Setting value is also called setting value, which means that in the automatic control system, when a certain physical quantity reaches a certain value, a certain action will occur.On the other hand, if the speed of a certain motor is automatically controlled, we set the speed control device to 1000 rpm, then this 1000 rpm is the setting value of the motor speed.
According to the requirements of nuclear safety regulations, the nuclear power plant must strictly comply with the written operating procedures during operation, and the operating procedures must comply with and ensure the implementation and execution of operating limits and conditions.Because of the paramount importance of nuclear safety,Nuclear power plantAs a specific document that directly guides operators to perform operation, operation procedures are of great significance to ensure the safe and reliable operation of nuclear power plants.For the third-generation passive nuclear power plants, there is little experience in the development of operating procedures. The analysis and research of various setting value information in operating procedures, including operating limits, can improve the procedure development technology and further ensure the long-term safe and reliable operation of nuclear power plants[1]。
System analysis
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The operation procedures of the demonstration project passive nuclear power plant are divided into general operation procedure (GOP), system operation procedure (SOP), alarm response procedure (ARP), abnormal operation procedure (AOP), emergency operation procedure (EOP), supervision and test procedure (STP), operation procedure after 72 hours (72H) and severe accident management guideline (SAMG).GOP provides guidance for normal startup and shutdown operation, power operation and mode switching operation of nuclear power plant, so as to ensure normal switching between different operating conditions of nuclear power plant.SOP provides operation guidance for startup and shutdown of various systems, system calibration, sequence switching, isolation of subsystems and components, operation and maintenance of nuclear power plants.72H is a special system operation procedure, which considers the long-term operation of nuclear power plants after accidents.ARP provides clear guidance for operators to respond to the system alarm.
AOP provides guidance for operation after failure of nuclear power plant systems, structures and components (SSCs) or corrective actions in case of abnormal conditions.The EOP provides guidance for plant response operations leading to reactor scram or engineered safety facility action events to mitigate accident consequences.STP is a regular test procedure developed to meet the supervision requirements in the technical specification.The operation steps of SAMG are not as detailed as those of other procedures. It mainly provides operation guidance for serious accidents to prevent the core damage and radioactive release caused by multiple failures and accidents beyond the design basis from threatening the integrity of the containment.
Operators continuously monitor the status of the nuclear power plant during the operation of the nuclear power plant, and execute operation procedures when necessary to ensure the stable and safe operation of the nuclear power plant. The entire operation procedure system is consistent with the design basis of the nuclear power plant and defense in depth considerations.The nuclear power plant first prevents abnormal operation and failure through conservative design and high-quality construction and operation, realizes normal operation required by SSCs according to GOP and SOP, and conducts regular tests according to STP to ensure that SSCs can operate.In case of abnormality or fault, control and fault detection of abnormal operation shall be realized through control, protection system and other supervision facilities, fault alarm shall be quickly recovered according to ARP, and countermeasures shall be taken for different abnormal events according to AOP and stable operation shall be conducted to avoid unplanned shutdown.If the event continues to deteriorate, resulting in an accident or even an accident beyond the design basis (the core outlet temperature does not exceed 650 ℃), the control within the scope of the base accident can be achieved through the specially designed safety facilities and EOP.In case of a serious accident, SAMG is used to control the severe working conditions of the nuclear power plant, including preventing the accident from worsening and mitigating the consequences of the serious accident.In case of radioactive release due to containment failure, the consequences of large release of radioactive materials shall be mitigated through off-site emergency response.
Constant value analysis
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Content and function
The main content of all kinds of operation procedures is the operation steps, which at least include the operation object, operation action and necessary information related to the operation object and operation action.Therefore, the setting value content of the operation procedure is related to the operation object (i.e. SSCs) (such as SSCs operation status indication and process control variables), or to the operation action (such as completion time, execution frequency, etc.).Since the operator mainly obtains display information from the main control room during the implementation of the procedure, most of the procedure setting value information is related to the instrument display of the nuclear power plant, and the instrument setting value can realize the functions of indication, alarm, control or protection.Since the operation procedure must ensure the implementation of the operation limits and conditions, the setting value information of the operation procedure includes or covers the safety limits, safety system setting values, normal operation limits and conditions, supervision requirements, etc.According to the requirements of nuclear safety regulations and guidelines on operating limits and conditions, it is assumed that an important process variable increases in the direction of reaching the safety limit, which may include setting value contents and interrelationships.
