Abrasion-resistant control rod

Abstract

The anti-abrasion control rod comprises a cladding tube, a lower end plug and an anti-abrasion structure, and the lower end plug is in sealing fit with the lower end of the cladding tube; the anti-abrasion structure comprises a groove for providing a retaining space for solid particles, and the groove is at least formed in the outer surface of the lower end plug; as the control rod moves up and down in the guide pipe, part of solid particles between the control rod and the guide pipe can automatically flow into the groove. According to the anti-abrasion control rod, the anti-abrasion structure is arranged on the outer surface of the control rod, so that the abrasion efficiency of the lower end plug is reduced, and the service life of the control rod is prolonged.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel assembly technology, and more particularly to an anti-erosion control rod. Background Technology

[0002] In a typical nuclear reactor, such as a pressurized water reactor, the reactor core comprises numerous fuel assemblies. Each fuel assembly includes an upper and lower nozzle, with multiple elongated, laterally spaced guide tubes extending longitudinally between nozzles. Multiple lateral support grids are axially spaced along and attached to the guide tubes. Additionally, each fuel assembly includes multiple elongated fuel elements (such as fuel rods), laterally spaced from each other, and the fuel elements and guide tubes are laterally spaced and supported by lateral grids between the upper and lower nozzles. Each fuel rod contains fissile material and is assembled in an array to provide a neutron flux sufficient to support high-rate nuclear fission, releasing heat. Liquid coolant is pumped upwards through the core to absorb some of the heat generated within the reactor core for useful operation.

[0003] Since the rate of heat generation in the reactor core is directly proportional to the rate of nuclear fission, and the rate of nuclear fission is determined by the neutron flux in the core, heat generation during reactor startup, operation, and shutdown is controlled by altering the neutron flux. This is typically achieved by using control rods containing neutron-absorbing material to absorb excess neutrons. Guide sleeves, in addition to serving as structural elements of the fuel assemblies, provide channels for the insertion of control rods into the core. The neutron flux level is generally adjusted by moving the control rods in and out of the guide sleeves, thereby regulating the core's heat output.

[0004] In existing technology, the control rod consists of upper and lower end plugs, an absorber, a spring, and a casing. The lower end plug is generally designed in a streamlined bullet shape. The casing undergoes nitriding treatment to improve its hardness and abrasion resistance. The absorber is made of cadmium-based ternary alloy (AIC, 80% silver, 15% indium, 5% cadmium) or stainless steel. Due to various reasons such as alignment and guide tube bending, the lower end of the control rod casing inevitably erodes against the guide tube, causing the casing to thin and eventually fail. The turning point for casing abrasion occurs when the casing begins to thin, because some oxide particles remain in the gap between the control rod and the guide tube after the casing thins. These oxide particles transform into abrasive particles, accelerating the thinning of the control rod casing. Therefore, to avoid or slow down the abrasion of the control rod casing by oxide particles, it is necessary to improve the structure of the control rod casing. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an improved anti-abrasion control rod.

[0006] The technical solution adopted by the present invention to solve its technical problem is: to provide an anti-abrasion control rod, including a shell tube, a lower end plug and an anti-abrasion structure, wherein the lower end plug is sealed and fitted at the lower end of the shell tube;

[0007] The anti-abrasion structure includes at least one groove that provides a retention space for solid particles, and the groove is provided at least on the outer surface of the lower end plug; as the control rod moves up and down in the guide tube, some of the solid particles between the control rod and the guide tube will automatically flow into the groove.

[0008] In one embodiment, the depth of the groove is ≤3mm.

[0009] In one embodiment, the lower end plug includes a straight tube portion and a tapered portion connected to the straight tube portion, the straight tube portion being connected to the lower end of the casing tube; the groove is disposed on the straight tube portion.

[0010] In one embodiment, the groove is an annular groove disposed along the circumference of the straight tube portion; and / or, the groove is a recessed point dispersedly disposed on the straight tube portion.

[0011] In one embodiment, the groove is also provided on the outer surface of the casing tube.

[0012] In one embodiment, the groove is an annular groove arranged along the circumference of the cladding tube; and / or, the groove is a recessed point dispersed on the cladding tube.

[0013] In one embodiment, the anti-abrasion structure further includes at least a protrusion disposed on the outer surface of the lower end plug.

