Nuclear power plant boric acid solution discharge control system and method

Abstract

The invention belongs to the technical field of nuclear power, and particularly relates to a boric acid solution discharge control system and method for a nuclear power plant. According to the boric acid solution discharge control system for the nuclear power plant, in the discharge process of the concentrated boron recirculation system, through cooperation of the adjusting assembly, the temperature sensor and the pneumatic adjusting valve, the flow of washing the RPE pipeline can be automatically adjusted according to the actual temperature change of the RPE pipeline, so that the flow rate of washing the RPE pipeline is increased; the purposes of controlling the temperature of the downstream RPE pipeline not to exceed the designed temperature in the whole discharging process, preventing equipment from being damaged, preventing the pipeline from generating boron crystals and preventing a large amount of waste water from being generated are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear power, and in particular relates to a boric acid solution emission control system and method for a nuclear power plant. Background Art

[0002] The concentrated boron recycling system of a nuclear power plant is used to keep the core in a subcritical state in the event of the most serious steam pipe rupture. The system is filled with a high-concentration boric acid solution with a boron concentration between 17,000 ppm and 19,000 ppm and a temperature of about 88°C. When the boric acid solution in the concentrated boron recycling system is no longer recycled, it will be discharged to the RPE (waste liquid collection system), and the SED (nuclear island desalted water system) will provide flushing water during the discharge. In related technologies, when the concentrated boron recycling system is discharged to the RPE, engineers are required to first open the upstream SED manual flushing diaphragm valve to an appropriate opening, establish a small flushing flow rate based on experience, and then open the concentrated boron recycling system series valves. During this process, engineers also need to observe the drainage and crystallization conditions through the downstream visual flow meter.

[0003] The following problems exist during discharge: the valve that provides SED flushing water is a diaphragm valve with no adjustment performance. If the valve opening is too small, insufficient cooling will cause the temperature of the RPE downstream pipeline and the visual flow meter to exceed the design temperature of 80°C, which can easily cause burns and equipment damage, and is very likely to cause boron crystallization, which can seriously block the pipeline. If the valve opening is too large, the SED flushing water volume will be too much, which will produce more radioactive wastewater, increasing the processing burden of the waste liquid treatment system. Summary of the invention

[0004] In order to overcome the problems existing in the related art, a boric acid solution emission control system and method for a nuclear power plant are provided.

[0005] According to one aspect of an embodiment of the present disclosure, a boric acid solution emission control system for a nuclear power plant is provided, the system comprising: a pneumatic regulating valve, a temperature sensor, and a regulating component;

[0006] A pneumatic regulating valve is arranged downstream of the manual flushing diaphragm valve in the SED flushing pipeline, and the flushing water of the SED flushing pipeline flows into the RPE pipeline through the pneumatic regulating valve. A temperature sensor is arranged upstream of the visual flow meter in the RPE pipeline;

[0007] The regulating component is connected to the pneumatic regulating valve and the temperature sensor respectively, and is used to compare the temperature value collected by the temperature sensor with the preset temperature threshold to obtain the difference, and determine the opening adjustment value according to the difference. The difference is positively correlated with the opening adjustment value, and the collected temperature value is positively correlated with the opening of the pneumatic regulating valve.

[0008] In one possible implementation, a pneumatic control valve opening limit range is set in the regulating component, the low limit corresponds to the minimum opening of the pneumatic control valve, and the high limit corresponds to the maximum opening of the pneumatic control valve. The output signal of the regulating component is subjected to high and low limits to generate a control signal for adjusting the pneumatic control valve.

[0009] In a possible implementation, the regulating component includes: a resistance-voltage conversion component, a regulator, and a voltage-current conversion component;

[0010] The resistance-voltage conversion component converts the resistance of the thermal resistor in the temperature sensor into a voltage signal, which is adjusted by the adjustment component to form an adjusted voltage signal, and then converted into a current signal by the voltage-current conversion component, and input into the pneumatic control valve to control the pneumatic control valve to adjust the preset opening.

[0011] In a possible implementation, the temperature threshold range of the temperature sensor is set between 25 and 30° C. in winter and between 42 and 45° C. in summer.

