JPS6039997B2 - pressure suppression device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is intended to safely maintain a nuclear reactor by suppressing pressure rise and uniformly absorbing energy when coolant is released into a reactor containment vessel in an electronic power generation plant. This invention relates to a pressure suppression device.

In electronic power generation plants, pressure suppression devices are used in the event of a loss of coolant accident such as a rupture of the primary system piping of the electronic furnace, steam exhaust pipes such as the main steam relief safety valve, and the exhaust of the turbine that drives the pumps of some emergency core cooling systems. The thermal energy of the steam released from the pipes is quickly absorbed within the primary containment vessel, suppressing the pressure rise, preventing the diffusion of reactor steam and water outside the reactor containment vessel, and forming a closed loop. It functions as a water source for the emergency core cooling system and protects the electronic power generation plant.

A reactor containment vessel is provided outside the reactor pressure vessel containing the reactor core, surrounding the reactor pressure vessel, and a drywell space is formed inside the reactor containment vessel.

A donut-shaped suppression chamber is provided below the reactor containment vessel, and pool water is stored in the suppression chamber. The dry well space and the suppression chamber are connected by a pent pipe that penetrates the reactor containment vessel. The pent tube is connected to a pent header within the subrepression chamber, and the pent header is provided with a plurality of downcomers having a closing portion in the pool water. others,
The steam exhaust pipe of the main steam relief safety valve installed in the main steam pipe that carried the reactor pressure vessel descends through the dry well space, passes through the pent pipe, enters the subreduction chamber, exits the vent pipe, and exits the pent pipe. Like the pipe, it is installed with an entrance into the pool water. Further, part of the exhaust machine for the pump driving turbine of the emergency core cooling system is also provided with a closed opening in the pool water, passing through the reactor containment vessel. Its function is that coolant such as steam released from the reactor pressure vessel is released into the pool water through the pent pipe, main steam safety relief valve exhaust pipe, pump drive turbine exhaust pipe, etc.
Thermal energy is absorbed and condensed by the pool water.

However, in such a pressure suppression device, it is desirable to design it more safely and effectively by considering the following points.

In other words, in these steam discharge pipes having a water entry point in the pool water, a non-condensable gas such as nitrogen gas or air is normally filled in the pipe.

For this reason, when coolant such as steam suddenly flows out into the swallow air discharge pipe, the non-condensable gas is released into the pool water in an overcompressed state, forming a non-condensable gas layer around the steam discharge pipe. Pushes up the pool water. [2] Coolant such as steam discharged into the pool water from the steam discharge pipe is designed to condense as uniformly as possible.The present invention takes the above points into consideration, and has an opening in the pool water. When a steam discharge pipe with a The purpose is also to obtain a pressure suppression device that condenses uniformly.

An embodiment of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a sectional view showing an embodiment of the pressure suppression device according to the present invention, and FIG. 2 is a side view of part 0 in FIG. 1 showing an embodiment of the discharge part in detail. shall be attached and explained.

A reactor pressure vessel 1 containing a reactor core (not shown) is installed, and a reactor containment vessel 2 is provided surrounding the reactor pressure vessel 1.

A reactor containment vessel 2 is provided surrounding the reactor pressure vessel 1 . A vedestal 3 is erected from the bottom of the reactor containment vessel 2 and supports the reactor pressure vessel 1 . A main steam pipe 11 is connected to the reactor pressure vessel 1,
The main steam pipe 11 is provided with a main steam relief safety valve (not shown). A suppression chamber 5 is provided below the reactor containment vessel 2 . Pool water 6 is stored in this subreduction chamber 5, and a space 7 is formed above it. The suppression chamber 5 is connected to the reactor containment vessel 2 through a plurality of pent pipes 8. The pent pipe 8 closes into the internal space of the reactor containment vessel 2, passes through the subreduction chamber 5, is provided in the upper space 7, and is connected to the pent header 9. A large number of downcomers 10 are attached to the pent header 9. The end of this downcomer 10 is submerged in the pool water 6, and the entrance part at the tip has a beveled surface cut at a certain face value, which is not perpendicular to the pipe axis, and the submerged part has a plurality of small holes. A hole 12a is provided. The beveled surfaces are oriented in arbitrary directions in each downcomer 10, and may be oriented in the same direction. The optimum size, arrangement, etc. of the small holes 12a vary depending on various discharge conditions, and are determined through experiments and the like. Of course, this discharge device 12 can be applied not only to the downcomer 10 but also to the main steam relief safety valve exhaust pipe and the exhaust pipe of the emergency core cooling pump driving turbine. In addition, the discharge devices 12 are not provided at the same level below the pool water 6, but in a staggered manner.
They may be provided adjacent to each other but not on the same level. Next, its effect will be explained.

