JPS6151752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for vertically separating a dry well and a suppression chamber in a nuclear reactor containment vessel to maintain airtightness.

Boiling water reactor containment vessels are equipped with a suppression chamber, which is a pressure suppression chamber, to ensure safety even in the event of a major accident that would normally not occur. This suppression chamber has a cylindrical shape, and there is a type commonly called MAPK-type in which a dry well for storing a reactor pressure vessel and the like is combined in the upper part of the suppression chamber. The dry well and suppression chamber are separated by a diaphragm floor, and in the event of an accident, the steam generated is guided into the water inside the suppression chamber through a vent pipe, condensed, and suppresses the pressure rise inside the dry well. It's summery. Therefore, the dry well and suppression chamber must be sealed.

FIG. 1 shows an overall sectional view of the MARK-type reactor containment vessel. In the figure, a nuclear reactor is provided with a reactor containment vessel 2 in a reactor building 1, this reactor containment vessel is partitioned into two by a diaphragm floor 10, and the upper space is a dry well 3 in which a reactor pressure vessel 11 is stored. , the lower space is used as a suppression chamber 4.

As mentioned above, the steam generated in the event of an accident is introduced into the water in the suppression chamber 4 through the vent pipe 5 and condensed, thereby suppressing the pressure increase in the dry well 3. For this reason, the dry well 3 and the suppression chamber 4 must be sealed, and a structure as shown in FIG. 2 has conventionally been used. In other words, in the figure, since the reactor containment vessel 2 and the diaphragm floor 10 have different displacements due to heat and internal pressure, a predetermined gap is provided to absorb this displacement, and the diaphragm floor is provided with this gap above the diaphragm floor 10. It is sealed by a seal bellows 12. Conventionally, the seal bellows 12 has been made of cloth-filled nylon, but this has the disadvantage that its service life is shorter than the life of the plant and it must be replaced several times during operation. For this reason, in recent years, it has been considered to make the seal bellows 12 from steel. However, if the seal bellows were made of steel, it would be impossible to bolt them together and they would have to be welded, but the Drywell 3
It has a conical shape, and because the equipment carrying-in hatch 7 and the control rod drive mechanism carrying-in/out hatch 8 are attached, it has the disadvantage that it cannot be carried in or installed in one piece. As a result, the construction process for the reactor will be significantly delayed.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a separation airtight device that can be carried in and installed as a unit even when a steel seal bellows is used.

Therefore, the feature of the separation airtight device of the present invention is that a diaphragm floor seal bellows is provided on the lower outer periphery of the diaphragm floor. This part is
As shown in FIG. 1, there is no equipment loading hatch 7, control rod drive mechanism loading/unloading hatch 8, vent pipe jet deflector 6, etc. located on the upper part of the diaphragm floor 10, so that space is secured. Therefore, installation and inspection of welded parts are easy, and the process can be shortened. Further, since the suppression chamber 4 is cylindrical, the seal bellows can be carried in as an integral unit, and then the diaphragm floor can be carried in and installation work can be carried out.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 3 shows an example of the detailed shape of the present invention. Since the reactor containment vessel 2 expands due to internal pressure during an accident, a reinforcing ring 9 that also serves as a diaphragm floor beam sheet 9 is attached to reduce this expansion. A support ring 16 is welded to this reinforcing ring 9, an outer bellows 14 is welded below this, and the other end is welded to the lower part of the diaphragm floor 10 via support rings 17 and 15. By doing this, since the support is removed from the reinforcing ring, the displacement caused by expansion due to internal pressure is small, and the stress applied to the bellows can be reduced. The bellows can therefore be simplified and made compact.

Bellows welding can be performed by providing an outer bellows 13 and applying pressure between it and the inner bellows 14 to enable a local leakage test.

FIG. 4 shows an example of the application of the shape shown in FIG. 3, in which the bellows 13 and 14 have a plurality of ridges, which absorbs more displacement than a single bellows, so the shape of the ridges can be made smaller. can.

In Figure 5, the shape of the seal bellows is circular, which eliminates the need for the support ring 17, and reduces the stress at the weld between the bellows and support rings 15 and 16 in the event of an accident (when internal pressure and heat are applied simultaneously). This can be considerably reduced compared to the embodiments shown in FIGS. 3 and 4.

[Brief explanation of the drawing]

FIG. 1 shows an overall sectional view of the reactor containment vessel, which is usually called the MARK-type, and FIG. 2 shows the diaphragm floor seal bellows 12 of the conventional dry well and suppression chamber partition device. Nearby sectional views, Figures 3, 4, and 5
The figure shows an embodiment of the present invention and is a diagram showing the installation state of seal bellows 13 and 14 of different shapes. 2...Reactor containment vessel, 3...Dry well,
4... Suppression chamber, 9... Diaphragm floor beam sheet, 10... Diaphragm floor, 13, 14... Bellows.

Claims (1)

[Scope of Claims] 1. A diaphragm floor that divides the inside of the reactor containment vessel into an upper and lower dry well and a suppression chamber, and a seal located below the diaphragm floor that seals the reactor containment vessel and the diaphragm floor. A separation airtight device for a dry well and a suppression chamber in a nuclear reactor containment vessel, characterized by comprising a bellows. 2. Airtight separation of the dry well and suppression chamber in the reactor containment vessel according to claim 1, wherein the seal bellows is provided between the reactor containment vessel reinforcing ring and the diaphragm floor. Device.