CN108695004A - Waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type - Google Patents

Abstract

Include hydraulic buffer cylinder, compressed spring and its base baffle, visualization casing, passive shut-down rod lower end plug structure on inlet piping flanges the invention discloses a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type;Wherein hydraulic buffer cylinder is divided into two parts up and down by compressed spring base baffle, and lower part is equidistantly uniformly provided with one group of inlet opening circumferential, and top is equidistantly provided with three groups of pressure relief vents in circumferential direction, and upper end is processed as tapered through-hole;Passive shut-down rod lower end plug structure includes the bottom end cover of damping block and cone, and wherein damping block is circumferentially equidistantly provided with one group of through flow hole, and passive shut-down rod intermediate casing is connected above damping block;The present invention combines necking down Transition Design and compressed spring, significantly reduces the total rod drop time of passive shut-down rod;Radial clearance intake design makes coolant velocity distribution more uniform simultaneously, improves the suspension stability of passive shut-down rod.

Description

Hydraulic Buffer Structure for Hydrodynamic Suspension Passive Shutdown Experimental Device

technical field

The invention belongs to the technical field of performance verification test research on protection system equipment of a nuclear power plant, and in particular relates to a hydraulic buffer structure for a hydraulic suspension type passive shutdown experimental device.

technical background

The hydraulic suspension passive shutdown experimental device is a platform for experimental research on the dynamic characteristics of the sodium-cooled fast reactor hydraulic suspension passive shutdown device using water as a substitute for sodium. The hydraulic suspension passive shutdown device is an emergency shutdown protection device for sodium-cooled fast reactors. When accidents and other working conditions cause the coolant flow rate to drop enough to keep the control rods suspended, the control rods will drop to the core position to shut down the reactor. It can be seen from the working principle that the action of the suspended control rod is based on the change of the flow rate. After each experiment is triggered, the control rod model will fall from the steady-state suspended position in a free-fall manner. When it falls to the bottom of the visualization casing, it may have the highest The speed reaches 4.43m/s, and the quality of the control rod model is about 18kg. Such a high speed and mass will cause impact damage to the flow regulator and the inlet flange structure at the bottom of the visualization casing, so it is necessary to install a The buffer device slows down the impact of the falling rod of the control rod model, and protects the lower end plug of the control rod model, the flow regulator and the inlet flange structure from damage. At the same time, due to the need to carry out repeated tests to test the dynamic response characteristics and the reliability of the action of the hydraulic suspension passive shutdown device, the buffer device should also be able to work for a long time in a water environment of 90 °C without any degradation in performance .

The basic principle of the rod drop buffer device for control rod accidents is to convert the kinetic energy of the falling control rod assembly into the internal energy, potential energy or strain energy of the buffer structure through various designs, reduce the impact force, and protect the control rod assembly and the cladding tube structure. Destruction occurs.

The traditional commercial water reactor nuclear power plant reactor control rod buffer device is to set a section of reduced diameter at the end of the control rod guide tube in the fuel assembly or to set the inner hole of the buffer plug, such as Chinese patents CN103971760A and CN105761765A, which are extruded by the control rod at the end of the rod drop The coolant in the guide tube generates an upward fluid force, which acts as a buffer for the control rod drive wire mechanism. The structure is simple, but it is only applicable to rod bundle control rod assemblies, and cannot be extended to control rod assemblies with other structural properties such as hydraulic suspension passive shutdown devices.

A new generation of advanced nuclear reactors often needs to adopt different control rod buffer structures according to the specific structural design. For example, Chinese patent CN103413577A proposes a thin-walled cylinder buffer for buffering the impact of falling control rods in high-temperature gas-cooled reactors. When an axial drop impact occurs, the thin-walled cylinder is compressed by the impact ring to produce plastic buckling deformation to absorb the impact energy. , so as to protect the structure under the base from damage. This design is a one-time buffer structure that sacrifices the buffer to protect the base structure, and is not suitable for hydraulic suspension passive shutdown devices that require long-term repetitive actions. Chinese patent CN102280146A aims at high-temperature gas-cooled reactors. The hybrid retarder with permanent magnet damping components and electromagnetic damping components needs to be installed on the transmission shaft of the control rod drive line, so that the speed of falling rods can be effectively controlled in the event of an accident. However, the control rods in the hydraulic suspension passive shutdown device operate independently from the control rod drive line in a passive state when the reactor is running, so the retarder cannot be used.

