JPS6024883B2 - How to shut off steam generators and piping in nuclear power plants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to preparatory work for inspecting the inside of a steam generator of a nuclear power plant.

Figure 1 schematically shows the main parts of a nuclear power plant currently in commercial operation.

In FIG. 1, a reactor vessel 1 installed at a relatively low position in a containment vessel (not shown) has a lid 2 provided with a control drive mechanism (not shown), and a steam generator 3 1 via piping 5, 6, and the primary coolant (reactor vessel 1
This constitutes a circulation loop 10 for a heat medium (heat medium) that removes the heat generated in the steam generator 3, cools it, transfers heat to the water supplied in the steam generator 3, and evaporates it.

The number of loops 10 varies depending on the size of the power plant. The steam generator 3 has a U-shaped heat exchanger tube 9, and a water chamber 11 communicating with the pipes 5 and 6 is formed at its lower part.

Nuclear fuel is loaded in the reactor vessel 1, and when replacing it with new fuel after a predetermined period of operation or performing some internal inspection, a cavity 13 formed in the upper part of the reactor vessel 1 is used. When inspecting the inside of the steam generator 3 by filling it with water and removing the lid 2, the primary coolant (hereinafter referred to as coolant) is used.

) is removed to empty the water chamber 11 and heat exchanger tubes 9. Therefore, it is required to perform the work on the reactor vessel 1 and the work on the steam generator 3 in parallel and at the same time in order to improve the efficiency of the plant.

The present invention was made in view of the above-mentioned requirements, and an object of the present invention is to provide a method for safely and reliably shutting off the connection between a steam generator and piping.

Next, the present invention will be explained based on examples. First, after stopping the output operation of the reactor, performing operations such as cooling operation degassing and coolant purification operation, the coolant is circulated until it reaches a predetermined water level near the coolant inlet/outlet nozzle position of the reactor vessel 1. Partially extracted from the loop 10, water chamber 11 of the steam generator 3
empty inside.

The water chamber 11 of the steam generator 3 is divided into a part where high-temperature coolant flows in and a part where low-temperature coolant flows out, but since both are shut off in the same way, explain.

FIG. 2 shows a simplified structure related to the water chamber 11 of the steam generator 3. As shown in FIG.

When the above-mentioned extraction operation is performed, the water surface of the coolant reaches the reference numeral 1 in the nozzle 15 connected to the pipe 5 or 6, as shown in FIG.
6.

Next, the cover 20 of the manhole 18 is removed and opened. As shown in detail in FIG. 3, a stepped annular support 25 in which annular seats 21, 22, and 23 are formed is fixed in advance to the inner wall of the water stalk 11 surrounding the nozzle 15 by an appropriate means such as welding. ing. Next, a circular plate wire mesh (hereinafter referred to as wire mesh) 27 as shown in FIG. 4A is deformed as shown in FIG.
8 and carried into the water chamber 11, and is seated on the annular seat 21 as shown in FIG. The wire mesh 27 includes a protective ring 27a that is thin and highly elastic, and a wire mesh main body 2 made of an elastic steel wire.
7b, and even if it is deformed as shown in FIG. 4, it immediately returns to its original shape as shown in FIG. 4A, if external force is removed.
Thereafter, the annular sealing member, ie, the ring 29, is deformed as shown in the opening in FIG. 5, carried into the water chamber 11, and installed between the wire mesh 27 and the support 25 as shown in FIG.

Next, a circular sheet 3 made of extremely thin metal as shown in Fig. 6A.
1 is rolled up as shown in the opening of the figure, carried into the water chamber 11 through the manhole 18, and spread out again to cover the wire mesh 27 and the circle ring 29.

A plurality of sheets 31 are stacked according to their thickness. Next, blocks 33a, 33b, 33c, 33d, 33 that constitute a roughly hat-shaped lid 33 as shown in FIG.
e are individually carried into the water chamber 11 through the manhole 18. The opening in Figure 7 is block 3 with a typical shape.
3d, the block 33d is a U-shaped plate 3 having an arcuate flange portion 36 with fixing bolt holes 36 drilled therein.
7 and two ribs 39 provided between the flange portion 36 and having dowel pin holes 38 drilled therein. Block 33a, 3
3e has pin holes 41 drilled in the flange portion in addition to bolt holes. To attach the lid 33 to the support 25, the pin 43 mounted on the annular seat 23 of the support 25 is passed through the pin hole 41 of the blocks 33a, 33e, and the flange portion is seated on the annular seat 23, and then the block is attached. 33b, 33
Layer c and 33d between them and assemble as shown in Figure 7a.

