EXPERT SYSTEM FOR ONLINE SURVEILLANCE OF NUCLEAR REACTOR COOLANT PUMPS
CONTRACTUAL ORIGIN OF THE INVENTION 5
The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the U.S. Department of Energy and The University of Chicago.
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BACKGROUND OF THE INVENTION
Reactor coolant pump degradation can produce severe economic penalties for nuclear power plants which have to shut down for extended periods of time in response to a possible coolant pump failure. As a result, 15 there is a strong economic incentive to develop and commercialize an effective apparatus to provide for early detection of coolant pump problems. Early detection of a coolant pump degradation would allow the reactor operator to manually trip the reactor before 20 major pump damage occurred as opposed to the operator experiencing an automatic rapid shutdown of the reactor due to the loss of coolant caused by a damaged pump or a false alarm caused by a defective sensor. A controlled response would allow maintenance to be 25 performed on the pump prior to failure or severe damage or to pinpoint a sensor problem and thus, limit the reactor down time.
The current general practice is to evaluate the condition of the reactor's coolant pump through the use of 30 high/low limit checks of the pump's operating parameters. Using this system, when the coolant pump parameters read outside of a zone defined by the high/low values, an alarm is sounded, and the pump is shut down resulting in lost operating time/This type of analysis can 35 result in a high number of false alarms and missed alarms when compared to an artificial intelligence technique which more closely analyzes the pump parameters as measured by a set of pump sensors.
Artificial intelligence techniques in an expert system 40 continually survey and diagnose pump performance and operability as a means of detecting the early stages of pump degradation. Since most pumps are equipped with numerous sensors to monitor the condition of the pump, the sensors provide a good data base for use by the 45 expert system. Applicants' expert pump diagnosis system continuously monitors and compares the digitized signals representing a variety of variables associated with the physical condition of the coolant pump: speed, vibration level, power, and discharge pressure. Varia- 50 tion of these variables is a possible indication of off-normal operation of the pump. Applicants' invention uses an expert system based on a mathematical comparison and analysis of multiple signals from a pair of nuclear reactor coolant pumps to analyze the condition of the 55 coolant pump using the aforementioned input signals.
Accordingly, it is an object of this invention to provide an expert system for early detection of coolant pump degradation so as to provide the operator with information on this condition prior to pump failure. 60
A further object of this invention is to provide an expert system for determining sensor degradation as opposed to pump failure.
Additional objects, advantages and novel features of the invention will be set forth in part in the description 65 which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The
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objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objectives and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides for a means to determine the degradation of a nuclear reactor cooling pump and the degradation of sensors used to measure various parameters associated with the cooling pump. Applicants' invention accomplishes this through the use of an expert system employing a sequential probability ratio test (SPRT) to evaluate parametric data associated with the function of the coolant pump. The SPRT technique requires the presence of duplicate sensors on each of two or more pumps. This system provides the reactor operator with an early warning system to allow an orderly shut down of the pump for sensor or pump degradation in lieu of a rapid emergency shut down of the pump.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents the expert system for online surveillance of a set of nuclear reactor coolant pumps.
FIG. 2 depicts the logic diagram for the expert pumpsurveillance system.
DETAILED DESCRIPTION OF THE
INVENTION
The subject invention teaches a expert system and method to determine the degradation of nuclear reactant coolant pumps and their respective sensors prior to failure.
FIG. 1 illustrates the architecture of the expert system for an online pump-surveillance system. The two coolant pumps 1 and 2 are each equipped with numerous sensors. A typical sensor arrangement is depicted in FIG. 1 where seven sensors are employed: three which monitor the rotor shaft speed 3, two accelerometers 4 which monitor the mechanical vibration of the pump, a pump power measuring device 5 which measures the power needed by the motor to turn the rotor, and a discharge pressure transducer 6 which measures the flow rate of coolant through the pump. The information from the sensors is transmitted to the data acquisition system 7 (DAS) which then interfaces with the artificial intelligence (AI) based inference engine 8. The AI inference engine 8 implements an operability logic algorithm illustrated in FIG. 2. The AI software for the inference engine 8 is supported by a layer of utility routines which perform generic functions such loading external tables, access to shared knowledge base, interprocess synchronization, and network communication. Output from the AI engine 8 is integrated to a color-graphics display 9 in the reactor room and is multiplexed back to the data acquisition system 7 for archive backup storage. If the inference engine 8 detects a degradation in the pump or its sensors an audible alarm is sounded indicating a pump sensor failure 10 or a pump disturbance 11.
FIG. 2 illustrates a flow chart for determining the condition of the cooling pumps through the employment of a sequence of mathematical algorithms associated with a series of sequential probability ratio test (SPRT) modules. The input signals 12 are acted on mathematically by a sensitive pattern recognition tech
