Pit recirculation filter screen, containment vessel recirculation system and PH value control method

Abstract

The invention provides a pit recirculation filter screen, a containment vessel recirculation system and a PH value control method.The pit recirculation filter screen comprises a filter screen body, one end of the filter screen body is installed on the inner wall of a pit, a cofferdam is arranged at the other end of the filter screen body, a containing cavity is formed between the cofferdam and the filter screen body, condensed water in the pit flows into the containing cavity through the cofferdam after an accident, and the PH value of the condensed water flows into the containing cavity through the cofferdam. The water flows into the recirculation pipeline through the filter screen body; wherein at least one PH adjusting basket is arranged in the accommodating cavity, so that the PH value of boron water in the containment within a certain period of time after an accident is not lower than a target value. According to the pit recirculation filter screen, the PH adjusting basket is combined with the filter screen body, so that large-particle fragments are filtered out when initial boron water passes through the filter screen body after an accident and enter a reactor coolant system, a channel of a fuel element is prevented from being blocked, and cooling of a reactor core is inhibited; and the filtered boron water can react with the pH adjusting basket, so that the pH value of the boron water in the containment vessel at the beginning of an accident and within 30 days is maintained to be greater than 7.0.

Description

Technical Field

[0001] The invention relates to the field of nuclear industry safety technology, and in particular to a pit recirculation filter, a containment recirculation system and a pH value control method. Background Art

[0002] The passive core cooling system is an important component of the passive safety system of the advanced pressurized water reactor. Through the passive design concept, it performs safe injection and removes the core heat, ensuring the integrity of the reactor and ultimately preventing the release of radioactive substances into the environment.

[0003] In order to actually eliminate the possibility of large-scale radioactive material release from a design perspective, the functionality of the passive core cooling system must be ensured in the event of an accident.

[0004] The traditional passive core cooling system generally includes high, medium and low pressure injection boxes and their related valves, pipelines and multiple pH adjustment devices. A large number of pH adjustment devices will undoubtedly make the cooling system structure more complicated, occupy a larger space, and have higher safety performance requirements.

[0005] Based on this, the inventor of the present application proposed a pit recirculation filter, a containment recirculation system and a pH value control method in order to solve the above technical problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art that the number of PH adjustment devices is large, the space occupied is large, and the safety performance requirements are high, and a pit recirculation filter, a containment recirculation system and a PH value control method are provided.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] The present invention provides a pit recirculation filter screen, which is characterized by comprising:

[0009] The filter body has one end mounted on the inner wall of the pit and the other end provided with a cofferdam, a receiving cavity is formed between the cofferdam and the filter body, and after an accident, the condensate in the pit flows through the cofferdam into the receiving cavity and flows through the filter body into the recirculation pipeline; wherein,

[0010] At least one pH adjustment basket is arranged in the accommodating chamber so that the pH value of the boron water in the containment vessel is not lower than the target value within a certain period of time after the accident.

[0011] According to one embodiment of the present invention,

[0012] The cofferdam cover is arranged on the outside of the filter body, and a plurality of filtering holes are opened at one end of the cofferdam away from the filter body; wherein,

[0013] The inner end surface of the cofferdam where the filter holes are formed is spaced apart from the filter body.

[0014] According to one embodiment of the present invention, the number of the pH adjustment baskets is at least two;

[0015] At least two of the pH adjustment baskets are evenly spaced along the length extension direction of the filter body.

[0016] According to one embodiment of the present invention, the pH adjustment basket has a placement cavity therein, and the pH adjustment basket is provided with a plurality of through holes in the circumference thereof which are in communication with the placement cavity;

[0017] A pH regulator is arranged in the placement cavity, and the condensed water entering the placement cavity is mixed with the pH regulator and then flows into the filter body.

[0018] According to one embodiment of the present invention, the pH regulator is trisodium phosphate.

[0019] According to one embodiment of the present invention, one end of the pH adjustment basket is detachably mounted on one side of the filter body.

[0020] According to one embodiment of the present invention, the filter body has a flow chamber on a side facing away from the cofferdam;

[0021] The recirculation pipelines communicating with the flow chamber are also provided on opposite sides of the filter body.

[0022] The present invention also provides a containment recirculation system, which is characterized in that the pit recirculation filter as described above is used, and the system comprises:

[0023] A pressure vessel, a pit and a recirculation pipeline, wherein the portion below the injection nozzle of the pressure vessel is located below the pit elevation, the pit recirculation filter is installed to the inner wall of the pit, one end of the recirculation pipeline is connected to the pit recirculation filter, and the other end is connected to the injection nozzle of the pressure vessel.

