Foreign matter preventing lower nozzle for nuclear fuel assembly

Abstract

The application provides a foreign matter preventing nuclear fuel assembly lower tube base, which comprises a base body and a foreign matter preventing plate, the base body comprises a top plate and a frame body, the frame body is arranged at the periphery of the top plate and defines a cavity, a plurality of water flow holes are arranged on the top plate and penetrate from the top surface to the cavity, the foreign matter preventing plate is arranged on the lower side of the top plate, the foreign matter preventing plate comprises a plurality of thick partitions and a plurality of thin partitions which are arranged longitudinally, the thickness of the thick partitions is greater than that of the thin partitions, the thick partitions define a plurality of large filter holes, and the thin partitions further separate each large filter hole into a plurality of small filter holes, the thick partitions with greater thickness ensure that the foreign matter preventing plate has high strength and is not easily damaged or even broken by foreign matters in the coolant, the thin partitions further separate the large filter holes into a plurality of small filter holes, so that the filtering effect is more detailed, the filtering effect is further improved, and meanwhile, the thin partitions make the pressure drop of the coolant liquid flow smaller.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel assemblies, and in particular to a nuclear fuel assembly lower tube socket that is protected against foreign objects. Background Technology

[0002] A nuclear fuel assembly typically consists of several fuel rods, several guide tubes and positioning grids, as well as an upper and lower tube assembly. The nuclear fuel assembly is located between the upper and lower plates of the reactor core. Coolant enters the fuel rod bundle inside the fuel assembly through pre-drilled holes in the core plates, flows out of the fuel assembly through the lower tube assembly, and carries away the heat generated by the nuclear reaction in the fuel rod bundle.

[0003] As the lower end support of the fuel assembly and the coolant flow inlet, the lower tube seat assembly needs to be able to support the fuel assembly and the forces it transmits, as well as support the fuel rod bundle.

[0004] The lower fuel assembly typically also includes a foreign object (FAO) shield to filter and block foreign objects in the coolant flow, thereby reducing the risk of foreign objects getting stuck in the nuclear fuel assembly and causing abrasion and damage. Common FAO shields are grid-type, requiring high reliability (including sufficient strength to prevent damage or even breakage by foreign objects) and effective filtration, while also minimizing coolant pressure drop.

[0005] Therefore, how to design a reliable fuel pipe assembly lower pipe seat that can prevent foreign objects from entering the plate has become an urgent problem to be solved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a nuclear fuel assembly lower tube socket that is resistant to foreign objects, in view of the above-mentioned defects in the related technologies.

[0007] The technical solution adopted by the present invention to solve its technical problem includes: providing a nuclear fuel assembly lower tube seat for foreign object protection, including a seat body and a foreign object protection plate. The seat body includes a top plate and a frame body. The frame body is located around the top plate and defines a cavity. The top plate is provided with a plurality of drainage holes extending from the top surface into the cavity. The foreign object protection plate is located on the lower side of the top plate. The foreign object protection plate includes a plurality of thick partitions and a plurality of thin partitions arranged longitudinally. The thickness of the thick partitions is greater than the thickness of the thin partitions. The plurality of thick partitions intersect and define a plurality of large filter holes located below the drainage holes. The thick partitions are not exposed in the drainage holes. The plurality of thin partitions are located in each of the large filter holes and divide the large filter holes into a plurality of small filter holes.

[0008] Preferably, each of the large filter holes is located below each of the water flow holes in a corresponding manner.

[0009] Preferably, the thick partition includes a first thick partition extending along a first direction and a second thick partition extending along a second direction, the first thick partition and the second thick partition intersecting to define the large filter pore.

[0010] Preferably, the thin partition includes a first thin partition and a second thin partition, the first thin partition and the second thin partition intersecting to define the small filter pores.

[0011] Preferably, the first thin partition extends along the first direction, and the second thin partition extends along the second direction.

[0012] Preferably, the first direction is perpendicular to the second direction.

[0013] Preferably, the top plate is provided with an assembly hole for assembly with the end of an external guide tube, the assembly hole extending longitudinally from the top surface into the cavity, and the foreign object protection plate is provided with a longitudinally penetrating through hole corresponding to the assembly hole below it.

