阅读说明：本技术 应对核电厂丧失正常给水atws事故的保护系统 (Protection system for dealing with ATWS (automatic water supply) accident of nuclear power plant caused by loss of normal water supply ) 是由 喻娜 卢毅力 吴清 李海颖 鲜麟 冉旭 李峰 杨帆 陈宏霞 周科 吴鹏 初晓 于 2020-05-18 设计创作，主要内容包括：本发明公开了应对核电厂丧失正常给水ATWS事故的保护系统,包括紧急停堆保护系统和主泵停运判定系统,采用连级联机关系将紧急停堆保护系统和主泵停运判定系统连接；所述主泵停运判定系统包括或逻辑单元Y、与逻辑单元,或逻辑单元Y：用于以出现再次紧急停堆控制信号时刻为初始时刻进行延时△T后的时刻获取的停堆失效状态信号进行或逻辑判定；与逻辑单元：用于依据或逻辑单元Y的判定结果和紧急停堆主保护系统产生的再次紧急停堆控制信号进行与逻辑判定而确定是否触发停运主泵控制信号。(The invention discloses a protection system for dealing with an ATWS (automatic train control) accident of losing normal water supply of a nuclear power plant, which comprises an emergency shutdown protection system and a main pump shutdown judgment system, wherein the emergency shutdown protection system is connected with the main pump shutdown judgment system by adopting a connecting and cascading organ system; the main pump outage determination system includes an or logic unit Y, and logic unit, or logic unit Y: performing OR logic judgment on the shutdown failure state signal acquired at the time delayed by delta T by taking the time when the re-emergent shutdown control signal occurs as the initial time; and logic unit: and the control unit is used for performing AND logic judgment according to the judgment result of the OR logic unit Y and a secondary scram control signal generated by the scram main protection system to determine whether to trigger shutdown of the main pump control signal.)

1. The protection system for dealing with the ATWS accident of the nuclear power plant which loses normal water supply comprises an emergency shutdown protection system and a main pump shutdown judgment system, and is characterized in that,

a cascade connection mechanism is adopted to connect the emergency shutdown protection system with the main pump shutdown judgment system;

the main pump shutdown determination system includes an or logic unit Y, and logic units,

or logic unit Y:

performing OR logic judgment on the shutdown failure state signal acquired at the time delayed by delta T by taking the time when the re-emergent shutdown control signal occurs as the initial time;

and logic unit:

and the control unit is used for performing AND logic judgment according to the judgment result of the OR logic unit Y and a secondary scram control signal generated by the scram protection system to determine whether to trigger shutdown of the main pump control signal.

2. The protection system for dealing with nuclear power plant loss of normal water supply ATWS accident according to claim 1,

the shutdown failure state signal at least comprises a change state criterion of the neutron injection rate of the reactor core obtained at the time delayed by delta T by taking the time when the re-emergency shutdown control signal occurs as the initial time, and a shutdown control rod overhigh state criterion obtained at the time delayed by delta T by taking the time when the re-emergency shutdown control signal occurs as the initial time.

3. The protection system for dealing with nuclear power plant loss of normal water supply ATWS accident according to claim 2,

the main pump outage judgment system also comprises a time delay device, a measuring device and a judgment device,

the time delay device:

the device is used for starting the measuring device by taking the time when the re-emergency shutdown control signal appears as a first starting time;

the device is used for starting the measuring device at a second starting time after the time of delaying delta T by taking the time of the occurrence of the secondary emergency shutdown control signal as an initial time;

a measuring device:

the reactor core neutron fluence rate acquisition unit is used for acquiring the reactor core neutron fluence rate when the reactor core is started at a first starting moment, and the acquired reactor core neutron fluence rate is called a first reactor core neutron fluence rate;

the reactor core neutron fluence rate acquisition unit is used for acquiring the reactor core neutron fluence rate when the reactor core is started at a second starting moment, and the acquired reactor core neutron fluence rate is called as a second reactor core neutron fluence rate;

a determination device: the change state criterion is used for judging the neutron injection rate in the reactor core according to the neutron injection rate in the first reactor core and the neutron injection rate in the second reactor core, and the judgment standard is as follows: if the neutron fluence rate of the second reactor core is higher than the neutron fluence X% of the first reactor core, the output of the judging device is true, if the neutron fluence rate of the second reactor core is lower than the neutron fluence X% of the first reactor core, the output of the judging device is false, and X% is a setting percentage value.

