Guide tube rod and test piece for critical heat flux density test of guide tube grid element

Abstract

This invention discloses a guide rod and its test piece for testing the critical heat flux density of a guide tube element. The guide rod includes a central core rod and a ceramic sleeve covering the central core rod along its entire length. Positioning pins extending from the central core rod are spaced apart along its length. Each positioning pin has a positioning ring. Two ceramic tube segments, each matching the shape of the positioning ring, are respectively positioned on the upper and lower sides of the positioning ring. The two ceramic tube segments are tightly abutted and together cover the positioning pins and positioning ring. In this invention, the ceramic sleeve covering the central core rod along its entire length provides ideal insulation, ensuring insulation between the guide rod and the heating rod, preventing discharge between them, preventing the heating rod from burning out, and ensuring the smooth conduct of the critical heat flux density test.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power technology. More specifically, this invention relates to a guide tube rod and its test piece for testing the critical heat flux density of a guide tube grid element. Background Technology

[0002] In the safety review of nuclear power plants, critical heat flux density is a crucial limiting thermo-hydraulic parameter, whose magnitude directly affects the safety and economics of the nuclear power plant. By optimizing the structure of nuclear fuel assemblies, the critical heat flux density can be increased, enabling the reactor system to generate maximum thermal power, thereby improving economic efficiency while ensuring the safety and reliability of the nuclear power plant's engineering design.

[0003] In the development of nuclear fuel assemblies, critical heat flux density is one of the key parameters characterizing the thermo-hydraulic performance of nuclear fuel assemblies. Currently, the critical heat flux density of nuclear fuel assemblies cannot be predicted using theoretical methods and can only be obtained through experiments.

[0004] In related technologies, if the guide tube rod in the critical heat flux density test piece of the guide tube grid element is not designed properly, it may cause discharge phenomena with the electrode or other charged heating rods or grids in the vicinity, which may lead to the risk of the heating rod burning. Summary of the Invention

[0005] The purpose of this invention is to overcome the insulation problem between the guide tube rod and the surrounding electrically charged heating rod during the critical heat flux density test of the guide tube grid element, and to provide a guide tube rod and its test piece for the critical heat flux density test of the guide tube grid element, so as to prevent the risk of the heating rod burning.

[0006] To achieve the above objectives, the present invention provides a guide tube rod for testing the critical heat flux density of a guide tube grid element, comprising: a central core rod and an insulating sleeve covering the central core rod along its entire length.

[0007] According to one embodiment of the guide tube rod for the critical heat flux density test of the guide tube grid element of the present invention, the insulating sleeve is a ceramic sleeve.

[0008] According to one embodiment of the guide tube rod for the critical heat flux density test of the guide tube grid element of the present invention, positioning pins extending out of the central core rod are provided at intervals along the length direction of the central core rod. A positioning ring is sleeved on the positioning pin. Two ceramic tube segments adapted to the shape of the positioning ring are respectively provided on the upper and lower sides of the positioning ring, and the two ceramic tube segments closely abut against each other and jointly cover the positioning pin and the positioning ring.

[0009] According to one embodiment of the guide tube rod for the critical heat flux density test of the guide tube grid element of the present invention, one of the ceramic tube segments has a groove at its end and the other ceramic tube segment has a protrusion at its end. The groove is fitted onto the positioning ring from one side and the protrusion extends onto the positioning ring from the opposite side, so that the positioning pin and the positioning ring are completely covered inside the ceramic sleeve. According to one embodiment of the guide tube rod for the critical heat flux density test of the guide tube grid element of the present invention, the central core rod is made of corrosion-resistant metal or metal alloy, such as nickel, nickel-based alloy or stainless steel.

[0010] According to one embodiment of the guide tube rod for the critical heat flux density test of the guide tube grid element of the present invention, the outer diameter of the ceramic sleeve is consistent with the outer diameter of the actual control rod guide tube.

[0011] To achieve the above-mentioned objectives, the present invention also provides a test specimen for the critical heat flux density of a guide tube grid element, which includes a guide tube rod and a heating rod surrounding the guide tube rod, wherein the guide tube rod is the guide tube rod for the critical heat flux density test of the guide tube grid element described above in the present invention.

[0012] According to one embodiment of the critical heat flux density test apparatus for guide tube grid element of the present invention, the top of the guide tube rod is fixed to the upper electrode and is insulated from the upper electrode.