Thereafter, when combined, an annular retaining ring 48 as shown in FIG. 8 is formed, and the arc-shaped pieces 48a, 48b, 48c, and 48d, each having a required number of bolt holes 49, are individually passed through the manhole 18 into the water chamber. 11.

an arcuate piece 48a having a pin hole 50 outside the bolt hole 49;
48d is first passed through the pin 43 and placed on the flange portion of the lid 33, and then the arcuate pieces 48b and 48c are placed on the flange portion of the lid 33 and roughened as shown in FIG. Then, a pin 45 is inserted into the pin hole 38 of the rib of the adjacent block of the lid 33 to integrate them. Finally, the lid 33 and ring 48 are fixed to the support 25 at the same time by screwing the bolts 51 into the screw holes of the support 25 through the bolt holes 35 and 49. By fixing the lid 33 and the ring 48, the O-ring 29 is slightly compressed and comes into close contact with the annular seat 22, the inner wall surface of the support 25, and the seat 31 with appropriate surface pressure.

According to the present embodiment described above, since the wire mesh 27 is first inserted, it is possible to prevent work tools and other objects from accidentally falling into the coolant in the pipe 5 during work, and also to prevent the O-ring 29 and the sheet from falling into the coolant in the pipe 5. 31 provides adequate sealing performance and allows the steam generator 3
It is possible to completely prevent the coolant from leaking into the reactor vessel, and as a result, the internal inspection and maintenance work of the steam generator 3 and the work on the reactor vessel 1 can be performed at the same time.

In the above embodiment, each member used for shutoff was carried into the water chamber 11 in the order of assembly, but it is of course possible to carry them in at the same time depending on the shape, size, etc. of the water chamber 11. It is.

[Brief explanation of the drawing]

Figure 1 is a layout diagram showing the main parts of a nuclear power plant, Figure 2 is a schematic sectional view showing the water chamber of the steam generator, and Figure 3 is a
Sectional view showing a state of interruption according to the embodiment of the present invention, No. 4
Figure A, the opening is a perspective view of the wire mesh 27, Figure 5 A, the opening is a perspective view of the circle ring 29, Figure 6 A and the opening are a perspective view showing the sheet 31 and the state in which the sheet 31 is rolled up, respectively, and Figure 7. A is lid 3
3 is a perspective view showing the assembled state, Figure 7 The opening is the lid 33
FIG. 8 is a perspective view showing one of the blocks constituting the presser ring, and FIG. 8 is a perspective view showing the assembled state of the presser ring. 1... Reactor vessel, 3... Steam generator, 5, 6... Piping, 9... Heat exchanger tube, 1
0...Loop, 11. ．． ．． ．． ．． ．． Water room, '15. ．．
... Nozzle, 16 ... Water surface, 18 ... Manhole, 20 ... Figure, 21, 22, 23 ... Annular seat, 25 ... Support, 27 ... ...Disc metal silk, 29...○ ring, 31...sheet, 33...lid,
33a-33e...Flock, 35...Bolt hole, 36
...Flange part, 37...U-shaped plate, 3
8...pin hole, 3 9...rib, 4 1...pin hole, 43...pin, 46...pin, 48...presser ring,
49...Bolt hole, 50...Pin hole. Little brother figure 4 figure 5 figure 2 figure 3 dancing figure 7 figure 8

Claims (1)

[Claims] 1. In a nuclear power plant that has a reactor vessel and a steam generator connected to the same vessel via piping, the primary coolant is removed from the steam generator and the manhole in the water chamber of the steam generator is opened. , a nuclear power plant characterized in that a circular metal mesh is inserted into the piping connection part of the water chamber, an annular sealing member is installed around the metal mesh, and then an assembly lid is installed to cover the metal mesh and the sealing member. How to shut off steam generators and piping in plants.