JPH0662398U - Fuel rod holding cylinder fixing mechanism - Google Patents

Abstract

(57) [Summary] [Object] To provide a fuel rod holding cylinder fixing mechanism capable of reliably fixing the fuel rod holding cylinder against the water pressure of the primary cooling water. A plug portion 13a formed in the lower portion of the fuel rod holding cylinder 13 is formed with an engaging protrusion 13f having tapered surfaces 13d and 13e on the outer periphery of the tip portion, and the plug portion 13a is divided into a plurality of pieces in the circumferential direction to form a plug. The segment 13h is formed, while the engaging projection 1 is formed in the fitting hole 4a of the core support plate 4.
An engaged projection 4f having tapered surfaces 4d and 4e that engages with 3f is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a fuel rod holding cylinder fixing mechanism for fixing a fuel rod holding cylinder provided in a reactor pressure vessel of a nuclear power plant to a core supporting plate.

[0002]

[Prior art]

 FIG. 5 is a schematic vertical cross-sectional view of the integrated pressurized water reactor pressure vessel, and FIG. 6 is a cross-sectional view taken along the line BB of FIG.

In FIGS. 5 and 6, 1 is a pressure vessel body, 2 is a poison tank having an outer cylinder 2 a and an inner cylinder 2 b, and 3 is a hexagonal planar shape arranged in the inner cylinder 2 b of the poison tank 2. An assembly 4 of the fuel rod holding cylinders 13 is a core support plate for holding the assembly 3. Reference numeral 5 is a cooling body passage pipe that is provided substantially radially through the outer cylinder 2a and the inner cylinder 2b at the lower end of the poison tank 2, 6 is a water supply header attached to the upper portion of the pressure vessel main body 1, and 7 is also the pressure vessel main body 1 Is a steam header attached to the upper part of the so as to face the water supply header 6, and both are in communication with each other via a once-through helical coil type steam generator 8. Reference numeral 9 denotes a water pressure operated valve installed at the upper end of the poison tank 2, and 10 denotes a primary cooling water which is placed above the pressure vessel main body 1 and passes through the portion of the assembly 3 upward to reach a high temperature state. It is a pump for sucking and flowing down from the upper portion of the steam generator 8, and has a suction port 10a and a discharge port 10b. Reference numeral 11 is a water flow passage between the pressure vessel body 1 and the poison tank 2.

A heat insulating material 12 is provided between the outer cylinder 2 a and the inner cylinder 2 b of the poison tank 2. Further, the assembly 3 is configured by arranging a large number of fuel rod holding cylinders 13 in a honeycomb shape, and each fuel rod holding cylinder 13 holds a large number of fuel rods therein, although not shown.

In the reactor pressure vessel having such a configuration, the primary cooling water taken from the cooling body passage pipe 5 rises between the assemblies 3 due to the pressure, but in the process, the temperature becomes high due to heat. The pump 10 sucks this high-temperature liquid from the suction port 10a and discharges it from the discharge port 10b.

On the other hand, the water taken in from the water supply header 6 flows into the steam generator 8, but is converted into high-pressure steam in the steam generator 8 by the above-mentioned high-temperature primary cooling water flowing down between the coils of the steam generator 8. Is sent from the steam header 7 to the next process side. The temperature of the high-temperature liquid passing between the steam generators 8 drops and flows down the water flow passage 11.

FIGS. 7 and 8 are vertical cross-sectional views showing a conventional fuel rod holding cylinder fixing mechanism used in the reactor pressure vessel of FIGS. 5 and 6.

FIG. 7 shows a state of the fuel rod holding cylinder fixing mechanism when the furnace is stopped, and FIG. 8 shows a state of the fuel rod holding cylinder fixing mechanism when the furnace is operating.

The fuel rod holding cylinder 13 has a cylindrical plug portion 13 a having a smaller diameter than the upper portion, which is fitted in the fitting hole 4 a of the core support plate 4 in the lower portion. The fuel rod holding cylinder 13 is positioned by bringing the positioning taper surface 13b tapering downward toward the base and the taper positioning taper surface 4b tapering toward the lower end of the upper end edge of the fitting hole 4a. .

At a plurality of locations on the outer periphery of the lower plug portion 13a connected to the positioning tapered surface 13b, for example, a plate-shaped shape memory alloy 14 made of TiPd-based alloy makes the plate surface vertical and the lower end It is attached with the free end.

