a great inherent negative reactivity feedback due to the increase in the fuel temperature. At first, control rods are withdrawn to such a position that the reactivity goes lower than one dollar by the control rod position control. The power is increased logarithmically but moderately under this state to a medium power level since the reactivity is reduced by the negative feedback in the course of the temperature rise. If it is increased to the medium power level, the control by the control rod position is automatically switched to the reactor core control and the power is directly increased to an aimed power, for example, up to 10 MW linearly. Thus, power-up can be obtained by the operation method of a simple identical pattern to the high power at each of the levels. (Horiuchi, T.)