Nuclear fuel assembly top nozzle including a hold-down device

Abstract

The top nozzle comprises: an intermediate plate (26) axially positioned between an upper plate (24) and a lower plate (22), the intermediate plate being axially movable between an upper position and a lower position; one or more main spring members (28) arranged to permanently urge the intermediate plate (26) towards the upper plate (24); one or more spring members (30) arranged to urge the intermediate plate (26) towards the upper plate (24) when the intermediate plate (26) is positioned between the lower position and an intermediate position associated with the auxiliary spring member (30); and a preloading element (32) associated with each auxiliary spring member (30) and arranged to cause the auxiliary spring member (30) to bear against the upper plate (24) via the preloading element (32) when the intermediate plate (26) is positioned between the intermediate position associated with said auxiliary spring member (30) and the upper position.

Description

Technical Field

[0001] This invention relates to a top nozzle for a nuclear fuel assembly. Background Technology

[0002] A nuclear fuel assembly (or “fuel assembly”) includes nuclear fuel rods (or “fuel rods”) arranged in a bundle and a frame supporting the fuel rods.

[0003] Each fuel rod includes a tubular cladding that contains nuclear fuel (e.g., nuclear fuel pellets, particularly UO2 pellets), with both ends of the tubular cladding sealed by corresponding end plugs.

[0004] The skeleton includes, for example, a bottom nozzle and a top nozzle spaced apart along the component axis, a guide sleeve extending along the component axis between the bottom nozzle and the top nozzle and connecting the bottom nozzle and the top nozzle together, and a positioning grid attached to the guide sleeve and distributed along the guide sleeve between the bottom nozzle and the top nozzle.

[0005] The fuel rods extend between the bottom and top nozzles and pass through the positioning grid. The positioning grid functions to support the fuel rods along and transverse to the component axis and to maintain the fuel rods in a spaced-out relationship.

[0006] During operation, fuel assemblies are inserted into the reactor core, which is received into the reactor vessel. The longitudinal axis of the fuel assembly extends substantially vertically, and coolant flows vertically through the fuel assembly to moderate the nuclear reaction and recover the heat generated by the fuel rods.

[0007] The coolant flowing upwards through the fuel assembly generates a force that tends to lift the fuel assembly. This force is often referred to as "hydraulic lift." Hydraulic lift can overcome the weight of the fuel assembly.

[0008] To counteract hydraulic lift, fuel assemblies are typically equipped with a clamping device that is configured to bias the fuel assembly downwards.

[0009] A clamping device, for example, is located on a top nozzle and is configured to press against the reactor superplate to push the fuel assembly downwards. The clamping device includes a spring member that generates a force substantially linearly proportional to the deflection of the spring member.

[0010] The clamping force required to prevent fuel assemblies from being pushed off varies with different operating conditions because the hydraulic lift depends on the coolant temperature (since coolant temperature affects coolant density, which in turn affects hydraulic lift) and the volumetric flow rate of coolant through the reactor.

[0011] During cold reactor startup, the high coolant density results in high hydraulic lift and requires high clamping force. In normal power operation, the lower coolant density requires lower clamping force.

[0012] Furthermore, due to the difference in thermal expansion between the fuel assemblies and the reactor vessel, the clamping force generated by the clamping device varies with temperature. For example, an increase in reactor temperature leads to a decrease in the clamping force generated by the clamping device.

[0013] Despite this effect, the clamping force generated by the clamping device during hot operation is usually higher than the required clamping force because the lower coolant density also results in lower hydraulic lift.

[0014] Furthermore, during the service life of the fuel assembly, radiation from the fuel assembly typically leads to a decrease in clamping force due to spring slack. This is compensated for by providing a clamping device that generates a higher clamping force than was required before the fuel assembly began to radiate.

[0015] As a result, the clamping device applied an unnecessarily high level of mechanical stress to the fuel assembly structure, which is one of the main causes of fuel assembly bending.

