JPS60181686A - Vaccum breaker - 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 a vacuum breaking device for a pressure suppression type reactor containment vessel,
More specifically, a loss of coolant accident due to a rupture in a reactor cooling system piping
The present invention relates to a vacuum breaking device that maintains the integrity of a containment vessel in the event that a dent (hereinafter referred to as LOCA) occurs.

[Background of the invention]

Figure 1 shows the internal structure of a conventional (pressure suppression type) reactor containment vessel. The reactor containment vessel 1 has a diaphragm floor 4
The wet well 3 is divided into a dry well 2 and a wet well 3 through a wet well 3. Suppression pool water 5 is stored in the wet well 3, and the dry well 2 and wet well 3 have a bottom opening in the pool water 5. are connected via a plurality of vent pipes 6, 6, . . . which are submerged in water. In the figure, numeral 7 indicates a vacuum break valve provided in the bend pipe 6, and the vacuum break valve 7 is located within the wet well gas phase section 8.

In the above configuration, if a 10,000-LOCA occurs due to a rupture in the reactor cooling system piping, the pressure change characteristics in containment volume 7:1 will be approximately as follows (in addition, the LOCA
(Figure 2 shows the pressure change characteristics inside the containment vessel 1 during eight shots).

(1) With the rupture of the reactor cooling system piping, the coolant in the pressure vessel blows down into the dry well 2 of the containment vessel 1 through the rupture port of the secondary system piping, and Increase the temperature and pressure (Fig. 2-■).

(2) As the pressure in the dry well 2 increases, the non-condensable gas present in the vent pipe 6 is pushed out into the suppression pool water 5, and then the steam in the dry well 2 is pushed out into the pool water 5. It is discharged. The non-condensable gas discharged from the vent pipe 6 into the pool water 5 moves to the wet well side gas phase section 8 and flows from the dry well 2 into the pool water 5.
The steam discharged into the tank is condensed by the pool water 5. Therefore, the temperature and pressure inside the wet well 3 rise (Fig. 2-■).

(3) As the coolant in the pressure vessel flows out, the reactor pressure decreases, and the energy of the coolant blowing down into the dry well 2 decreases accordingly. The coolant t-1 blown down into the dry well 2 continues to flow out into the suppression pool water 5 through the vent pipe 6, but the energy of the coolant blown down into the dry well 2 is discharged from the vent pipe 6. As the discharge energy of the coolant becomes smaller, the temperature and pressure inside the dry well 2 begin to decrease (Fig. 2-■).

(4) Since the amount of coolant discharged from the vent pipe 6 into the suppression pool water 5 decreases as the pressure inside the dry well 2 decreases, The pressure difference between them approaches the head differential pressure of the vent pipe 6 (Fig. 2-■).

(5) After a LOCA occurs, when the core is re-flooded by the emergency core cooling system, the overflow water flows into the dry well 2 from the break in the primary system piping.
The steam inside is condensed. When the steam in the dry well 2 is condensed, the vacuum breaker valve 7 connecting the dry well 2 and wet well 3 is activated, and the air that has migrated to the wet well side gas phase 8 after entering the LOC eight is released. It is returned to the dry well 2 (Fig. 2-■).

(6) Next, the residual heat removal system (re5idual he
alremoval system (hereinafter referred to as RHR) heat exchanger is activated, and the suppression pool water 5 cooled by the RHRHR heat exchanger is transferred to the inside of the dry well 2 and the wet well side gas phase part 8 by the containment vessel spray.
(Fig. 2-■).

(7) While the amount of heat generated in the reactor is larger than the amount of heat removed by the RHR and heat exchanger, the temperature and pressure inside the containment vessel 1 gradually increase (Fig. 2-■).

(8) When the amount of heat generated in the reactor becomes less than the amount of heat removed by the R and HR heat exchangers due to the decrease in decay heat within the reactor, the temperature and pressure within the containment vessel 1 gradually decrease.