[0014] In one embodiment, the height of the protrusion is ≤3mm.

[0015] In one embodiment, the protrusion is an annular protrusion arranged circumferentially along the lower end plug; and / or, the protrusion is a series of protrusions distributed on the lower end plug.

[0016] In one embodiment, the protrusion is also provided on the outer surface of the casing tube.

[0017] In one embodiment, the protrusion is an annular protrusion arranged along the circumference of the cladding tube; and / or, the protrusion is a protrusion distributed on the cladding tube.

[0018] In one embodiment, the anti-abrasion control rod further includes an upper end plug, which is sealed to the upper end of the casing tube.

[0019] The present invention also provides another anti-abrasion control rod, including a casing tube, a lower end plug, and an anti-abrasion structure, wherein the lower end plug is sealed to the lower end of the casing tube;

[0020] The anti-abrasion structure includes at least one protrusion, which is disposed at least on the outer surface of the lower end plug to delay the time when the lower end plug contacts the guide tube.

[0021] In one embodiment, the height of the protrusion is ≤3mm.

[0022] In one embodiment, the lower end plug includes a straight tube portion and a tapered portion connected to the straight tube portion, the straight tube portion being connected to the lower end of the casing tube;

[0023] The protrusion is provided on the straight pipe section.

[0024] In one embodiment, the protrusion is an annular protrusion arranged circumferentially along the straight tube portion; and / or, the protrusion is a protrusion distributed on the straight tube portion.

[0025] In one embodiment, the protrusion is also provided on the outer surface of the casing tube.

[0026] In one embodiment, the protrusion is an annular protrusion arranged along the circumference of the cladding tube; and / or, the protrusion is a protrusion distributed on the cladding tube.

[0027] In one embodiment, the anti-abrasion control rod further includes an upper end plug, which is sealed to the upper end of the casing tube.

[0028] The beneficial effects of this invention are: by setting an anti-abrasion structure on the outer surface of the control rod, the abrasion efficiency of the lower end plug is reduced, thereby extending the service life of the control rod. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of the anti-wear control rod according to the first embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the anti-wear control rod according to the second embodiment of the present invention;

[0032] Figure 3A This is a schematic diagram showing the flow direction of solid particles between the control rod and the guide tube in this invention;

[0033] Figure 3B This is a schematic diagram showing the flow direction of solid particles between the control rod and the guide tube without grooves.

[0034] Figure 4 This is a schematic diagram of the anti-wear control rod according to the third embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the diffusion of solid particles within a ring-shaped groove.

[0036] Figure 6 This is a schematic diagram of the anti-wear control rod according to the fourth embodiment of the present invention;

[0037] Figure 7 This is a schematic diagram of the anti-abrasion control rod according to the fifth embodiment of the present invention. Detailed Implementation

[0038] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] refer to Figure 1 , Figure 2 , Figure 4 , Figures 6 to 7 The anti-corrosion control rod of the present invention includes a casing tube 10, a lower end plug 20, and an anti-corrosion structure 40. The lower end plug 20 is sealed to the lower end of the casing tube 10, forming a closed end at the lower end of the casing tube 10. The anti-corrosion structure 40 is at least disposed on the outer surface of the lower end plug 20. By reducing the concentration of solid particles between the lower end plug 20 and the guide tube, the abrasion efficiency of solid particles on the lower end plug 20 is reduced, thereby extending the service life of the control rod; and / or, by delaying the contact time between the lower end plug 20 and the guide tube, the abrasion efficiency on the lower end plug 20 is reduced, thereby extending the service life of the control rod.

[0040] like Figure 1 and Figure 2 As shown, in some embodiments of the present invention, the anti-abrasion control rod has an anti-abrasion structure 40 including at least one groove 41, which provides a retention space for solid particles. Due to various situations such as alignment of the control rod with the guide tube and bending of the guide tube, the lower end of the control rod casing will inevitably and first experience abrasion with the guide tube. Therefore, the groove 41 is at least provided on the outer surface of the lower end plug 20.

[0041] Combination Figure 1 and Figure 3A When the control rod 1 moves up and down in the guide tube 2, the groove 41 moves up and down with the control rod. Some of the solid particles between the control rod 1 and the guide tube 2 will automatically flow into the groove 41, thereby reducing the concentration of solid particles between the control rod 1 and the guide tube 2, and thus reducing the abrasion efficiency of the solid particles on the lower end plug 20.