[0016] The consequences of a bent fuel assembly include difficulties during handling operations such as loading / removing the fuel assembly from the reactor core, and safety issues such as incomplete insertion of control rods into the guide sleeves used to reduce the nuclear reactivity of the fuel assembly. Summary of the Invention

[0017] One of the objectives of this invention is to provide a clamping device that can better adjust the clamping force.

[0018] Therefore, the present invention provides a top nozzle for a nuclear fuel assembly, the top nozzle extending along a nozzle axis and comprising:

[0019] - Lower board;

[0020] - An upper plate that is axially spaced from the lower plate;

[0021] - An intermediate plate axially positioned between the upper and lower plates, which can move axially between the upper and lower positions;

[0022] - One or more main spring components, each main spring component being arranged to permanently push the middle plate towards the upper plate;

[0023] - One or more spring members, each auxiliary spring member being arranged to push the intermediate plate toward the upper plate when the intermediate plate is between the lower position and the intermediate position associated with the auxiliary spring member; and

[0024] - A preload element associated with each auxiliary spring member and arranged such that when the intermediate plate is located between the intermediate position and the upper position associated with the auxiliary spring member, the auxiliary spring member abuts against the upper plate via the preload element.

[0025] The top nozzle, which incorporates this clamping device, allows for better adjustment of the clamping force under various operating conditions and throughout the fuel assembly's service life, thereby reducing the risk of fuel assembly bending.

[0026] The clamping device provides sufficient and customizable clamping force in a cold operating state (e.g., the beginning of an operating cycle), during which the main spring member and at least one auxiliary spring member act to generate clamping force, while allowing the clamping force to be reduced in a hot operating state (e.g., normal operating cycle), during which only the main spring member acts and the auxiliary spring members no longer act on the intermediate plate.

[0027] In a specific embodiment, the top nozzle includes one or more of the following optional features, either individually or in any technically feasible combination:

[0028] - Each preloaded element extends through the middle plate;

[0029] - The lower plate is connected to the upper plate via at least one connecting element, each connecting element extending axially between the lower plate and the upper plate;

[0030] - Each main spring component is assembled onto the connecting element;

[0031] - Each connecting element to which the main spring assembly is assembled is a tube, particularly a guide sleeve;

[0032] - Each auxiliary spring component is assembled onto the connecting element;

[0033] - Each connecting element to which the auxiliary spring assembly is assembled is a tube, particularly a guide sleeve;

[0034] - It includes a retaining member configured to restrict axial movement of the intermediate plate toward the upper plate;

[0035] - To maintain the axial elongation of the member and to include a fixed end that is fixedly attached to one of the lower plate and the upper plate, and to maintain the axial sliding of the member through the other of the lower plate and the upper plate;

[0036] It comprises a tubular lower part and a tubular upper part, which are telescopically mounted on each other along the nozzle axis, an intermediate plate being received in the upper part and fixedly attached to the upper part, and a lower plate being received in the lower part and fixedly attached to the lower part.

[0037] The present invention also relates to a nuclear fuel assembly extending along a longitudinal axis and including a bottom nozzle, a top nozzle as defined above, a guide sleeve extending between and connecting the bottom nozzle and the top nozzle, a nuclear fuel rod located between the bottom nozzle and the top nozzle, and a positioning grid fixedly attached to the guide sleeve, the nuclear fuel rod extending between the bottom nozzle and the top nozzle and passing through the positioning grid. Attached Figure Description

[0038] The invention and its advantages will be better understood by reading the following description, which is given by way of non-limiting example only and with reference to the accompanying drawings, wherein:

[0039] - Figure 1 It is a side elevation view of a nuclear fuel assembly including a top nozzle with a clamping device.

[0040] - Figures 2 to 4 These are cross-sectional views of three different types of clamping devices. Detailed Implementation

[0041] Figure 1 The nuclear fuel assembly 2 includes a bundle of nuclear fuel rods 4 and a frame 6 for supporting the fuel rods 4. The fuel rods 4 extend parallel to each other and parallel to the assembly axis L.