[0024] The present invention also provides a method for controlling pH value in a containment, which is implemented by using the containment recycling system as described above, and the control method comprises:

[0025] Step 1, injecting a target amount of test water into the pit, wherein the initial pH value of the test water is lower than 7;

[0026] Step 2: at the initial time of the reactor accident and at a time point after the target time period, sampling the water in the recirculation pipeline and measuring the pH value thereof;

[0027] Step 3, adjusting the number of pH adjustment baskets in the pit recirculation filter so that the pH value of the water in the recirculation pipeline is at least not lower than the target value at the time of the initial time of the reactor accident and after the target time period, and then recording the number of the pH adjustment baskets and the amount of the test water injected;

[0028] Step 4: Change the amount of the test water injected into the pit and the initial pH value of the test water to repeat the test of steps 1 to 3, and obtain the number of settings of the pH adjustment basket corresponding to different injection amounts of the test water and different initial pH values ​​of the test water.

[0029] The positive and progressive effects of the present invention are:

[0030] The pit recirculation filter of the present invention combines the pH adjustment basket with the filter body, so that the initial boron water after the accident can filter out large particles of debris when passing through the filter body and enter the reactor coolant system to prevent the passage of the fuel element from being blocked and the core cooling from being inhibited; the filtered boron water can also react with the pH adjustment basket to maintain the pH value of the boron water in the containment greater than 7.0 at the beginning of the accident and within 30 days. Such a setting can not only reduce the difficulty of designing and installing the passive core cooling system, but also improve the safety of the system design and the reliability and economy of the reactor operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0032] Figure 1 It is a schematic diagram of the structure of the pit recirculation filter screen of the present invention;

[0033] Figure 2 for Figure 1 A front view of the pH adjustment basket from one angle;

[0034] Figure 3 is a schematic diagram of a containment recirculation system of the present invention;

[0035] Figure 4 The present invention is a flow chart of the pH value control method in the containment.

[0036] 1. Filter body; 11. Accommodation cavity; 12. PH adjustment basket; 121. Placement cavity; 122. Through hole; 123. PH adjustment substance; 13. Flow chamber;

[0037] 2. Pit;

[0038] 3. Cofferdam; 31. Filter hole;

[0039] 4. Recirculation pipeline;

[0040] 5. Pressure vessel. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0043] Please refer to Figures 1 to 3 The present invention proposes a pit recycling filter, including a filter body 1, one end of the filter body 1 is installed on the inner wall of the pit 2, and the other end is provided with a cofferdam 3, and a receiving chamber 11 is formed between the cofferdam 3 and the filter body 1. After an accident, condensate in the pit 2 flows into the receiving chamber 11 through the cofferdam 3, and flows into the recycling pipeline 4 through the filter body 1; wherein, at least one pH adjustment basket 12 is arranged in the receiving chamber 11, so that the pH value of the boric water in the containment is not lower than the target value within a certain period of time after the accident.

[0044] The number of conventional passive pressurized water reactor pH regulating baskets 12 is relatively large, which results in a large space occupation and higher safety performance requirements.

[0045] Based on this, the present application sets a cofferdam 3 on the basis of the pit recycling filter, and then sets the pH adjustment basket 12 in the accommodating cavity 11 between the cofferdam 3 and the filter body 1.

[0046] Such arrangement not only enables the initial boron water after the accident to filter out large particles of debris when passing through the filter body 1 and enter the reactor coolant system (recirculation line 4), thereby preventing the passage of the fuel elements from being blocked and inhibiting the cooling of the core; but also enables the filtered boron water to react with the pH adjustment basket 12, so as to maintain the pH value of the boron water in the containment vessel greater than 7.0 at the beginning of the accident and within 30 days.

[0047] Please refer to Figure 1The cofferdam 3 is covered on the outside of the filter body 1, and a plurality of filter holes 31 are opened at one end of the cofferdam 3 away from the filter body 1; wherein, the inner end surface of the cofferdam 3 where the filter holes 31 are opened is spaced apart from the filter body 1.

[0048] That is, both the cofferdam 3 and the filter body 1 can filter the condensate, and the condensate filtered by the cofferdam 3 reacts with the pH adjustment basket 12 in the accommodating chamber 11, thereby maintaining the pH value of the boron water in the containment at the beginning of the accident and within 30 days.

[0049] Specifically, the circumferential size of the cofferdam 3 corresponds to the circumferential size of the filter body 1, and the cofferdam 3 is covered on the outside of the filter body 1, so that the condensate entering the filter body 1 will pass through the cofferdam 3, making it convenient for the condensate entering the recycling pipeline 4 in the pit 2 to react with the pH adjustment basket 12.

[0050] Optionally, one end of the cofferdam 3 is connected to the filter body 1 by welding.

