A foreign body prevention net and fuel assembly

Abstract

The present invention relates to the field of nuclear fuel technology, and in particular to a foreign body prevention net and a fuel assembly. The foreign body prevention net is in the shape of a spatial curved surface, and the normal direction of the spatial curved surface is convex facing the coolant flow direction; the foreign body prevention net includes ribs and water flow holes, and the ribs are multiple, cross-connected with each other, and combined into the basic frame of the foreign body prevention net; the water flow holes are regularly arranged on the spatial curved surface of the foreign body prevention net; the edge of the foreign body prevention net is connected to a foreign body receiving groove, and the opening direction of the foreign body receiving groove is consistent with the convex direction of the foreign body prevention net; the outer side of the foreign body receiving groove is connected to a connecting plate. The fuel assembly includes the foreign body prevention net. The foreign body prevention net of the present invention has good structural stability, low flow resistance, and is not easy to be blocked, ensuring that the coolant flow entering the fuel assembly does not fluctuate over a large range.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear fuel, and in particular to a foreign matter prevention net and a fuel assembly. Background Art

[0002] The fuel assembly is the core component of the nuclear reactor, which directly determines the safety and economy of the reactor. The coolant circulates in the reactor, flows through the fuel assembly in the core part and takes away the heat. The fuel rod bundle in the assembly has a compact structure and a narrow and long flow channel. In actual situations, there are many reasons for the reactor coolant loop to cause foreign matter to enter the fuel rod bundle due to the falling of external foreign matter, pipeline corrosion, failure and shedding of mechanical parts, scale accumulation, etc., which may cause foreign matter to enter the fuel rod bundle, resulting in blockage of the assembly coolant channel and eventually cause the fuel rod to burn. In order to eliminate this effect, the fuel assembly generally has an anti-foreign matter net at the assembly coolant inlet. For example, in commercial pressurized water reactors, the coolant enters the fuel assembly from bottom to top, and the anti-foreign matter net is connected to the lower pipe seat to form an integral arrangement at the bottom of the assembly; in some research reactors, the coolant enters the fuel assembly from top to bottom, and the upper enclosure that plays the role of the anti-foreign matter net is arranged at the upper part of the assembly.

[0003] In the existing design of anti-foreign matter nets, a flat plate design is generally adopted. A number of water flow holes with regular arrangement, same size and shape or different shapes are designed in the flat plate. The hole size is large enough to resist foreign objects of the same size level that can block the coolant channel of the fuel rod bundle, and at the same time balance the flow rate entering each coolant channel of the fuel assembly, so that the coolant flows into each coolant channel more evenly. However, due to the large coolant flow rate in the reactor and the flow direction being perpendicular to the anti-foreign matter net, when there is a large-sized foreign object and it is blocked in the anti-foreign matter net, the foreign object will be stuck in the water flow hole of the anti-foreign matter net and will always exist. At this time, the coolant channel flow corresponding to the stuck foreign object is reduced and there is a possibility of fuel rod failure due to heat accumulation in the fuel rod. If the number of foreign objects is too large, it will also cause major risks to the safety of the fuel assembly and even the reactor. At the same time, due to many reasons such as the impact force of the coolant flow and the reduced strength of the material under neutron irradiation conditions, the anti-foreign matter net may fail mechanically. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a foreign body prevention net and a fuel assembly, which have good structural stability, low flow resistance and are not easy to be blocked, so as to ensure that the coolant flow entering the fuel assembly does not fluctuate in a large range.

[0005] The present invention provides a foreign body prevention net, which is in the shape of a space curved surface, and the normal direction of the space curved surface is convex facing the coolant flow direction;

[0006] The anti-foreign-object net comprises ribs and water holes, and the ribs are multiple and cross-connected with each other to form a basic frame of the anti-foreign-object net;

[0007] The water flow holes are regularly arranged on the space curved surface of the anti-foreign matter net;

[0008] The edge of the anti-foreign-matter net is connected with a foreign-matter receiving groove, and the opening direction of the foreign-matter receiving groove is consistent with the protruding direction of the anti-foreign-matter net;

[0009] The outer side of the foreign matter receiving groove is connected with a connecting plate.

[0010] Preferably, it also includes an opening, and the opening is arranged at the center of the anti-foreign matter net.

[0011] Preferably, the water flow hole is in a circular, triangular or polygonal shape.

[0012] Preferably, the thickness of the anti-foreign matter net is 2-4 mm.

[0013] Preferably, fixing holes are provided on the connecting plate.

[0014] Preferably, a grid-shaped groove is arranged inside the foreign matter receiving groove.

[0015] The present invention also provides a fuel assembly, comprising the foreign matter prevention net described in the above technical solution.

[0016] Preferably, the foreign body prevention net is fixed below the lower tube seat body of the fuel assembly; the protrusion normal points to the lower side of the lower tube seat body.

