JPS61251791A - Fuel-rod space measuring device - 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 (Field of Application of the Invention) The present invention relates to the inspection of irradiated fuel assemblies, and more particularly to an illumination device that is optimal for carrying out visual inspections of fuel assemblies, and a fuel inspection device equipped with the illumination device. .

[Background of the invention]

Conventionally, inspection of irradiated fuel bodies has been carried out using a fuel channel attachment/detachment machine, and as shown in FIG. 3, the main equipment of the conventional fuel channel attachment/detachment machine 1 is a frame 2.3. fuel cart 4
．． It consists of an operation console 5 with a built-in drive mechanism, etc.

The fuel cart 4 includes a lower support 7 that receives the weight of the fuel body 6 at the bottom, a fuel support 8 that vertically holds the fuel body 6 and is rotatable together with the lower support 7, and a side wall 10 of the spent fuel storage pool 9. A guide 13 consisting of nine and two rollers 11 and 12 provided to constantly move up and down on the same line with frames 2 and 3 mounted vertically along the track as tracks.
A guide 15 consisting of one roller 14 is formed into one body, and is stretched around a sprocket 16 and an idler sprocket 17 installed at the bottom of the frames 2 and 3 by a drive mechanism (not shown) built in the operation console 5. chain 18
Driven through.

As shown in FIGS. 5 and 6, the fuel pellets 19 are suitably sealed within a large number of fuel rods 20, and
are supported at their tips 25° and 26 by holes 23 and 24 provided in a lattice pattern in the upper and lower tie plates 21 and 22, respectively.

The upper and lower tie plates 21 and 22 are connected by screws 28 and 29 of several tie rods 27, and the upper and lower intervals H are determined. The fuel rod 2o has a tie rod 27 and several spacers 3
0 and held straight, forming a prismatic fuel bundle 31.

The fuel rods 20 thermally expand during combustion in the reactor core, and extend particularly in the longitudinal direction. The coolant flowing in the core rises from below along the fuel body 6 and cools each part of the fuel body 6, but due to differences in pressure loss in each part of the fuel body 6, the flow of coolant is not uniform in each part, and the fuel body The cooling of each part of 20 is also different. Therefore, there is variation in the expansion of the fuel rods 20, and due to these factors, the fuel rods 2o may be bent due to thermal strain between the upper and lower tie plates 21, 22.

The fuel body 20 is located between H between the upper and lower tie plates 21 and 22.
If the fuel rods 2o are deformed and the distance between adjacent fuel rods 20 becomes close, nuclear reactions will become active and overheating may occur, resulting in burnout of the fuel rods 2o. In order to deal with this, the fuel bodies 6 that have been burned for a certain period of time are taken out from the core during periodic inspections, and their integrity is inspected in water in the spent fuel pool to determine whether or not they can be reused.

Currently, fuel assemblies in use at nuclear power plants are tested for fuel damage using a chemical inspection method using shipping.

There are two types of physical inspection methods such as visual visual inspection of one dimension.
As one of these physical methods, a light transmission method is used to measure the straightness of the fuel rods and the fuel rod spacing Ω dimension.

The outline of the inspection method using the light transmission method is shown in FIG. 7. An underwater TV camera 32 and a fuel bundle 31 are placed in the vicinity of a fuel bundle 31, and an underwater lighting lamp 33 is placed on the opposite side of the fuel exchange work blower. Hang it from 34. Viewed from the underwater television camera 32, the part illuminated by the light beam of the underwater lighting lamp 33 is bright, and the back side of the fuel rod 20, which is not exposed to the light beam, becomes a black shadow. The boundary line between the bright part and the black part is the outermost periphery of the fuel body 20, and when measuring with the underwater television camera 32, the curvature of the boundary line or the distance between the boundary lines is read and the fuel bundle 31 is reused. A decision is made as to whether or not it is possible.

Since the fuel bundle 31 is loaded with a large number of fuel rods 20, the fuel rods 20.
Adjust the position where the light beam of the lighting lamp 33 hits each fuel rod 2.
A complete zero inspection is performed.

Further, the longitudinal direction of the fuel rods 20 can be inspected by moving the fuel cart 4 up and down.

Although these techniques are already well known and have been widely adopted at nuclear power plants, they have the following drawbacks, which hinder inspection work, and there has been a strong desire to improve the equipment and work methods.

(1) The underwater illumination lamp 33 used for visual inspection of the fuel bundle 31 includes a rod-shaped light emitting body 34 and a pipe-shaped transparent case 35.
The structure is such that the light rays are emitted all around the light emitter 34 so that there is no problem in use even if the underwater lighting lamp 33 turns horizontally due to the twisting of the cable 36, so the light rays are not diffused into the pool water. , the fuel bundle 31, the underwater television camera 32, etc. are made bright throughout the vicinity of the inspected position, making the boundary line between bright and dark of the inspected fuel rod unclear, which is a factor in reducing inspection work efficiency and inspection accuracy.

(2) When suspending or lifting the underwater light 33 into the pool 9 or moving the underwater light 33, the underwater light 33 may collide with the fuel cart 4, fuel bundle 31, etc., and the transparent case of the underwater light 33 may 35, etc.

In addition, as a spent fuel inspection device, Japanese Patent Application Laid-Open No. 59-22
Some examples include those described in Publication No. 4595.

