Patent Application
20140368219
The present application relates generally to rod control systems, and more particularly relates to systems and methods of monitoring rod control systems of nuclear power plants to determine whether the rod control system is operating properly.
In a nuclear Pressurized Water Reactor (PWR), the power level of the reactor is controlled by inserting and retracting control rods, which may include shutdown rods, in a reactor core.
Current designs of many nuclear power plants are equipped with control and shutdown rods which are inserted and withdrawn from the reactor core to control the reactivity by absorbing neutrons. Specifically, in Pressurized Water Reactors (PWRs), the movement of each rod is facilitated by its own electromechanical magnetic jack mechanism located atop the reactor vessel. Two examples of rod control systems that use this mechanism are the Control Rod Drive Mechanism (CRDM) and Control Element Drive Mechanism (CEDM). Both of these mechanisms consist of a set of coils that provide precise vertical movement to the rod by sequentially inducing a magnetic field in the coils to operate the mechanical parts of the system. The magnetic flux provides the energy needed to hold, insert, or withdraw the rod from the reactor core.
Efforts regarding such systems have led to continuing developments to improve their versatility, practicality and efficiency. For example, impedance measurements can be used to verify proper operation of the coils, cables, and connectors that make up the mechanism. Changes in impedance can be used to detect degradation and aging.
Example embodiments of the present general inventive concept provide systems and methods of systems and methods of monitoring rod control systems of nuclear power plants to determine whether the rod control system is operating properly.
Additional features and embodiments of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present general inventive concept.
Example embodiments of the present general inventive concept can be achieved by providing a method of monitoring a rod control system of a nuclear power plant, including calculating impedance of at least one coil of a rod movement mechanism during plant operation using a non-intrusive method for evaluation of the coil(s), comparing a measured impedance to a reference impedance, and determining if the measured impedance deviates from the reference impedance value by a predetermined amount to indicate degradation of the rod control system.
The measuring operation can include analyzing rod control system current and voltage signals of the at least one coil while the system is in operation in the plant.
The measuring operation consists of non-intrusive measurements that do not hinder operations.
The measuring operation can include analyzing the impedance, consisting of resistance and inductance measurements, of any of the coils that make up the rod control mechanism. .
The measurements can determine health of coils, cables, and connectors which together make up the rod control mechanism.
The reference impedance can be based on a recorded impedance of the rod movement mechanism during operation of the nuclear power plant.
Example embodiments of the present general inventive concept can also be achieved by providing a method of monitoring a rod control system of a nuclear power plant, including measuring voltage and current signals of at least one coil of a rod movement mechanism during plant operation using a non-intrusive method for evaluation of the coil(s), calculating an impedance of the least one coil based on measured voltage and current signals, recording a plurality of impedance calculations over a period of time, and determining whether a current recorded impedance changes relative to a prior recorded impedance by a predetermined amount to indicate degradation of the rod control system.
Example embodiments of the present general inventive concept can also be achieved by providing a system to monitor a rod control system of a nuclear power plant, including an impedance determining unit to determine an impedance of at least one coil of a rod movement mechanism during a rod movement sequence of the rod control system, and a controller to compare a measured impedance to a reference impedance, and to determine if the measured impedance deviates from the reference impedance value by a predetermined amount to indicate degradation of the rod control system.
The controller can be configured to analyze current and voltage measurements of the at least one coil over a plurality of rod movement sequences.
Example embodiments of the present general inventive concept can also be achieved by providing a system to monitor a rod control system of a nuclear power plant, including an impedance determining unit to determine an impedance of at least one coil of a rod movement mechanism during a rod movement sequence of the rod control system during operation of the nuclear power plant, and a controller to record a plurality of impedance calculations over a period of time, and to determine whether a current recorded impedance changes relative to a prior recorded impedance by a predetermined amount to indicate degradation of the rod control system.
The following example embodiments are representative of example techniques and structures designed to carry out the objects of the present general inventive concept, but the present general inventive concept is not limited to these example embodiments. In the accompanying drawings and illustrations, the sizes and relative sizes, shapes, and qualities of lines, entities, and regions may be exaggerated for clarity. A wide variety of additional embodiments will be more readily understood and appreciated through the following detailed description of the example embodiments, with reference to the accompanying drawings in which:
Reference will now be made to example embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings and illustrations. The example embodiments are described herein in order to explain the present general inventive concept by referring to the figures.
In the embodiment of
Example systems and methods of the present general inventive concept can be used to make non-intrusive impedance measurements on rod control system coils in-situ. Coil signal measurements such as coil voltage and coil current can be acquired from existing plant test points.
An example method of monitoring a rod control system of a nuclear power plant, comprises calculating impedance of at least one coil of a rod movement mechanism using a non-intrusive method that utilizes existing plant signals, thereby allowing impedance to be calculated in-situ while the rod control system is online. An example for calculating may comprise comparing a measured impedance to a reference impedance; and determining if the measured impedance deviates from the reference impedance value by a predetermined amount to indicate degradations or failures of the rod control system. An example for calculating may comprise analyzing current and voltage signals. An example for calculating may comprise measuring a resistance of at least one of the following: a coil, a cable, and at least one connector and wherein a measured resistance is used to determine the coil temperature of a rod movement mechanism above a reactor core. An example for calculating may comprise measuring an inductance of at least one of the following: a coil, a cable, and at least one connector. An example for calculating may comprise analyzing the impedance of at least one coil. An example reference impedance is based on historical impedance calculations of the at least one coil.
An example method of monitoring a rod control system of a nuclear power plant may comprise: measuring voltage and current signals of at least one coil of a rod movement mechanism while the system is in operation in the plant; recording a plurality of impedance calculations over a period of time; calculating an impedance of the least one coil based on the measured voltage and current signals; and determining whether a current recorded impedance changes relative to a prior recorded impedance by a predetermined amount indicate degradation of the rod control system.
A system to monitor a rod control system of a nuclear power plant, comprising: an impedance measuring unit to measure an impedance of at least one coil of a rod movement mechanism during plant operation using a non-intrusive method for evaluation of the at least one coil; a controller to compare a measured impedance to a reference impedance, and to determine if the measured impedance deviates from the reference impedance value by a predetermined amount to indicate degradation of the rod control system. An example controller is configured to analyze current and voltage measurements of the at least one coil. An example reference impedance is based on historical impedance measurements of the rod movement mechanism during operation of the nuclear power plant.
A example system to monitor a rod control system of a nuclear power plant, comprising: an impedance determining unit to determine an impedance of at least one coil of a rod movement mechanism during plant operation using a non-intrusive method for evaluation of the at least one coil; a controller to record a plurality of impedance calculations over a period of time, and to determine whether a current recorded impedance changes relative to a prior recorded impedance by a predetermined amount to indicate degradation of the rod control system.
The examples described herein provide a metric which may be utilized to diagnose rod movement problems because the calculation results may be predictable from step to step wherein a significant variation from normal may be noticed because of one or more problems, such as improper rod movement, rod movement failure, electrical degradation, mechanical degradation, etc., exists.
While embodiments of the present general inventive concept are described herein, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional modifications will readily appear to those skilled in the art. The present general inventive concept in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.