[0012] According to one aspect of an embodiment of the present disclosure, a method for controlling boric acid solution discharge from a nuclear power plant is provided, the method comprising:

[0013] Step 101, if it is necessary to discharge the concentrated boron recirculation system to the RPE, fully open the manual flushing diaphragm valve of the SED in advance, and set the pneumatic regulating valve of the downstream RPE to the minimum limit opening;

[0014] Step 102, when a small flushing flow is established, opening a series of valves of a concentrated boron recirculation system;

[0015] Step 103, when the regulating component detects that the temperature collected by the temperature sensor increases, the regulating component controls the opening of the pneumatic regulating valve to increase the preset opening; when the regulating component detects that the temperature collected by the temperature sensor decreases, the regulating component controls the opening of the pneumatic regulating valve to decrease the preset opening.

[0016] In one possible implementation, a pneumatic control valve opening limit range is set in the regulating component, the low limit corresponds to the minimum opening of the pneumatic control valve, and the high limit corresponds to the maximum opening of the pneumatic control valve. The output signal of the regulating component is subjected to high and low limits to generate a control signal for adjusting the pneumatic control valve.

[0017] In a possible implementation, the temperature range of the temperature sensor is determined according to environmental parameters, the physical property relationship between water and steam, and the following formula. The environmental parameters include the initial temperature and water pressure of the boric acid solution discharged from the concentrated boron recycling system; the initial temperature and water pressure of the desalted water discharged from the SED; the temperature and water pressure in the RPE waste liquid collection pit;

[0018]

[0019] Among them, the enthalpy of the exhaust fluid of the concentrated boron recycling system is h 1 ; The enthalpy of the fluid in the SED flushing pipeline is h 2 ; The enthalpy of the mixed fluid in the downstream pipeline of the flow meter is h 3 .

[0020] In a possible implementation, the temperature threshold range of the temperature sensor is set between 25 and 30° C. in winter and between 42 and 45° C. in summer.

[0021] The beneficial effects of the present disclosure are as follows: in the boric acid solution discharge control system of the nuclear power plant provided by the present disclosure, during the discharge process of the concentrated boron recycling system, the flow rate of flushing the RPE pipeline can be automatically adjusted according to the actual temperature change of the RPE pipeline through the coordination between the adjustment component, the temperature sensor and the pneumatic control valve, so that the temperature of the downstream RPE pipeline is controlled not to exceed the design temperature during the entire discharge process, the equipment is prevented from being damaged and boron crystals are generated in the pipeline, and a large amount of wastewater is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a boric acid solution emission control system for a nuclear power plant shown in an embodiment of the present disclosure.

[0023] Figure 2 It is a schematic diagram of an adjustment component shown in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0024] The present disclosure is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Unless otherwise defined, the technical and scientific terms used in the present disclosure have the same meanings as those generally understood by those skilled in the art to which the present disclosure belongs; the terms used in the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure; the term "including" and any variations thereof in the present disclosure are intended to cover non-exclusive inclusions. Obviously, the embodiments described in the present disclosure are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative efforts are within the scope of protection of the present disclosure.

[0026] Reference to "embodiments" in this disclosure means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the disclosure. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] Figure 1 is a schematic diagram of a boric acid solution emission control system for a nuclear power plant shown in an embodiment of the present disclosure, Figure 2 is a schematic diagram of an adjustment component shown in an embodiment of the present disclosure, such as Figure 1 and Figure 2 As shown, the system of the present disclosure includes a pneumatic control valve 8, a temperature sensor 9 and a control component, and the control component includes a resistance-voltage conversion component 12, a regulator 13, and a voltage-current conversion component 14. Figure 1 As shown, a pneumatic regulating valve 8 is arranged downstream of a manual flushing diaphragm valve 3 in the SED flushing pipeline, and flushing water 2 of the SED flushing pipeline flows into the RPE pipeline 1 through the pneumatic regulating valve 8. A temperature sensor 9 is arranged upstream of a visible flow meter 5 in the RPE pipeline 1, and a regulating assembly is connected to the pneumatic regulating valve 8 and the temperature sensor 9, respectively. Figure 1 and Figure 2 The resistance-voltage conversion component 12 converts the resistance of the thermal resistor 11 in the temperature sensor into a voltage signal, which is adjusted by the regulator 13 to form an adjusted voltage signal. The regulator 13 compares the voltage signal with the preset temperature voltage signal to obtain a difference. If the difference is not 0, the opening adjustment value is determined according to the difference. For example, the difference can be processed by the regulator through a proportional integral link to generate an output signal. Where δ is the proportional band, and T_i is the integral time constant. It should be noted that the regulating component can obtain the output voltage signal according to the difference in any manner, and the present disclosure does not limit this. The temperature threshold range of the temperature sensor is set in the regulating component, and the low limit corresponds to the minimum opening of the pneumatic regulating valve to ensure the minimum flushing flow, and the high limit corresponds to the maximum opening of the pneumatic regulating valve to meet the flushing pipeline flow limit. The output signal generates the required value of the opening of the pneumatic regulating valve after high and low limits. It is then converted into a current signal by the voltage-current conversion component 14. The higher the temperature collected by the temperature sensor, the greater the deviation from the set temperature in the regulating component, and the greater the opening of the pneumatic regulating valve. The lower the temperature collected by the temperature sensor, the smaller the deviation from the set temperature in the regulating component, and the smaller the opening of the pneumatic regulating valve.