When the furnace is stopped, the plate surface of the shape memory alloy 14 is vertical as shown in FIG. 7, and the diameter of the shape memory alloy 14 formed below the positioning taper surface 4b of the core support plate 4 increases as it goes downward. The shape memory alloy 14 is not engaged with the retaining taper surface 4c of the shape as shown in FIG. The taper surface 4c is curved toward the tapered surface 4c. In this state, the lower end of the shape memory alloy 14 is engaged with the retaining taper surface 4c, so that the fuel rod holding cylinder 13 can be prevented from rising due to the flow of the primary cooling water. That is, the shape memory alloy 14 is used to form the fuel rod holding cylinder fixing mechanism.

[0012]

[Problems to be solved by the device]

 In the above conventional mechanism, the fuel rod holding cylinder is fixed by utilizing the rigidity of the shape memory alloy itself, but the rigidity of the shape memory alloy is not so strong, so the fixing force (lifting prevention force) is insufficient. There was a problem. There was also the drawback of high costs.

An object of the present invention is to provide a fuel rod holding cylinder fixing mechanism that solves the above-mentioned drawbacks of the conventional mechanism and can securely fix the fuel rod holding cylinder against the water pressure of the primary cooling water. .

[0014]

[Means for Solving the Problems]

 In order to achieve this object, the present invention provides a plug portion that can be fitted into a fitting hole provided in a core support plate of a reactor pressure vessel at the lower end of a fuel rod holding cylinder capable of accommodating fuel rods inside. The plug part is divided in the circumferential direction to form a plurality of plug segments that can be bent in the radial direction of the plug part with the upper end as a reference, and the diameter of the plug segment increases as it goes downward at a position corresponding to the outer circumference of the plug part An engaging projection having a larger tapered surface and a tapered surface connected to the lower end of the tapered surface and having a diameter that decreases as it goes downward is provided, and the hole diameter becomes smaller at the inner periphery of the fitting hole of the core support plate as it goes downward. It becomes smaller and is connected to the taper surface that can abut against the taper surface below the plug segment and the lower end of the taper surface, and the hole diameter increases as it goes downward and above the plug segment. Those were Unishi by providing the engaged protrusion having a tapered surface engageable with the tapered surface.

[0015]

[Action]

 Insert the plug provided at the lower end of the fuel rod holding cylinder into the fitting hole of the core support plate and push the fuel rod holding cylinder into the fitting hole, and the tapered surface below the engaging projection formed on the plug segment will fit. As a result of sliding on the tapered surface above the engaged projection formed on the inner periphery of the mating hole, each plug segment is pushed toward the center of the plug in the radial direction, and when the engaging projection gets over the engaged projection. The engaging protrusion of the plug segment enters below the engaged protrusion of the fitting hole due to the restoring force of the plug segment, and the tapered surface above the engaging protrusion abuts the tapered surface below the engaged protrusion. In this state, the engaging protrusion and the engaged protrusion engage with each other. For this reason, the fuel rod holding cylinder is firmly fixed to the core support plate, and there is no risk of it coming off due to the water pressure of the primary cooling water.

[0016]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. The same parts as those in the conventional example are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is an exploded vertical cross-sectional view showing a fuel rod holding cylinder fixing mechanism according to an embodiment without breaking a part thereof, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. FIG. 4 is a longitudinal sectional view of an essential part showing a state in the middle, and FIG. 4 is a longitudinal sectional view of an essential part showing a state after mounting.

The plug portion 13a at the tip of the fuel rod holding cylinder 13 has a plurality of slits 13c (eight in this embodiment, as shown in FIG. 2) slits 13c from the vicinity of the upper end base portion to the lower end. Is provided to form a plurality of plug segments 13h which are divided into a plurality of portions in the circumferential direction, and the outer circumference of the lower end of the plug portion 13a has a tapered surface 13d which becomes larger in diameter as it goes downward and the tapered surface 13d. An engaging protrusion 13f having a triangular vertical section is formed for each plug segment 13h, which has a tapered surface 13e that is connected to the lower side of the surface 13d and becomes smaller in diameter as it goes downward.

On the other hand, on the inner circumference of the lower end portion of the fitting hole 4a of the core support plate 4, the fitting hole 4a is connected to the tapered surface 4d which becomes smaller in diameter and the downward direction of the tapered surface 4d. An engaged protrusion 4f having a triangular vertical section is formed, which has a tapered surface 4e with which the fitting hole 4a has a large diameter.