[0042] Figure 3B The diagram shows the flow of solid particles between control rod 1 and guide tube 2. Without grooves on the surface of control rod 1, solid particles flow and accumulate between control rod 1 and guide tube 2. The high concentration of solid particles will cause abrasion on the surface of control rod 1. Figure 3A and Figure 3B In contrast, the groove 41 on the surface of the control rod 1 diverts some solid particles, reducing the concentration of solid particles between the control rod 1 and the guide tube 2, and reducing the abrasion efficiency of solid particles on the lower plug 20.

[0043] Preferably, the depth of the groove 41 is ≤3mm, which is sufficient to accommodate solid particles without affecting the gap between the control rod and the guide tube, and therefore does not affect the drop time of the control rod.

[0044] The lower end plug 20 of the control rod serves to seal and guide the centering; therefore, the lower end plug 20 is typically designed in a streamlined bullet shape. Further, the lower end plug 20 may include a straight tube portion 21 and a tapered portion 22 connected to the straight tube portion 21. The lower end plug 20 is connected to the lower end of the casing tube 10 via the straight tube portion 21. The lower end plug 20 can be connected to the lower end of the casing tube 10 by at least one of the following methods: snap-fit, interference fit, and welding.

[0045] The groove 41 is preferably provided on the straight tube portion 21 of the lower end plug 20.

[0046] like Figure 1 As shown, in the first embodiment, the groove 41 is provided at the connection between the straight tube portion 21 and the tapered portion 22. When the control rod enters the guide tube, the connection between the straight tube portion 21 and the tapered portion 22 of the lower end plug 20 first contacts the inner wall of the guide tube, and is therefore the first place to be eroded. The groove 41 is provided at this position so that solid particles are introduced into the groove 41 at the same time as the contact, thereby reducing the erosion efficiency at this position and also reducing the concentration of solid particles that enter and erode the surface of the straight tube portion 21 of the lower end plug 20 and the surface of the casing tube 10.

[0047] Figure 1 In the fabrication of the anti-abrasion control rod of the illustrated embodiment, after obtaining the lower end plug 20, pressure is applied to the connection between the straight tube portion 21 and the tapered portion 22 by extrusion or other pressurizing methods, causing the tube wall at the connection to indent inward to form a groove 41; alternatively, after obtaining the lower end plug 20, the groove 41 is punched into the tube wall at the connection between the straight tube portion 21 and the tapered portion 22 by stamping or other methods; or the lower end plug 20 is integrally formed thereon during its molding. The specific fabrication method is determined according to the requirements of the wall thickness of the lower end plug 20 and the depth of the groove 41.

[0048] like Figure 2 As shown, in the second embodiment, a groove 41 is provided at the connection between the straight tube portion 21 and the tapered portion 22, and also on the outer surface of the straight tube portion 21 away from the connection. Compared to Figure 1 In the embodiment shown, the area where the groove 41 is set is larger, further ensuring that the lower end of the control rod, which is prone to abrasion, has more grooves 41 to accommodate solid particles.

[0049] Alternatively, the groove 41 can be an annular groove arranged circumferentially along the straight tube portion 21, or it can be a series of recesses distributed on the straight tube portion 21, or it can be a combination of an annular groove and recesses.

[0050] Figure 2 In the fabrication of the anti-abrasion control rod of the illustrated embodiment, after obtaining the lower end plug 20, pressure is applied to the straight tube portion 21 and the connection between the straight tube portion 21 and the tapered portion 22 by means of extrusion or other pressure methods, causing the tube wall of the straight tube portion 21 and the connection to be recessed inward to form a groove 41; or, after obtaining the lower end plug 20, the groove 41 is punched out on the tube wall of the straight tube portion 21 and the connection between the straight tube portion 21 and the tapered portion 22 by means of stamping or other methods; or, the lower end plug 20 is integrally formed thereon during its molding. The specific fabrication method is determined according to the requirements of the wall thickness of the lower end plug 20 and the depth of the groove 41.