[0017] Preferably, the anti-foreign-object net is fixed above the upper grid plate, and the protrusion normal points to above the upper grid plate.

[0018] Preferably, a four-sided net is provided between the anti-foreign matter net and the upper grid plate, the four-sided net forms a square shape consistent with the shape of the fuel box, the bottom of the four-sided net is connected to the upper part of the upper grid plate, and the top is covered with the anti-foreign matter net.

[0019] Compared with the prior art, the foreign body protection net and fuel assembly of the present invention have the following beneficial effects:

[0020] (1) The spatial curved surface anti-foreign matter net designed by the present invention can block foreign matter in the reactor while guiding some foreign matter into the foreign matter holding tank, thereby ensuring that the coolant flow entering the fuel assembly does not fluctuate over a large range;

[0021] (2) The spatial curved surface anti-foreign matter net designed by the present invention has high rigidity and bending resistance, which can ensure the structural stability of the anti-foreign matter net under reactor operating conditions;

[0022] (3) The spatial curved surface anti-foreign matter net designed by the present invention can retain reactor foreign matter and take out the reactor foreign matter together when the components are taken out of the reactor, thereby ensuring the cleanliness of the reactor;

[0023] (4) The spatial curved surface foreign body prevention net designed by the present invention can increase the overall area of ​​the foreign body prevention net and open smaller water flow holes, which can take into account both low pressure drop and high foreign body prevention capability;

[0024] (5) The spatial curved surface anti-foreign matter net designed by the present invention has a wide range of design uses and can be used in commercial pressurized water reactors, research reactors, low-temperature heating reactors, boiling water reactors and other reactor-type fuel assemblies, and can be directly applied in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram showing the structure of a space curved surface foreign body protection net;

[0026] Figure 2 A schematic diagram showing the structure of a lower pipe socket assembly of a nuclear fuel pressurized water reactor with a foreign body protection net;

[0027] Figure 3 A schematic diagram showing the structure of a space curved surface foreign body protection net for a pool-type reactor;

[0028] Figure 4 A schematic diagram showing the structure of a pool-type reactor fuel assembly with a foreign body protection net;

[0029] 1- water flow hole, 2- rib, 3- foreign matter receiving groove, 4- connecting plate, 5- opening hole, 6- fixing hole, 7- foreign matter prevention net, 8- lower pipe seat body, 9- upper grid plate, 10- four-side net, 11- fuel box, 12- lower grid plate, 13- lifting head, 14- lower end head. DETAILED DESCRIPTION

[0030] In order to further understand the present invention, the embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the present invention.

[0031] The embodiment of the present invention discloses a foreign body prevention net, such as Figure 1 As shown, the shape is a space curved surface, and the normal direction of the space curved surface is convex toward the coolant flow direction;

[0032] The anti-foreign-object net comprises ribs 2 and water holes 1, and the ribs 2 are multiple and cross-connected with each other to form the basic frame of the anti-foreign-object net;

[0033] The water flow holes 1 are regularly arranged on the curved surface of the anti-foreign matter net space;

[0034] The edge of the anti-foreign-matter net is connected with a foreign-matter receiving groove 3, and the opening direction of the foreign-matter receiving groove 3 is consistent with the protruding direction of the anti-foreign-matter net;

[0035] The outer side of the foreign matter receiving groove 3 is connected with a connecting plate 4 .

[0036] According to the present invention, the ribs 2 constitute the basic frame of the anti-foreign object net, with the purpose of providing the anti-foreign object net with sufficient strength. At the same time, since the basic frame is convex facing the coolant flow direction, it can enhance the ability of the anti-foreign object net to resist the coolant impact load and bending stress, and maintain the structural stability of the anti-foreign object net.

[0037] The water flow hole 1 provides a basic flow channel for the coolant entering the fuel assembly. The shape of the water flow hole 1 can be circular, triangular or polygonal, and the shapes of each water flow hole are the same or different. The design purposes of the water flow hole are twofold: 1) to homogenize the coolant flow field, provide the same or different coolant flow rates for each sub-channel inside the fuel assembly, and ensure the coolability of the fuel rods; 2) to prevent reactor foreign matter generated by many reasons such as the falling of external foreign matter, pipeline corrosion, failure and shedding of mechanical parts, and scale accumulation from entering the interior of the fuel assembly; 3) to retain reactor foreign matter, so that the foreign matter can be taken out at the same time when the fuel assembly is unloaded from the reactor.

[0038] Preferably, it also includes an opening 5, which is arranged at the center of the anti-foreign matter net to provide a through space for the in-pile instrument pipe, lifting head or other monitoring and mechanical devices.

[0039] The thickness of the anti-foreign-object net is 2-4 mm, which can provide sufficient rigidity for the anti-foreign-object net.