[Purpose of the invention]

The purpose of the present invention is to shorten the inspection time of fuel rods by clearly defining the outermost periphery of the fuel rods without leaking excessive light into the pool water, and to reduce the radiation radiation caused by the visual inspection of irradiated fuel bodies. An object of the present invention is to provide a fuel rod spacing measuring device that can reduce radiation exposure and improve inspection accuracy.

[Summary of the invention]

Placing an illumination light between the main frames 2 and 3 poses a maintenance problem, and the present invention focuses on the fact that indirect light is easier to observe than direct light when inspecting fuel rods.
It is equipped with an elevating device that raises and lowers the fuel body, and a main frame that guides the elevating device up and down.An underwater lighting lamp is installed on the outside of the main frame, and a reflector for the lighting lamp is installed inside the main frame. In addition to providing a means for cutting off the frame to allow illumination light to pass through, a cover is provided to prevent the light from the illumination lamp from directly entering observation means such as a television camera.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows an overall schematic view of a fuel channel attachment/detachment machine equipped with the fuel rod spacing measuring device of the present invention. The fuel cart 4 has a lower support 7 that receives the weight of the fuel body 6 at the bottom, and a fuel support 8 that holds the fuel body 6 vertically at the top and is rotatable together with the lower support 7. and a guide 13 consisting of two rollers 10 and 11 provided to move up and down at the same position using frames 2 and 3 installed vertically along the side wall 10 of the spent fuel storage pool 9 as tracks. A guide 15 consisting of rollers 14 is integrally formed and is driven by a drive mechanism built into the operating table 5 by a chain 18 that is stretched around a sprocket 16 and an idler sprocket 17 installed at the bottom of the frame 2.3.

Underwater illumination lights 40 and 41 are attached to the outside of the frames 2 and 3 in parallel to the vertical direction of the fuel cart 4 so as not to obstruct the vertical movement of the fuel cart 4, and cables (not shown) are attached to the outside of the frames 2 and 3.
Power is supplied from a power source (not shown) installed above the pool 34 via a power source 34 to enable lighting.

The reflective shade 44, 45 is shaped to surround the illumination lamp from the opposite side of the frames 2 and 3, and prevents the impact force from being applied directly to the lamp 40, 41 due to contact with a general-purpose pole (not shown), etc. The light beam from the illumination lamp 40.41 is directed towards the frame 2°3 extending along the side wall 10 of the spent fuel pool 9 and the bend 42.43 of said frame.
The light is shielded by reflective shades 44 and 45, which restricts light leakage into the water of the pool 9 and prevents the light from diffusing.

A reflector plate 39 is attached to the inside of the frame 2.3 corresponding to the illumination light 40.41, and the reflector plate 39 and the illumination light 40.4
Cutouts 37 and 38 are provided in the frames 2 and 3 between the frames 2 and 3 through which illumination light can pass. The light beam reaching the reflector plate 39 is reflected and transmitted through the fuel rod to be inspected, thereby making it possible to inspect the spacing of the fuel rods.

The underwater television camera 32 is set at a position facing a reflector 39 with the fuel bundle 31 in the middle.

The straightness and spacing of each fuel rod 20 can be measured using the conventional light transmission method, and the fuel rods 20 can be measured by a combination of rotating the fuel support 4, moving the set position of the underwater television camera 32, and lifting and lowering the fuel cart 4. It is possible to measure the entire length of the rod.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) When inspecting the spacing of the fuel rods 20 of the fuel bundle 31,
The light beam of the illumination device can be focused only on the necessary part, so it is possible to clearly define the boundary line representing the outermost circumference of the fuel rod 20 without diffusing the light into the pool water, and the inspection accuracy can be improved. It can be measured.

(2) Maintenance of underwater lighting becomes easier and there is no need to worry about breakage.

(3) The cost of the device is low, and it can be applied to conventional fuel channel attachment/detachment machines.

[Brief explanation of drawings]

FIG. 1 is a main explanatory diagram of the present invention, and is a view taken along line A-A in FIG. 2. FIG. 2 is an overall schematic diagram of the present invention. FIG. Fig. 4 is a diagram explaining the engagement state of the fuel cart and frame, Fig. 5 is an overall view of the fuel bundle, 6WI is an overall view of the fuel rod, Fig. 7 is a schematic diagram showing the conventional fuel inspection method, FIG. 8 is a schematic diagram showing a conventional underwater lighting lamp. 2.3...Frame, 42.43...Frame bent part, 37.38...Frame notch part, 40,41.
...Underwater lighting lamp, 39...Reflector plate, 32...Underwater television camera, 31...Fuel bundle, 20...Fuel rod, 44°45...Reflector shade. 〆□

Claims (1)

[Scope of Claims] 1. A fuel rod spacing measuring device that is used in a nuclear power plant, etc., and which has a fuel assembly in the middle and a lighting lamp, a television camera, etc. arranged in the front and rear, and a lifting device that raises and lowers the fuel assembly. , equipped with a main frame that guides the lifting device up and down, with an underwater lighting lamp on the outside of the main frame and a reflector for the lighting light on the inside, so that illumination light can pass through the main frame between the underwater lighting lamp and the reflector. A fuel rod spacing measuring device characterized in that a notch is provided and a cover is provided to prevent light from an illumination lamp from directly entering an observation means such as a television camera. 2. The fuel rod spacing measuring device according to claim 1, characterized in that the reflecting plate has a concave or convex shape to condense light from an underwater illumination lamp and transmit the light through the fuel body. .