[0014] Preferably, the lower tube seat includes a fixing member, the cavity of the seat body is open downward, the fixing member is disposed in the cavity, located below the foreign object protection plate and connected to the inner wall of the frame, and supports the foreign object protection plate.

[0015] Preferably, the fixing member includes a first columnar portion and a second columnar portion connected to the first columnar portion. The first columnar portion and the second columnar portion are eccentrically arranged. The inner wall of the frame is provided with a fixing hole. The first columnar portion is rotatably fitted in the fixing hole. The side of the second columnar portion away from the center of the first columnar portion abuts against and fixes the foreign object protection plate.

[0016] Preferably, the cavity opens downwards, and the seat includes a plurality of legs provided on the lower side of the frame, the legs extending toward the center of the cavity; the foreign object protection plate includes a first plate and a second plate, the edge portion of the first plate is located above some of the legs, and the edge portion of the second plate is located above the other part of the legs.

[0017] The technical solution of the present invention has at least the following beneficial effects: In the nuclear fuel assembly lower tube seat of the present invention, the thick partition of the foreign object protection plate defines a plurality of large filter holes, and the thin partition further divides each large filter hole into a plurality of small filter holes. The thick partition ensures that the foreign object protection plate has high strength and is not easily damaged or even broken by foreign objects in the coolant. The thin partition further divides the large filter holes into a plurality of small filter holes, making the filtration effect more refined and further improving the filtration effect. At the same time, the thin partition makes the pressure drop of the coolant flow smaller. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a top view of the lower tube seat of the nuclear fuel assembly for foreign object protection according to the present invention.

[0020] Figure 2 yes Figure 1 A magnified view of part P.

[0021] Figure 3 yes Figure 1 A cross-sectional view of position AA.

[0022] Figure 4 yes Figure 3 A magnified view of part Q.

[0023] Figure 5 yes Figure 1 A bottom view of the lower tube seat.

[0024] Figure 6 yes Figure 5 A magnified view of the R part.

[0025] Figure 7 yes Figure 1 A three-dimensional view of the bottom of the lower tube seat facing upwards.

[0026] Figure 8 yes Figure 7 A magnified view of part S.

[0027] Figure 9 yes Figure 7 A top view of the foreign object protection plate of the lower pipe seat.

[0028] Figure 10 yes Figure 9 A magnified view of the T-section.

[0029] Figure 11 This is a top view of the foreign object protection plate of the lower tube seat of the nuclear fuel assembly of the present invention, which has reliable foreign object protection and low coolant pressure drop (the first plate and the second plate are in the separated state).

[0030] Figure 12 yes Figure 3 A three-dimensional view of the fixing component of the lower tube seat.

[0031] The labels in the diagram represent: lower pipe seat 1, seat body 11, top plate 111, water flow hole 1111, assembly hole 1112, frame body 112, fixing hole 1121, cavity 113, support leg 114, foreign object prevention plate 12, thick partition 121, first thick partition 1211, second thick partition 1212, thin partition 122, first thin partition 1221, second thin partition 1222, large filter hole 123, small filter hole 124, through hole 125, first plate body 126, second plate body 127, fixing member 13, first columnar part 131, second columnar part 132, longitudinal direction 30, first direction 31, second direction 32. Detailed Implementation

[0032] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. It should be understood that if terms such as "upper," "lower," "longitudinal," "horizontal," "top," or "bottom" appear in the text to indicate orientation or positional relationships, these are based on the orientation or positional relationships shown in the accompanying drawings, and refer to construction and operation in a specific orientation. They are merely for the purpose of describing the technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on this invention. It should also be noted that unless otherwise explicitly specified and limited, terms such as "install," "connect," "join," "fix," or "set" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or integration; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. When an element is referred to as being "upper" or "lower" than another element, the element can be located "directly" or "indirectly" on top of the other element, or there may be one or more intermediary elements. If the terms "first," "second," etc., appear in the text merely for the convenience of describing the technical solution, and are not to be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features, then features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0034] See Figure 1-6According to one embodiment of the present invention, the lower tube seat 1 of the nuclear fuel assembly with foreign object protection includes a seat body 11 and a foreign object protection plate 12. The seat body 11 includes a top plate 111 and a frame 112. The frame 112 is located around the top plate 111 and defines a cavity 113. The top plate 111 is provided with a plurality of drainage holes 1111 extending from the top surface into the cavity 113. The foreign object protection plate 12 is arranged laterally on the lower side of the top plate 111. The foreign object protection plate 12 includes longitudinally arranged... The system consists of multiple thick partitions 121 and multiple thin partitions 122. The thickness of the thick partitions 121 is greater than that of the thin partitions 122. The multiple thick partitions 121 intersect and define multiple large filter holes 123 that are longitudinally connected below the water flow holes 1111. The thick partitions 121 are not exposed in the water flow holes 1111. The multiple thin partitions 122 are disposed in each large filter hole 123 and divide the large filter hole 123 into multiple small filter holes 124 that are longitudinally connected.