As another example, Chinese patent CN103646673A discloses a rod drop system and method of a control rod drive mechanism. The system is connected with a sleeve of a screw transmission mechanism composed of a rotating friction disc and a friction plate through a chain and a fixed pulley, and the control rod falls. When sticking, the chain drives the guide rod of the sleeve to move, and the guide rod is effectively buffered and fully damped by the screw transmission mechanism. The system is designed for the molten salt reactor structure, and the control rod operating head is always connected with the chain, so it is not suitable for the hydraulic suspension passive shutdown device where the control rods operate independently.

As another example, Chinese patent CN106653104A discloses a reactivity control mechanism for liquid heavy metal cooling reactors, the design of the rod drop buffer mechanism included in it is similar to that of traditional water reactor nuclear power plants. The zone provides fall guidance and cushioning for the control rod assembly. This structure is only applicable to the rod bundle control rod assembly, without considering the large coolant flow in the control rod guide tube and the suspension maintenance at the low working position, so it is also not suitable for the hydraulic suspension passive shutdown device.

In order to meet the needs of rod drop buffering in the hydraulic suspension passive shutdown experimental device, our research team once designed and processed a straight-through hydraulic buffer, as shown in Figure 1, including: hydraulic buffer 1', visualization sleeve Pipe 2', control rod guide pipe 3', limit mechanism 4', upper header' and passive shutdown rod model 6'; the principle is that the coolant enters the visualization sleeve directly from the through hole in the center of the hydraulic buffer 1' The pipe 2' and the control rod guide pipe 3' flow upward to provide hydraulic thrust to maintain the passive shutdown rod model 6' suspended in the upper working position; when the rod drop test is carried out, the flow rate drops, and the passive shutdown rod model 6' is under the action of gravity Insert it into the hydraulic buffer 1', compress the buffer spring and the coolant inside and below the buffer to convert the impact energy until the drop of the rod is terminated. However, in its experiments and calibration calculations, it was found that this design has a greater impact on the suspension stability of the control rods due to uneven water intake, which increases the uncertainty of the experimental data measurement, and there will be obvious water when the rods are dropped. The hammer effect is not conducive to protecting the safety of the test section and the centrifugal pump. In view of the foregoing, it is currently necessary to improve this straight-through hydraulic buffer.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art, and to provide a long-term reliable use at high temperatures to achieve effective deceleration and buffering of falling rods, to ensure stable suspension of control rods and to suppress water hammer effects, suitable for sodium-cooled fast The hydraulic buffer of the reactor hydraulic suspension passive shutdown experimental device.

The purpose of the present invention is achieved by adopting the following technical solutions:

A hydraulic buffer structure for a hydraulic suspension type passive shutdown experimental device, the buffer structure includes a hydraulic buffer and a passive shutdown rod model lower end plug structure set in the visualization sleeve 15; the hydraulic buffer Including the hydraulic buffer cylinder 7, the hydraulic buffer cylinder 7 is vertically installed on the center of the upper end face of the inlet pipe flange 2 of the visualization sleeve 15, the lower end of the hydraulic buffer cylinder 7 is the coolant inlet channel 1, and the hydraulic buffer cylinder The barrel 7 is divided into upper and lower parts by the compression spring base baffle 4 inside, the lower part is provided with a number of water inlet holes 3 in the circumferential direction, and the upper part is provided with a number of pressure relief holes 9 in the circumferential direction, and the end of the upper part is processed into a tapered through hole. Hole 8; one end of cylindrical compression spring 5 is fixed on compression spring base baffle plate 4, and the other end is connected with buffer washer 6; the lower end plug structure of passive shutdown rod model includes damping block 12 and lower end cover 11 arranged at the lower end of damping block 12 , wherein the damping block 12 is evenly spaced with a number of flow holes along the circumferential direction to ensure that the shutdown rod model will not float up under low flow conditions, and the middle casing 13 of the passive shutdown rod model is connected above the damping block 12. The outer diameter of the damping block 12 is smaller than the inner diameter of the hydraulic buffer cylinder 7, the outer diameter of the intermediate sleeve 13 of the passive shutdown rod model is larger than the inner diameter of the hydraulic buffer cylinder 7, and the length of the hydraulic buffer cylinder 7 is shorter than the damping block 12 and the lower end cover 11 The sum of the lengths; several absorber rod models 14 arranged in an equilateral triangle are compressed and fixed in the middle casing 13 of the passive shutdown rod model, and as the passive shutdown rod model falls along the direction of gravity, the damping block 12 and the lower end The cover 11 can be guided and inserted into the corresponding hydrodynamic damper cylinder 7 .