[0051] It can be seen that the welding connection method can improve the connection strength between the cofferdam 3 and the filter body 1. In some other embodiments, the cofferdam 3 and the filter body 1 can also be connected by other methods such as snaps and threaded connectors, and the specific form is not limited here.

[0052] Please continue to refer to Figure 1 The number of the pH adjustment baskets 12 is at least two; at least two pH adjustment baskets 12 are evenly spaced along the length extension direction of the filter body 1.

[0053] The number of pH adjustment baskets 12 can be determined according to actual needs, and the number is not limited here.

[0054] Evenly distributing at least two pH adjusting baskets 12 along the length extension direction of the filter body 1 facilitates the condensate to contact the pH adjusting basket 12 more evenly, thereby improving the uniformity of the reaction between the condensate and the pH adjusting basket 12 .

[0055] Please refer to Figure 1 and Figure 2 The pH adjusting basket 12 has a placement cavity 121, and a plurality of through holes 122 communicating with the placement cavity 121 are arranged on the outer circumference of the pH adjusting basket 12; a pH adjusting substance 123 is arranged in the placement cavity 121, and the condensed water entering the placement cavity 121 is mixed with the pH adjusting substance 123 and then flows into the filter body 1.

[0056] Specifically, the pH regulator 123 is trisodium phosphate, which can react with boric acid to increase the pH value.

[0057] Furthermore, the pH adjusting basket 12 is in a box structure, and a plurality of through holes 122 are arranged around the pH adjusting basket 12 to facilitate the condensed water to enter the placement cavity 121 more evenly to react with the pH adjusting substance 123 .

[0058] It can be seen that the outer structure of the pH adjustment basket 12 can be made of the same material and shape as the filter body 1, so that after the trisodium phosphate in the pH adjustment basket 12 reacts, the vacant position can also play a filtering role, thereby alleviating the problem of reduced filtration area caused by impurity clogging of the filter body 1 during the circulation process.

[0059] The integrated design of the pit recirculation filter is conducive to reducing the difficulty of designing and installing the passive core cooling system, improving the safety of the system design, and the reliability and economy of the reactor operation.

[0060] In one embodiment, one end of the pH adjustment basket 12 is detachably mounted on one side of the filter body 1 .

[0061] The pH adjustment basket 12 and the filter body 1 can be detachably connected by a threaded connector or a snap fastener, which is not limited here.

[0062] It can be seen that the filter body 1 has a flow chamber 13 on the side away from the cofferdam 3 ; and recirculation pipelines 4 communicating with the flow chamber 13 are also provided on opposite sides of the filter body 1 .

[0063] The filter body 1 may be formed by splicing a plurality of filter units. Supports may be provided on the circulation pipe and the filter body 1 to install the circulation pipe. The shape of the support is not limited herein.

[0064] The present invention also proposes a containment recirculation system, which adopts the above-mentioned pit recirculation filter. The system includes: a pressure vessel 5, a pit 2 and a recirculation pipeline 4. The part below the injection nozzle of the pressure vessel 5 is located below the elevation of the pit 2. The pit recirculation filter is installed to the inner wall of the pit 2. One end of the recirculation pipeline 4 is connected to the pit recirculation filter, and the other end is connected to the injection nozzle of the pressure vessel 5.

[0065] Because the containment recirculation system includes the above-mentioned pit recirculation filter, it has all the beneficial effects of the above-mentioned pit recirculation filter, which will not be described in detail here.

[0066] Please refer to Figure 4 The present invention also proposes a method for controlling pH value in a containment, which is implemented by using the above containment recycling system. The control method includes:

[0067] S1. Inject a target amount of test water into the pit, with the initial pH value of the test water being less than 7;

[0068] S2. At the time point after the initial time of the reactor accident and after the target time period, sample the water in the recirculation pipeline and measure the pH value thereof;

[0069] S3, adjusting the number of pH adjustment baskets in the pit recirculation filter so that the pH value of the water in the recirculation line is at least not less than the target value at the time of the initial reactor accident and after the target time period, and then recording the number of pH adjustment baskets and the amount of test water injected;

[0070] S4. Change the amount of test water injected into the pit and the initial pH value of the test water to repeat the test from step 1 to step 3, and obtain the number of settings of the pH adjustment baskets corresponding to different injection amounts of test water and different initial pH values ​​of test water.

[0071] It can be seen that the containment recirculation system is a simulated test system, so repeated tests can be carried out to determine the number of pH adjustment baskets and the effect of the pH adjustment baskets.

[0072] With reference to the above test method, the present invention can provide a reference for determining the number of pH adjustment baskets and the use effect.