[0040] The edge of the anti-foreign-matter net is connected with a foreign-matter containing groove 3, and the opening direction of the foreign-matter containing groove 3 is consistent with the protruding direction of the anti-foreign-matter net; the foreign-matter containing groove 3 has a depth.

[0041] Preferably, a grid-shaped groove is provided inside the foreign matter receiving groove 3. Since the anti-foreign matter net is in the shape of a spatial curved surface, when a foreign matter that enters the anti-foreign matter net is stuck in the water flow hole, the impact of the coolant will generate a force along the spatial curved surface toward the foreign matter receiving groove, and the existence of this force will drive the foreign matter into the foreign matter receiving groove. At the same time, due to the grid design of the foreign matter receiving groove, the foreign matter can be retained and taken out together when the fuel assembly is unloaded, thereby ensuring the cleanliness in the reactor.

[0042] The outer side of the foreign matter receiving groove 3 is connected with a connecting plate 4 , and the connecting plate 4 is provided with a fixing hole 6 .

[0043] The connecting plate 4 is used to fix the foreign body protection net in the fuel assembly, and can be fixed in the lower tube seat or the upper grid plate according to actual use requirements, and the fixing method can be screw connection or welding.

[0044] An embodiment of the present invention further discloses a fuel assembly, comprising the foreign matter prevention net described in the above technical solution.

[0045] The foreign body prevention net can be connected to the lower tube seat or the upper grid plate of the fuel assembly to achieve the preset goals in the present invention.

[0046] When connected to the lower tube socket of the fuel assembly:

[0047] The anti-foreign matter net 7 is fixed below the lower tube seat body 8 of the fuel assembly; the convex normal direction points to the lower side of the lower tube seat body, that is, the convex surface is away from the lower tube seat body 8.

[0048] When connected to the upper grid plate of the fuel assembly, the foreign body prevention net 7 is fixed above the upper grid plate 9, and the convex normal direction points to the upper side of the upper grid plate, that is, the convex surface is away from the upper grid plate.

[0049] Preferably, a four-sided net 10 is provided between the anti-foreign matter net 7 and the upper grid plate 9. The four-sided net 10 is formed into a square, which is consistent with the shape of the fuel box 11. The bottom of the four-sided net 10 is connected to the upper part of the upper grid plate 9, and the top is covered with the anti-foreign matter net 7.

[0050] The fuel assembly can be a commercial pressurized water reactor, a research reactor, a low-temperature heating reactor, a boiling water reactor or other reactor type fuel assembly.

[0051] In order to further understand the present invention, the foreign body prevention net and the fuel assembly provided by the present invention are described in detail below in conjunction with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0052] Example 1

[0053] like Figure 1 As shown, a spatial curved surface foreign body prevention net for a pressurized water reactor comprises a water flow hole 1, ribs 2, a foreign body receiving groove 3, a connecting plate 4, an opening 5, and a fixing hole 6.

[0054] The ribs 2 are cross-overlapped to form the basic framework of the anti-foreign matter net, providing sufficient structural strength and rigidity for the anti-foreign matter net; the water flow holes 1 are arranged in a certain pattern on the spatial curved surface of the anti-foreign matter net, providing a flow channel for the coolant flowing through the fuel assembly from bottom to top and blocking foreign matter from entering the assembly;

[0055] The opening 5 is located at the center of the space curved surface foreign body protection net, providing an inlet and outlet space for the instrument tubes loaded with the fuel assembly;

[0056] The edge of the anti-foreign object net is connected with a foreign object receiving groove 3, and the opening direction of the foreign object receiving groove 3 is consistent with the protruding direction of the anti-foreign object net; a grid-shaped groove is arranged inside the foreign object receiving groove 3, which can provide a receiving space for foreign objects flowing through the anti-foreign object net and retain the foreign objects.

[0057] The outer side of the foreign matter receiving groove 3 is connected with a connecting plate 4 to provide connection and support for the anti-foreign matter net and the lower pipe seat.

[0058] Example 2

[0059] like Figure 2 As shown, a lower pipe seat assembly of a nuclear fuel pressurized water reactor using a foreign body prevention net comprises a space curved surface foreign body prevention net 7 and a lower pipe seat body 8;

[0060] The anti-foreign matter net 7 is located below the lower tube seat body 2, and the two are connected and fixed by screws;

[0061] The convex surface of the anti-foreign matter net 7 points normally to the bottom of the lower tube seat body 2, playing the role of an anti-foreign matter net;

[0062] The pressurized water reactor lower pipe base assembly provides lower integral support for the pressurized water reactor fuel assembly.

[0063] Example 3

[0064] like Figure 3 and 4 As shown, a fuel assembly for a pool-type reactor includes a foreign body protection net 7, an upper grid plate 9, four-side nets 10, a fuel box 11, a lower grid plate 12, a lifting head 13, and a lower end head 14.