[0042] The skeleton 6 includes a bottom nozzle 8, a top nozzle 10, multiple guide sleeves 12, and multiple positioning grids 14.

[0043] Bottom nozzle 8 and top nozzle 10 are spaced apart along the component axis L. A guide sleeve 12 extends parallel to the component axis L and connects the bottom nozzle 8 to the top nozzle 10, maintaining a predetermined distance between the bottom nozzle 8 and the top nozzle 10 along the component axis L. Fuel rod 4 is received between the bottom nozzle 8 and the top nozzle 10.

[0044] Positioning grids 14 are distributed along the bundle of fuel rods 4. Each positioning grid 14 is fixedly attached to a guide sleeve 12, which extends through the positioning grid 14.

[0045] Fuel rods 4 extend through spaced grids 14. Each positioning grid 14 is configured to support fuel rods 4 at lateral intervals. Each positioning grid 14 is configured to support fuel rods 4 along and transversely to the component axis L.

[0046] During operation, nuclear fuel assembly 2 is inserted into the reactor core within the reactor vessel, located between the lower and upper core plates. The bottom nozzle 8 is configured to press against the lower core plate. The top nozzle 10 is configured to abut against the upper core plate and push the nuclear fuel assembly 2 downwards against hydraulic lift.

[0047] exist Figure 1 As can be seen above, the top nozzle 10 extends along the nozzle axis N. The nozzle axis N coincides with the component axis L.

[0048] The top nozzle 10 includes a lower portion 16 fixedly attached to the guide sleeve 12 and an upper portion 18 movable relative to the lower portion 16 along the nozzle axis N. The upper portion 18 is configured to press against the upper core plate.

[0049] like Figures 2 to 4 As shown, the top nozzle 10 includes a clamping device 20, which is configured to push the upper part 18 upward relative to the lower part 16 along the nozzle axis N.

[0050] Therefore, when the upper part 18 abuts against the upper core plate, the lower part 16 is pushed downward, and the fuel assembly 2 is thus pushed downward to resist the hydraulic lift and press the fuel assembly 2.

[0051] The clamping device 20 includes a lower plate 22, an upper plate 24 axially spaced from the lower plate 22, and an intermediate plate 26 disposed between the lower plate 22 and the upper plate 24. The intermediate plate 26 can be positioned at the upper part ( Figure 2 ) and lower position ( Figure 4 The nozzle moves axially along the nozzle axis N relative to the lower plate 22 and the upper plate 24.

[0052] Preferably, the lower plate 22 and the upper plate 24 are held in a fixed position along the nozzle axis N.

[0053] In one example, the lower plate 22 and the upper plate 24 are connected to each other via a connecting element, and the intermediate plate 26 moves axially between the lower plate 22 and the upper plate 24 and slides along the connecting element.

[0054] Preferably, the lower plate 22 and the upper plate 24 are connected by a connecting element, such that the lower plate 22 and the upper plate 24 are held in their respective fixed positions along the connecting element.

[0055] In a particular embodiment, the upper plate 24 is axially fixed relative to the connecting element and / or the lower plate 22 is permanently pushed downward against at least one lower stop member by at least one elastic member, which restricts the downward movement of the lower plate 22 along the connecting element.

[0056] like Figures 2 to 4 As shown, the connecting element includes, for example, a guide sleeve 12 for nuclear fuel assembly 2.

[0057] The guide sleeve 12 extends through the lower plate 22, the upper plate 24 and the intermediate plate 26.

[0058] The lower plate 22 is held axially along the guide sleeve 12 to limit downward movement of the lower plate 22 relative to the guide sleeve 12.

[0059] In this view, at least one guide sleeve 12, or each guide sleeve 12, is provided with a lower stop member to restrict downward movement of the lower plate 22 along the guide sleeve 12. The lower stop member is, for example, the shoulder 12A of the guide sleeve 12.

[0060] As will be explained later, the lower plate 22 is permanently pushed downward by one or more spring members.