[0051] like Figure 4 As shown, the anti-erosion control rod of the third embodiment of the present invention includes a casing tube 10, a lower end plug 20, and an anti-erosion structure 40. The anti-erosion structure 40 includes at least one groove 41, which provides a retention space for solid particles. In this embodiment, the groove 41 is disposed at the connection between the straight tube portion 21 and the tapered portion 22 of the lower end plug 20, on the outer surface of the straight tube portion 21 away from the connection, and also on the outer surface of the casing tube 10. The depth of the groove 41 is ≤3mm.

[0052] The groove 41 on the outer surface of the casing tube 10 is preferably provided on the outer surface of the lower end of the casing tube 10.

[0053] The groove 41 on the casing tube 10 can be an annular groove arranged along the circumference of the casing tube 10, or it can be a recessed point dispersed on the casing tube 10, or it can be an annular groove and a recessed point distributed together.

[0054] In the above Figure 1 , Figure 2 and Figure 4 In the embodiments shown, when the groove 41 is an annular groove, its space for accommodating solid particles is larger than the space for accommodating solid particles at the concave point. Solid particles entering the annular groove will diffuse circumferentially along the groove, thus preventing accumulation at the entry point of the groove 41 or in one location. Figure 5 As shown, the control rod 1 is usually eccentric within the guide tube 2. Most of the abrasion on the control rod 1 occurs at the contact point between the control rod 1 and the inner wall of the guide tube 2. Solid particles can also enter the groove 41 from the contact point between the control rod 1 and the guide tube 2. When the groove 41 is an annular groove, the solid particles can diffuse circumferentially along the groove 41 after entering (e.g., ...). Figure 5(In the direction indicated by the middle arrow) to make room for subsequent solid particles, and also to allow the groove 41 to accommodate more solid particles, reducing the concentration of solid particles between the control rod 1 and the guide tube 2, thereby reducing the abrasion efficiency of solid particles on the lower end plug 20.

[0055] With a dispersed arrangement of concave dots, solid particles are also dispersed into each concave dot, preventing excessive accumulation in one place. The dispersed arrangement of concave dots includes at least one of circumferential spacing and axial spacing.

[0056] like Figure 6 As shown, the anti-abrasion control rod of the fourth embodiment of the present invention includes a casing tube 10, a lower end plug 20, and an anti-abrasion structure 40. The anti-abrasion structure 40 includes at least one groove 41 and at least one protrusion 42. The groove 41 is used to provide a retention space for solid particles, and the protrusion 42 is used to delay the time when the control rod contacts the guide tube. Both of them effectively reduce the abrasion efficiency of solid particles on the surface of the control rod.

[0057] The depth of groove 41 is ≤3mm; the height of protrusion is ≤3mm.

[0058] The groove 41 can be provided on the outer surface of the lower end plug 20, or on the outer surface of both the lower end plug 20 and the outer surface of the casing tube 10. On the lower end plug 20, the groove 41 is preferably provided on the straight tube portion 21; on the casing tube 10, the groove 41 is preferably provided on the outer surface of the lower end of the casing tube 10.

[0059] The groove 41 can be an annular groove, or a series of dispersed recesses, or a combination of annular grooves and recesses. The protrusion 42 can be an annular protrusion arranged circumferentially along the lower end plug 20 and / or the casing tube 10, or a series of dispersed protrusions on the lower end plug 20 and / or the casing tube 10, or a combination of annular protrusions and protrusions.

[0060] Due to the presence of the groove 41, solid particles near the groove 41 will flow and diffuse into the groove 41, reducing the concentration of solid particles on the outside of the control rod, thereby effectively reducing the wear rate of the control rod. The protrusion 42 delays the contact between the control rod and the guide tube, extending the life of the control rod.

[0061] The groove 41 and the protrusion 42 can be formed by extrusion, stamping, etc. They can be integrally formed on the lower end plug 20 / shell tube 10 during molding, or formed after the lower end plug 20 / shell tube 10 is formed.

[0062] like Figure 7As shown, the fifth embodiment of the anti-erosion control rod of the present invention includes a casing tube 10, a lower end plug 20, and an anti-erosion structure 40. The anti-erosion structure 40 includes at least one protrusion 42, which is disposed at least on the outer surface of the lower end plug 20 to delay the contact time between the lower end plug 20 and the guide tube, thereby reducing the abrasion efficiency of the lower end plug 20 by solid particles.