The water inlet holes 3 are keyway-shaped holes, the number is M, and the M is an even number greater than or equal to 2. The water inlet holes are evenly distributed along the circumferential interval of 360°/M at the lower part of the hydraulic buffer cylinder 7, and the water inlet holes The upper edge of the hole 3 is flush with the lower end surface of the compression spring base baffle plate 4 , and the total cross-sectional area of the flow channel provided by the water inlet hole 3 is not less than one-third of the cross-sectional area of the coolant inlet flow channel 1 .

The pressure relief holes 9 are circular holes, 12 in number, arranged in three rows at a certain interval along the upper part of the hydraulic buffer cylinder 7, and each row of 4 pressure relief holes is evenly distributed along the circumferential interval of 90°. The diameter of each pressure relief hole 9 ranges from 0.5 mm to 2 mm.

The tapered through hole 8 is located at the upper end of the hydraulic buffer cylinder 7, and the included angle with the axial direction is 15°, and the upper edge is processed as a reduced inlet section with a 0.5mm rounded corner, and the lower edge is processed with a rounded corner transition.

The outer diameter of the cylindrical compression spring 5 matches the inner diameter of the hydraulic buffer cylinder 7, the free height is lower than the lower end of the tapered through hole 8, the two ends of the cylindrical compression spring 5 are ground flat, and the lower end is welded on the compression spring base baffle plate 4 The end face is concentric with the cylinder 7 of the hydraulic buffer, and the upper end is bonded with the buffer washer 6 with waterproof glue, and reinforced by winding steel wire; the buffer washer 6 is a circular right-angled triangle section, and the hypotenuse is connected with the lower end cover 11 of the passive shutdown rod model To match, preferably, the inner angle of the hypotenuse is 15-30°.

The outer diameter of the hydraulic buffer cylinder 7 matches the inner diameter of the inlet flange of the visualization sleeve 15 .

The lower end cap 11 is a conical structure, and the lower end caps with different cone angles can be replaced for experimental research; the damping block 12 is a cylindrical thin tube structure with a wall thickness of 2-4mm, and the height of the damping block 12 is 100% of its outer diameter. 2-4 times, the damping block 12 is uniformly spaced circularly with a number of circular flow holes, the diameter of each flow hole is 5-10mm, and the flow hole is of any shape; the lower end cover 11 and the damping block 12, damping The block 12 and the intermediate sleeve 13 of the passive shutdown rod model are coaxially connected by pipe threads, and the outer diameter gradually increases from bottom to top. Machining has a chamfer transition.

The material of the visualization sleeve 15 is plexiglass, the material of the cylindrical compression spring 5 is manganese steel and the outer surface is treated with antirust, the material of the buffer gasket 6 is silicon rubber, the material of the absorber rod model 14 is nylon, and other structural materials are 304 Stainless steel.

During the test, the coolant enters the visualization casing flow path 10 in the visualization casing 15 from the coolant inlet flow path 1 through the water inlet hole 3, and flows from bottom to top to keep the passive shutdown rod model suspended in the working position; when the flow rate drops to When the fluid force is smaller than the gravity, the passive shutdown rod model begins to fall, and the lower end cover 11 first enters the hydraulic buffer cylinder 7 along the tapered through hole 8, and squeezes out the coolant in the upper inner hole of the hydraulic buffer cylinder 7 , to realize the hydraulic buffer function, as the damping block 12 is further inserted into the hydraulic buffer cylinder 7, the lower end cover 11 starts to contact the buffer washer 6, and the deceleration and buffering are realized by the action of the cylindrical compression spring 5, which is optimized by the double action of the shrinking diameter and the compression spring cushioning effect.

The present invention has the following advantages and beneficial effects:

1. The hydraulic buffer of the present invention organically combines the neck transition design and the compression spring, which significantly reduces the drop time of the passive shutdown rod and realizes effective deceleration and buffering of the drop rod.

2. The hydraulic buffer cylinder adopts a circular gap water inlet design to make the coolant velocity distribution more uniform and greatly improve the suspension stability of the passive shutdown rod.