[0061] The upper plate 24 is held in a fixed position, for example, along the axial direction of the guide sleeve 12.

[0062] In this view, the upper plate 24 is mounted on at least one guide sleeve 12 or on each guide sleeve 12, for example, by means of an axially fixed between the upper shoulder 12B of the guide sleeve 12 and a nut 27 screwed onto the external thread of the guide sleeve 12.

[0063] The intermediate plate 26 can slide along the guide sleeve 12 between the lower plate 22 and the upper plate 24.

[0064] The clamping device 20 includes at least one main spring member 28, each main spring member 28 being arranged between the lower plate 22 and the intermediate plate 26 to permanently push the intermediate plate 26 toward the upper plate 24.

[0065] Each main spring component 28 is located at the upper position along the intermediate plate 26. Figure 2 ) and lower position ( Figure 4 It works permanently throughout the entire journey between ( ).

[0066] The lower plate 22 is permanently pushed downward by each main spring member 28, preferably against each lower stop member 12A. Thus, the lower plate 22 is held in a fixed position along the guide sleeve 12.

[0067] The clamping device 20 includes one or more auxiliary spring members 30, each auxiliary spring member 30 being arranged when the intermediate plate 26 is in the lower position and the intermediate position associated with the auxiliary spring member 30. Figure 3 When the middle plate 26 is pushed towards the upper plate 24, the middle position is located between the lower position and the upper position.

[0068] Each auxiliary spring member 30 is arranged to function to push the intermediate plate 26 toward the upper plate 24 when the intermediate plate 26 is between the lower position and the associated intermediate position, and not to function when the intermediate plate 26 is between the associated intermediate position and the upper position.

[0069] When the intermediate plate 26 is located between the lower position and the intermediate position associated with one or more auxiliary spring members 30, the intermediate plate 26 is pushed toward the upper plate 24 by each main spring member 28 and each auxiliary spring member 30 associated with the intermediate position.

[0070] When the intermediate plate 26 is located between the intermediate position and the upper position associated with one or more auxiliary spring members 30, the intermediate plate 26 is pushed toward the upper plate 24 by each main spring member 28, but not by each auxiliary spring member 30 associated with the intermediate position.

[0071] The clamping device 20 includes a preload element 32 associated with each auxiliary spring member 30 and arranged such that when the intermediate plate 26 is located between the intermediate position and the upper position associated with the auxiliary spring member 30, the auxiliary spring member 30 abuts against the upper plate 24 via the preload element 32.

[0072] The preload element 32 associated with each auxiliary spring member 30 is configured such that the auxiliary spring member 30 abutting against the upper plate 24 via the preload element 32 is preloaded.

[0073] The preload element 32 extends through the intermediate plate 26, for example. The auxiliary spring member 30 is located between the lower plate 22 and the intermediate plate 26, and when the intermediate plate 26 is located between the intermediate position and the upper position associated with the auxiliary spring member 30, the auxiliary spring member 30 abuts against the upper plate 24 via the preload element 32 extending through the intermediate plate 26.

[0074] In such an example, advantageously, when the intermediate plate 26 is located between the intermediate position and the lower position associated with the auxiliary spring member 30, the auxiliary spring member 30 abuts against the intermediate plate 26 via the preload element 32.

[0075] Each guide sleeve 12 has an upper axial portion 34 extending axially between the lower plate 22 and the upper plate 24.

[0076] The upper axial portion 34 of each guide sleeve 12 extends through the intermediate plate 26. The intermediate plate 26 is provided with a corresponding opening 26A for the upper axial portion 34 of each guide sleeve 12.

[0077] Each main spring element 28 is, for example, a coil spring, with its lower end abutting against the lower plate 22 and its upper end abutting against the intermediate plate 26.

[0078] Each main spring member 28 is, for example, mounted on the upper axial portion 34 of the guide sleeve 12, such that the main spring member 28 is guided by the upper axial portion 34 of the guide sleeve 12. Each main spring member 28 is, for example, configured as a helical spring that extends around the upper axial portion 34 on which the main spring member 28 is mounted.

