JPH0326996A - Pressure vessel with built-in emergency core cooling system - Google Patents

Abstract

PURPOSE:To attain simplification of a facility by reseving cooling water between a reactor pressure vessel and a partition provided in the inside thereof. CONSTITUTION:A partition 13 is provided in the inside of a reactor pressure vessel 1 to reserve cooling water 7 in a space formed between the vessel 1 and the partition 13 and a reactor core 6 in a primary cooling circuit can be immersed by its quantity of the cooling water. In addition, a small hole 8 is drilled on the upper part of the partition 13 to communicate a steam phase of a primary coolant circuit and a cooling water supply side steam phase each other to provide a rupture disc 9 on the lower part of the partition 13 so as to isolate the cooling water 7 and the primary coolant circuit each other. And at the time of an accident, for instance, in a case where main steam tubing 3 connected to the vessel 1 is broken, the pressure at the side of the primary coolant circuit lowers suddenly to break the disc 9 so as to allow the cooling water 7 to flow in the reactor core 6 since the pressure in the side of the cooling water 7 lowers slowly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to emergency core cooling equipment for boiling water nuclear reactors and steam cooled nuclear reactors.

[Conventional technology]

In the conventional system, as described in Japanese Patent Application Laid-Open No. 61-213792, the primary coolant circuit that transfers heat generated from the core and the cooling water pool surrounding it are hydrodynamically locked by hydrodynamic pressure balance. This is cut off by the provision of a Uritsu clock. This is because when an event such as the primary coolant circulation pump stops, the hydrodynamic pressure balance is disrupted and cooling water flows from the cooling water pool side to the primary coolant circuit side, causing a large amount of water to flow into the reactor core. It is designed to cool the air.

[Problem to be solved by the invention]

In the technology disclosed in JP-A No. 61-213792, the primary coolant circuit is submerged in a huge pool-shaped pressure vessel, which makes the pressure vessel huge and causes problems for the plant. There was a problem with the lack of feasibility in terms of the construction process and economic efficiency.

Furthermore, because the conventional technology uses the density difference between the high-temperature fluid and the low-temperature fluid (hydraulic lock) and the internal and external pressure balance of the primary coolant circuit, there is a risk that the lock mechanism will collapse due to fluctuations in the operating status of the reactor. Moreover, the conventional technology can only be applied to pressurized wooden reactors that have a stable flow state in the core during normal operation, that is, a single-phase flow state. Another problem is that it is difficult to apply to reactors with two-phase flow, such as boiling water reactors.

[Means for solving cms] In order to solve the three conventional problems, the present invention provides a partition inside the pressure vessel and stores cooling water in the space formed by the partition and the pressure vessel. This eliminates the need to submerge the coolant circuit in a huge pool.

Furthermore, in the present invention, the primary coolant circuit and the cooling water surrounding it are physically isolated by the partition wall and the rupture disk attached to the partition wall, so that the isolation function may be lost depending on the flow state of the primary coolant circuit. No such situation will occur. Furthermore, as mentioned above, in the present invention, the partition wall has a stable isolation function regardless of the flow state of the primary coolant circuit, that is, single-phase flow or two-phase flow, so that it can be used in pressurized water reactors, boiling water reactors, It can be applied not only to nuclear reactors but also to steam-cooled high conversion reactors.

[Effect]

FIG. 2 shows a schematic sectional view of the present invention. In the present invention. yX
A partition wall 3 is provided inside the sub-reactor pressure vessel l, and cooling water 7 is stored in a space formed between the partition wall 13 and the inner wall of the reactor pressure vessel. A small hole is provided at the top of the bulkhead to equalize the pressure between the reactor dome l9 and the cooling water 7 side. Also,
A rupture disk 9 is provided at the bottom of the partition wall, which ruptures when a predetermined differential pressure is applied. In the normal operating state of the reactor, the pressure on the reactor dome 19 side and the pressure on the cooling water 7 side are equalized through the small holes 8.
Almost no pressure acts on the rupture disk 9, and the primary coolant circuit and the cooling water 7 are isolated via the rupture disk 9. Here, in the event that a pipe connected to the reactor pressure vessel works, for example, the main steam pipe 3, ruptures, the coolant in the primary coolant circuit will be released outside the reactor pressure vessel through the rupture port. Therefore, the pressure on the primary coolant circuit side rapidly decreases.

