Data processing: measuring – calibrating – or testing – Measurement system – Performance or efficiency evaluation
Reexamination Certificate
1999-09-17
2002-11-19
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Performance or efficiency evaluation
C376S215000
Reexamination Certificate
active
06484126
ABSTRACT:
This application is a continuation in part of, and also related to subject matter disclosed in copending U.S. patent applications Ser. Nos. 09/069,869, filed on Apr. 30, 1998, (Attorney Docket No. ABB-164, C970270) and 09/076,094, filed on Jun. 6, 1997, (Attorney Docket No. ABB-165, C970330).
FIELD OF THE INVENTION
The present invention relates to the field of nuclear power plants. More specifically, the present invention relates to an improved monitoring system for monitoring nuclear power plant operation and effecting emergency safety procedures in the event plant operations exceed established parameters. Still more specifically, this invention relates to an improved Engineered Safety Features (ESF) Component Control System (CCS) for a Digital Plant Protection System (DPPS).
BACKGROUND OF THE INVENTION
For safety, nuclear power plants include complex monitoring or “plant protection” systems. These systems monitor the operation of the nuclear reactor and the power plant in general. If any portion of the reactor or other important functions of the plant that is being monitored exceed established safe parameters, the plant protection system can effect emergency procedures, such as shutting down the reactor, to prevent complications from arising.
Additionally, plant protection systems are designed to be redundant and self-validating so that any malfunctions that arise will be identified before they result in serious problems. For example, for a particular monitoring function of the plant protection system, two or more redundant systems may be provided. The redundant systems monitor the same parameter or perform the same calculations. The outputs of the redundant systems are then compared to verify the proper functioning of all the systems. Disagreement between redundant systems signals a potential problem.
Many of the existing nuclear power plants have been in operation for some time and employ plant protection systems that are aging or obsolete in comparison with modern technology. For example, most existing plant protection systems for nuclear power plants are Solid State Protection Systems (“SSPS”) which employ an extensive network of discrete digital electronics, mechanical switches and electromechanical relays. These relays and switches having moving parts which are actuated using electromagnetism to effect the necessary connections between the various parts of the plant protection system.
In an SSPS system, two redundant logic channels may be provided to monitor a single parameter of the nuclear power plant's operation. If one channel fails, the other channel maintains the necessary monitoring function.
Given the service age of many of the components of such solid state systems, increasing failure rates are expected as the components begin to exhibit the normal problems associated with the end phase of the product life cycle. For example, industry reliability models predict an increasing failure rate for electromechanical relays of the type and vintage in question due to stuck and pitted contacts or open coils. These failures will obviously threaten the reliability of the plant protection system and the safety of the nuclear power plant being protected.
Additionally, the coincidence logic in an SSPS for checking the coincidence between redundant monitoring systems is performed by custom circuit cards that are generally obsolete. For example, these cards typically employ Motorola High Threshold Logic (MHTL) circuits. Industry reports indicate that MHTL circuits are susceptible to aging failures that can result in intermittent logic levels. Thus, increasing age and the complexity of the existing logic circuitry can result in decreased system reliability, increased trouble shooting difficulty and decreased plant availability due to the unnecessary activation of emergency shut down and other emergency response mechanisms.
Consequently, there is a need in the art for an improved plant protection system. More particularly, there is a need in the art for an improved plant protection system that makes use of current technology to provide high reliability throughout an extended life cycle.
The two cited copending parent applications to this application respectively disclose an all-digital logic Digital Plant Protection System (DPPS) and a Digital Engineering Safety Features Actuation System (DESFAS) which act as an interface between a Plant Protection System (DPP) and Engineered Safety Features (ESF) in a nuclear power plant. Such nuclear plant safety systems have multiple channels, each channel having bistable functions, with local coincidence testing systems. Such channels exist to interconnect a main control room, a remote shutdown panel, an interface and test processor (an ITP net) through a control network, such as an AF
100
Net. It nevertheless is desired in such a system to increase the speed of actuation through an HSSL Actuation Link, or Actuation Net HSSL diverse from the AF
100
Net which overrides upon actuation.
SUMMARY OF THE INVENTION
It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide an improved emergency response system operating on the data provided by the plant protection system. More particularly, it is an object of the present invention to provide an improved emergency response system that makes use of current technology to provide high reliability throughout an extended life cycle. Still more particularly, it is an overall object of this invention to increase speed of actuation through an HSSL Actuation Link diverse from an Actuation network which ovrides upon actuation.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims.
To achieve these stated and other objects, the present invention may be embodied and described as an engineered safety features component control system which receives signals from a digital plant protection system that is monitoring parameters of the plant operation. The system includes two or more, preferably four, logic channels monitoring a particular parameter of the plant operation. Each of the logic channels includes a bistable processor for receiving input from the digital plant protection system relating to the particular parameter which the logic channel is to monitor and for determining if that particular parameter of the plant operation is within predetermined safe limits.
A coincidence processor is associated with each bistable processor for comparing an output of the bistable processor with outputs from bistable processors in the others logic channels. One or more component control system processors receive the output of each coincidence processor and actuate the components of the emergency response systems based on that output.
In a preferred embodiment, there are four logic channels all monitoring the same parameter of plant operation. Additionally, a series of component control system processors are used, each controlling a predetermined group of emergency response devices. Preferably, at least one of the component control system processors is redundant.
Each logic channel preferably includes a second, redundant bistable processor that receives input and performs functions identical to those of the other bistable processor in the channel. A second coincidence processor is provided in connection with the second bistable processor. The second coincidence processor receives output from the second bistable processor and compares that output with output from other corresponding redundant bistable processors in the other logic channels. The output from the second coincidence processor is also provided to the component control system processors or controllers which actuate the components of the emergency response systems based on the output of bo
Brown, Sr. Edgar Mel
Kessler, Jr. Frank Martin
Manazir, Jr. Richard Michael
Senechal Raymond Robert
Charioui Mohamed
Hoff Marc S.
Westinghouse Electric Company LLC
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