Here, the operation of the vacuum breaker valve 7 when a LOCA occurs will be explained in detail using FIGS. 3 and 4. When a LOCA occurs, the steam in the dry well 2 is It is sent into the suppression pool water 5 of the wet well 3 and is subjected to a condensation effect by the pool water 5. At this time, the non-condensable gas present in the vent pipe 6 is discharged into the pool water 5, and due to the discharge of this non-condensable gas, the liquid level of the pool water 5 rises (pool swell phenomenon). The pressure in the well 3 becomes higher than the pressure in the dry well 2, and the vacuum breaker valve 7 provided in the vent pipe 6 opens (see section X in FIGS. 4(a) and 4(b)). . After the pool swell described above, steam is discharged from the vent pipe 6 for a long time, but in the state t, the steam condenses discontinuously at the lower end opening (exit) of the vent pipe 6 ( chugging phenomenon), the pressure inside the vent pipe 6 also fluctuates discontinuously. When the pressure in the wet well 3 becomes higher than the pressure in the dry well 2 due to the discontinuous pressure fluctuations in the vent pipe 6, the vacuum breaker valve 7 opens as in the case of a pool swell. However, (see section Y in FIGS. 4A and 4B), the opening operation of the vacuum breaker valve 7 during chugging is approximately several hundred times. For this reason, in the past, it was necessary to design and manufacture the vacuum breaker valve 7 to be robust and precise enough to withstand hundreds of valve opening operations during the chugging process, thereby maintaining the integrity of the reactor. From this point of view, the vacuum breaker valve 7 has to be replaced one after another, and the effort and cost required for maintenance are enormous.

[Purpose of the invention]

The present invention was made as a result of various studies in order to solve the above-mentioned problems of the prior art. At the time of chugging that follows a swell, the present invention aims to provide a vacuum breaker device with an unprecedented new structure that can avoid hundreds of continuous operations like conventional vacuum breaker valves. .

[Summary of the invention]

In order to achieve the above object, the present invention stores pool water between a dry well and a wet well side gas phase part of a pressure suppression type reactor containment vessel, and a pipe having one end opened in the wet well side gas phase part. It is characterized in that the other end is opened into the pool water.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on an embodiment of FIG. 5. This figure shows the internal structure of a pressure suppression type reactor containment vessel incorporating the device of the present invention, and the same reference numerals as in FIG. 1 indicate the same parts. In other words, 1 is a general term for the entire containment vessel, 2 is a dry well, 3 is a wet well, 4 is a diaphragm floor, and 6 is a general term for the entire containment vessel.
8 is a vent pipe, and 8 is a gas phase part on the wet well side. In the present invention, pool water 10 is stored between the dry well 2 of the containment vessel 1 and the gas phase part 8 on the wet well side. The gist is that one end of the pipe 11 is opened at 8, and the other end of the pipe 11 is opened into the pool water 10. In the embodiment shown in FIG. 5, an annular pool 9 is provided at the boundary between the wall of the containment vessel 1 and the diaphragm floor 4, and a pipe 11 is provided between the wet well side gas phase section 8 and the pool water 10. is composed of double pipes 11a and llb, and the inner pipe 11a of the double pipes tia and 1tb is integrally molded with the pool bottom wall 9a, and its lower end opening faces the wet well side gas phase part 8, The above double Wi'ta,
communicating the inner tube passage 12 and the outer tube passage 13 of llb,
A case is shown in which the opening of the outer tube 11b faces into the pool water 10. In the figure, 11C indicates an expanded part provided in the middle of the pipe 11 connecting the wet well side gas phase part 8 and the pool water 10.

In the above configuration, if a LOCA occurs due to a rupture in the reactor cooling system piping, the pressure in the dry well 2 will be higher than the pressure in the wet well 3.
Although the water level in the pipe 11 rises, since the expansion part 11C is provided in the middle of the pipe 11, the pool water 10 can be raised without increasing the length of the pipe 11 located in the dry well 2. This can prevent the liquid from flowing into the wet well 3, contributing to making the device more compact. As the pressure within the dry well 2 increases, the steam within the dry well 2 is sent into the suppression pool water of the wet well 3 via the vent pipe 6 and is condensed by the pool water. , Prior to this, the non-condensable gas present in the vent pipe 6 is discharged into the suppression pool water, and due to the discharge of this non-condensable gas, the liquid level of the suppression pool water rises (false well phenomenon), wet. When the pressure in the well 3 becomes higher than the pressure in the dry well 2, the air in the wet well gas phase section 8 flows into the dry well 2 over the head differential pressure of the water immersion section of the pipe 11. The operating pressure differential of the conventional vacuum breaker valve built into the pressure suppression type reactor containment vessel is 0.5 ps id (pound per
5qUare 1nch different)
However, in the present invention, the head differential pressure of the water immersion part of the pipe 11 is set to 0.5 psid, and this is the operating differential pressure of the device of the present invention, that is, the vent clear value, and the pool water 10 If the highest water level (indicated by the symbol t1 in FIG. 5) is made to match the inlet height of the vent pipe 6 (indicated by the symbol t2 in FIG. Even if the gas flows into the interior, the vent clear value described above can always be maintained at 0.5 psid or less.

