Primary loop flushing and foreign matter checking method for pressurized water reactor nuclear power plant

Abstract

The invention discloses a primary circuit washing and foreign matter checking method for a pressurized water reactor nuclear power plant. The primary circuit washing and foreign matter checking method for the pressurized water reactor nuclear power plant comprises the following steps: S10, obtaining the size and morphology of a foreign matter; s20, according to the flowing direction of the operation medium of the loop system, the size of the foreign matter and the intercepting area of the passing equipment, the pipeline where the foreign matter possibly flows through and the position of the equipment where intercepting is possible are obtained; s30, calculating the critical flow velocity of the foreign matter in the primary loop medium; s40, quantitatively judging possible paths and closure points of the foreign matters; and S50, determining a flushing path and a flushing flow according to the possible path and the interception point of the foreign matter. According to the primary loop flushing and foreign matter checking method for the pressurized water reactor nuclear power plant, the foreign matter can be effectively checked, and the checking efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power technology, and in particular to a primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant. Background Art

[0002] Due to improper design, installation, and maintenance processes, foreign objects are a common occurrence in the primary circuits of pressurized water reactor (PWR) nuclear power plants. This poses a significant threat to the safe operation of critical equipment and fuel assemblies. The detection and removal of foreign objects in the primary circuits severely restricts the ability to optimize downtime for nuclear power plant maintenance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant.

[0004] The technical solution adopted by the present invention to solve the technical problem is to construct a primary circuit flushing and foreign matter detection method for a pressurized water reactor nuclear power plant, comprising the following steps:

[0005] S10: Obtain the size and shape of the foreign body;

[0006] S20: Based on the flow direction of the primary system's operating medium, the size of the foreign matter, and the intercepting area of ​​the equipment it passes through, obtain the pipes through which the foreign matter may flow and the location of the equipment that may intercept the flow;

[0007] S30: Calculate the critical flow velocity of foreign matter in the primary circuit medium;

[0008] S40: Quantitatively determine the possible path and interception point of foreign matter;

[0009] S50: Determine a flushing path and flushing flow rate according to the possible paths and interception points of the foreign matter.

[0010] In some embodiments, in step S10 , the size, weight, and material of the foreign object are obtained to determine the volume V of the foreign object, the density ρ of the foreign object, and the water-facing projection area S of the foreign object.

[0011] In some embodiments, in step S30, according to the hydraulic load calculation formula (1) and the foreign matter weight calculation formula (2), when F>G, the foreign matter can be moved by the system operating medium, and the critical water flow rate for driving the migration of the foreign matter is calculated:

[0012]

[0013] G=ρ 异物 V 异物 g (2)

[0014] Where: ρ is density, unit is kg / m 3; v is the fluid velocity, in m / s; S is the projected area of ​​the water, in m2; CL is the resistance coefficient, dimensionless; V is the volume, in m 3 ; g is the acceleration due to gravity, unit is m / s 2 .

[0015] In some embodiments, in step S40, based on the pipelines through which the foreign matter may flow and the locations of the equipment that may intercept the flow, the actual medium flow rate of each pipeline and equipment is obtained section by section, and the actual medium flow rate of each pipeline and equipment is compared with the critical water flow rate for the migration of foreign matter. If the actual medium flow rate of any pipeline or equipment is greater than the critical water flow rate for the migration of foreign matter, it is determined that the foreign matter can pass through any of the pipelines or equipment; if the actual medium flow rate of any pipeline or equipment is less than the critical water flow rate for the migration of foreign matter, it is determined that the foreign matter is intercepted by any of the pipelines or equipment, and there is no need to check the downstream pipelines and equipment.

[0016] In some embodiments, in step S50 , the flushing path covers the foreign matter migration path.

[0017] In some embodiments, in step S50 , the flow rate of the flushing flow in the flushing path is greater than the critical water flow rate for migration of foreign matter.

[0018] In some embodiments, the foreign matter is an object that has fallen off a component of a circuit system.