On the other hand, the pressure on the cooling water 7 side also decreases because it communicates with the primary coolant circuit through the small holes 8, but the release of steam from the cooling water side is restricted by the small holes 8, so the pressure decreases. The degree of decrease is smaller than the degree of decrease on the primary coolant circuit side. This phenomenon is shown in Figure 3. Figure 3 shows that the pressure 11 on the primary coolant side decreases rapidly when a pipe rupture occurs, whereas the pressure 10 on the cooling water side decreases slowly due to restrictions on steam outflow from the small holes. , the pressure remains high.

Therefore, due to the differential pressure generated across the rupture disk,
The rupture disk ruptures and cooling water flows into the core, cooling the core and flooding it.

In the present invention, the rupture disk will not rupture except in situations where the pressure on the primary coolant circuit and the cooling water side changes rapidly, so there is no possibility of malfunctions occurring during gradual pressure rises or pressure drops during reactor startup and shutdown. No. [Example] An example of the present invention will be described below with reference to FIG. 1st
The figure shows a partition wall 13 provided on the outside of the downcomer section 2 of a boiling water reactor pressure vessel, and the vapor phase of the primary coolant circuit and the vapor phase of the cooling water side communicated through a small hole 8 attached to the top of the partition wall 13. It is something. The amount of cooling water stored in the space formed by the bulkhead 13 and the inner wall of the reactor pressure vessel is greater than the amount of water that can submerge the reactor core located in the primary cooling circuit, and is stored in a portion higher than the upper end 20 of the reactor core. This allows the reactor core 6 to be submerged in water in the event of a pipe rupture connecting to the pressure vessel. Here, in the case of a rupture in a large-diameter pipe connected to a pressure vessel, the reactor pressure will rapidly decrease, but in the case of a rupture in a small-diameter pipe, the reactor water level will drop, but the pressure will drop. Since the rate is small, a pressure difference between the primary coolant circuit side and the cooling water side is less likely to occur.In order to cope with this situation, automatic depressurization equipment that automatically opens the relief safety valve 14 is installed to prevent the reactor water level from being low. Alternatively, the reactor pressure is forcibly reduced using a high containment vessel pressure signal, allowing cooling water to flow into the reactor core and restoring the reactor water level. According to this embodiment, although the pressure vessel is somewhat larger in shape than the conventional boiling water reactor pressure vessel, it is possible to cool the emergency core, which was previously composed of an emergency diesel generator, electric pump, piping, and valves. Equipment can be deleted, and safety equipment can be made S-based. Furthermore, in this embodiment, all structural elements are static devices such as partition walls, small holes, and rupture disks, so reliability can be improved. Furthermore, in this example, since cooling water is stored in the outer periphery of the core, this cooling water functions as a damping material.
It is possible to reduce the amount of neutron irradiation to the yX nuclear reactor pressure vessel, and it is also possible to alleviate the irradiation embrittlement curse of the pressure vessel material.