[0028] In the present disclosure, if it is necessary to perform the operation of discharging the concentrated boron recycling system to the RPE, the manual flushing diaphragm valve of the SED is fully opened in advance, and the pneumatic control valve of the downstream RPE is set to the minimum limit opening. When a small flushing flow is established, the concentrated boron recycling system series valve 4 is opened, and the pneumatic control valve is controlled to adjust the visual flow meter downstream pipeline and fluid temperature according to the set temperature of the temperature sensor so that it does not exceed the limit.

[0029] In the process of discharging waste liquid from the concentrated boron recycling system to the RPE, according to the law of conservation of energy, the following rules apply:

[0030] m 1 h 1 +m 2 h 2 =(m 1 +m 2 )h 3

[0031]

[0032] Among them, the mass flow rate (kg / s) of high-temperature fluid discharged from the concentrated boron recycling system is m 1 , the fluid enthalpy (kJ / kg) is h 1 ; The mass flow rate of cryogenic fluid in the SED flushing pipeline is m 2 , the fluid enthalpy is h 2 ; The enthalpy of the mixed fluid in the downstream pipeline of the flow meter is h 3 ,h 1 >h 3 >h 2 .

[0033] is the dilution multiple. According to the crystallization characteristics of boric acid solutions of different concentrations, when the dilution multiple is between 3 and 4, daily discharge will not cause boron crystallization and the wastewater is minimal. Therefore, if you want to achieve the effect of low RPE pipeline temperature, no boron crystallization, and no large amount of wastewater during the discharge process, h 1 、h 2 、h 3 The following conditions must be followed:

[0034]

[0035] In the application scenario of the present disclosure, the 17000-19000ppm boric acid solution discharged from the concentrated boron recycling system has an initial temperature of about 88°C and normal pressure; the desalted water discharged from the SED is affected by the ambient temperature, with a temperature between 10-30°C and a water pressure of 0.49Mpa throughout the year; the mixed fluid finally flows into the RPE waste liquid collection pit at normal pressure.

[0036] According to the relationship between the physical properties of water and steam, it can be determined that: h 1 ≈368.58 kJ / kg; h 3 ∈(107.72,124.02)∪(174.67,186.79)kJ / kg.

[0037] It can be concluded that the temperature threshold range of the temperature sensor is set between 25 and 30°C in winter and between 42 and 45°C in summer, which meets the design benchmark limit of the RPE pipeline.

[0038] In the boric acid solution discharge control system of a nuclear power plant provided by the present invention, during the discharge process of the concentrated boron recycling system, the flow rate of flushing the RPE pipeline can be automatically adjusted according to the actual temperature change of the RPE pipeline through the coordination between the adjustment component, the temperature sensor and the pneumatic control valve, so that the temperature of the downstream RPE pipeline is controlled not to exceed the design temperature during the entire discharge process, the equipment is prevented from being damaged and boron crystals are generated in the pipeline, and a large amount of wastewater is avoided.

[0039] According to one aspect of an embodiment of the present disclosure, a method for controlling boric acid solution discharge from a nuclear power plant is provided, the method comprising:

[0040] Step 101, if it is necessary to discharge the concentrated boron recirculation system to the RPE, fully open the manual flushing diaphragm valve of the SED in advance, and set the pneumatic regulating valve of the downstream RPE to the minimum limit opening;

[0041] Step 102, when a small flushing flow is established, opening a series of valves of a concentrated boron recirculation system;

[0042] Step 103, when the regulating component detects that the temperature collected by the temperature sensor increases, the regulating component controls the opening of the pneumatic regulating valve to increase the preset opening; when the regulating component detects that the temperature collected by the temperature sensor decreases, the regulating component controls the opening of the pneumatic regulating valve to decrease the preset opening.