[0013] According to one embodiment of the critical heat flux density test device for guide tube grid element of the present invention, the upper electrode is provided with a through hole, the guide tube rod passes through the through hole and is fastened by a fastener, and an insulating pad is provided between the fastener and the upper electrode.

[0014] According to one embodiment of the test apparatus for critical heat flux density of the guide tube grid element of the present invention, the end of the guide tube rod is suspended.

[0015] Compared with the prior art, the guide tube rod and its test piece for the critical heat flux density test of the guide tube grid element of the present invention have the following advantages: 1) A ceramic sleeve covering the central core rod is provided along its entire length. The ceramic sleeve has ideal insulation properties, which ensures the insulation between the guide tube rod and the heating rod, avoids the discharge phenomenon between the guide tube rod and the heating rod, prevents the heating rod from burning, and ensures the smooth progress of the critical heat flux density test.

[0016] 2) The outer side of the central core rod is covered with ceramic tube segments. The central core rod ensures the strength of the guide tube, while the outer ceramic tube segments ensure the flexibility of the guide tube, so as not to reduce the toughness due to excessive length of ceramic tube. 3) The top of the guide tube is insulated from the upper electrode, and the bottom is suspended and not in contact with conductive parts. The entire length of the guide tube is wrapped with a ceramic sleeve. The triple insulation design ensures that there is no discharge between the guide tube and the surrounding heating rod, effectively ensuring the smooth progress of the experiment. 4) The guide tube is provided with positioning pins at intervals. There are multiple positioning pins on the entire central core rod. The guide tube is divided into multiple segments with the positioning pins as nodes. The positioning pins are all covered inside the ceramic sleeve, which eliminates the risk of metal parts being exposed on the outer surface due to the inconsistent thermal expansion between the metal and ceramic under hot conditions, thus preventing the risk of discharge between the central core rod and the surrounding heating rods. The setting of positioning ring, positioning pins and ceramic tube segments ensures that the entire length of the guide tube is covered inside the ceramic sleeve, ensuring the insulation between the entire length of the guide tube and the heating rod. 5) The outer diameter of the ceramic sleeve is consistent with the outer diameter of the control rod guide tube, ensuring that the sub-channel size between the guide tube rod and the surrounding electric heating rod in the guide tube grid critical heat flux density test piece is consistent with the prototype.

[0017] 6) The segmented arrangement of ceramic sleeves enables mass production of ceramic tubes. Compared to using a whole rod with a single ceramic tube, this reduces production and transportation requirements and enhances the replaceability of ceramic tubes. Attached Figure Description

[0018] The guide tube rod and its test piece for the critical heat flux density test of the guide tube grid element of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a cross-sectional schematic diagram of the guide tube rod used for the critical heat flux density test of the guide tube grid element of the present invention.

[0019] Figure 2 This is a partially enlarged schematic diagram of the guide tube rod used for the critical heat flux density test of the guide tube grid element of the present invention.

[0020] Figure 3 For along Figure 1 Schematic diagram of the cross section along line AA.

[0021] Figure 4 This is a schematic diagram of the heating rod arrangement for the critical heat flux density test specimen of the guide tube grid element of the present invention.

[0022] Figure 5 This is a schematic diagram of the installation of the guide tube rod and the upper electrode in the critical heat flux density test specimen of the guide tube grid element of the present invention.

[0023] In the picture: 1--Central core rod; 2--Ceramic tube segment; 3--Positioning pin; 4--Positioning ring; 5--Ceramic sleeve; 6--Fixing screw; 7--Flat washer; 8--First insulating pad; 9--Upper electrode; 10--Second insulating pad; 11--Washing ring. Detailed Implementation

[0024] To make the objectives, technical solutions, and effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described in this specification are merely for explaining the invention and are not intended to limit the invention.

[0025] Please refer to Figures 1 to 3 As shown, the present invention provides a guide tube rod for testing the critical heat flux density of a guide tube grid element, which includes: a central core rod 1 and an insulating sleeve covering the central core rod 1 along its entire length.

[0026] The central core rod 1 is a slender rod-shaped structure made of a metal or metal alloy with ideal corrosion resistance, such as nickel, nickel-based alloys, or stainless steel. The material of the insulating sleeve is not particularly limited, as long as it can withstand high temperatures and has ideal insulation properties in water. For example, according to one embodiment of the invention, the insulating sleeve is a ceramic sleeve 5, the outer diameter of which is consistent with the outer diameter of the actual control rod guide tube.