3. The design of the flow hole of the damping block can not only prevent the accidental floating of the shutdown rod during low-flow refueling conditions, but also effectively reduce the rod drop time.

4. Both the passive shutdown rod and the hydraulic buffer are located in the visible sleeve, which can observe and measure the entire rod drop buffering process.

5. The structural design is reasonable, and it can be used reliably for a long time in a high temperature environment (90°C) without performance attenuation.

In short, the device of the present invention can effectively decelerate and buffer the shutdown rods, protect related components and structures, and has reasonable design, simple structure, durability, high efficiency and reliability, integrated design saves space, and is suitable for assembly in hydraulic suspension passive shutdown Heap experimental setup.

Attachment description

Fig. 1 is a three-dimensional cross-sectional view of the overall structure of a hydrodynamic suspension passive shutdown experimental device in the prior art.

Fig. 2 is a three-dimensional cross-sectional view of the hydraulic buffer structure used in the hydraulic suspension passive shutdown experimental device according to the present invention.

Detailed ways

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 2, a hydraulic buffer structure for a hydraulic suspension type passive shutdown experimental device according to the present invention includes an inlet pipe flange 2, a water inlet hole 3, a compression spring base baffle plate 4, a cylinder compression Spring 5, buffer washer 6, hydraulic buffer cylinder 7, tapered through hole 8, pressure relief hole 9, lower end cover 11, damping block 12, passive shutdown rod model middle sleeve 13 and visualization sleeve 15.

What Fig. 2 shows is the structural representation of hydraulic buffer of the present invention and supporting parts, and hydraulic buffer cylinder 7 is vertically welded on inlet pipe flange 2 upper end face center, organic glass system hexagonal visualization sleeve pipe 15 and inlet pipe method Flange 2 is installed vertically through a flange connection with a positioning key, and is double-sealed with a Y-ring and an O-ring. The inside of the cylinder 7 of the hydraulic buffer is divided into upper and lower parts by the compression spring base baffle plate 4, and the lower part is provided with M keyway-shaped water inlet holes 3 in the circumferential direction, where M is an even number greater than or equal to 2, and each water inlet hole is arranged along the circumferential direction. Evenly distributed at an interval of 360°/M, the upper edge of the water inlet hole is flush with the lower end surface of the compression spring base baffle plate 4, and the total cross-sectional area of the flow channel provided by the water inlet hole 3 should not be less than one-third of the cross-sectional area of the coolant inlet flow channel 1 One; the upper part has 12 circular pressure relief holes 9 in the circumferential direction, which are arranged in three rows at a certain interval along the circumferential direction, and 4 pressure relief holes in each row are evenly distributed along the circumferential direction at intervals of 90°, and each pressure relief hole 9 The recommended hole diameter is 0.5mm-2mm; the upper end is processed as a tapered through hole 8, and the angle with the axial direction is 15°, and the upper edge is processed as a reduced inlet section with a 0.5mm fillet, and the lower edge is processed with a 10mm round corner transition.

The outer diameter of the manganese steel cylindrical compression spring 5 matches the inner diameter of the hydraulic buffer cylinder 7, the free height is lower than the lower end of the tapered through hole 8, the two ends of the cylindrical compression spring 5 are ground flat, and the lower end is welded to the compression spring base baffle plate The upper end face is concentric with the hydraulic buffer cylinder 7, and the upper end is bonded with the buffer washer 6 with waterproof glue, and is reinforced by winding steel wire. The silicone rubber buffer washer 6 is an annular right-angled triangle cross-section, and the hypotenuse matches the lower end cover 11 of the passive shutdown rod model. It is recommended that the inner angle of the hypotenuse be 15-30°.