FIG. 4 shows another embodiment of the invention. This embodiment also applies the present invention to a boiling water reactor like the previous embodiments, but a partition plate 18 is provided in the circumferential direction of the downcomer between the lower core shrou 13 in the pressure vessel and the inner wall of the pressure vessel. A part of the reactor coolant is used as a flow path for circulating reactor coolant as a primary cooling circuit, and the remaining part is used as a cooling water storage space isolated from the primary cooling circuit. As in the previous embodiment, the cooling water storage space is provided with a small hole 8 that communicates the reactor dome with the steam phase part of the cooling water storage space, and a rupture disk is placed at the bottom. According to this embodiment, a part of the downcomer section is used as a cooling water storage space, so compared to the embodiment shown in FIG.
The feature is that the inner diameter of the reactor pressure vessel can be made smaller. In the embodiment shown in FIGS. 1 and 4, the primary coolant circuit and the cooling water are completely separated by the rupture disk 9, so that the two fluids do not mix. Therefore, if the stored cooling water is filled with a neutron absorbing material such as boric acid water, boric acid water can be injected into the test water in the event of an accident, and in addition to inserting a control plug, it is possible to shut down the reactor. You can also back up the functionality.

FIG. 5 shows an embodiment in which this concept is applied to a steam-cooled high conversion reactor. In the case of this embodiment, as in Figures 3 and 4, a small hole is provided in the upper part of the partition wall inside the pressure vessel, and a rupture disk is provided in the lower part, but in the case of a steam-cooled furnace, the primary coolant circuit side is Since it is steam, the difference in water head between the rupture disk and the cooling water surface always acts on the rupture disk as differential pressure. Therefore, in this case, the rupture setting pressure of the rupture disk is set higher than that of the boiling water reactor by the water head difference to prevent the rupture disk from rupturing during normal operation.

FIG. 6 shows an embodiment in which a check valve for controlling the flow from the cooling water side to the primary cooling circuit side is provided in place of the rupture disk. According to this embodiment, in order to obtain the closing force of the check valve, the water level of the primary cooling circuit, that is, the reactor water level, is made higher than the water level of the emergency core cooling water. Keep the valve closed. [Effects of the Invention] According to the present invention, since cooling water is injected into the reactor core in the event of an accident using the pressure difference between the pressure vessel dome and the cooling water reservoir as a driving source, pressure boosting equipment such as pumps is not required. It has become.
Furthermore, there is no need for pressurizing equipment such as nitrogen gas such as a pressure accumulator, and the equipment can be simplified. Furthermore, since a water barrier material will be added to the outer periphery of the reactor core, the amount of neutron irradiation to the inner wall of the pressure vessel can be reduced, contributing to the extension of the neutron irradiation embrittlement life of the pressure vessel material. can.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention applied to a boiling water reactor, FIG. 2 is a sectional view showing an overview of the present invention,
Fig. 3 is a characteristic diagram showing the reactor dom pressure and cooling water storage space pressure behavior in the present invention, Fig. 4 is a sectional view of another embodiment of the present invention applied to BWR, and Fig. 5 is a steam A system diagram of an embodiment applied to a cooling furnace, and FIG. 6 is a sectional view of still another embodiment of the present invention. 1... Ryoko furnace pressure vessel, 2... Downcomer, 3...
・Main steam piping, 4... Water supply piping, 5... Dryer,
6...Reactor core, 7...Emergency core cooling water, 8...Small hole, 9...Rapcha tea 2 Ro $3 4th mouth (a no (l) Otsu mouth 1 (-A ＼ 7 chestnut Bin

Claims (1)

[Scope of Claims] 1. An emergency core cooling facility characterized in that a partition is provided within a reactor pressure vessel, and cooling water is stored in a space formed by the partition and the inner wall of the pressure vessel. 2. The internal partition wall of a nuclear reactor pressure vessel according to claim 1, wherein a small hole smaller than the inner diameter of a minimum diameter pipe connected to the pressure vessel is provided in the upper part of the partition wall to equalize the pressure inside and outside the partition wall. 3. An emergency core cooling facility, characterized in that a rupture disc is provided at the lower part of the partition wall according to claim 1 or 2. 4. According to claim 1 or 2, a check valve is provided at the lower part of the partition wall to form a flow path flowing from the space formed by the partition wall and the inner wall of the pressure vessel to the coolant side of the reactor. Features of emergency core cooling equipment. 5. An emergency core cooling facility characterized in that boric acid water is added to the cooling water stored in the space according to claim 1.