[0035] Nuclear fuel assemblies typically include several fuel rods and guide tubes. In this invention, the lower tube seat 1 of the nuclear fuel assembly, which balances foreign object protection strength and low pressure drop, is used such that the fuel rods and guide tubes are positioned on the upper side of the lower tube seat 1. The lower tube seat 1 supports the guide tubes and fuel rods. Coolant enters the fuel assembly through the large filter holes 123 and small filter holes 124 of the foreign object protection plate 12, and then through the water flow holes 1111 of the seat body 11. The foreign object protection plate 12 filters and blocks foreign objects in the coolant flow, thereby reducing the risk of foreign objects getting stuck in the nuclear fuel assembly and causing abrasion and damage. The thicker partition plate 121 ensures that the foreign object protection plate 12 has high strength and is not easily damaged or even broken by foreign objects in the coolant. The thinner partition plate 122 further divides the large filter holes 123 into multiple small filter holes 124, making the filtration more refined and further improving the filtration effect. At the same time, the thinner partition plate 122 results in a smaller pressure drop in the coolant flow.

[0036] See Figure 2 and 6 -8. Preferably, each large filter hole 123 is located below each water flow hole 1111 in a one-to-one correspondence.

[0037] See Figure 9 and 10 Preferably, the thick partition 121 includes a first thick partition 1211 extending along a first direction 31 and a second thick partition 1212 extending along a second direction 32, the first thick partition 1211 and the second thick partition 1212 intersecting to define a large filter hole 123. In each large filter hole 123, the thin partition 122 includes a first thin partition 1221 and a second thin partition 1222, the first thin partition 1221 and the second thin partition 1222 intersecting to define a small filter hole 124. The first thin partition 1221 also extends along the first direction 31, and the second thin partition 1222 also extends along the second direction 32. Preferably, the first direction 31 is perpendicular to the second direction 32. More preferably, the pore size of the small filter hole 124 is 2.7-3 mm.

[0038] See Figure 1-3 Preferably, the top plate 111 has an assembly hole 1112 for assembling with the end of the external guide tube. The assembly hole 1112 extends longitudinally from the top surface into the cavity 113. The anti-foreign object plate 12 has a longitudinally extending through hole 125 located below the assembly hole 1112. In use, the assembly hole 1112 of the base 11 and the through hole 125 of the anti-foreign object plate 12 allow fasteners such as screws to pass through, enabling the assembly of the base 11 with the lower end of the guide tube. Here, "external guide tube" means that the guide tube is external relative to the lower tube seat 1. See also Figure 3 , 4 7 and 8, preferably, the lower tube seat 1 includes a fixing member 13, the cavity 113 of the seat body 11 is open downward, the fixing member 13 is provided in the cavity 113, located on the lower side of the foreign object protection plate 12 and connected to the inner wall of the frame 112, supporting the foreign object protection plate 12.