[0027] Please refer to this carefully. Figure 2 As shown, positioning holes (not labeled) are provided at regular intervals along the length of the central core rod 1. The positioning ring 4 has mounting holes (not shown) corresponding to these positioning holes. The positioning pin 3 passes through the mounting hole and the positioning hole and extends out of the central core rod 1. Two ceramic tube segments 2, matching the shape of the positioning ring 4, are respectively provided on the upper and lower sides of the positioning ring 4. The end faces of the two ceramic tube segments 2 are tightly abutted and together cover the positioning pin 3 and the positioning ring 4. The positioning pin 3 and the positioning ring 4 can fix the ceramic tube segments 2, preventing the ceramic tube segments 2 from sliding down due to inconsistent axial expansion between them and the central core rod 1, thus avoiding the central core rod 1 being exposed and accumulating at the top of the guide tube, which could lead to leakage and discharge risk.

[0028] According to one embodiment of the present invention, one of the two ceramic tube segments 2 has a groove (not marked) at its end, and the other ceramic tube segment 2 has a protrusion (not marked) at its end. The groove fits onto the positioning ring 4 from top to bottom, and the protrusion extends onto the positioning ring 4 from bottom to top, so that the positioning pin 3 and the positioning ring 4 are completely covered inside the ceramic sleeve 5, so that the positioning ring 4 is insulated from the surrounding heating rod. The groove is stuck on the positioning ring 4 to ensure that the ceramic tube segment 2 will not fall off.

[0029] Understandably, in addition to the aforementioned ceramic tube segment 2 with grooves and ceramic tube segment 2 with protrusions, multiple ceramic tube segments 2 with flat ends are fitted onto the central core rod 1 as needed. At this time, the ceramic tube segment 2 with grooves is installed on the positioning pin 3 and the positioning ring 4. Multiple ceramic tube segments 2 with flat ends are installed on the ceramic tube segment 2 with grooves as needed. Then, a ceramic tube segment 2 with a protrusion is installed on the ceramic tube segment 2 with flat ends. After that, another positioning pin 3 and positioning ring 4 are installed. The two positioning pins 3 form a unit, and the entire guide rod is composed of several units.

[0030] Please refer to Figure 4 As shown, the present invention also provides a test specimen for the critical heat flux density of a guide tube grid element, comprising: a guide tube rod for testing the critical heat flux density of the guide tube grid element of the present invention, and electrically heated rods surrounding the guide tube rod. The guide tube rod for testing the critical heat flux density of the guide tube grid element of the present invention is located in the central position and is used to simulate the guide tube of a non-heat-generating fuel assembly control rod; the outer diameter of the guide tube rod is the same as the outer diameter of the control rod guide tube. Twenty-four electrically heated rods are located around the guide tube rod and are used to simulate nuclear exothermic fuel rods; the outer diameter of the 24 electrically heated rods is the same as the outer diameter of the nuclear fuel rods. The guide tube rod and the surrounding heated rods form a sub-channel to simulate the actual flow path of the fuel assembly guide tube grid element.

[0031] To prevent the guide rod from moving up and down due to fluid impact during the experiment, one end of the guide rod needs to be fixed to the upper electrode 9. Please refer to... Figure 5 As shown, a washer ring 11 and a second insulating pad 10 are installed on the guide rod. The top of the guide rod is inserted into the through hole in the middle of the top nickel plate. A ceramic sleeve 5 is fitted between the guide rod and the positioning hole of the nickel plate. After the guide rod passes through the conductive nickel plate, a first insulating pad 8 and a washer 7 are fitted. A fixing screw 6 is installed at the top to fix the guide rod to the small nickel plate. At this time, the end of the guide rod is suspended and spaced apart from the lower electrode.

[0032] Based on the above description, the insulation design of the guide rod during installation includes: 1) Insulation of the guide rod itself: First, the outer side of the central core rod 1 of the guide rod is covered with a ceramic sleeve 5 to ensure overall insulation; second, the setting of the positioning pin 3 and positioning ring 4 ensures that the entire metal part of the guide rod is completely insulated from the surrounding electric heating rods and grids; 2) Lower insulation design: Compared with other electric heating rods, the guide rod does not have a lower electrode. The bottom of the heating rod is suspended and not connected to the lower electrode. A sufficiently long electrical insulation gap ensures that the guide rod is insulated from the lower electrode; 3) Upper insulation design: The guide rod is fixed to the upper electrode 9 by fixing screws 6. A first insulating pad 8 and a ceramic sleeve 5 are installed between the guide rod and the upper electrode 9, so that there is no direct contact between the guide rod and the upper electrode 9, ensuring the insulation between the guide rod and the upper electrode 9.