During the normal operation of the nuclear power plant, the best state of the SSCs that have been put into operation is to continue to operate within the stable operation range.Considering the normal fluctuation of an important process variable during normal operation, the alarm setting value, normal control and protection setting value can be set to remind the operator to pay attention to the fluctuation trend or ensureautomatic control systemPerform the expected action.In order to give the operator time to take action after the alarm occurs to prevent or avoid the operating parameters from exceeding the normal operating limit, margin shall be reserved between the alarm setting value and the normal operating limit.In case of abnormal events or SSCs failure, the corresponding important process variables deviate from the normal operation range and reach the normal operation limit. According to the results of safety analysis, the shutdown protection system and other safety systems may be required to act to stabilize the plant state.There is a margin between the normal operation limit value and the safety system trigger setting value, so that the operator has time to take corrective measures in a timely manner after the process variable exceeds the normal operation limit value, so as to prevent the process variable from continuing to deviate from the safety system trigger setting value and triggering the system action, so that the reactor enters a worse working condition.The trigger setting value of the safety system is the setting value of the safety system instrument. Considering the uncertainty of the instrument, the limit value, i.e. the allowable value, is specified for the periodic test and calibration of the instrument to ensure the operability of the instrument.The triggering setting value of the safety system is determined based on the results of accident analysis in the safety design of the nuclear power plant. Considering the instrument calibration and measurement errors, there is a margin between the allowable value and the analysis setting value.In order to ensure that all specified limits of radioactive release and acceptable limits of potential radiation exposure dose under various working conditions are not violated, the safety analysis limits and the results of safety analysis shall ensure that the safety limits of the nuclear power plant are not exceeded.
The setting value content and expected function of this important process variable are closely related to the operation status and control requirements of the nuclear power plant, and the setting of various setting values is consistent with the defense in depth considerations of the nuclear power plant design.According to the operating procedure architecture, most of the SSCs' normal control, protection and operating setting values are in the GOP, SOP and other normal operating procedures;Most SSCs alarm setting values in ARP;The normal operation limit of SSCs in AOP is mostly;Most of the safety system trigger setting values in EOP;In STP, the normal operation limit value and monitoring frequency constant value are mostly.This is consistent with the analysis results of the setting value information of the operation regulations of the demonstration project nuclear power plant.
Source and calculation
The technical specification of the nuclear power plant clearly stipulates the basic status and parameters of the nuclear power plant operation, as well as the restrictions and supervision requirements that must be observed by the operation of each system, and describes the basis for ensuring safety according to this operation, so as to meet the requirements of the nuclear safety regulations on the operating limits and conditions.Therefore, the safety related normal operation limit, safety system instrument setting value, completion time of measures taken in case of violation of operation limit conditions, supervision test frequency and other setting values in the operating procedure setting value information are mainly from the technical specification of nuclear power plant.The operation of SSCs in the operation procedure cannot violate the design basis of SSCs, so the operation setting values related to the performance parameters of SSCs mainly come from the design description and calculation documents of SSCs.
The setting values that are part of the safety related design of the nuclear power plant and are required to maintain the integrity of the fission product barrier need to be determined through safety analysis. Therefore, the setting values related to the key safety functions in the operating procedures mainly come from the safety analysis report.As the detailed operation guidance for the operation of nuclear power plants, the operation procedures also need to meet the specific site characteristics and operation management requirements. Therefore, the SSCs operation control setting values in the procedures may also come from the operation and maintenance technical documents, experience feedback or expert suggestions, etc[2]。
Determine process
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According to the system and structure of the operation procedure, the expected functional objectives of the procedure operation steps are defined, the SSCs (non safety related/safety related) used in the operation steps and their expected functions are defined, and then the setting values in the procedure operation can be determined by calculating according to the SSCs design criteria and related constraints and restrictions, and according to the content and source of the procedure setting values.
Take some setting values in the response procedure for triggering reactor or special safety facilities as an example: the purpose of this procedure is to ensure that the automatic protection system makes appropriate response after manually or automatically triggering the reactor shutdown or safety injection signal, and determine the corresponding recovery operation procedure by evaluating the status of the nuclear power plant.In the operation step of evaluating the status of the nuclear power plant, the operator needs to check twoSteam generator(SG) water level, passive residual heat removal heat exchanger (PRHR HX) flow andReactor coolant system(RCS) cold leg temperature and other parameters.
In order to determine the setting values of these parameters in the procedure, it is necessary to clarify the functions of parameters in the procedure operation steps and relevant design criteria, so as to carry out relevant calculations according to the structure and composition of the setting values.The operating procedure setting value determined by calculation also needs to be verified based on the modeling calculation of the simulator, and through the verification of the actual operation such as system pre operation and plant startup during the commissioning stage of the nuclear power plant. When necessary, the plant can be used for the actual procedure operation after the adaptability adjustment of the plant.The setting value of the operation procedure must ensure that the process realized by the procedure operation steps fully complies with the relevant design requirements and safety criteria of the nuclear power plant, and ensure that the results of the procedure operation steps are fully consistent with the expected functional objectives.According to the consistent defense in depth considerations in the procedure system and the setting value structure, the setting value content in the specific operation procedure can be determined according to the function of the operation steps.
summary
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The operation procedure document system and setting value content follow the defense in depth criteria of nuclear power plant design. The procedure setting value information supports the realization of SSCs' expected functions in the procedure operation steps, and is related to the operation object or operation action.In the process of determining the regulation setting value, it is necessary to consider the SSCs design basis setting value determined in the process of system design and safety analysis, the uncertainty of SSCs parameter measurement and display under different environmental conditions, as well as engineering experience and control margin requirements.
Through the analysis of the operation procedure system and setting value of the demonstration project nuclear power plant, systematic methods and processes are obtained to determine the procedure setting value applicable to the operation steps, which can effectively support the independent development of the operation procedure of the third generation passive nuclear power plant[3]。