[0065] The anti-foreign matter net 7 comprises a water flow hole 1, ribs 2, a foreign matter receiving groove 3, a connecting plate 4, an opening 5, and a fixing hole 6.

[0066] The ribs 2 are cross-overlapped to form the basic framework of the anti-foreign matter net, providing sufficient structural strength and rigidity for the anti-foreign matter net; the water flow holes 1 are arranged in a certain pattern on the spatial curved surface of the anti-foreign matter net, providing a flow channel for the coolant flowing through the fuel assembly from bottom to top and blocking foreign matter from entering the assembly;

[0067] The edge of the anti-foreign object net is connected with a foreign object receiving groove 3, and the opening direction of the foreign object receiving groove 3 is consistent with the protruding direction of the anti-foreign object net; a grid-shaped groove is arranged inside the foreign object receiving groove 3, which can provide a receiving space for foreign objects flowing through the anti-foreign object net and retain the foreign objects.

[0068] The outer side of the foreign matter receiving groove 3 is connected with a connecting plate 4 , and the connecting plate 4 is connected to the four-side nets 10 .

[0069] The anti-foreign matter net 7 has an opening 5 in the center, which is used to provide an entry and exit space for the lifting head of the fuel assembly;

[0070] The fuel assembly comprises, from top to bottom, a foreign body prevention net 7, four-side nets 10, an upper grid plate 9, a fuel box 11, a lower grid plate 12, and a lower end head 14.

[0071] The four-sided net 10 is in a square shape, which is consistent with the shape of the fuel box 11 . The bottom of the four-sided net 10 is connected to the upper part of the upper grid plate 12 , and the top is covered with the anti-foreign matter net 7 .

[0072] The lifting head 13 is connected and fixed through the opening 5 of the anti-foreign matter net 7, and the upper grid plate 9 and the anti-foreign matter net 7 are aligned and welded through the interface to achieve the connection and fixation of the two.

[0073] The coolant flows from the lifting head 13 to the lower end head 14, and the coolant inlet into the fuel assembly is only the water flow hole 1 of the anti-foreign matter net 7. The fuel assembly is in the fuel box 11, and the anti-foreign matter net 7 can block the reactor foreign matter from entering the assembly.

[0074] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0075] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A foreign body protection net, characterized in that: The shape is a spatial curved surface, and the normal direction of the spatial curved surface is convex toward the coolant flow direction; The anti-foreign-object net comprises ribs and water holes, and the ribs are multiple and cross-connected with each other to form a basic frame of the anti-foreign-object net; The water flow holes are regularly arranged on the space curved surface of the anti-foreign matter net; The edge of the anti-foreign-matter net is connected with a foreign-matter receiving groove, and the opening direction of the foreign-matter receiving groove is consistent with the protruding direction of the anti-foreign-matter net; A connecting plate is connected to the outer side of the foreign matter receiving groove; A grid-shaped groove is arranged inside the foreign object holding groove; the anti-foreign object net is in the shape of a spatial curved surface. When a foreign object entering the anti-foreign object net is stuck in the water flow hole, a force will be generated along the spatial curved surface toward the foreign object holding groove along with the impact of the coolant. The existence of this force will drive the foreign object into the foreign object holding groove. At the same time, due to the grid design of the foreign object holding groove, the foreign object can be retained and taken out together when the fuel assembly is unloaded, thereby ensuring the cleanliness of the reactor.

2. The foreign body protection net according to claim 1, characterized in that: It also includes an opening, which is arranged at the center of the anti-foreign matter net.

3. The foreign body protection net according to claim 1, characterized in that: The shape of the water flow hole is circular, triangular or polygonal.

4. The foreign body protection net according to claim 1, characterized in that: The thickness of the anti-foreign matter net is 2-4 mm.

5. The foreign body protection net according to claim 1, characterized in that: The connecting plate is provided with fixing holes.

6. A fuel assembly, characterized in that: The invention comprises the anti-foreign matter net as described in any one of claims 1 to 5.

7. The fuel assembly according to claim 6, characterized in that The anti-foreign matter net is fixed below the lower tube seat body of the fuel assembly; the protrusion normal direction points to the lower part of the lower tube seat body.

8. The fuel assembly according to claim 6, characterized in that The anti-foreign-object net is fixed above the upper grid plate, and the protrusion normal direction points to the upper side of the upper grid plate.

9. The fuel assembly according to claim 8, characterized in that A four-sided net is also arranged between the anti-foreign matter net and the upper grid plate. The four-sided net is surrounded by a square shape, which is consistent with the shape of the fuel box. The bottom of the four-sided net is connected to the upper part of the upper grid plate, and the top is covered with the anti-foreign matter net.

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