Patent Number: 
Section: claims

1. A diagnostic system for performing diagnostics on rod position indication (RPI) coils of a digital rod position indication system (DRPI) of a nuclear reactor, the DRPI system having a plurality of detector coils for monitoring the position of a control rod, the plurality of detector coils being energized by an operating power source of the DRPI system at an operational frequency when the nuclear reactor is operating such that during operation of the nuclear reactor each detector coil generates an electronic signal having identifiable characteristics based on the operational frequency, said diagnostic system comprising:a data acquisition unit having a number of analog inputs configured to respectively connect to outputs of the plurality of detector coils to monitor electrical signals from the plurality of detector coils, the data acquisition unit having RPI coil diagnostic electronics configured to sample the electronic signals generated from each detector coil to create sampled data indicative of the electrical signals output from the plurality of detector coils while the nuclear reactor is operating, the number of the analog inputs being equal to the number of detector coils in the DRPI system and an additional analog input to receive a reference signal;a processing unit in electrical communication with said data acquisition unit, the processing unit being configured to receive sampled data from the data acquisition unit corresponding to each detector coil, said processing unit having a calculator to calculate a value of at least one identifiable characteristic of a particular detector coil independently from other detector coils, and a comparator to compare a calculated value of the at least one identifiable characteristic to a reference value corresponding to the particular detector coil without influence from calculated values of other detector coils to indicate the health of the particular detector coil while the nuclear reactor is operating; andan interface unit configured to transmit the sampled data from the data acquisition unit to the processing unit in real time during normal operation of the nuclear reactor,wherein the identifiable characteristics include a combination of impedance and at least one of resistance and inductance. 2. The diagnostic system of claim 1 wherein the calculator calculates an impedance of each detector coil by subtracting a voltage of each said detector coil from a reference voltage produced by the operating power source and dividing by a current passing through each said detector coil, respectively, wherein the operating power source is an ac power source producing the reference voltage at the operational frequency, and the operational frequency is the line frequency of the operating power source. 3. The diagnostic system of claim 1 wherein the processing unit derives an inductance and/or resistance of each detector coil from the impedance of each detector coil, respectively, and anomalies in the inductance and/or the resistance of each detector coil are indicative of a problem with the respective detector coil. 4. The diagnostic system of claim 3 wherein said inductances associated with a plurality of detector coils have a substantially linear relationship, said processing unit including a detector to detect deviations from said substantially linear relationship and to identify the detector coil corresponding to said deviation. 5. The diagnostic system of claim 2 wherein said data acquisition unit measures the current passing through each detector coil of said plurality of detector coils, wherein said identifiable characteristics include an ac voltage component and an ac current component, and wherein said calculator calculates said impedance value from said ac voltage component and said ac current component. 6. The diagnostic system of claim 2 wherein said identifiable characteristics include an ac voltage component relative to a known resistance, wherein said calculator calculates an ac current from said ac voltage component and said known resistance, and wherein said calculator calculates said impedance value from said ac voltage component and said ac current. 7. The diagnostic system of claim 1 wherein the reference value is determined by moving the control rod through an entire range of motion and obtaining and storing a baseline value. 8. The diagnostic system of claim 1 wherein the reference value is obtained during a calibration process of the DRPI system. 9. The diagnostic system of claim 1 wherein the reference value is determined by a calibration process that is repeated, and the results of each calibration process are averaged to determine the reference value. 10. The diagnostic system of claim 1, wherein the data acquisition unit has an independent channel corresponding to the number of detector coils of a coil stack associated with a particular control rod, and the processing unit processes sampled data from all detector coils together in real time. 11. A diagnostic system for performing diagnostics on rod position indication (RPI) coils of a digital rod position indication system (DRPI) of a nuclear reactor, the DRPI system having a plurality of detector coils to monitor a position of a control rod, the detector coils being energized by an operational frequency of the nuclear reactor, the diagnostic system comprising:a data acquisition unit having a number of analog inputs equal to a number of detector coils within an independent channel of a coil stack of detector coils and a reference input as a reference line, each analog input configured to respectively connect to an output of to a particular detector coil to monitor electrical signals from the plurality of detector coils, the data acquisition unit having RPI coil diagnostic electronics configured to sample electronic signals generated from each detector coil independently to create sampled data indicative of the electrical signals output from each detector coils respectively, while the plurality of detector coils are energized with the operational frequency of the nuclear reactor; anda processing unit configured to receive the sampled electronic signals from each detector coil independently from the data acquisition unit, the processing unit having a calculator to calculate values of identifiable characteristics of each detector coil independently without influence of the other detector coils based on the sampled electronic signals and a comparator to compare the calculated values of the identifiable characteristics of each detector coil to determined deviations based on a relationship between the identifiable characteristics to determine a health of each detector coil;wherein a deviation beyond a predetermined amount indicates a problem in the health of the corresponding detector coil. 12. The diagnostic system of claim 11, wherein the identifiable characteristics include impedance, resistance, and inductance. 13. The diagnostic system of claim 12, wherein the identifiable characteristics are in a linear relationship.