[0063] The height of protrusion 42 is ≤3mm, which does not affect the gap between the control rod and the guide tube, and therefore does not affect the drop time of the control rod.

[0064] The protrusion 42 is preferably provided on the straight tube portion 21 of the lower end plug 20, and can be located at any position on the straight tube portion 21, including the connection between the straight tube portion 21 and the tapered portion 22, and on the outer surface of the straight tube away from the connection.

[0065] The protrusion 42 can be an annular protrusion arranged along the circumference of the lower end plug 20, or it can be protrusions scattered on the lower end plug 20, or it can be an annular protrusion and protrusions distributed together.

[0066] Depending on the option, the protrusion 42 can also be provided on the outer surface of the casing tube 10, preferably on the outer surface of the lower end of the casing tube 10. On the casing tube 10, the protrusion 42 can be an annular protrusion provided along the circumference of the casing tube 10, or it can be protrusions dispersed on the casing tube 10, or it can be a combination of annular protrusions and protrusions.

[0067] The anti-corrosion control rod of the present invention, after at least preparing the casing tube 10, the lower end plug 20 and the anti-corrosion structure 40, further includes nitriding treatment to improve the hardness, wear resistance and corrosion resistance of the control rod.

[0068] The nitriding treatment of control rods may include the following steps:

[0069] (1) Pretreatment removes oil stains, oxide layers, etc. from the surface of the control rod's casing tube 10 and lower plug 20, improves surface roughness, and ensures uniformity of the nitriding layer.

[0070] Control rods are typically made of zirconium alloy or stainless steel.

[0071] For control rods made of zirconium alloy, pretreatment can be performed using nuclear-grade pickling (such as an HF-HNO3 mixture) to remove the zirconium alloy oxide layer. Then, high-purity water rinsing and vacuum drying are carried out to avoid residual impurities.

[0072] Further preheating can be performed to remove residual moisture and stress; the preheating temperature can be 200℃-300℃.

[0073] (2) Insert the control rod into the nitriding furnace.

[0074] (3) Vacuuming / atmosphere replacement:

[0075] Vacuuming or introducing inert gases (such as nitrogen or argon) removes oxygen from the furnace to prevent oxidation.

[0076] (4) Slowly increase the temperature to the nitriding temperature (depending on the material) to avoid deformation.

[0077] For control rods made of zirconium alloy, the nitriding temperature is 400℃-500℃ to avoid zirconium alloy phase transformation (α→β phase). For control rods made of stainless steel, the nitriding temperature is 500℃-580℃.

[0078] (5) Introduce nitriding medium:

[0079] Ammonia (NH3): decomposes into active nitrogen atoms, which penetrate into the surface of the material.

[0080] Mixed gases: such as NH3+H2 (to adjust nitrogen potential and control the performance of the infiltration layer).

[0081] Temperature: 500℃-580℃; Time: 4-12 hours (affects the thickness of the infiltration layer).

[0082] (6) Cooling:

[0083] Slowly cool with the furnace or in a protective atmosphere to prevent oxidation of the control rod surface.

[0084] (7) Post-processing:

[0085] Depending on the needs, a debrittlement treatment can be selected: the high-hardness nitrided layer is tempered at low temperature (e.g., 300℃-400℃) to reduce brittleness.

[0086] Surface cleaning: Remove any oxide layer or residue that may be present.

[0087] Quality Inspection:

[0088] Hardness testing (microhardness tester).

[0089] Infiltration layer thickness detection (metallographic microscope or microhardness gradient method).

[0090] Corrosion resistance testing (such as salt spray test).

[0091] Eddy current testing: screening for surface cracks.

[0092] XRD analysis: composition of nitrided phases (e.g., ZrN, CrN).

[0093] The above quality inspections can be carried out using existing technical methods, and will not be elaborated further here.

[0094] refer to Figure 1The anti-abrasion control rod of the present invention may further include an upper end plug 30, which is sealed and fitted on the upper end of the casing tube 10, so that the upper end of the casing tube 10 forms a closed end. Thus, the arrangement of the upper end plug 30 and the lower end plug 20 at both ends of the casing tube 10 makes the casing tube 10 form a closed casing.

[0095] It is understood that the anti-abrasion control rod may also include an absorber (not shown) and a spring (not shown) housed in the casing tube 10, etc. For details, please refer to the control rods in the prior art, which will not be described in detail here.