After the pool swell phenomenon described above, from the vent pipe 6,
Steam is released over a long period of time and is discontinuously condensed at the outlet of the vent pipe 6, resulting in a so-called chugging phenomenon.However, at this time of year when LOCA is low, the air in the wet well gas phase section 8 is dry. There is no so-called vent clear phenomenon in which water flows into well 2.

FIG. 6 shows another embodiment of the device of the present invention. In FIG. 6, the same symbols as in FIG. 5 indicate the same parts, and in the embodiment of FIG. 6, the wet well side gas phase part 8 and the pool water 1
A case is shown in which the pipe 11 connecting between the pipe 11 and the pipe 11 is not made into a double pipe, but one end of the pipe 11 is made to penetrate the diaphragm floor 4 and face the wet well side gas phase part 8.

FIG. 7 shows still another embodiment of the device of the present invention.

In FIG. 7, the same symbols as in FIG. 6 indicate the same parts,
In the embodiment shown in FIG. 7, the wet shell side gas phase section 8
A case is shown in which one end opening of the pipe 11 connecting between the pool water 10 and the pool water 10 is made to face the wet well side gas phase part 8 via a passage in the vent pipe 6.

Therefore, in the embodiment shown in FIG. 5 and the embodiment shown in FIG. 7, the number of diaphragm floor tributary holes can be reduced compared to the embodiment shown in FIG. There is no problem that the strength of the diaphragm floor 4 is reduced or the heat insulation is impaired, and no special efforts are required to solve the above problems.

〔Effect of the invention〕

The present invention is as described above, and the vacuum breaker according to the present invention operates during pool swell when LOCA occurs due to rupture of reactor cooling system piping, but during chugging following pool swell. It can avoid the continuous operation of hundreds of times as with conventional vacuum breaker valves, and since it does not have mechanically driven parts like vacuum breaker valves, it is highly reliable and maintenance-free. According to the present invention, it is possible to easily realize a vacuum breaking device with a novel structure that has never existed before.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view showing the internal structure of a conventional (pressure suppression type) reactor containment vessel, Figure 2 is a pressure change characteristic diagram inside the containment vessel during a loss of coolant accident, and Figure 3 is A partially enlarged view of the figure, Figures 4 (a) and (b) are operating pressure characteristic diagrams of the vacuum breaker valve in a coolant loss accident, and Figure 5 shows an embodiment of the vacuum breaker device according to the present invention. The longitudinal sectional view, FIG. 6, and FIG. 7 are all longitudinal sectional views showing other embodiments of the device of the present invention. 1...Reactor containment vessel, 2...Dry well, 3.
...Wetwell, 4...Diaphragm floor, 6
...Vent pipe, 8...Wetwell side gas phase section, 9
...Circular pool, 9a...Pool Jjl wall, 10.
...7'-#Water, 11...Pipe, lla...Inner pipe, iib...Outer pipe, 11C...Expansion part, 12.
...Inner pipe passage, 13...Outer pipe passage. Agent Patent Attorney Hiroo Nagasaki (and 1 other person) Koma 4 Zu Sen 5 Zu

Claims (1)

[Claims] 1. Pool water is stored between the dry well and the wet well side gas phase part of the pressure suppression type reactor containment vessel, and one end of the pipe is opened to the wet well side gas phase part, and the other end of the pipe is as described above. A vacuum breaking device characterized by opening into pool water. 2. In accordance with the invention set forth in claim 1, the pipe connecting the wet well side gas phase part and the pool water is constructed of a double pipe, and the inner pipe of the double pipe is connected to the bottom wall of the pool. The lower end opening faces the wet well side gas phase part, and the inner pipe passage and the outer pipe passage of the double pipe are communicated, and the opening of the outer pipe faces the pool water. Vacuum breaking device. 3. In the invention set forth in claim 1, a vacuum is provided in which one end of the pipe is opened into the pool water and the other end is opened into the gas phase part on the wet well side through a passage in the vent pipe attached to the diaphragm floor. Destructive device. 4. In the invention according to any one of claims 1 to 3, the vacuum breaking device has an expanded part in the middle of the pipe connecting the wet well side gas phase part and the pool water. 5. In the invention according to any one of claims 1 to 4, the highest water level of the pool water stored between the dry well and the wet well side gas phase section is attached to the diaphragm floor. Vacuum breaking device matched to the inlet height of the vent pipe.