When high-temperature, high-pressure steam flows into the downcomer 10 having an opening in the pool water 6 or other steam discharge pipes such as the main steam relief safety valve exhaust pipe, the non-condensable gas previously sealed in these steam discharge pipes is compressed. It is released into the pool water 6. At this time, the non-condensable gas flows out from the oblique opening at the tip and the small hole 12a at the side. For this reason, the non-condensable gas becomes medium-sized bubbles and small bubbles, making it difficult to form a gas layer. Even if a gas layer is formed, the air bubbles generated by the oblique incision and the air bubbles generated by the small holes 12a,
Since they are close to each other, it is relatively easy for the air bubbles to fit into the subrepression chamber space.

FIG. 3 is an explanatory diagram qualitatively showing this behavior, where the broken line shows the behavior of the conventional pressure suppression device and the solid line shows the behavior of the pressure suppression device according to the present invention.

The dynamic pressure due to the water jet indicates the jet force of the removed water when removing the water head in the pipe, but its peak value is reduced because of the compressed non-condensable water that produces the jet force. This is because the gas passes through the small hole 12a and is released into the pool water 6, and because the water jet force is dispersed by the oblique cut opening. Furthermore, pressure vibrations caused by non-condensable gas can be suppressed to minute fluctuations by forming small bubbles. Next, when the steam starts to be released into the pool water 6, the steam is first released from the oblique cut opening, and good steam condensation can be performed as before. Next, when the steam flow rate is low, the steam is discharged from the small holes 12a in the entire circumferential direction, so that the condensation becomes extremely uniform. FIG. 4 qualitatively shows this behavior, where the broken line shows the conventional behavior and the solid line shows the behavior by the pressure rise device of the present invention. Even in the stage of steam condensation, the steam dispersed and released from the small holes 12a is
Since the contact area with the pool water 6 increases and a small steam flow occurs, condensation is good and uniform. As described above, the discharge device 12 having the oblique cut opening and the small holes 12a can achieve good, uniform and rapid concentration, and even when non-condensable gas is released, the diagonal cut opening of the discharge device allows for appropriate expansion. The pressure amplitude due to expansion and contraction of the non-condensable gas can be suppressed to an extremely small level by forming small bubbles by the small holes 12a.

Water jet forces can be reduced as well. In this way, uniform condensation is achieved, the pressure amplitude due to non-condensable gas and the water jet force are reduced, and the force acting on the steam discharge pipe is also reduced. The above explanation has been given regarding the pressure suppression device for the Mark 1 type reactor containment vessel, but the generality is not limited to the Mark 1 type reactor containment vessel, and the generality is not limited to the pressure suppression device for other types of reactor containment vessels. do not have.

As an example, FIG. 5 is a sectional view showing an embodiment of the pressure suppression device for the Mark O type reactor containment vessel. In this embodiment, a pent pipe 88 is directly submerged in the pool water 6 as the steam discharge pipe. A discharge device 12 will be provided at this end. As explained above, the steam discharge pipe submerged in the pool water 6 is provided with a diagonal incision at its tip and a discharge device having a large number of small holes, thereby providing a good, uniform and quick steam discharge. In addition to obtaining condensation, even when non-condensable gas is released, it expands appropriately at the oblique cut opening, forms a group of small bubbles through the small hole 12a, and reduces the pressure amplitude, and the water jet is also used to remove the water head inside the discharge pipe. Reducing the force will improve the safety of the boiler, the steam discharge pipe, the suppression chamber 5 and its internal structures.

Therefore, the safety of the entire nuclear reactor will also be improved.
Although the present invention has been described above with reference to specific examples, the present invention is not limited to these specific embodiments, and it goes without saying that many changes and modifications can be made without departing from the spirit of the invention.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the internal structure of a nuclear reactor containment vessel equipped with a discharge device according to the present invention, and FIG.
3 is an explanatory diagram qualitatively showing the pressure fluctuation, FIG. 4 is an explanatory diagram qualitatively showing the load acting on the structure, and FIG. 5 is a diagram showing the discharge device according to the present invention. FIG. 3 is a cross-sectional view showing another example of the internal structure of the containment vessel of the nuclear reactor. 5...Subrection chamber, 6...
Pool water, 7...Space, 8...Vent pipe, 9...Vent header, 10...Downcomer, 12...Discharge device, 12a... Small hole. Figure 4 Figure 1 Figure 2 Figure 3 Figure 5

Claims (1)

[Scope of Claims] 1. A sealed container that contains pool water and is located below the reactor containment vessel that surrounds the reactor pressure vessel; In the pressure suppression device consisting of an open steam discharge pipe in the pool water to suppress rising, the end of the steam discharge pipe is cut in a plane inclined with respect to the pipe axis, and the tip thereof is made open. A pressure suppression device characterized by: 2. Located below the reactor containment vessel that surrounds the reactor pressure vessel, there is a sealed container that contains pool water, and the above-mentioned container that penetrates this container in a watertight manner to condense steam and suppress pressure rise inside the container. In a pressure suppression device consisting of a steam discharge pipe that opens into pool water, the end of the steam discharge pipe is cut in a plane inclined with respect to the pipe axis, the tip thereof is opened, and a plurality of pipes are installed near the opening. A pressure suppression device characterized by having a small hole.