[0039] See Figure 12 Preferably, the fixing member 13 includes a first columnar portion 131 and a second columnar portion 132 connecting the first columnar portion 131. The first columnar portion 131 and the second columnar portion 132 are eccentrically arranged. The radial dimension of the first columnar portion 131 is smaller than the radial dimension of the second columnar portion 132. The inner wall of the frame 112 is provided with a fixing hole 1121. The first columnar portion 131 is circumferentially rotatable and fitted in the fixing hole 1121. The side of the second columnar portion 132 away from the center of the first columnar portion 131 abuts against and fixes the foreign object protection plate 12. Thus, by rotating the fixing member 13, the central axis and side of the second columnar part 132 can be brought close to the anti-foreign object plate 12 and the side can be pressed against the anti-foreign object plate 12, thereby the anti-foreign object plate 12 presses against the top plate 111 of the seat body 11, or the central axis and side of the second columnar part 132 can be moved away from the anti-foreign object plate 12 and the anti-foreign object plate 12 can be released, thereby the anti-foreign object plate 12 does not press against the top plate 111 of the seat body 11. Specifically, the fastener 13 can be a pin. When the foreign object protection plate 12 needs to be installed, the foreign object protection plate 12 is placed into the cavity 113 of the seat body 11, with the fastener 13 located below the foreign object protection plate 12. The fastener 13 is rotated circumferentially so that the central axis and side of the second columnar part 132 are close to the foreign object protection plate 12 and the side abuts against the foreign object protection plate 12. As a result, the foreign object protection plate 12 abuts against the top plate 111 of the seat body 11, thereby achieving the installation and fixation of the foreign object protection plate 12. When the foreign object protection plate 12 needs to be removed, the fastener 13 is rotated circumferentially so that the central axis and side of the second columnar part 132 are away from the foreign object protection plate 12 and the foreign object protection plate 12 is released. As a result, the foreign object protection plate 12 no longer abuts against the top plate 111 of the seat body 11, thereby allowing the foreign object protection plate 12 to be removed. The installation and fixation method is reliable and convenient.

[0040] See Figure 3 , 7Preferably, the cavity 113 opens downwards, and the seat 11 includes a plurality of legs 114 disposed on the lower side of the frame 112. The legs 114 extend laterally toward the center of the cavity 113. In other words, the lower opening of the cavity 113 is blocked by the legs 114. The foreign object blocking plate 12 includes a first plate 126 and a second plate 127 assembled together. The edge portion of the first plate 126 is located above a portion of the legs 114, and the edge portion of the second plate 127 is located above the other portion of the legs 114. Specifically, if the foreign object prevention plate 12 is a single piece, the edge portion will be difficult to install into the cavity 113 above the support leg 114 due to the obstruction of the support leg 114. However, in this embodiment, since the foreign object prevention plate 12 includes a first plate 126 and a second plate 127, the first plate 126 and the second plate 127 can be installed separately. First, the first plate 126 is installed into the cavity 113 with its edge portion located above part of the support leg 114. Then, the second plate 127 is installed into the cavity 113 with its edge portion located above the other part of the support leg 114, thereby achieving the overall installation of the foreign object prevention plate 12. The foreign object prevention plate 12 is then fixed by the fastener 13, making the installation and fixing of the foreign object prevention plate 12 more flexible and convenient.

[0041] Preferably, the foreign object shield 12 includes intersecting edges forming an angle, and the foreign object shield 12 is provided with a first pin clearance hole 126 at the angle. Specifically, the foreign object shield 12 is quadrilateral, and the first pin clearance hole is provided at each of the two opposite angles. The support leg 114 is provided with a second pin clearance hole 1141, which is located below the first pin clearance hole 126. The function of the first pin clearance hole 126 and the second pin clearance hole 1141 is to avoid the pins when the fuel assembly is loaded into the nuclear reactor core, where there are pins on the core plate.