The main structure of the passive shutdown rod model is made of 304 stainless steel cold-drawn tube, the lower end plug structure includes the lower end cover 11 and the damping block 12, and the lower end cover 11 is processed into a conical structure to increase the suspension stability and the falling speed of the rod , and the lower end caps with different cone angles can be replaced for experimental research; the damping block 12 is a cylindrical thin tube structure with a wall thickness of 2-4mm, the height of the damping block 12 is 2-4 times its outer diameter, and the damping block 12 is cylindrical A number of circular flow holes are evenly spaced in the circumferential direction to ensure that the shutdown rod model will not float up under low flow conditions. The preset diameter of each flow hole is 5-10mm, and the flow holes can also be any other The shape is not limited to circle. The upper part of the damping block 12 is connected to the intermediate sleeve 13 of the passive shutdown rod model, and several nylon absorber rod models 14 arranged in an equilateral triangle are compressed and fixed in the intermediate sleeve of the passive shutdown rod model, and the passive shutdown rod The model falls along the direction of gravity, and the damping block 12 and the lower end cover 11 can be guided and inserted into the corresponding hydraulic buffer cylinder 7 . The lower end cover 11 and the damping block 12, the damping block 12 and the intermediate sleeve 13 of the passive shutdown rod model are coaxially connected by pipe threads, and the outer diameter gradually increases from bottom to top. The middle casing 13 of the model is processed with suitable chamfer transition near the connection; the outer diameter of the damping block 12 is smaller than the inner diameter of the hydraulic buffer cylinder 7, and the outer diameter of the intermediate casing 13 is larger than the inner diameter of the hydraulic buffer cylinder 7.

The outer diameter of the hydraulic buffer cylinder 7 matches the inner diameter of the inlet flange of the visualization sleeve 15, and the length of the hydraulic buffer cylinder 7 is less than the sum of the lengths of the passive shutdown rod model damping block 12 and the lower end cover 11.

In practical application, the hydraulic buffer is an integral structure assembled together, and is located in the visualization sleeve 15. The coolant flows from the inlet flow channel 1 through the water inlet hole 3 into the visualization sleeve flow channel 10 evenly, from bottom to bottom. The upper flow keeps the passive shutdown rod model suspended at the working position; when the flow rate drops to a point where the fluid force is smaller than gravity, the passive shutdown rod model begins to fall, and the lower end cover 11 first enters the hydraulic buffer circle along the tapered through hole 8 Cylinder 7 squeezes out the coolant in the upper inner hole of the hydraulic buffer cylinder 7 to realize the hydraulic buffer function. As the damping block 12 is further inserted into the hydraulic buffer cylinder 7, the lower end cover 11 begins to contact the buffer washer 6, and the cylinder The compression spring 5 provides elastic damping and deceleration buffering, and optimizes the buffering effect through the double action of the diameter reduction and the compression spring.

After being used in a hydraulic suspension passive shutdown experimental circuit and measuring and analyzing the speed and force at the end of the drop rod during the experiment, it is proved that the design of the hydraulic buffer can meet the relevant experimental requirements and protect the passive shutdown. The rod model and casing structure are not damaged. After several tests, the hydraulic buffer and the lower end cover of the passive shutdown rod were observed, and no obvious damage or wear was found. And because of its simple and compact design, it greatly saves the test cost and reduces the required height of the test section. Therefore, the invention is very suitable for assembly and use of a hydraulic suspension type passive shutdown experiment device.

The above content is only used to illustrate the present invention, and it can not be determined that the specific embodiment of the present invention is limited thereto. For those of ordinary skill in the technical field of the present invention, as long as various changes and modifications are made to the present invention without departing from the essence of the present invention All should be regarded as within the scope of the claims of the present invention and their equivalent technologies.

Claims (8)

1. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type, which is characterized in that the buffering Structure includes:Setting hydraulic buffer and passive shut-down rod model lower end plug structure in visualization casing (15);The water Power buffer includes hydraulic buffer cylinder (7), and hydraulic buffer cylinder (7) is vertically mounted on the import of visualization casing (15) Pipe flange (2) upper surface center, hydraulic buffer cylinder (7) lower end are coolant inlet runner (1), hydraulic buffer cylinder (7) two parts, lower part up and down are divided by the compressed spring base baffle (4) in it and are being arranged circumferentially several inlet openings (3), Top is provided with several pressure relief vents (9) in circumferential direction, and upper end is processed as tapered through-hole (8);Cylindrical compression spring (5) one end is solid It is scheduled on compressed spring base baffle (4), the other end is connected with buffer gasket (6);Passive shut-down rod model lower end plug structure Including damping block (12) and setting in the bottom end cover (11) of damping block (12) lower end, wherein damping block (12) is circumferentially equidistantly equal Even shut-down rod model when being provided with several through flow holes to ensure low discharge operating mode will not float, and connection is passive above damping block (12) Shut-down rod model intermediate casing (13), damping block (12) outer diameter are less than hydraulic buffer cylinder (7) internal diameter, passive shutdown Stick model intermediate casing (13) outer diameter is more than hydraulic buffer cylinder (7) internal diameter, and hydraulic buffer cylinder (7) length is less than damping The sum of block (12) and bottom end cover (11) length;The absorber stick model (14) of several positive triangles arrangement is pressed abd fixed on passive In shut-down rod model intermediate casing (13), and as passive shut-down rod model falls along gravity direction, damping block (12) and under End cap (11) can be guided insertion in corresponding hydraulic buffer cylinder (7).

2. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type according to claim 1, It is characterized in that, the inlet opening (3) is key-way shape hole, quantity is M, and the M is the even number more than or equal to 2, each inlet opening Along hydraulic buffer cylinder (7) lower part, circumferentially spaced-apart 360 °/M is uniformly distributed, and inlet opening (3) top edge is kept off with compressed spring pedestal Plate (4) lower face flushes, and total cross section of fluid channel product that the inlet opening (3) provides is not less than coolant inlet runner (1) sectional area One third.

3. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type according to claim 1, It is characterized in that, the pressure relief vent (9) is the round hole of pore diameter range 0.5mm-2mm, quantity is 12, is justified along hydraulic buffer Cylinder (7) top is set with three arrangement of a determining deviation point, is often arranged circumferentially spaced 90 ° of 4 pressure relief vents and is uniformly distributed.

4. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type according to claim 1, It is characterized in that, the tapered through-hole (8) is located at hydraulic buffer cylinder (7) upper end, it is 15 ° with axial angle, and Top edge is processed as the decrement inducer with 0.5mm fillets, and lower edge is machined with 10mm round-corner transitions.

5. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type according to claim 1, It is characterized in that, cylindrical compression spring (5) outer diameter matches with hydraulic buffer cylinder (7) internal diameter, free height is less than Tapered through-hole (8) lower end, cylindrical compression spring (5) both ends polish, and lower end is welded on compressed spring base baffle (4) upper end Face, upper end waterproof glue sticking buffer gasket (6) concentric with hydraulic buffer cylinder (7), and reinforced using steel wire winding;Institute It states buffer gasket (6) and uses silastic material, annular right-angle triangular-section, bevel edge interior angle angle and passive shut-down rod model Bottom end cover (11) angle of taper matches.

6. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type according to claim 1, It is characterized in that, the visualization casing (15) uses pmma material, inside and outside is regular hexagon structure, hydraulic buffer Cylinder (7) outer diameter matches with visualization casing (15) suction flange internal diameter.

7. a kind of waterpower buffer structure for the passive shutdown experimental provision of hydraulic suspension type according to claim 1, It is characterized in that, the bottom end cover (11) is conical structure, and the replaceable bottom end cover with different cone angle carries out experiment and grinds Study carefully;Damping block (12) is the thin barrel structure of cylinder, and wall thickness 2-4mm, the height of damping block (12) is 2-4 times of its outer diameter, damping Block (12) cylinder is circumferential to be equidistantly uniformly provided with several round through flow holes, a diameter of 5-10mm of each through flow hole;Bottom end cover (11) It is coaxially connected by pipe screw thread between damping block (12), damping block (12) and passive shut-down rod model intermediate casing (13), Outer diameter gradually increases from bottom to top, all adds close to junction in bottom end cover (11) and passive shut-down rod model intermediate casing (13) Work has chamfered transition.

8. a kind of according to any one of claim 1~7 is for the passive shutdown experimental provision of hydraulic suspension type Waterpower buffer structure, it is characterised in that:Coolant enters through inlet opening (3) from coolant inlet channel (1) and visualizes when experiment Visualization casing runner (10) in casing (15), from bottom to top flowing maintain passive shut-down rod model to be suspended in working position It sets;When flow drops to fluid force less than gravity, passive shut-down rod model starts to fall, and bottom end cover (11) is at first along tapered Shape through-hole (8) enters hydraulic buffer cylinder (7), squeezes out the coolant in the endoporus of hydraulic buffer cylinder (7) top, realizes Waterpower pooling feature, as damping block (12) is further inserted into hydraulic buffer cylinder (7), bottom end cover (11) starts and cushion pad (6) contact is enclosed, is acted on by cylindrical compression spring (5) and realizes deceleration buffer, is optimized by undergauge and compressed spring double action slow Rush effect.