[0043] In one possible implementation, a pneumatic control valve opening limit range is set in the regulating component, the low limit corresponds to the minimum opening of the pneumatic control valve, and the high limit corresponds to the maximum opening of the pneumatic control valve. The output signal of the regulating component is subjected to high and low limits to generate a control signal for adjusting the pneumatic control valve.

[0044] In a possible implementation, the temperature range of the temperature sensor is determined according to environmental parameters, the physical property relationship between water and steam, and the following formula. The environmental parameters include the initial temperature and water pressure of the boric acid solution discharged from the concentrated boron recycling system; the initial temperature and water pressure of the desalted water discharged from the SED; the temperature and water pressure in the RPE waste liquid collection pit;

[0045]

[0046] Among them, the enthalpy of the exhaust fluid of the concentrated boron recycling system is h 1 ; The enthalpy of the fluid in the SED flushing pipeline is h 2 ; The enthalpy of the mixed fluid in the downstream pipeline of the flow meter is h 3 .

[0047] In a possible implementation, the temperature threshold range of the temperature sensor is set between 25 and 30° C. in winter and between 42 and 45° C. in summer.

[0048] For the description of the above method, please refer to the description of the above system, which will not be repeated here.

[0049] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A boric acid solution emission control system for a nuclear power plant, characterized in that: The system comprises: a pneumatic regulating valve, a temperature sensor, and a regulating component; A pneumatic regulating valve is arranged downstream of the manual flushing diaphragm valve in the SED flushing pipeline, and the flushing water of the SED flushing pipeline flows into the RPE pipeline through the pneumatic regulating valve. A temperature sensor is arranged upstream of the visual flow meter in the RPE pipeline; The regulating component is respectively connected to the pneumatic regulating valve and the temperature sensor, and is used to compare the temperature value collected by the temperature sensor with the preset temperature threshold to obtain a difference, and determine the opening adjustment value based on the difference. The difference is positively correlated with the opening adjustment value, and the collected temperature value is positively correlated with the opening of the pneumatic regulating valve.

2. The system according to claim 1, characterized in that The pneumatic control valve opening limit range is set in the regulating component. The low limit corresponds to the minimum opening of the pneumatic control valve, and the high limit corresponds to the maximum opening of the pneumatic control valve. The output signal of the regulating component generates a control signal for adjusting the pneumatic control valve after high and low limits.

3. The system according to claim 2, characterized in that The temperature threshold range of the temperature sensor is set between 25 and 30° C. between November of the current year and April of the next year, and is set between 42 and 45° C. between May of the current year and October of the next year.

4. A method for controlling the discharge of boric acid solution from a nuclear power plant, characterized in that: The method comprises: Step 101, if it is necessary to discharge the concentrated boron recirculation system to the RPE, fully open the manual flushing diaphragm valve of the SED in advance, and set the pneumatic regulating valve of the downstream RPE to the minimum limit opening; Step 102, when a small flushing flow is established, opening a series of valves of a concentrated boron recirculation system; Step 103, when the regulating component detects that the temperature collected by the temperature sensor increases, the regulating component controls the opening of the pneumatic regulating valve to increase the preset opening; when the regulating component detects that the temperature collected by the temperature sensor decreases, the regulating component controls the opening of the pneumatic regulating valve to decrease the preset opening.

5. The method according to claim 3, characterized in that: The pneumatic control valve opening limit range is set in the regulating component. The low limit corresponds to the minimum opening of the pneumatic control valve, and the high limit corresponds to the maximum opening of the pneumatic control valve. The output signal of the regulating component generates a control signal for adjusting the pneumatic control valve after high and low limits.

6. The method according to claim 3, characterized in that The temperature range of the temperature sensor is determined based on environmental parameters, the physical properties of water and steam, and the following formula. The environmental parameters include the initial temperature and water pressure of the boric acid solution discharged from the concentrated boron recycling system; the initial temperature and water pressure of the desalted water discharged from the SED; the temperature and water pressure in the RPE waste liquid collection pit; Among them, the enthalpy value of the discharged fluid of the concentrated boron recycling system is h1; the enthalpy value of the fluid in the SED flushing pipeline is h2; and the enthalpy value of the mixed fluid in the pipeline downstream of the flow meter is h3.

7. The method according to claim 3, characterized in that The temperature threshold range of the temperature sensor is set between 25 and 30° C. between November of the current year and April of the next year, and is set between 42 and 45° C. between May of the current year and October of the next year.

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