JPH01316687A - Guide structure for control rod assembling body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a structure for guiding and protecting a control rod assembly of a nuclear reactor.

[Prior Art] In order to control the reactivity of a fuel assembly constituting a core of a nuclear reactor, as is well known, a control rod can be inserted into and withdrawn from the fuel assembly. A plurality of control rods are assembled into a cluster by a spider to constitute a control rod assembly, and the control rod assembly is a guide structure disposed in an upper reactor internal structure above the reactor core. provides sufficient mechanical guidance for its insertion and withdrawal and is protected from vibrations due to coolant fluid flowing upwardly in and out of the guide structure. For this reason, the guide structure is equipped with a protection tube with a C-shaped cross section that surrounds each of the plurality of control rods, and due to the C-shaped cross section, slits are formed in the axial direction of the protection tube. , guiding the axial movement of the spider of the restraining rod assembly.

Therefore, from the viewpoint of insertion and movement of the control rod assembly into the guide structure, an appropriate gap must be provided between the spider of the control rod assembly and the slit of the C-shaped protection tube.

[Problems to be Solved by the Invention] However, if this gap is large, the gap is provided over the entire length of the protection tube, which is less effective in suppressing the vibration of the control rod as a whole.On the other hand, if the gap is set small, the control In addition to making insertion of the rod assembly difficult, the guide structure's protection tubes must be arranged radially to match the control rod array pattern of the control rod drive, making it difficult to accurately insert individual protection tubes. It becomes very difficult to position and assemble.

Therefore, there is a need for a guide structure for a control rod assembly that can accurately position and assemble the protective tube while having a sufficient effect on vibration suppression of the entire control rod. It is an object of the present invention to provide a control rod assembly guide structure that can meet such needs.

[Means for Solving the Problems] To achieve this object, the present invention provides a hub, a first group of gussets extending radially outwardly from the hub in a cross shape, and a first set of gussets extending radially outward from the hub, receiving and guiding a control rod assembly comprising a second group of gussets extending radially outwardly from the gussets and a plurality of control rods extending axially from the first and second groups of gussets; A guide structure installed above inside the reactor vessel includes a rectangular cylindrical casing, a guide support plate provided across the casing and having spaces for the hub, gasket, and control rods; a C-shaped cross-section protective tube fixed to a guide support plate and surrounding each of the control rods, and a C-shaped cross-section protective tube that corresponds to the first group of gussets is inserted into the slit of the other C-shaped cross-section protective tube. It is characterized by being relatively small.

[Function] When the guide structure is configured as described above, when the control rod assembly is inserted into the guide structure, or when the control rod assembly is inserted into the guide structure, the control rod assembly is inserted into the protective tube having a relatively narrow slit. A group of cruciform gussets cooperate with relatively narrow slits in the protection tube to dampen fluid-induced vibrations of the entire control rod assembly. Furthermore, since the control rod assembly is guided and positioned through the narrow slit, high precision is no longer required for the position of the protective tube that receives the control rods supported by the second group of gussets. This facilitates assembly of the guide structure.

In a preferred embodiment, when inserting the control rod assembly into the guide structure, the tip of the protective tube that receives the control rods supported by the first group of gussets projects upwardly more than the others; A group of gussets is initially guided securely in a relatively narrow slit in the protective tube.

[Embodiments] Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts.

FIG. 2 shows a cross section of a nuclear reactor 1 including a control rod assembly guide structure in which the present invention is implemented.
, a reactor field 82, a cylindrical core tank 3 suspended within the reactor vessel 2, and a plurality of fuel assemblies supported between a lower core support plate 4 and an upper core support plate 5 within the core tank 3. body 6
The reactor core 7 consists of a reactor core 7, an upper reactor internal structure 8 above the reactor core 7, etc., and a plurality of control rods 9 are installed in the upper reactor internal structure 8 as shown in FIG. spider 20
A guide structure 11 is provided for guiding and protecting the known control rod assembly IO assembled in a tuft-like configuration.