4. The protection system for dealing with nuclear power plant loss of normal water supply ATWS accident according to claim 2,

the main pump outage judgment system also comprises a time delay device, a measuring device and a judgment device,

the time delay device:

the device is used for starting the measuring device by taking the time when the re-emergency shutdown control signal appears as a first starting time;

the device is used for starting the measuring device at a second starting time after the time of delaying delta T by taking the time of the occurrence of the secondary emergency shutdown control signal as an initial time;

a measuring device:

the reactor core control rod height acquisition device is used for acquiring the height value of the reactor shutdown control rod when the reactor is started at a first starting moment, and the acquired reactor core neutron fluence rate is called the height value of the first reactor shutdown control rod;

the reactor core neutron fluence rate acquisition unit is used for acquiring the height value of the shutdown control rod when the reactor core is started at a second starting moment, and the acquired reactor core neutron fluence rate is called the height value of the second shutdown control rod;

a determination device: and the criterion is used for judging the over-high state of the shutdown control rod according to the height value of the first shutdown control rod and the height value of the second shutdown control rod, and the judgment criterion is as follows: and if the height value of the second shutdown control rod is higher than the height value of the first shutdown control rod, the output of the judging device is true, and if the height value of the second shutdown control rod is lower than the height value of the first shutdown control rod, the output of the judging device is false, and the I% is a setting percentage value.

5. The protection system for dealing with nuclear power plant loss of normal water supply ATWS accident according to claim 2,

the judgment result of the change state criterion of the neutron injection rate in the reactor core is as follows:

when M is more than N X%, the judgment result is true, and when M is less than N X%, the judgment result is false;

wherein M is: the reactor core neutron fluence rate obtained after the time delay delta T is carried out by taking the time when the re-emergency shutdown control signal appears as the initial time; n is: the reactor core neutron fluence rate at which the scram control signal occurs again.

6. The protection system for dealing with nuclear power plant loss of normal water supply ATWS accident according to claim 2,

the judgment result of the change state criterion of the neutron injection rate in the reactor core is as follows:

when G is more than H I%, the judgment result is true, and when G is less than N H I%, the judgment result is false;

wherein G is: the height value of the shutdown control rod is obtained after the time delay delta T is carried out by taking the time when the re-emergency shutdown control signal appears as the initial time; h is: the height value of the shutdown control rod when the emergency shutdown control signal occurs again.

7. The protection system for dealing with nuclear power plant loss of normal water supply ATWS accident according to claim 2,

the judgment result of the criterion of the over-high state of the shutdown control rod is as follows:

when the height value of the shutdown control rod is higher than the setting height value, the judgment result is true,

and when the height value of the shutdown control rod is lower than the set height value, the judgment result is false.

8. Protection system against nuclear power plant loss of normal feedwater ATWS accident according to any of claims 1-7,

the scram protection system comprises an or logic unit X,

or logic unit Y:

and the control device is used for determining whether to trigger the re-emergency shutdown control signal or not according to logic judgment at least according to the SG water level low state criterion, the superposition state criterion of low steam generator feed water flow and high reactor core neutron fluence.

9. The protection system for dealing with nuclear power plant loss of normal feedwater ATWS accident of claim 8,

the judgment result of the SG water level low state criterion is as follows:

and when the SG water level value is lower than the set water level value, the judgment result is true, and when the SG water level value is higher than the set water level value, the judgment result is false.

10. The protection system for dealing with nuclear power plant loss of normal feedwater ATWS accident of claim 8,

the judgment result of the criterion of the superposition state of low feedwater flow of the steam generator and high neutron fluence of the reactor core is as follows:

and when the flow value of the feed water of the steam generator is lower than the set water flow value and the neutron fluence value of the reactor core is higher than the set fluence value, judging that the result is true, otherwise, judging that the result is false.

Technical Field

The invention relates to the field of reactor control, in particular to a protection system for nuclear power plant ATWS (abnormal water supply) accident.

Background

When the nuclear power plant loses normal water supply-ATWS accident, the water content of the secondary side of the steam generator is rapidly reduced, the capacity of the steam generator for discharging the heat of the reactor coolant system is rapidly reduced, the temperature and the pressure of the reactor coolant system are continuously increased, and the emergency shutdown protection setting value is reached.