[0042] In summary, the nuclear fuel assembly lower tube seat 1 of the present invention provides reliable foreign object protection and low coolant pressure drop. The thick partition 121 ensures that the foreign object protection plate 12 has high strength and is not easily damaged or even broken by foreign objects in the coolant. The thinner partition 122 further divides the large filter holes 123 into multiple small filter holes 124, making the filtration effect more refined and further improving the filtration effect. At the same time, the thinner partition 122 results in a smaller pressure drop of the coolant flow. The mounting holes 1112 of the seat body 11 and the through holes 125 of the foreign object protection plate 12 allow fasteners such as screws to pass through, realizing the assembly of the seat body 11 with the lower end of the guide tube. The lower tube seat 1 includes a fixing member 13. The cavity 113 of the seat body 11 opens downwards. The foreign object prevention plate 12 is installed and fixed in the cavity 113 by the fixing member 13. The fixing member 13 includes a first columnar part 131 and a second columnar part 132 connecting the first columnar part 131. The first columnar part 131 and the second columnar part 132 are eccentrically arranged, and the installation and fixing method is reliable and convenient. The foreign object prevention plate 12 includes a first plate body 126 and a second plate body 127. The first plate body 126 and the second plate body 127 can be respectively bypassed by the branch feet 114 and inserted into the cavity 113 of the seat body 11 for installation and fixing, making the installation and fixing of the foreign object prevention plate 12 more flexible and convenient.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications, combinations, and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A nuclear fuel assembly lower tube socket (1) for preventing foreign objects from entering, characterized in that, The system includes a base (11) and a foreign object shield (12). The base (11) includes a top plate (111) and a frame (112). The frame (112) surrounds the top plate (111) and defines a cavity (113). The top plate (111) has multiple drainage holes (1111) extending from the top surface into the cavity (113). The foreign object shield (12) is located below the top plate (111) and includes multiple thick partitions (121) and multiple thin partitions (122) arranged longitudinally. The thickness of the thick partitions (121) is... The thickness of the thick partition (121) is greater than that of the thin partition (122). Multiple thick partitions (121) intersect and define multiple large filter holes (123) located below the water flow hole (1111). The thick partitions (121) are not exposed in the water flow hole (1111). Multiple thin partitions (122) are located in each of the large filter holes (123) and divide the large filter holes (123) into multiple small filter holes (124). The lower pipe seat (1) includes a fixing member (13). The cavity (113) of the seat body (11) opens downward. The fixing member (13) is located in the... In the cavity (113), a fixing member (13) is located below the foreign object protection plate (12) and connected to the inner wall of the frame (112) to support the foreign object protection plate (12). The fixing member (13) includes a first columnar part (131) and a second columnar part (132) connecting the first columnar part (131). The first columnar part (131) and the second columnar part (132) are eccentrically arranged. The radial dimension of the first columnar part (131) is smaller than the radial dimension of the second columnar part (132). The inner wall of the frame (112) is provided with a fixing hole (1121). The columnar part (131) is rotatably fitted in the fixing hole (1121). The side of the second columnar part (132) away from the center of the first columnar part (131) abuts against and fixes the foreign object plate (12). By rotating the fixing member (13) circumferentially, the central axis and side of the second columnar part (132) are brought close to the foreign object plate (12) and the side abuts against the foreign object plate (12), or the central axis and side of the second columnar part (132) are moved away from the foreign object plate (12) and the foreign object plate (12) is released.

2. The lower tube seat (1) according to claim 1, characterized in that, Each of the large filter holes (123) is located below each of the water flow holes (1111).

3. The lower tube seat (1) according to claim 1, characterized in that, The thick partition (121) includes a first thick partition (1211) extending along a first direction (31) and a second thick partition (1212) extending along a second direction (32), the first thick partition (1211) and the second thick partition (1212) intersecting to define the large filter hole (123).

4. The lower tube seat (1) according to claim 1, characterized in that, In each of the large filter holes (123), the thin partition (122) includes a first thin partition (1221) and a second thin partition (1222), which intersect to define the small filter hole (124).

5. The lower tube seat (1) according to claim 4, characterized in that, The first thin partition (1221) extends along the first direction (31), and the second thin partition (1222) extends along the second direction (32).

6. The lower tube seat (1) according to claim 3 or 5, characterized in that, The first direction (31) is perpendicular to the second direction (32).

7. The lower tube seat (1) according to claim 1, characterized in that, The top plate (111) is provided with an assembly hole (1112) for assembly with the end of an external guide tube. The assembly hole (1112) extends longitudinally from the top surface into the cavity (113). The anti-foreign object plate (12) is provided with a longitudinal through hole (125) located below the assembly hole (1112).

8. The lower tube seat (1) according to claim 1, characterized in that, The cavity (113) opens downwards, and the seat (11) includes a plurality of legs (114) located on the lower side of the frame (112), the legs (114) extending toward the center of the cavity (113); the foreign object protection plate (12) includes a first plate (126) and a second plate (127), the edge portion of the first plate (126) is located above a portion of the legs (114), and the edge portion of the second plate (127) is located above another portion of the legs (114).

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