In Fig. 2, the reactor coolant is, as indicated by the arrow,
It enters the reactor vessel 2 through the inlet nozzle 12 and flows down an annular descending region 13 between the reactor vessel 2 and the core barrel 3 to a plenum 14 below the lower core support plate 4. It reverses and flows upward in the core 7. The coolant heated by the fuel assembly 6 of the reactor core 7 flows further upward inside and outside the guide structure 11 described above, changes its flow sideways at the calandria structure image 15 of the upper core internal structure 8, and flows from the outlet nozzle 16. It is discharged.

Since the coolant flows in and out of the guide structure 11 in this manner, it is necessary to protect each control rod 9 of the control rod assembly 10 (FIG. 3) within the guide structure 11 from vibrations caused by the coolant flow. There is. FIG. 1 shows an embodiment of a guiding relic 11 of the present invention having such a protective function.

In FIG. 1, this guide structure 11 is composed of, for example, three guide units lla to lle assembled in stacked relationship in the longitudinal direction via a rectangular cylindrical casing 18'. Each guide unit may have substantially the same structure, as can be understood from FIGS. 1, 18, and 1B, which representatively show the casing 18 formed in a rectangular tube shape and the guide unit lla. , the casing 1
Upper and lower guide support plates 1, which may be of substantially the same structure, are attached to the upper and lower ends of the frame by welding at the protruding portions 18c.
8a and 18b, and the guide support plates 18a and 18 described above so as to be able to individually surround the control rod 9 of FIG.
b A protective tube group 19 with a C-shaped cross section attached to E.

Each protection tube of the protection tube group 19 is attached to each guide support plate by welding. Casing 18' between the guide units
may have substantially the same structure as the casing 1B of each guide unit, and its upper and lower ends are attached to the guide support plate of the adjacent guide unit by welding.

Now, the control rod assembly 10 received in such a guide structure 11 may be of known construction and is coupled at its upper end to a control rod drive shaft (not shown), as shown schematically in FIG. It is composed of a central hub 10a, a spider 20 extending radially outward from the hub 10a, and the plurality of control rods 9 described above depending from the spider 20.

In the embodiment, each spider 20 has two control rods 9
It has a first group of gussets 20a criss-crossed to support the control rods 9, and a second group of gussets 20b each supporting four control rods 9. Since FIG. 3 is a schematic diagram, it does not actually represent the positional relationship of the gussets in the first group and the second group, but these gussets 20a and 20b are
As shown in Fig. 3Δ, which shows the control rod assembly 10 when viewed from above,
The four gussets 20a belonging to the first group are separated from each other by 90 degrees in the circumferential direction from the hub 10a and extend radially outward in a cross shape, and each of the four gussets 20b belonging to the second group is adjacent to each other. The two gussets 120a have a positional relationship extending radially outward. As described above, each gusset l'' 20a of the first group supports two control rods 9, and each gusset 20b of the second group has a pair of branch arms 20c, and each branch arm 20c has two control rods 9. control rod 9,
A total of four control rods 9 are supported.

Since the control rod assembly 10 is of the structure described above, each guide support plate 18&, 18b which must receive the control rod assembly 10 as shown in FIG.
Spaces 10a', 2 are arranged in a pattern corresponding to the arrangement shown in FIG.
0a', 20b' and 9' are in Fig. 1 and Fig. 4, respectively.
The holes are drilled as shown in the figure. Each protection tube of the protection tube group 19 is fitted and welded into a corresponding space 9' formed in the upper and lower guide support plates 18a and 18b.