[0079] Each auxiliary spring element 30 is, for example, a coil spring, with its lower end abutting against the lower plate 22 and its upper end abutting against the preload element 32.

[0080] Each auxiliary spring member 30 is, for example, fitted onto the upper axial portion 34 of the guide sleeve 12 so as to be guided by the upper axial portion 34 of the guide sleeve 12.

[0081] Each auxiliary spring member 30 is configured, for example, as a helical spring that extends around the upper axial portion 34 to which the auxiliary spring member 30 is mounted.

[0082] Each preload element 32 is, for example, tubular and slidably mounted on the guide sleeve 12, located axially between the auxiliary spring member 30 and the upper plate 24.

[0083] Each preloaded element 32 has, for example: a lower support surface 32A, which is pushed upward by an auxiliary spring member 30; an upper support surface 32B, which abuts against an upper plate 24 when the intermediate plate is between the intermediate position and the upper position; and an actuating support surface 32C, which abuts against the intermediate plate 26 when the intermediate plate 26 is between the intermediate position and the lower position.

[0084] The intermediate plate 26 can slide along the preloaded element 32 between the middle position and the upper position.

[0085] When the intermediate plate 26 is located between the intermediate position and the lower position associated with the auxiliary spring member 30, the auxiliary spring member 30 pushes the intermediate plate 26 via the preload element 32. The auxiliary spring member 30 presses against the lower support surface 32A and the intermediate plate 26 presses against the actuation support surface 32C.

[0086] When the intermediate plate 26 is located between the intermediate position and the lower position associated with the auxiliary spring member 30, the preload element 32 moves downward toward the lower plate 22 together with the intermediate plate 26, so that the preload element 32 no longer abuts against the upper plate 24. Figure 4 ).

[0087] The lower plate 22 is permanently pushed downward by each auxiliary spring member 30, preferably against each lower stop member 12.

[0088] In a preferred example, at different positions, the main spring member 28 and the auxiliary spring member 30 permanently push the lower plate 22 downward, thereby keeping the lower plate 22 against each lower stop member 12A in a fixed position along the guide sleeve 12.

[0089] Optionally, the top nozzle 10 includes a retaining member 40 configured to restrict axial movement of the intermediate plate 26 relative to the lower plate 22 toward the upper plate 24. This retaining member 40 is useful, for example, during installation / removal operations, particularly in the current case, when removing the nut 27.

[0090] The retaining member 40 is axially elongated, and includes a fixed end 42 fixedly attached to one of the lower plate 22 and the intermediate plate 26, the retaining member 40 sliding axially through a hole provided on the other of the lower plate 22 and the intermediate plate 26.

[0091] Optionally, the other end 44 of the retaining member 40 is provided with a stop member 46 for limiting the distance between the lower plate 22 and the intermediate plate 26.

[0092] In one exemplary embodiment, the fixed end 42 is fixedly attached to the intermediate plate 26, the retaining member 40 slides axially through a hole provided on the lower plate 22, and the other end 44 of the retaining member 40 is provided with a stop member 46.

[0093] The lower part 16 of the top nozzle 10 is rigidly connected to the lower plate 22 and the upper part 18 of the top nozzle 10 is rigidly connected to the intermediate plate 26, such that the intermediate plate 26 and the upper part 18 move axially together.

[0094] The lower part 16 and the upper part 18 are preferably tubular and telescopically mounted on each other, with the lower plate 22 received in the lower part 16 and the upper plate 24 and the middle plate 26 received in the upper part 18.

[0095] Now refer to Figures 2 to 4 Describe the operation of the clamping device 20.

[0096] The upper part 18 of the top nozzle 10 is initially in the highest position, so the middle plate 26 is in the upper position adjacent to the upper plate 24.

[0097] When the upper part 18 of the top nozzle 10 abuts against the upper core plate, the upper part 18 tends to move downward, thereby causing the intermediate plate 26 to move downward toward the lower plate 22.