However, due to the failure of the scram (which may be the failure of a protection signal or the failure of a shutdown control rod), the nuclear power of the core cannot be timely reduced, so that the pressure and the temperature of the reactor coolant system tend to rise, the pressure limit of the reactor coolant system may be broken, and the integrity of the pressure boundary of the reactor coolant system is threatened.

In order to solve the threat caused by scram failure, a redundant idea of repeatedly starting scram is proposed in the prior art, such as CN 103985421. The method is characterized in that after main feed water flow and reactor power are detected, AND logic judgment is carried out so as to trigger a secondary emergency shutdown control signal and simultaneously trigger a main pump to shut down; or after detecting the main feed water flow, the reactor power and the SG water level, carrying out AND logic judgment so as to trigger a secondary emergency shutdown control signal and simultaneously trigger the main pump to shut down;

the purpose of setting and triggering the shutdown of the main pump is as follows: the shutdown of the main pump under the accident condition is beneficial to relieving accident consequences, because after the shutdown of the main pump, on one hand, the forced flow of the reactor coolant is reduced, the heat transfer of the reactor core is deteriorated in a short period of time, and the temperature of the coolant is increased, and negative feedback can be introduced into the reactor core due to the negative feedback effect of the reactor core to reduce the nuclear power, and on the other hand, the reduction of the forced circulation flow of the reactor coolant system can be matched with the state that the secondary side charge of the steam generator is reduced, so that the difference of heat production and heat conduction of the primary side and the secondary side.

However, since the triggering of a main pump shutdown proposed in this patent is triggered by an and logic determination of the main feedwater flow, stack power, SG water level; as shown in fig. 1, this processing method is performed by comprehensively determining the state of each circuit of the reactor system. In the patent, the concept of the adopted scheme is a parallel system relationship, the main pump is triggered to stop operation while the emergency shutdown main protection system is triggered in parallel, and the collected states of all loops of the reactor system are comprehensively judged; it is inherently a redundant design.

In the actual work, for the accident that the water content of the secondary side of the steam generator is reduced, because the scheme adopts the parallel starting to trigger the emergency shutdown again and simultaneously trigger the main pump to stop running, the emergency shutdown can be triggered again and the main pump is triggered to stop running at the same time with high probability; therefore, this would result in a large probability of the main pump being shut down; although the main pump is shut down to facilitate the introduction of negative feedback to the core; however, the redundancy concept is adopted to easily trigger the main pump to stop running, which can cause a very complicated program control process on later recovery, and lead to very complicated recovery of normal running state. Therefore, it is an important issue to reduce the false triggering of the shutdown of the main pump and how to trigger the shutdown of the main pump at a reasonable time.

Disclosure of Invention

The invention aims to provide a protection system for dealing with the ATWS accident of the loss of normal water supply of a nuclear power plant, which sets a reasonable control trigger main pump shutdown time so as to avoid reducing the false trigger of shutdown of the main pump.

The invention is realized by the following technical scheme:

the protection system for dealing with the ATWS accident of the nuclear power plant which loses normal water supply comprises an emergency shutdown protection system and a main pump shutdown judgment system,

a cascade connection mechanism is adopted to connect the emergency shutdown protection system with the main pump shutdown judgment system;

the main pump shutdown determination system includes an or logic unit Y, and logic units,

or logic unit Y:

performing OR logic judgment on the shutdown failure state signal acquired at the time delayed by delta T by taking the time when the re-emergent shutdown control signal occurs as the initial time;

and logic unit:

and the control unit is used for performing AND logic judgment according to the judgment result of the OR logic unit Y and a secondary scram control signal generated by the scram main protection system to determine whether to trigger shutdown of the main pump control signal.

The design concept of the technical scheme is as follows:

in order to avoid the problem that the shutdown of the main pump is started by adopting the comprehensive parameters of the reactor system in the prior art, the high risk of the shutdown of the main pump is caused. The application is equivalent to the improvement of the traditional mitigation protection system and comprises the following steps: separating the main pump for triggering shutdown and the control signal for triggering secondary emergency shutdown, forming hierarchical control of the two, triggering the main pump for shutdown after obtaining the control signal for secondary emergency shutdown, and performing time delay processing on the two by taking the control signal for secondary emergency shutdown as a boundary between 2 systems to obtain a boundary; the improvement of the invention on the criterion is as follows: data which can directly represent shutdown failure is collected, and then whether the main pump is shut down or not is determined. The data which can directly represent the shutdown failure is regarded as effective data only after the data which can directly represent the shutdown failure and is collected after time delay based on the re-emergency shutdown control signal. Meanwhile, in the scheme, when the logical unit and the logical unit of the main pump shutdown judging system perform logical judgment, a secondary emergency shutdown control signal generated by the emergency shutdown protection system needs to be introduced, so that the emergency shutdown protection system and the main pump shutdown judging system form a cascade relation, and therefore the main pump shutdown judging system can output the shutdown main pump control signal only when the emergency shutdown protection system effectively triggers the emergency shutdown control signal. Therefore, a cascade relation is provided, the control signal of the shutdown main pump can appear only after the control signal of the emergency shutdown is triggered, and the false triggering caused by the traditional parallel processing is avoided.

In addition, the shutdown failure state signal in the above-mentioned technical solution is a state determination signal after shutdown, which is a procedural indicator, and is not a specific determination value of 1, and the determination is to compare the change of data when the emergency shutdown control signal is triggered with the change of data after a certain time delay, for example, the present technical solution may adopt the change state of the neutron injection rate in the reactor core as the shutdown failure state signal, where the change state of the neutron injection rate in the reactor core means that the neutron injection rate in the reactor core at the time of triggering the emergency shutdown control signal is observed first, then the neutron injection rate in the reactor core obtained at the time of triggering the emergency shutdown control signal + a certain time delay is observed, and then the change state at these 2 times is observed; the shutdown failure is determined by the mode of observing change in time delay, so that the shutdown main pump is restarted. In order to enable the data diversity of direct representation shutdown failure, the technical scheme includes that the logic unit Y receives various data capable of directly representing the shutdown failure, wherein the data capable of directly representing the shutdown failure can also be a shutdown control rod overhigh state criterion.

Generally speaking, the technical scheme forms a state change criterion by using data when the emergency shutdown control signal is triggered and delayed data, so that shutdown failure can be directly, truly and reliably represented, and the criterion can be directly related to the emergency shutdown control signal. Meanwhile, the main pump shutdown judging system is effectively triggered only after the main system triggers the emergency shutdown control signal by utilizing the cascade connection of 2 systems; the time for triggering the shutdown of the main pump by the main pump shutdown judging system is limited, and based on the 2 important points, the system controls whether the main pump needs to be shut down in a cascade relation, and the traditional parallel control of whether the main pump needs to be shut down is not available. The necessity and the time for shutting down the main pump are reasonably arranged; unnecessary shutdown operations of the main pump are avoided. Compared with the prior art, the technical scheme can truly represent shutdown failure, and the condition that the main pump is started by mistake can be completely avoided.

Therefore, specifically, on the basis of the above technical solution, it is preferable that:

the shutdown failure state signal at least comprises a change state criterion of the neutron injection rate of the reactor core obtained at the time delayed by delta T by taking the time when the re-emergency shutdown control signal occurs as the initial time, and a shutdown control rod overhigh state criterion obtained at the time delayed by delta T by taking the time when the re-emergency shutdown control signal occurs as the initial time.

In order to realize the criterion of the change state of the neutron injection rate in the reactor core, the main pump shutdown judging system also comprises a time delay device, a measuring device and a judging device,

the time delay device:

the device is used for starting the measuring device by taking the time when the re-emergency shutdown control signal appears as a first starting time;

the device is used for starting the measuring device at a second starting time after the time of delaying delta T by taking the time of the occurrence of the secondary emergency shutdown control signal as an initial time;

a measuring device:

the reactor core neutron fluence rate acquisition unit is used for acquiring the reactor core neutron fluence rate when the reactor core is started at a first starting moment, and the acquired reactor core neutron fluence rate is called a first reactor core neutron fluence rate;

the reactor core neutron fluence rate acquisition unit is used for acquiring the reactor core neutron fluence rate when the reactor core is started at a second starting moment, and the acquired reactor core neutron fluence rate is called as a second reactor core neutron fluence rate;

a determination device: the change state criterion is used for judging the neutron injection rate in the reactor core according to the neutron injection rate in the first reactor core and the neutron injection rate in the second reactor core, and the judgment standard is as follows: if the neutron fluence rate of the second reactor core is higher than the neutron fluence X% of the first reactor core, the output of the judging device is true, if the neutron fluence rate of the second reactor core is lower than the neutron fluence X% of the first reactor core, the output of the judging device is false, and X% is a setting percentage value.