The protective tube group 19 is supported by a first C-shaped cross-section protective tube 19a serving as a reference for protecting the control rod 9 supported by the first group of gussets 20a, and a second group of gussets 1-20b. a second C-shaped cross-section protection tube 19 for protecting the control rod 9;
Among these protective tubes, the control rod protective tube 19 is supported by the first group of gussets 20m located on the gusset center line 2 which intersect at right angles as shown in FIG.
Regarding a, the distance Ai by which the upper end thereof protrudes upward from the upper surface of the upper guide support plate 18a is slightly larger than the distance IB by which the upper end of the protective tube 19b of the control rod supported by the second group of gussets also protrudes. Largely designed. Furthermore, regarding the slits formed in each protection tube due to the C-shaped cross section, as can be understood from FIGS. 4B and 4C showing the upper ends of protection tubes 19a and 19b,
The width of the slit 19a' formed in the longitudinal direction in a is narrower than the slit l19b' formed in the protection tube 19b, and the width of the upper end of the slit 19a' of the protection tube 19a gradually increases. Expand and at the top end, protect tube 19
It is substantially equivalent to the slit 19b' of b.

If the guide structure 11 is configured as above, when the control rod assembly 10 is inserted into the guide structure 11, the first group of gussets with the control rods 9 inserted into the protective tube 19a having a narrow slit will be removed. 20a cooperates with the relatively narrow slit in the protective tube 19a to suppress fluid-induced vibrations of the entire a control rod assembly. Furthermore, when the control rod assembly 10 is inserted into the guide structure 11, the tip of the protective tube 19& is more protruded upward than the other parts, so the control rod assembly 10
is first guided through the narrow slit 19a' of the protective tube 19a.

[Effects of the Invention] During insertion of the control rod assembly, the 1nth gusset is guided and vibration is prevented by the 111 narrow slit of the protection tube,
The slit of the protection tube that guides the second group of gussets can be made relatively large, and as a result, the position of the protection tube that guides the second group of gussets does not need to be so accurate. Structure assembly work becomes easier.

Additionally, in a preferred embodiment, the upper end of the protective tube guiding the first group of gussets projects upwardly relative to the others, thereby ensuring that the first group of gussets in the control rod assembly are aligned first. The control rod assembly is guided by a corresponding protective tube, which makes the positioning of the control rod assembly more reliable and makes the assembly work of the guide ff13n easier. Furthermore, since the protective tubes have different overall lengths, they can be easily identified, which facilitates assembly of the guide structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a guide structure for a control rod assembly according to the present invention, FIG. 18 is an enlarged sectional view taken along the 1^-1Δ line in FIG. FIG. 2 is a schematic cross-sectional view of a nuclear reactor equipped with the guide structure shown in FIG. 1, and FIG. 38 is a schematic plan view of the control rod assembly shown in FIG. 3, and FIG. 4 is a schematic diagram of the control rod assembly guided by the guide structure shown in FIG. 1B. FIG. 3 is a top view of the control rod assembly with the control rod assembly inserted, and FIG. 48 is a top view of the fourth
4B and 4C are partial side views taken along the line 4^-4^ of the figure, which illustrate the relationship between the slits of two types of C-section protection tubes; It is a side view of an upper end part. 2...Reactor vessel 9...Control rod 9'...
-Space 10 for receiving control rods...Control rod assembly 10a...Hub 108'...Space 11 for receiving hubs...Guiding structure 18...
- Casings 18a, 18b...Guiding and supporting plates 19a, 19b...C-shaped cross section protection tubes 198', 19 b', - -Slit 20a...First group gusset 20b...Second group gusset 20a'... Space for accepting the first group of gussets 20b'... Space for accepting the 2mth gusset Patent applicant's agent So Ga Do @jshi・°
Figure 2, Figure 3, Figure 4B, Figure 19o. Figure 4C

Claims (1)

[Claims] a hub; a first group of gussets extending radially outwardly from the hub in a cross-shape; a second group of gussets extending radially outwardly from the hub; A control rod assembly consisting of a plurality of control rods extending in the axial direction from two groups of gussets is received and guided, and is installed in the upper part of the reactor vessel. a guide support plate disposed across the hub, a guide support plate having a space for the hub, the gusset, and the control rod; and a C-shaped cross-section protective tube fixed to the guide support plate and separately surrounding the control rods; A guide structure for a control rod assembly, characterized in that a slit width of a C-shaped protection tube corresponding to a group of gussets is made relatively smaller than that of other C-shaped protection tubes.