[0098] As long as the intermediate plate 26 is located between the upper position and the intermediate position associated with the auxiliary spring member 30, the main spring member 28 pushes the intermediate plate 26 and the lower plate 22 away from each other, but the auxiliary spring member 30 does not function and does not act on the intermediate plate 26. The clamping force generated by the clamping device 20 is generated solely by the main spring member 28.

[0099] As long as the intermediate plate 26 is located between the upper position and the intermediate position associated with the auxiliary spring member 30, the intermediate plate 26 will not abut against the preload element 32 associated with the auxiliary spring member 30, which abuts against the upper plate 24 via the preload element 32.

[0100] When the intermediate plate 26 reaches the intermediate position associated with the auxiliary spring member 30 and is located between the intermediate position and the lower position, the main spring member 28 and the auxiliary spring member 30 act simultaneously and cooperate to push the intermediate plate 26 upward.

[0101] Below a given intermediate position of the intermediate plate 26, the clamping force generated by the clamping device 20 is jointly generated by the main spring member 28 and each auxiliary spring member 30 associated with the intermediate position or lower intermediate position.

[0102] Therefore, as the intermediate plate 26 moves below each intermediate position, the clamping force generated by the clamping device 20 becomes higher, and due to the preload of the auxiliary spring member 30, the clamping force generated when the intermediate plate 26 passes through the intermediate position exhibits a step.

[0103] Due to the different thermal expansion of the reactor vessel and nuclear fuel assemblies, the intermediate plate 26 tends to move upward relative to the lower plate 22 under normal operating conditions, while it tends to move downward under cold start conditions.

[0104] In the cold start state, the main spring component 28 and the auxiliary spring component 30 work together to provide the maximum clamping force.

[0105] As the temperature rises, the intermediate plate 26 tends to move upward relative to the lower plate 22. The force generated by each auxiliary spring member 30 decreases until the intermediate plate 26 reaches its associated intermediate position and the auxiliary spring members 30 abut against the upper plate 24 via the associated preload element 32.

[0106] At each intermediate position of the intermediate plate 26, the clamping force decreases by a force step corresponding to the preload of the auxiliary spring member 30 associated with that intermediate position.

[0107] Using a clamping device 20 with a step force relative to the upper part of the top nozzle 10, the clamping force follows the load required to prevent the nuclear fuel assembly from being pushed off under different operating conditions.

[0108] The dimensions of the stepped clamping system can be determined such that, during the service life of the fuel assembly, due to the extension of the fuel assembly caused by radiation, the auxiliary spring member 30 becomes active during operation to compensate for the loss of clamping force caused by the relaxation of spring members 28 and 30. The total clamping force can remain relatively constant during the radiation time.

[0109] While preventing fuel assembly jacking during cold starts and hot operation, the stepped clamping system reduces excessive clamping force during normal (hot) operation. Mechanical stress applied throughout the fuel assembly's lifespan is significantly reduced, resulting in less bending of the fuel assembly.

[0110] This invention is not limited to the examples and variations discussed above. Other examples and variations are conceivable.

[0111] In the illustrated example, the lower plate 22 and the upper plate 24 are connected via the guide sleeve 12.

[0112] Alternatively or optionally, the lower plate 22 and the upper plate 24 are connected to each other by a connecting element different from that of the guide sleeve 12. In this case, the main spring member 28 and the auxiliary spring member 30 are optionally mounted on the connecting element for guidance by said connecting element.

[0113] Therefore, in a general manner, the lower plate 22 and the upper plate 24 are connected to each other via a connecting element, and the main spring member 28 and the auxiliary spring member 30 are optionally mounted on the connecting element for guidance by the connecting element.

[0114] Furthermore, the clamping device 20 can be configured such that the clamping force generated by the clamping device 20 moves along the axial direction of the intermediate plate 26 in a single step or several consecutive steps.

