JP3137558B2 - Inspection table and inspection method for inserts in reactor fuel assemblies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for inspecting non-nuclear fuel core components used in a nuclear reactor.

[0002]

2. Description of the Related Art For example, in a pressurized water reactor, non-nuclear fuel core components such as a control rod cluster, a burnable poison rod assembly, and a thimble plug assembly are inserted into a reactor fuel assembly and used. Briefly describing these structures, as shown in FIG. 9, the control rod cluster has a large number of elongated control rods 2 fixed to a hub 4 via spider arms 3 to form a tuft. In the control rod cluster 1, control rods 2 are used separately inserted into control rod guide tubes of a reactor fuel assembly to absorb neutrons and control the reactivity of the core.

As shown in FIG. 10, the thimble plug assembly has a large number of thimble plugs 6 hanging down and fixed to a mounting plate 7, and a holder 8 provided at the upper center. Although more than one hundred fuel assemblies loaded into the reactor core have the same mechanical structure, the control rod cluster 1 is not necessarily used for all fuel assemblies at the same time. In a reactor fuel assembly in which the control rod cluster 1 is not used, the control rod guide tube is in an empty state. The thimble plug assembly 5 is used to substantially close the unused control rod guide tube of such a fuel assembly.

As shown in FIG. 11, a burnable poison stick assembly (burnable poison assembly) is obtained by replacing a part of a thimble plug 6 of a thimble plug assembly 5 with a burnable poison stick 11. The burnable poison rod assembly 9 is mainly used for adjusting the neutron flux distribution in the core. Since such non-nuclear fuel core components are used by being inserted into the fuel assembly, they are generally referred to as so-called fuel assembly inserts. Since these inserts are used in the reactor core, periodic inspections are needed for safe reactor operation.

A method of inspecting such an inserted object will be described by taking the control rod cluster 1 as an example. In FIG. 12, the control rod cluster 1 is placed in the radiation shielding water 15 of the fuel inspection pit 13 by using a tool. It is suspended by a crane 18 via 17. Then, the underwater television camera 19 suspended via the elevating mechanism is moved up and down along the outer surface of the control rod cluster 1, and the appearance of the control rod cluster 1 is inspected.

[0006]

As described above, when the appearance inspection is performed while the control rod clusters and the like are suspended in the water,
Since the water has a large refractive index, it cannot be accurately inspected if it slightly sways. Therefore, the time to wait for the roll stop is lengthened, and the inspection takes a long time.
In addition, TV camera operating personnel and crane operating personnel are required at the same time, it takes time to set the insert to the inspection position, and the crane is occupied during the inspection and other operations can not be performed. Work efficiency as a whole was poor. Accordingly, an object of the present invention is to provide an apparatus and a method that can efficiently perform an appearance inspection of an insert in a reactor fuel assembly.

[0007]

According to the present invention, there is provided, in accordance with the present invention, an inspection table as an apparatus used for inspecting inserts in a reactor fuel assembly, comprising: an upper nozzle of the reactor fuel assembly; A simulated upper nozzle and a simulated lower nozzle that respectively simulate a lower nozzle, a column connecting the both simulated nozzles to each other by simulating the reactor fuel assembly, and the reactor fuel assembly disposed at an intermediate portion of the column. Of the control rod guide tube. Further, according to the inspection method of the present invention, the inspection table as described above is placed on a rotary table provided in radiation shielding water, and the insert in the reactor fuel assembly is inserted and held in the simulated upper nozzle of the inspection table. The outer surface of the insert is scanned by a television camera while rotating the rotary table.

[0008]

The inspection table having the above structure simulates a nuclear fuel assembly in which an insert such as a control rod cluster, a thimble plug assembly, and a burnable poison rod assembly is actually used. Stably supports such an insert, and the guide tube of the intermediate cylinder is the control rod of the control rod cluster,
Laterally supporting the burnable poison sticks of the burnable poison stick assembly,
The part to be inspected is exposed by the upper and lower struts to enable the inspection. By mounting the inspection table as described above on the rotary table in the radiation-shielded water, the outer surface to be inspected of the insert is opposed to the television camera fixed in the circumferential direction.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, a simulated upper nozzle 21 of an inspection table 20 simulates an upper nozzle of a reactor fuel assembly (not shown), and particularly includes a portion (including a hole 23) into which an outer shape or an insert is inserted. Although the shape and dimensions are completely matched, the parts not directly related, such as the attachment part such as a hold-down spring, are appropriately structured as appropriate. Similarly, a simulated lower nozzle 2 simulating the lower nozzle of the fuel assembly
5 are provided, and the upper column 2 is provided so that the relative relationship between the two nozzles 21 and 25 simulates that of the fuel assembly.
7, are connected by the lower support 29 and the intermediate body 31. The supports 27 and 29 are connected so as to be located at the four corners of the nozzles 21 and 25, respectively, as can be clearly understood from the drawing. These structures are more clearly shown in FIGS. 2, 3, 4 and 5.