[0033] Based on the above detailed description of the embodiments of the present invention, it can be seen that, compared with the prior art, the guide tube grid element critical heat flux density test device and its guide tube rod of the present invention have the following advantages: 1) The setting of positioning pin 3, positioning ring 4 and ceramic tube section 2 ensures that the entire length of the guide tube is covered inside the ceramic sleeve 5, thus ensuring the insulation between the entire length of the guide tube and the heating rod. 2) The top of the guide tube is insulated from the upper electrode 9, and the bottom is suspended and not in contact with conductive parts. The entire length of the guide tube is wrapped with ceramic sleeve 5. The triple insulation design ensures that there is no discharge between the guide tube and the surrounding heating rod, effectively ensuring the smooth progress of the experiment. 3) The outer side of the central core rod 1 is covered with ceramic tube segments 2 in sections. The central core rod 1 ensures the strength of the guide tube rod, and the outer ceramic tube segments 2 ensure the flexibility of the guide tube rod, so that the ceramic sleeve 5 is not too long and thus the toughness decreases. 4) A positioning pin 3 is provided at intervals of the guide tube rod. The positioning pins 3 are all covered inside the ceramic sleeve 5. Multiple positioning pins 3 are provided on the entire central core rod 1. The guide tube rod is divided into multiple segments with the positioning pins 3 as nodes. The metal will expand thermally in the hot state. The positioning pins 3 divide the guide tube rod into multiple segments, eliminating the risk of metal parts being exposed on the outer surface due to the inconsistent thermal expansion between the metal and ceramic in the hot state, which would lead to the risk of discharge between the central core rod 1 and the surrounding electric heating rods. 5) The outer diameter of the ceramic sleeve 5 is consistent with the outer diameter of the control rod guide tube, ensuring that the sub-channel size between the guide tube rod and the surrounding electric heating rod in the guide tube grid critical heat flux density test device is consistent with the prototype.

[0034] 6) The 5-segment arrangement of the ceramic sleeve enables mass production of ceramic tubes. Compared with a whole rod wrapped with a single ceramic tube, it reduces the requirements for production process and transportation, and enhances the replaceability of ceramic tubes.

[0035] Based on the above principles, the present invention can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A guide tube rod for testing the critical heat flux density of a guide tube grid element, characterized in that, include: A central core rod and an insulating sleeve covering the central core rod along its entire length are provided. The insulating sleeve is a ceramic sleeve. Positioning pins extending from the central core rod are provided at intervals along its length. Positioning rings are fitted on the positioning pins. Two ceramic tube segments adapted to the shape of the positioning ring are provided on the upper and lower sides of the positioning ring, and the two ceramic tube segments abut against and jointly cover the positioning pins and positioning rings. One ceramic tube segment has a groove at its end, and the other ceramic tube segment has a protrusion at its end. The groove is fitted onto the positioning ring from one side, and the protrusion extends onto the positioning ring from the opposite side, so that the positioning pins and positioning rings are completely covered within the ceramic sleeve.

2. The guide tube rod for testing the critical heat flux density of the guide tube grid element according to claim 1, characterized in that, The central core rod is made of corrosion-resistant metal or metal alloy.

3. The guide tube rod for testing the critical heat flux density of the guide tube grid element according to claim 1, characterized in that, The outer diameter of the ceramic sleeve is the same as the outer diameter of the actual control rod guide tube.

4. A test specimen, comprising a guide tube and a heating rod surrounding the guide tube, characterized in that, The guide rod is the guide rod used for the critical heat flux density test of the guide tube grid element as described in any one of claims 1 to 3.

5. The test specimen according to claim 4, characterized in that, The top of the guide tube is fixed to the upper electrode and is insulated from the upper electrode.

6. The test specimen according to claim 5, characterized in that, The upper electrode has a through hole, and the guide tube rod passes through the through hole and is fastened by a fastener. An insulating pad is provided between the fastener and the upper electrode.

7. The test specimen according to claim 4, characterized in that, The end of the guide tube is suspended.

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