In order to realize the criterion of the over-high state of the shutdown control rod, the shutdown judging system of the main pump also comprises a time delay device, a measuring device and a judging device,

the time delay device:

the device is used for starting the measuring device by taking the time when the re-emergency shutdown control signal appears as a first starting time;

the device is used for starting the measuring device at a second starting time after the time of delaying delta T by taking the time of the occurrence of the secondary emergency shutdown control signal as an initial time;

a measuring device:

the reactor core control rod height acquisition device is used for acquiring the height value of the reactor shutdown control rod when the reactor is started at a first starting moment, and the acquired reactor core neutron fluence rate is called the height value of the first reactor shutdown control rod;

the reactor core neutron fluence rate acquisition unit is used for acquiring the height value of the shutdown control rod when the reactor core is started at a second starting moment, and the acquired reactor core neutron fluence rate is called the height value of the second shutdown control rod;

a determination device: and the criterion is used for judging the over-high state of the shutdown control rod according to the height value of the first shutdown control rod and the height value of the second shutdown control rod, and the judgment criterion is as follows: and if the height value of the second shutdown control rod is higher than the height value of the first shutdown control rod, the output of the judging device is true, and if the height value of the second shutdown control rod is lower than the height value of the first shutdown control rod, the output of the judging device is false, and the I% is a setting percentage value.

In particular, the method comprises the following steps of,

the judgment result of the change state criterion of the neutron injection rate in the reactor core is as follows:

when M is more than N X%, the judgment result is true, and when M is less than N X%, the judgment result is false;

wherein M is: taking the time when the emergency shutdown control signal appears as the initial time to obtain the reactor core neutron fluence rate after the time delay delta T; n is: the neutron fluence rate in the core in the presence of the scram control signal.

If the incomplete dropping of the shutdown control rod is considered as a starting point, the judgment result of the criterion of the overhigh state of the shutdown control rod can be as follows:

the judgment result of the change state criterion of the neutron injection rate in the reactor core is as follows:

when G is more than H I%, the judgment result is true, and when G is less than N H I%, the judgment result is false;

wherein G is: the height value of the shutdown control rod is obtained after the time delay delta T is carried out by taking the time when the re-emergency shutdown control signal appears as the initial time; h is: the height value of the shutdown control rod when the emergency shutdown control signal occurs again.

The change state criterion can be understood as an observation of the rate of change.

The shutdown control rod overhigh state criterion can also be as follows:

the judgment result of the criterion of the over-high state of the shutdown control rod is as follows:

when the height value of the shutdown control rod is higher than the setting height value, the judgment result is true,

and when the height value of the shutdown control rod is lower than the set height value, the judgment result is false.

The scram main protection system comprises an or logic unit X,

or logic unit Y:

and the control device is used for determining whether to trigger the re-emergency shutdown control signal or not according to logic judgment at least according to the SG water level low state criterion, the superposition state criterion of low steam generator feed water flow and high reactor core neutron fluence.

The judgment result of the SG water level low state criterion is as follows:

and when the SG water level value is lower than the set water level value, the judgment result is true, and when the SG water level value is higher than the set water level value, the judgment result is false.

The judgment result of the criterion of the superposition state of low feedwater flow of the steam generator and high neutron fluence of the reactor core is as follows:

and when the flow value of the feed water of the steam generator is lower than the set water flow value and the neutron fluence value of the reactor core is higher than the set fluence value, judging that the result is true, otherwise, judging that the result is false.

The set water flow value is (5-8)% > rated main water supply flow, and the set injection value is (25-30)% > rated reactor core neutron injection.

And the delta T is set to be 10s-20 s.

The invention can achieve the following effects:

by the system, the main pump can be triggered to stop running after the normal water supply loss-ATWS accident happens, so that negative reactivity is introduced into a reactor core, the change of the nuclear power of the reactor core is limited, and the pressure of a reactor coolant system is ensured not to break through an acceptable pressure limit value. Meanwhile, the time for introducing the shutdown of the main pump and the adopted criterion are designed, reasonable time control is adopted, and the criterion capable of directly representing shutdown failure is adopted for triggering. Thereby effectively avoiding unnecessary shutdown of the main pump.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

fig. 1 is a schematic diagram of a prior art system.

Fig. 2 is a schematic structural diagram of the cascade system of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.