[0019] In some embodiments, the foreign object comprises a screw.

[0020] In some embodiments, the foreign object comprises a pin.

[0021] In some embodiments, the foreign object comprises a ball bearing.

[0022] The present invention has the following beneficial effects: A primary circuit flushing and foreign object detection method for a pressurized water reactor nuclear power plant comprises the following steps: S10: obtaining the size and shape of the foreign object; S20: determining the pipes through which the foreign object may flow and the location of the equipment that may intercept the flow based on the flow direction of the primary circuit system operating medium, the size of the foreign object, and the intercepting area of ​​the equipment passing through; S30: calculating the critical flow velocity of the foreign object in the primary circuit medium; S40: quantitatively determining the possible path and interception point of the foreign object; and S50: determining the flushing path and flushing flow rate based on the possible path and interception point of the foreign object. This primary circuit flushing and foreign object detection method for a pressurized water reactor nuclear power plant can effectively detect foreign objects and improve detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0024] Figure 1 is a schematic diagram of a primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant in some embodiments of the present invention;

[0025] Figure 2 Schematic diagram of the flow path of foreign matter in some embodiments of the present invention. DETAILED DESCRIPTION

[0026] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings and are constructed and operated in specific directions. They are only for the convenience of describing the technical solution and do not indicate that the devices or components referred to must have specific directions. Therefore, they should not be understood as limiting the present invention.

[0027] It should also be noted that, unless otherwise clearly specified and limited, terms such as "installed", "connected", "connected", "fixed", and "set" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there may be one or more intervening elements. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0028] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0029] The current common method for detecting foreign objects in the primary circuit of nuclear power plants is to qualitatively analyze the object's size to determine where it may be throttling the flow, and then perform disassembly or endoscopic inspection of locations where the object may be blocking the flow. However, this method suffers from inaccurate analysis of the object's blocking location, potentially leading to failure in detection due to insufficient system flow velocity to carry the object to the blocking location. Furthermore, traditional pipeline inspections rely on endoscopic inspections, resulting in highly random results and inability to achieve a comprehensive investigation.

[0030] This invention primarily builds upon the traditional qualitative analysis of foreign matter migration paths by adding quantitative analysis of foreign matter size, weight, and the flow field forces within primary piping equipment, identifying the pipelines through which the foreign matter may have passed. Using existing fluid systems or an additional flushing system, the foreign matter is flushed to the interception point, which is then carefully inspected.

[0031] See Figure 1 The present invention shows a method for flushing a single loop and detecting foreign matter in a pressurized water reactor nuclear power plant. The method for flushing a single loop and detecting foreign matter in a pressurized water reactor nuclear power plant can effectively detect foreign matter and improve the detection efficiency.

[0032] The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant comprises the following steps:

[0033] S10: Obtain the size and shape of the foreign body;

[0034] S20: Based on the primary system's operating medium flow direction, the foreign object's size, and the flow-blocking area of ​​the equipment it passes through, determine the possible pipelines through which the foreign object may flow and the locations of the equipment that may intercept the flow. A preliminary analysis of the possible pipelines through which the foreign object may flow and the locations of the equipment that may intercept the flow is performed based on the system's operating medium flow direction, the foreign object's size, and the flow-blocking area of ​​the equipment it passes through. The pipelines and equipment determined in this step must encompass all possible paths through which the foreign object may flow.

[0035] S30: Calculate the critical flow velocity of foreign matter in the primary circuit medium;

[0036] S40: Quantitatively determine the possible path and interception point of foreign matter;

[0037] S50: Determine the flushing path and flushing flow rate according to the possible path and interception point of the foreign matter.

[0038] In some embodiments, the foreign object is an object that has fallen off from a component of a primary circuit system. In some embodiments, the foreign object includes a screw. In some embodiments, the foreign object includes a pin. In some embodiments, the foreign object includes a ball. The components of the primary circuit system include but are not limited to valves. The foreign object can be a screw, pin and / or ball that has fallen off the valve. During the overhaul or temporary shutdown of the primary circuit system of a pressurized water reactor nuclear power plant, the components can be inspected and checked. For example, when a screw is found to have fallen off a component, the size and shape of the foreign object can be confirmed based on the same type of screw on the component, or the size and shape of the foreign object (such as a screw) can be checked through the component manual.

