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The Digital Control System Design And Its Reliability Study Of Reactor Power Control In Nuclear Power Plant

Posted on:2011-10-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:C LiuFull Text:PDF
GTID:1102360308977268Subject:Nuclear science and technology, nuclear technology and applications
Abstract/Summary:PDF Full Text Request
Reactor is the core unit of a nuclear power plant. The reactor rod control and position monitoring or measurement system (hereinafter referred to as the rod control / position measurement system) is the key instrumentation and control system in the reactor power control.With the development of digital technology, the digitization of reactor instrumentation and control system in nuclear power plant, especially that of the reactor power control and protection system, has become an inevitable trend. The reactor rod control / position measurement systems of Qinshan Phase I project, whose instrumentation and control system was self-developed and designed based on analog technology in 1970s, has shown many faults in the reactor rod control / position control units in actual operation due to the technology and design level at that time.This research deals with the digital modification and design of Phase I 300MW reactor control rod / position measurement systems in Qinshan Nuclear Power Plant. First of all, the basic principle of the control object-the reactor power control-is introduced. The functions and design requirements of the control system are analyzed and studied. Since there are such problems as difficult modification of the system logic interrelation and rare recurrence of the system operation status and other issues in reactor power control system during the actual operation, in this renovation project, a novel digital design scheme based on CPU redundancy and network redundancy has been proposed to conduct the control system design and equipment development work. The electrical schematic diagram of the hardware system and control procedures have been completed, and the control system equipment development and debugging been fulfilled.The control system design project applied 1756-L63 digital controller of the U.S. Rockwell's ControlLogix control system as the core controller, and the star topology redundant ControlNet networks based on fiber optics and coaxial cable as communication means to perform the logic function and parameter measurement of the entire power control system. The function control switchboards are composed of three parts: logic switchboards, power supply switchboards and rod position processing switchboard. CPU redundancy control structure is used in logic switchboards. The non-disturbance switching capability of this redundant system has greatly improved the system reliability. Each power supply switchboard is equipped with an independent CPU to generate precise step cycles timing instructions. Rod position switchboard achieves rod position detection, fault alarm, Gray code conversion and other functions. In addition, as man-machine interface and debugging platform, touch-screens are also used for human-computer interaction through which the system states, operation-related information are offered and system initialization parameters are presented. The electromagnetic coil current timing of the control rod drive mechanisms, rod position trends and fault alarms and other important parameters have been displayed in real-time operation.On the basis of reliability theory in control system, this research focused on the reliability of redundant control system, in particular, the reliability and availability problems of dual-redundant control system. The relationship between redundancy design of control system and reliability, the relationship between reliability and redundancy, and the selection ways of control system redundancy are also analyzed and discussed.Finally, the reliability of modified digital redundancy control system of reactor power is comprehensively studied in detail. Reliability models of redundant segments, rod control system and rod position system have been established respectively. Main performance indicators to evaluate system reliability such as reliability and failure rate have been analyzed and calculated. Reliability block diagram is used to implement the modeling, simulation analysis and study on the reliability of domestic commercial reactor power digital control system, and the reliability prediction and assessment of the retrofitted system.This research has achieved the digital modification design and equipment development of the rod control / rod position system of reactor power control. This modification project has significantly improved such functions as system logic control, fault alarm, data records of rod position, on-line monitoring, 72-hour rod-move waveform records as well as the changes of key parameters granted by high-level privileges. The system's capabilities of network communication and monitoring, the digital interface of human-computer interaction have been enhanced. The maintenance costs and accident risk have been reduced. The security, reliability and operating efficiency of nuclear power plants have been improved. The system is characterized by novel design, advanced technology and in line with the development requirements in this field. It is significant in designing home-made, independent R&D of the digital instrumentation and control system in nuclear power plant.
Keywords/Search Tags:nuclear power plant, reactor power control, digital technology, redundancy control, reliability study
PDF Full Text Request
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