Patent Number: 059995831
Section: claims

1. A method for analyzing an electromagnetic drive mechanism for a nuclear control rod while positioning the control rod relative to a core of a reactor for controlling nuclear flux during generation of power by the core, the mechanism having at least one stationary gripper and coil, at least one movable gripper and coil, at least one armature and coil for displacing the movable gripper relative to the stationary gripper, and a timing circuit coupled to a coil current driver operable to provide current to said coils in sequences of operations in which said coils are energized individually and in combinations for advancing and retracting the control rod relative to the core, the method comprising: positioning the control rod relative to the core of the reactor for controlling said nuclear flux by executing said sequences of operations while: 2. The method of claim 1, wherein the current variation comprises a notch occurring upon pull-in of at least one of the stationary gripper and the movable gripper. 3. The method of claim 2, wherein the nominal current amplitudes include occurrence of said notch at a nominal delay and amplitude following application of a current to said at least one of the stationary gripper coil and the movable gripper coil, and further comprising comparing at least one of an actual delay and an actual amplitude of the notch to the nominal delay and amplitude for identifying one of mechanical impairment of the gripper and degradation of a magnetic flux of said at least one of the coils. 4. The method of claim 1, further comprising sensing at least one of current and voltage at a plurality of points between an ac power source and said coils, the points including at least one circuit interrupter, at least one switching device and power regulator, a controller for operating the switching device and the coils, and wherein said current and voltage at the plurality of points are compared to nominal levels for identifying an electrical or mechanical failure point between the power source and the coils, and further comprising indicating said failure point. 5. The method of claim 4, wherein the failure point is determined as at least one of: loss of the ac power source, operation of the circuit interrupter to disengage the ac power source, failure of the switching device, failure of the power regulator and malfunction of the controller. 6. The method of claim 1, wherein the stationary and movable grippers are operable in a grip mode at a higher current amplitude and a hold mode at a lower current amplitude, and further comprising comparing the higher and lower current amplitudes to nominal values. 7. The method of claim 1, further comprising comparing the coil current data of said each later one of the sequences of operations to said nominal amplitudes and timing relationships for the coil current signals.