[0039] In step S10 , the size, weight, and material of the foreign object are obtained to determine the volume V of the foreign object, the density ρ of the foreign object, and the water-facing projection area S of the foreign object.

[0040] In some embodiments, in step S30, according to the hydraulic load calculation formula (1) and the foreign matter weight calculation formula (2), when F>G, the foreign matter can be moved by the system operating medium, and the critical water flow rate for driving the migration of the foreign matter is calculated:

[0041]

[0042] G=ρ 异物 V 异物 g (2)

[0043] Where: ρ is density, unit is kg / m 3 ; v is the fluid velocity, in m / s; S is the projected area of ​​the water, in m2; CL is the resistance coefficient, dimensionless; V is the volume, in m 3 ; g is the acceleration due to gravity, unit is m / s 2 .

[0044] Specifically, according to the hydraulic load calculation formula (i.e., formula (1)) and the foreign body weight calculation formula (i.e., formula (2)), the fluid drag force is proportional to the square of the foreign body's one-dimensional size, and the foreign body weight is proportional to the cube of the foreign body's one-dimensional size. The smaller the foreign body, the greater the hydraulic load relative to its weight ratio in a flow field with a certain flow velocity. That is, for a foreign body with a certain density, the smaller the weight, the easier it is to transfer with the fluid flow. When F>G, the foreign body can be moved by the medium. The critical water flow velocity that drives the foreign body migration is calculated based on this formula.

[0045] In some embodiments, in step S40, based on the pipelines that the foreign matter may flow through and the locations of the equipment that may intercept the flow, the actual medium flow rate of each pipeline and equipment is obtained section by section, and the actual medium flow rate of each pipeline and equipment is compared with the critical water flow rate for the migration of foreign matter. If the actual medium flow rate of any pipeline or equipment is greater than the critical water flow rate for the migration of foreign matter, it is determined that the foreign matter can pass through any pipeline or equipment; if the actual medium flow rate of any pipeline or equipment is less than the critical water flow rate for the migration of foreign matter, it is determined that the foreign matter is intercepted by any pipeline or equipment, and there is no need to check the downstream pipelines and equipment.

[0046] For example, the pipelines include pipeline A, pipeline B, pipeline C, and pipeline D arranged from top to bottom, and the equipment include equipment a, equipment b, equipment c, and equipment d. In step S40, based on the pipelines that the foreign object may flow through and the locations of the equipment that may intercept the flow, the actual medium flow rates of pipeline A, pipeline B, pipeline C, pipeline D and equipment a, equipment b, equipment c, and equipment d are obtained section by section, and the actual medium flow rates of pipeline A, pipeline B, pipeline C, pipeline D and equipment a, equipment b, equipment c, and equipment d are compared with the critical water flow rate for foreign object migration. If the actual medium flow rate of pipeline A is greater than the critical water flow rate for foreign object migration, it is determined that the foreign object can pass through pipeline A. Alternatively, if the actual medium flow rate of equipment a is greater than the critical water flow rate for foreign object migration, it is determined that the foreign object can pass through equipment a. If the actual medium flow rate of pipeline A is less than the critical water flow rate for foreign object migration, it is determined that the foreign object can be intercepted by pipeline A. Alternatively, if the actual medium flow rate of equipment a is less than the critical water flow rate for foreign object migration, it is determined that the foreign object can be intercepted by equipment a. There is no need to check the downstream pipelines (such as pipeline B, pipeline C, pipeline D) and equipment (such as equipment b, equipment c, and equipment d).