As shown in FIGS. 2 and 3, the simulated upper nozzle 21 has the same outer shape and dimensions as the upper nozzle of the fuel assembly, and has a hole 23 through which the control rod 2 of the control rod cluster 1 is inserted. A positioning hole 22 formed and used when engaging with a fuel assembly handling tool (not shown) is formed on the upper surface of a corner at a diagonal position. In this manner, the simulated upper nozzle 21 is completely simulated with the outer shape and dimensions and the positioning holes, and thus can be securely gripped by the fuel assembly handling tool approaching from above. As shown in FIGS. 2 and 4, the guide tube 33 is aligned with the hole 23 in the intermediate cylinder 31.
Are arranged, and the upper and lower ends thereof are fixed to the upper plate 35 and the lower plate 37. The lower plate 37 and the upper plate 35 have a central column 39.
And are connected to each other by side frames 41 at the corners. The control rod 2 and the burnable poison rod 11 are inserted through these guide tubes 33. Further, the simulated lower nozzle 25 is shown in FIGS.
As shown in Fig. 7, the outer dimensions of the lower nozzle of the fuel assembly and the positioning holes 43 of the legs when loading the core on the core plate are simulated. The positioning holes 43 are used when setting the inspection table 20 on the rotary table 45 when performing an inspection as described later.

FIG. 6 shows a state in which the above-described control rod cluster 1 is inserted into the inspection table 20 having the above-described structure for performing the inspection. The portion of the control rod cluster 1 which requires substantial visual inspection is located at the column 29 and is accessible from the outside. Similarly, FIG. 7 shows a state where the thimble plug assembly 5 is inserted and set on the inspection table 20. The thimble plug 6 that needs to be inspected is located in the region of the upper column 27 and is accessible from the outside. As can be inferred from the above description, the position and the size of the intermediate barrel 33 of the inspection table 20 are set to such a level as not to hinder a substantial inspection operation.

An apparatus and method for inspecting the appearance of an inserted object using the inspection table 20 will be described below. As shown in FIG. 8, a rotary table 45 is provided in the radiation shielding water 51 of the inspection pit 50 and communicates with a rotary drive motor 49 on the floor of the pit 50 via a power transmission mechanism 47. I have. A support base 53 is erected around the rotary table 45, and supports the simulated upper nozzle 21 from the side when the inspection table 20 is placed upright on the rotary table 45. An elevating motor 57 mounted on a frame 55 extending from the floor supports an underwater television camera 59 so as to be able to move up and down. Then, using a crane and a tool for handling the fuel assembly, the inspection table 20 is used.
On the rotary table 45. And. The control rod cluster 1 is inserted and set in the inspection table 20 as shown by a dashed line. Next, the elevation motor 57 is driven to cause the underwater television camera 59 to scan the outer surface of the control rod cluster 1 which is the inspected portion. The obtained appearance image is converted into an electric signal and displayed on a monitor television screen (not shown). When the scanning of one side is completed, the rotary table 45 is rotated by a required angle, for example, 90 °, the side to be inspected of the control rod cluster 1 is opposed to the underwater television camera 59, and the above-described scanning is repeated. Of course, the rotation angle of the rotary table 45 can be appropriately changed and adjusted according to the count of non-inspection inserts, and the vertical scanning distance can also be changed.

[0013]

As described above, according to the first aspect of the present invention, the insert to be inspected is inserted and set on the inspection table simulating the fuel assembly in which the fuel assembly is actually used. Therefore, it is possible to stabilize in a short time and to efficiently perform a required inspection. According to the second aspect of the present invention, since the inspection table as described above is placed on the rotary table for the inspection, the external surface to be inspected facing the television camera as the inspection device can be quickly switched, and the interpolation can be performed. The whole appearance inspection of an object can be efficiently performed in a short time.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention.

FIG. 2 is a partially cut-away vertical sectional view showing an embodiment of the present invention.

FIG. 3 is a top view of the embodiment.

FIG. 4 is a plan sectional view taken along the line IV-IV in FIG. 2;

FIG. 5 is a partially enlarged side view showing a portion V in FIG. 2;

FIG. 6 is an operation explanatory view of the embodiment.

FIG. 7 is an operation explanatory view of the embodiment.

FIG. 8 is an operation explanatory view of the embodiment.

FIG. 9 is a perspective view showing one inspection object of the present invention.

FIG. 10 is a perspective view showing one inspection object of the present invention.

FIG. 11 is a perspective view showing one inspection object of the present invention.

FIG. 12 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 Reference Signs List 20 inspection table 21 simulated upper nozzle 25 simulated lower nozzle 27 upper support 29 lower support 31 intermediate cylinder 33 guide tube 45 rotary table

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21C 17/06 G21C 19/02 G21C 19/07

Claims (2)

(57) [Claims] A simulated upper nozzle and a simulated lower nozzle that respectively simulate an upper nozzle and a lower nozzle of a reactor fuel assembly, a column connecting the simulated nozzles to each other by simulating the reactor fuel assembly, and An inspection table for an insert in a reactor fuel assembly, comprising an intermediate body provided with a guide tube simulating a control rod guide tube of the reactor fuel assembly, which is disposed at an intermediate portion of the column. 2. The inspection table according to claim 1 is mounted on a rotary table provided in radiation shielding water, and an insert in a reactor fuel assembly is inserted and held in a simulated upper nozzle of the inspection table. A method for inspecting an insert in a reactor fuel assembly, wherein an outer surface of the insert is scanned by a television camera while rotating a table.