Reference numeral 15 is a first O-ring fitted to a ring groove 13g provided on the outer periphery above the plug portion 13a of the fuel rod holding cylinder 13, and 16 is a ring groove 4g provided on the upper surface of the core support plate 4. It is the second O-ring that fits.

Next, the mounting operation of the fuel rod holding cylinder 13 to the core support plate 4 will be described with reference to FIGS. 3 and 4.

First, the fuel rod holding cylinder 13 is lowered from above, and the plug portion 13a is inserted into the fitting hole 4a from above as shown in FIG. 3 to engage with the tapered surface 13e of the engaging protrusion 13f. When a force F is applied to the fuel rod holding cylinder 13 at the time point when the tapered surface 4d of the projection 4f comes into contact, the tapered surface 13e and the tapered surface 4d relatively slide, and the plug segment having a spring function in the radial direction. Since 13h bends toward the center of the plug portion 13a in the radial direction, the engaging protrusion 13f rides over the engaged protrusion 4f, and the restoring force of each plug segment 13h outward in the radial direction as shown in FIG. The tapered surface 13d and the tapered surface 4e come into contact with each other, and the engaging protrusion 13f engages with the engaged protrusion 4f.

In this state, a large fixing force can be obtained by providing each plug segment 13h with rigidity so as not to be deformed toward the radial center of the plug portion 13a even by the force based on the water pressure of the primary cooling water. It is possible to reliably prevent the fuel rod holding cylinder 13 from rising due to the primary cooling water, and to securely fix the fuel rod holding cylinder 13 to the core support plate 4.

When pulling out the fuel rod holding cylinder 13 from the core support plate 4, the diameter of the plug portion 13a of the force acting on the contact surface between the tapered surface 13d of the engaging projection 13f and the tapered surface 4e of the engaged projection 4f. When the fuel rod holding cylinder 13 is pulled up with a predetermined force so that the component force in the direction bends each plug segment 13h toward the center of the plug portion 13a, the engagement protrusion 13f is engaged with the engaged protrusion 4f. Get over and get off.

[0025]

As described above, according to the present invention, the engaging projection formed on the plug segment formed by being divided into a plurality in the circumferential direction and capable of bending in the radial direction of the plug portion. Since the engaged projections of the fitting holes provided in the core support plate are engaged with each other, the fuel rod holding cylinder can be reliably fixed to the core support plate.

[Brief description of drawings]

FIG. 1 is an exploded vertical cross-sectional view showing a part of a fuel rod holding cylinder fixing mechanism according to an embodiment of the present invention without a cross section.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a longitudinal sectional view of an essential part showing a state in which a fuel rod holding cylinder is being attached.

FIG. 4 is a longitudinal sectional view of an essential part showing a state after the fuel rod holding cylinder is attached.

FIG. 5 is a schematic vertical sectional view of a reactor pressure vessel.

6 is a sectional view taken along line BB of FIG.

FIG. 7 is a vertical sectional view showing a fuel rod holding cylinder fixing mechanism according to a conventional example.

FIG. 8 is a vertical cross-sectional view showing a fuel rod holding cylinder fixing mechanism according to a conventional example.

[Explanation of symbols]

 4 Core Support Plate 4a Fitting Holes 4d, 4e Tapered Surface 4f Engagement Projection 13 Fuel Rod Holding Cylinder 13a Plug Part 13d, 13e Tapered Surface 13f Engagement Projection 13h Plug Segment

Claims (1)

[Scope of utility model registration request] 1. A fuel rod holding cylinder capable of accommodating a fuel rod therein is provided with a plug portion at a lower end thereof which can be fitted into a fitting hole provided in a core support plate of a reactor pressure vessel, and the plug portion is circumferentially surrounded. Forming a plurality of plug segments that can be bent in the radial direction of the plug portion based on the upper end as a reference, and at a position corresponding to the outer circumference of the plug portion of each plug segment, a tapered surface whose diameter increases as it goes downward, and An engaging protrusion having a tapered surface connected to the lower end of the tapered surface and having a diameter that decreases as it goes downward is provided, and the hole diameter becomes smaller as it goes downward and the inner diameter of the fitting hole of the core support plate becomes smaller. A taper surface that can come into contact with the lower taper surface, and a taper that is connected to the lower end of the taper surface and that has a larger hole diameter as it goes downward and that can engage with the upper taper surface of the plug segment. A fuel rod holding cylinder fixing mechanism comprising an engaged projection having a surface.