[0047] In addition, for a comparative analysis of the uniform flow velocity and the critical flow velocity in a vertical pipe, if the difference between the actual medium flow velocity and the critical water flow velocity for foreign matter migration is within 50% of the critical water flow velocity, the relationship between the maximum flow velocity and the critical water flow velocity can be calculated based on the velocity field distribution of the medium in the circular pipe, or conservatively consider including this section of the pipe in the investigation scope. The relationship between the maximum flow velocity and the average flow velocity in a circular pipe can be preliminarily calculated by referring to the following relationship:

[0048] When the fluid flows at a lower speed (Reynolds number Re<2300), the maximum flow velocity is equal to 1.5 times the average flow velocity.

[0049] When the fluid flows at a higher speed (Reynolds number Re>2300), the maximum flow rate is calculated as 1.25 times the average flow rate for conservative consideration.

[0050] For equipment, especially complex equipment such as reactor pressure vessels and internal components, it is necessary to determine the flow velocity in different areas through the core flow field, and the migration path of foreign matter can be determined by comparing the critical water flow velocity.

[0051] It is important to note that for the analysis of the path of foreign matter in the core area, in addition to analyzing the conventional fuel assembly cooling path (i.e., the medium flows from the pressure vessel inlet nozzle through the lower reactor internals to cool the fuel assembly), it is also necessary to analyze the bypass flow of the primary circuit medium in the core. Figure 2 As shown, for a CPR1000 unit, 2.2% of the reactor coolant flow enters the upper core components and the top cover space through the guide tube support plate flange water holes. The primary circuit medium has an upward flow velocity of approximately 4-6 m / s between the basket outer wall and the pressure vessel inner wall. If the foreign object is smaller than the top cover water holes and the critical water velocity is less than the velocity between the pressure vessel cylinder and the core basket, there is a small probability that the foreign object will enter the upper core components and the top cover space with the bypass flow. If foreign matter may enter the upper core components and the top cover space, an inspection above the guide tube support plate of the upper core components is required. After the foreign object enters the lower core components, since 0.6% of the primary circuit medium flow in the core area flows through the core web, the possibility of foreign matter entering the interior of the web plate should be considered.

[0052] In some embodiments, in step S50, the flushing path covers the foreign matter migration path. In some embodiments, in step S50, the flow rate of the flushing flow on the flushing path is greater than the critical water flow rate for foreign matter migration.

[0053] In step S50, a flushing plan is formulated based on the foreign body path. The flushing plan is formulated based on the following principles: (1) The flushing path covers the foreign body migration path; (2) The flow rate of the flushing flow on the flushing path is greater than the critical water flow rate (or critical water speed) of the foreign body migration; (3) The flushing path is simple, and the main circuit is selected as the flushing object during the flushing process, and the bypass isolation valve is closed; the number of interception points on the flushing path is as small as possible, and the final interception point is determined according to the size of the foreign body. The final interception point can be a heat exchanger (RRA heat exchanger, RCV heat exchanger, etc.), a pressure vessel or PTR water tank, or a system drain point. (4) The flushing pump in the original system is used as the flushing power first. If the flow rate is not sufficient, an external pump can be considered.

[0054] As an example, the main flushing circuit is as follows:

[0055] Serial number Flushing circuit 1 RRA cooling circuit 2 RRA circuit to RCV low-pressure discharge circuit 3 Safety injection circuit 4 PTR drainage circuit 5 Charging circuit

[0056] For the RRA cooling circuit: Start the RRA dual pumps, close the low-pressure downpipe and the RRA to PTR pipeline. Open RRA014 / 015VP to flush the RRA system pipeline to the RCP 1-3 loop cooling section. After flushing, inspect the interception points and the bottom of the pressure vessel along the route.

[0057] RRA circuit to RCV low-pressure discharge circuit: Use the maximum flow rate (about 27.2m 3 / h) flushing, and after flushing is completed, check the 2RCV002RF or downstream filter.

[0058] Safety injection loop: Start the high-pressure safety injection pump to flush the high-pressure safety injection loop pipeline. The flushing water enters the pressure vessel. After the flushing is completed, check the possible interception points on the path and the bottom of the pressure vessel.