[0115] In this view, the clamping device 20 includes, for example, a single intermediate position or several consecutive intermediate positions, at which the clamping force generated by the clamping device 20 presents a step, wherein one or more auxiliary spring members 30 are associated with each intermediate position.

[0116] When consecutive intermediate positions are provided, the intermediate positions are different from each other.

[0117] In one example, the clamping device includes at least a first intermediate position and a second intermediate position different from the first intermediate position, one or more first auxiliary spring members 30 associated with the first intermediate position, and one or more second auxiliary spring members 30 associated with the second intermediate position. The second intermediate position is, for example, lower than the first intermediate position, that is, closer to a lower position than the first intermediate position.

Claims

1. A top nozzle for a nuclear fuel assembly, the top nozzle extending along a nozzle axis and comprising: - Lower plate (22); - An upper plate (24) that is axially spaced from the lower plate (22); - An intermediate plate (26) is axially positioned between the upper plate (24) and the lower plate (22), and the intermediate plate (26) is axially movable between an upper position and a lower position; - One or more main spring members (28), each main spring member (28) being arranged to permanently push the intermediate plate (26) toward the upper plate (24); - One or more auxiliary spring members (30), each auxiliary spring member (30) being arranged to push the intermediate plate (26) toward the upper plate (24) when the intermediate plate (26) is located between the lower position and the intermediate position associated with the auxiliary spring member (30); and - A preload element (32), which is associated with each auxiliary spring member (30) and is arranged such that when the intermediate plate (26) is located between the intermediate position associated with the auxiliary spring member (30) and the upper position, the auxiliary spring member (30) abuts against the upper plate (24) via the preload element (32).

2. The top nozzle according to claim 1, wherein, Each preloaded element (32) extends through the intermediate plate (26).

3. The top nozzle according to claim 1 or 2, wherein, The lower plate (22) is connected to the upper plate (24) via at least one connecting element, each connecting element extending axially between the lower plate (22) and the upper plate (24).

4. The top nozzle according to claim 3, wherein, Each main spring component (28) is assembled onto the connecting element.

5. The top nozzle according to claim 4, wherein, Each connecting element to which the main spring assembly (28) is assembled is a tube.

6. The top nozzle according to claim 4, wherein, Each connecting element to which the main spring assembly (28) is assembled is a guide sleeve (12).

7. The top nozzle according to claim 3, wherein, Each auxiliary spring component (30) is assembled onto the connecting element.

8. The top nozzle according to claim 7, wherein, Each connecting element to which the auxiliary spring component (30) is assembled is a tube.

9. The top nozzle according to claim 7, wherein, Each connecting element to which the auxiliary spring component (30) is assembled is a guide sleeve (12).

10. The top nozzle according to claim 1, comprising a retaining member (40) configured to restrict axial movement of the intermediate plate (26) toward the upper plate (24).

11. The top nozzle according to claim 10, wherein, The retaining member (40) is axially elongated and includes a fixed end (42) fixedly attached to one of the lower plate (22) and the upper plate (24), the retaining member (40) sliding axially through the other of the lower plate (22) and the upper plate (24).

12. The top nozzle according to claim 1, comprising a tubular lower portion (16) and a tubular upper portion (18), the lower portion (16) and the upper portion (18) being telescopically mounted on each other along a nozzle axis (N), the intermediate plate (26) being received within the upper portion (18) and fixedly attached to the upper portion (18), and the lower plate (22) being received within the lower portion (16) and fixedly attached to the lower portion (16).

13. A nuclear fuel assembly extending along a longitudinal axis (L) and including a bottom nozzle (8), a top nozzle (10) according to claim 1, a guide sleeve (12) extending between the bottom nozzle (8) and the top nozzle (10) and connecting the bottom nozzle (8) and the top nozzle (10), a nuclear fuel rod (4) located between the bottom nozzle (8) and the top nozzle (10), and a positioning grid (14) fixedly attached to the guide sleeve (12), the nuclear fuel rod (4) extending between the bottom nozzle (8) and the top nozzle (10) and passing through the positioning grid (14).

Images