[0073] For example, based on experience, the amount of test water under accident can be estimated, and the number of pH adjustment baskets can be adaptively determined based on the amount of test water, so that the number of pH adjustment baskets set can ensure that the pH value of boric water in the containment is greater than 7.0 initially and within 30 days after the accident.

[0074] Reference Figure 1 , this application selects 5 pH adjustment baskets, so that it can adapt to the pH adjustment requirements under normal accident conditions. The specific number of pH adjustment baskets is not limited, and the number of different sizes and dimensions of the piles is different, which can be adaptively adjusted according to actual needs, thereby not making the overall size of the pit recirculation filter too large, and ensuring the pH adjustment requirements.

[0075] In summary, compared with the traditional recirculation filter, the pit recirculation filter provided by the present invention is combined with a pH adjustment basket, so that the pit recirculation filter has both a filtering function and can adjust the pH value of the boric water after filtration.

[0076] The integrated pit recirculation filter with pH adjustment function will not reduce the filter area and pressure drop requirements. After the dissolution of trisodium phosphate, the filter area can be increased, improving the safety of system design and the reliability and economy of reactor operation. In addition, the pit recirculation filter saves the equipment space occupied by the traditional design pH adjustment basket, which not only meets the requirement that the top of the pH adjustment basket should be below the minimum water level of recirculation, but also meets the requirement that the pH adjustment basket is a Class C device and meets the requirements of Class I seismic resistance.

[0077] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "install", "connect", "connect", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can also be a mechanical connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0078] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0079] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A pit recirculation filter, characterized in that: include: The filter body has one end mounted on the inner wall of the pit and the other end provided with a cofferdam, a receiving cavity is formed between the cofferdam and the filter body, and after an accident, the condensate in the pit flows through the cofferdam into the receiving cavity and flows through the filter body into the recirculation pipeline; wherein, At least one pH adjustment basket is arranged in the accommodating chamber so that the pH value of the boron water in the containment vessel is not lower than the target value within a certain period of time after the accident.

2. The pit recirculation filter according to claim 1, characterized in that: The cofferdam cover is arranged on the outside of the filter body, and a plurality of filtering holes are opened at one end of the cofferdam away from the filter body; wherein, The inner end surface of the cofferdam where the filter holes are formed is spaced apart from the filter body.

3. The pit recirculation filter according to claim 2, characterized in that: One end of the cofferdam is connected to the filter body by welding.

4. The pit recirculation filter according to claim 1, characterized in that: The number of the pH adjustment baskets is at least two; At least two of the pH adjustment baskets are evenly spaced along the length extension direction of the filter body.

5. The pit recirculation filter according to claim 4, characterized in that: The pH adjustment basket has a placement cavity inside, and the outer circumference of the pH adjustment basket is provided with a plurality of through holes communicating with the placement cavity; A pH regulator is arranged in the placement cavity, and the condensed water entering the placement cavity is mixed with the pH regulator and then flows into the filter body.

6. The pit recirculation filter according to claim 5, characterized in that: The pH regulator is trisodium phosphate.

7. The pit recirculation filter according to claim 5, characterized in that: One end of the pH adjustment basket is detachably mounted on one side of the filter body.

8. The pit recirculation filter according to claim 1, characterized in that: The filter body has a flow chamber on one side away from the cofferdam; The recirculation pipelines communicating with the flow chamber are also provided on opposite sides of the filter body.

9. A containment recirculation system, characterized in that: Using the pit recirculation filter according to any one of claims 1 to 8, the system comprises: A pressure vessel, a pit and a recirculation pipeline, wherein the portion below the injection nozzle of the pressure vessel is located below the pit elevation, the pit recirculation filter is installed to the inner wall of the pit, one end of the recirculation pipeline is connected to the pit recirculation filter, and the other end is connected to the injection nozzle of the pressure vessel.

10. A method for controlling pH value in a containment vessel, characterized in that: The containment recirculation system according to claim 9 is used to implement the control method, wherein: Step 1, injecting a target amount of test water into the pit, wherein the initial pH value of the test water is lower than 7; Step 2: at the initial time of the reactor accident and at a time point after the target time period, sampling the water in the recirculation pipeline and measuring the pH value thereof; Step 3, adjusting the number of pH adjustment baskets in the pit recirculation filter so that the pH value of the water in the recirculation pipeline is at least not lower than the target value at the time of the initial time of the reactor accident and after the target time period, and then recording the number of the pH adjustment baskets and the amount of the test water injected; Step 4: Change the amount of the test water injected into the pit and the initial pH value of the test water to repeat the test from step 1 to step 3 to obtain the number of settings of the pH adjustment basket corresponding to different injection amounts of the test water and different initial pH values ​​of the test water.

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