JPH0237557B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a method for remotely inspecting the inside of a reactor vessel (hereinafter referred to as the reactor vessel) of a fast breeder reactor that uses liquid sodium as a coolant, for example. The present invention relates to an inspection device inside a nuclear reactor.

(Technical background of the invention and its problems) Generally, in a fast breeder reactor that uses liquid sodium as a coolant, a core consisting of a core fuel assembly and a blanket fuel assembly is placed approximately in the center of the reactor vessel. This core is supported by a core support structure.

Further, this core support structure is mounted and fixed by a mounting flange attached to a lower side wall within the reactor vessel.

The mounting flange acts as a partition plate to differentiate the pressure areas through which the coolant flows, maintaining a high pressure plenum area below the flange and a low pressure plenum area above the flange.

The flow rate of the coolant is regulated so that it flows into each fuel assembly at a predetermined pressure.

Furthermore, the coolant inside the reactor vessel is covered with a cover gas, making it difficult to allow an inspection device to directly access the lower high-pressure region within the reactor vessel from the top surface of the shielding plug of the reactor vessel.

Furthermore, when replacing fuel in the core of a fast breeder reactor, a double rotating plug known as the under-the-plug method is operated by a drive mechanism from the top of the reactor vessel, and grippers grip the fuel assembly. Container shielding plug cannot be easily removed.

Therefore, inspection or repair work inside the reactor vessel is generally performed without removing the shielding plug.

When inspecting abnormal conditions in the reactor core, for example, when monitoring the uplift of core fuel assemblies due to coolant, a sodium fluoroscopy system with an ultrasonic transducer is used, and the cover gas space area and low pressure plenum area are inspected. When inspecting the surface condition
ITV (industrial television camera) etc. are used.

However, ITV or sodium fluoroscopy equipment has the disadvantage that if you want to inspect every corner of the reactor vessel as much as possible, it cannot be inspected easily because its wide-angle range is limited, and inspection of the high-pressure plenum region is particularly difficult.

Therefore, there is a need for an apparatus that can easily inspect the surface condition and abnormalities within the reactor vessel, particularly in the high pressure plenum region.

(Objective of the present invention) The present invention has been made to satisfy the above-mentioned needs.The present invention has been made in order to satisfy the above-mentioned needs. An object of the present invention is to provide a nuclear reactor core inspection device that allows the inner surface of a high-pressure plenum region below a mounting flange and its surroundings to be easily inspected by remote control.

(Structure of the present invention) In order to achieve the above object, the present invention provides a through hole in a shielding plug that closes the upper opening of the furnace vessel,
In addition, an inspection plug is inserted into this through hole, and a guide tube that extends and opens to a mounting flange in the furnace vessel is connected to this inspection plug via a partition mechanism, so that it can be moved arbitrarily within this guide tube. This is an inspection device that is equipped with an in-furnace detector, and when inspecting the inside of the reactor, a partition mechanism is opened remotely from the top of the reactor vessel, and a dedicated high-pressure plenum inspection device is installed to inspect the surface of the high-pressure plenum area and The purpose is to enable inspection of the surrounding conditions.

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

In FIG. 1, reference numeral 1 indicates a reactor vessel of a fast breeder reactor, and below the approximately central portion of the reactor vessel 1 are a group of core fuel assemblies and a group of blanket assemblies arranged around the core fuel assemblies. A reactor core 2 consisting of

This core 2 is supported by a core support structure 3,
This core support structure 3 is mounted and fixed on a mounting flange 4 connected to the inner wall surface of the reactor vessel 1.

The upper opening of the furnace vessel 1 is closed by shielding plugs, that is, a large rotation plug 5 and a small rotation plug 6.

The small rotating plug 6 has a central portion that penetrates through the core 2.
A core upper mechanism 7 is provided that reaches above the core.

Also, at the bottom of the reactor vessel 1, there is a coolant inlet nozzle 8 for distributing sodium coolant to the reactor core 2.
However, outlet nozzles 9 for flowing out the heated sodium coolant are connected to the sides of the furnace vessel 1, and a space 11 above the sodium 10 in the furnace vessel 1 is provided with an outlet nozzle 9 to prevent the coolant from oxidizing. An inert gas such as argon gas is filled as a cover gas.

Furthermore, the large rotation plug 5 has a large through hole 12.
is provided, and a test plug 13 is inserted into this through hole 12.

The inspection plug 13 is provided with a medium diameter through hole 14 and a small diameter through hole 15.

An extension pipe 17 connected to the lower part of a drive mechanism 16 serving as a furnace inspection device is inserted into the medium-diameter through hole 14, and partition mechanisms 18a and 18 are inserted into this extension pipe 17.
b is connected.

A guide tube 1 is provided at the bottom of the partition mechanisms 18a and 18b.
9 is connected, and this guide pipe 19 is connected to the furnace vessel 1.
The guide tube 19 is supported by a support 20 provided on the inner surface thereof, and the end portion of the guide tube 19 is connected to the opening 21 of the mounting flange 4.

An operating rod 22 is inserted into the guide tube 19, and the upper part of the operating rod 22 is connected to the drive mechanism 1.
6 and is operated in vertical and rotational directions.

In addition, a detector 23 is located at the bottom of the operating rod 22,
For example, an ultrasonic transducer is connected.