[0059] PTR drainage circuit: Start one RRA pump, shut down RCV310 / 082VP and RRA014 / 015VP, and open RRA114VP. Drain to 11.3 m and flush the 2RRA system to the 2PTR001BA drainage pipeline.

[0060] Start PTR002PO and continue draining to PTR001BA to a water level of 8.55 m. Flush the PTR002PO to PTR001BA pipeline. After flushing, check the bottom of PTR001BA and any possible interception points along the flushing path.

[0061] Charging Circuit: Start the RCV charging pump and RCV050VP to flush the charging line. Start the RCV227VP, RCP001VP / 002VP, and RCV046VP to flush the pressurizer spray line. After flushing, inspect the bottom of the pressure vessel, the bottom of the pressurizer, and any possible interception points along the path.

[0062] The steps for primary loop flushing are as follows: before flushing, first conduct a foreign body inspection on the bottom of the pressure vessel and the grid plate under the core of the lower component and the area below, then start the primary loop flushing, let it stand for 1-2 hours after flushing, and then conduct another foreign body inspection on the bottom of the pressure vessel and other possible interception points.

[0063] It can be understood that the above embodiments only express the preferred implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A method for flushing a primary circuit and detecting foreign matter in a pressurized water reactor nuclear power plant, characterized in that: The following steps are involved: S10: Obtain the size and shape of the foreign body; S20: Based on the flow direction of the primary system's operating medium, the size of the foreign matter, and the intercepting area of ​​the equipment it passes through, obtain the pipes through which the foreign matter may flow and the location of the equipment that may intercept the flow; S30: Calculate the critical flow velocity of foreign matter in the primary circuit medium; S40: Quantitatively determine the possible path and interception point of foreign matter; S50: Determine a flushing path and flushing flow rate according to the possible paths and interception points of the foreign matter.

2. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 1 is characterized in that: In step S10 , the size, weight, and material of the foreign object are obtained to determine the volume V of the foreign object, the density ρ of the foreign object, and the water-facing projection area S of the foreign object.

3. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 2, characterized in that: In step S30, according to the hydraulic load calculation formula (1) and the foreign matter weight calculation formula (2), when F>G, the foreign matter can be moved by the system operating medium, and the critical water flow rate for driving the foreign matter migration is calculated: G=ρ 异物 V 异物 g (2) Where: ρ is density, unit is kg / m 3 ; v is the fluid velocity, in m / s; S is the projected area of ​​the water head, in m 2 ; CL is the drag coefficient, dimensionless; V is the volume, unit is m 3 ; g is the acceleration due to gravity, unit is m / s 2 .

4. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 3 is characterized in that: In step S40, based on the pipelines through which the foreign matter may flow and the locations of the equipment that may intercept the flow, the actual medium flow rate of each pipeline and equipment is obtained section by section, and the actual medium flow rate of each pipeline and equipment is compared with the critical water flow rate for the migration of foreign matter. If the actual medium flow rate of any pipeline or equipment is greater than the critical water flow rate for the migration of foreign matter, it is determined that the foreign matter can pass through any of the pipelines or equipment; if the actual medium flow rate of any pipeline or equipment is less than the critical water flow rate for the migration of foreign matter, it is determined that the foreign matter is intercepted by any of the pipelines or equipment, and there is no need to check the downstream pipelines and equipment.

5. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 4, characterized in that: In step S50 , the flushing path covers the foreign matter migration path.

6. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 5, characterized in that: In step S50, the flow rate of the flushing flow in the flushing path is greater than the critical water flow rate for foreign matter migration.

7. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to any one of claims 1 to 6, characterized in that: The foreign matter is an object that falls off from a component of a primary circuit system.

8. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 7, characterized in that: The foreign object includes a screw.

9. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 7, characterized in that: The foreign object includes a pin.

10. The primary loop flushing and foreign matter detection method for a pressurized water reactor nuclear power plant according to claim 7, characterized in that: The foreign matter includes a ball.

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