[0096] In summary, by setting an anti-abrasion structure on the surface of the control rod, the present invention reduces the abrasion efficiency of the control rod cladding, extends the life of the control rod, and thus significantly reduces the amount of solid waste generated by nuclear power plants.

[0097] As the lifespan of control rods increases, the number of control rods required for the entire lifespan of a nuclear power unit will decrease significantly, reducing nuclear power operating costs.

[0098] This invention can be widely applied to CPR, HPR, EPR, AP1000 units or other reactors that use rod-shaped reactive control elements, and has broad market demand.

[0099] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An anti-abrasion control rod, characterized in that, It includes a casing tube, a lower end plug, and an anti-abrasion structure, wherein the lower end plug is sealed to the lower end of the casing tube; The anti-abrasion structure includes at least one groove that provides a retention space for solid particles, and the groove is provided at least on the outer surface of the lower end plug; as the control rod moves up and down in the guide tube, some of the solid particles between the control rod and the guide tube will automatically flow into the groove.

2. The anti-wear control rod according to claim 1, characterized in that, The depth of the groove is ≤3mm.

3. The anti-wear control rod according to claim 1, characterized in that, The lower end plug includes a straight tube section and a tapered section connected to the straight tube section, the straight tube section being connected to the lower end of the casing tube; The groove is provided on the straight pipe section.

4. The anti-wear control rod according to claim 3, characterized in that, The groove is an annular groove arranged along the circumference of the straight pipe section; and / or, the groove is a recessed point distributed on the straight pipe section.

5. The anti-wear control rod according to claim 1, characterized in that, The groove is also provided on the outer surface of the casing tube.

6. The anti-wear control rod according to claim 5, characterized in that, The groove is an annular groove arranged along the circumference of the cladding tube; and / or, the groove is a recessed point dispersed on the cladding tube.

7. The anti-wear control rod according to any one of claims 1-6, characterized in that, The anti-abrasion structure also includes at least a protrusion disposed on the outer surface of the lower end plug.

8. The anti-wear control rod according to claim 7, characterized in that, The height of the protrusion is ≤3mm.

9. The anti-wear control rod according to claim 8, characterized in that, The protrusion is an annular protrusion arranged along the circumference of the lower end plug; and / or, the protrusion is a protrusion distributed on the lower end plug.

10. The anti-wear control rod according to claim 8, characterized in that, The protrusion is also provided on the outer surface of the casing tube.

11. The anti-wear control rod according to claim 10, characterized in that, The protrusion is an annular protrusion arranged along the circumference of the cladding tube; and / or, the protrusion is a protrusion distributed on the cladding tube.

12. The anti-wear control rod according to any one of claims 1-6, characterized in that, The anti-abrasion control rod also includes an upper end plug, which is sealed to the upper end of the casing tube.

13. An anti-abrasion control rod, characterized in that, It includes a casing tube, a lower end plug, and an anti-abrasion structure, wherein the lower end plug is sealed to the lower end of the casing tube; The anti-abrasion structure includes at least one protrusion, which is disposed at least on the outer surface of the lower end plug to delay the time when the lower end plug contacts the guide tube.

14. The anti-wear control rod according to claim 13, characterized in that, The height of the protrusion is ≤3mm.

15. The anti-wear control rod according to claim 13 or 14, characterized in that, The lower end plug includes a straight tube section and a tapered section connected to the straight tube section, the straight tube section being connected to the lower end of the casing tube; The protrusion is provided on the straight pipe section.

16. The anti-wear control rod according to claim 15, characterized in that, The protrusion is an annular protrusion arranged along the circumference of the straight pipe section; and / or, the protrusion is a protrusion distributed on the straight pipe section.

17. The anti-wear control rod according to claim 13 or 14, characterized in that, The protrusion is also provided on the outer surface of the casing tube.

18. The anti-wear control rod according to claim 17, characterized in that, The protrusion is an annular protrusion arranged along the circumference of the cladding tube; and / or, the protrusion is a protrusion distributed on the cladding tube.

19. The anti-wear control rod according to claim 13 or 14, characterized in that, The anti-abrasion control rod also includes an upper end plug, which is sealed to the upper end of the casing tube.

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