In addition, the small diameter through hole 15 of the inspection plug 13
An operating mechanism 25 of the opening/closing device 24 is inserted into the opening/closing device 24, and below the operating mechanism 25, the partition mechanisms 18a,
Opening/closing mechanism 26 formed on each side of 18b
a, 26b are provided and the partition mechanism 18a,
It is connected to and interlocks with 18b.

That is, by driving the opening/closing device 24, shutters (not shown) provided in the partition mechanisms 18a, 18b are opened and closed.

Note that below the mounting flange 4 in the furnace vessel 1 as a boundary is a high pressure plenum region HP, and above it is a low pressure plenum region LP.

In addition, the drive mechanism 16, extension tube 17, detector 23, and switchgear 2 as a furnace inspection device
4. When the operating mechanism 25 is not used, dummy plugs 27 and 28 are inserted into the through holes 14 and 15, respectively, as shown in FIG.

Incidentally, if necessary, it is also possible to provide multiple through-holes 12 for in-furnace inspection equipment at other positions on the shielding plug to improve the capability of in-furnace inspection.

FIG. 3 shows another embodiment of the present invention, in which a heat shielding body 29 is provided on the outer or inner surface of the guide tube 19 to protect the guide tube 19 from sudden changes in the temperature of sodium. show.

(Effects of the Invention) Next, a method of inspecting the surface of the reactor vessel, particularly the high-pressure coolant plenum region, using the in-core inspection device configured as described above will be described.

During power operation of the reactor, as shown in Figure 3,
Through hole 1 of inspection plug 13 on large rotating plug 5
Dummy plugs 27 and 28 are inserted into the holes 4 and 15 to serve as a cover gas powder and to protect against heat and radiation.

Also, a partition mechanism 18 at the upper end of the guide tube 19
a and 18b are closed by an opening/closing device 24, and the coolant serves as a partition between the high pressure plenum HP and the low pressure plenum LP.

On the other hand, when inspecting the reactor interior after reactor shutdown, the reactor mode is switched to maintenance mode, the dummy plug 28 is pulled out as shown in FIG. An opening/closing mechanism 26a at the tip of the operating mechanism 25,
After mechanically coupling with the drive part of 26b, the opening/closing mechanism 2
The partition mechanism 18a, through the operation of 6a, 26b.
18b is opened.

Thereafter, the dummy plug 27 is pulled out from the other through hole 14 of the inspection plug 13, and the drive device 16, extension tube 17, and detector 23 of the furnace inspection device are installed.

The extension tube 17 is extended by the operation of the drive device 16, and the detector 23 at the lower end is positioned in the space below from the mounting flange 4 of the core support structure 3, and the detector 23 is positioned in a desired direction, and the detector 23 is positioned in the high pressure plenum area HP.
Perform surface inspection of objects located in

After the inspection work is completed, the reactor can restart its output operation by reversing the above procedure to return to the state shown in Figure 2.

The plurality of opening/closing mechanisms 26a, 26b are, for example, a fourth opening/closing mechanism 26a, 26b.
One operating mechanism 25 is arranged in a plane as shown in the figure.
It is possible to operate reliably by In FIG. 4, reference numerals 30a and 30b indicate connecting portions into which the distal end portion of the operating mechanism 25 is inserted.

(Effects of the present invention) As explained above, the nuclear reactor internal inspection apparatus according to the present invention has the following effects.

Using the under-the-plug concept used in sodium-cooled fast breeder reactors, surface inspections of equipment that forms the high-pressure coolant plenum, such as core support structures and reactor vessels, can be performed completely remotely and with high radiation exposure. It can be done without any additional work.

Despite having communication holes in the high-pressure plenum area, leakage of high-pressure coolant can be reliably prevented, and when inspection is desired, equipment through-holes can be drilled into the high-pressure and low-pressure plenum partition members relatively easily from the top of the furnace. Therefore, surface inspection of high-pressure plenum forming equipment can be performed without any loss in reactor performance or functionality.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view partially showing a side view of a nuclear reactor in which an embodiment of the inspection device for a nuclear reactor according to the present invention is installed, and FIG. 2 is a state of the reactor during power operation in FIG. 1. FIG. 3 is a schematic sectional view showing only the left half of another embodiment of the present invention, and FIG. 4 is a view taken in the - direction arrow of FIG. 2. 1...Furnace vessel, 4...Mounting flange, 5...
Large rotation plug, 6... Small rotation plug, 13... Inspection plug, 17... Extension tube, 18... Partition mechanism,
19... Guide tube, 23... Detector, 24... Switching device, 25... Operating mechanism, 26... Opening/closing mechanism, 2
9...Heat shield.

Claims (1)

[Claims] 1. An inspection plug inserted into a shielding plug that closes the upper opening of the furnace vessel, a plurality of through holes provided in the inspection plug, an extension tube inserted into the through holes, and the through holes. an operating mechanism inserted into the hole; a drive mechanism provided at the top of the test plug and connected to the extension tube; an opening/closing device adjacent to the drive mechanism and connected to the operation mechanism; and a partition mechanism attached to the extension tube. a guide tube whose end portion is open and connected to a mounting flange mounted below in the furnace vessel; an in-furnace detector inserted into the guide tube and movable up and down; An inspection device for a nuclear reactor, comprising: the partition mechanism arranged therein; and an opening/closing mechanism connected to the partition mechanism and connectably provided to a lower end of the operating mechanism. 2. The inspection device for a nuclear reactor according to claim 1, wherein the guide tube has a heat shield on its outer peripheral surface.