Reactor containment vessel
The reactor containment vessel's innovative design with a diaphragm floor and communication hole structure retains water on the upper drywell floor during LOCA, enhancing leak detection efficiency by preventing overflow into the lower drywell.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KK TOSHIBA
- Filing Date
- 2025-01-16
- Publication Date
- 2026-07-29
AI Technical Summary
In a nuclear power plant, during a loss-of-coolant accident (LOCA), water injected into the reactor pressure vessel flows out into the upper drywell and accumulates on the floor without being effectively transferred to the sump tank, complicating leak detection.
The reactor containment vessel is designed with a diaphragm floor and reactor pressure vessel pedestal to divide the internal space into upper and lower drywells, with a communication hole positioned above the water level to retain injected water on the upper drywell floor, and a vent pipe to direct excess water to the suppression chamber.
This design allows for efficient retention of water on the upper drywell floor during accidents, facilitating quick detection of leaks by preventing overflow into the lower drywell and enabling effective leak detection.
Smart Images
Figure 2026122687000001_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present invention relate to a reactor containment vessel used in a boiling water reactor.
Background Art
[0002] In a nuclear power plant, a leakage water detection device is installed to quickly detect any breakage or leakage event of the reactor coolant pressure boundary in the reactor containment vessel that encloses the reactor pressure vessel. Among these, for the detection of leakage water in the upper drywell (hereinafter referred to as D / W), a drain sump tank is installed at the bottom of the reactor containment vessel, and the upper D / W floor surface and the drain sump tank are connected by a drain pipe, so that the leakage water flowing out onto the upper D / W floor surface is collected by gravity in the drain sump tank, and a method for detecting the rise in the sump tank water level with a leakage water detector has been devised.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] In a nuclear power plant, in the event of a loss-of-coolant accident (hereinafter referred to as LOCA), which is an accident in which the primary coolant system piping connected to the reactor pressure vessel breaks due to some cause, the reactor is cooled by the automatic startup of the reactor isolation cooling system (hereinafter referred to as RCIC) or the reactor emergency cooling system (hereinafter referred to as ECCS). The water injected into the reactor pressure vessel by these cooling systems flows out to the upper D / W through the pipe break, and flows into the lower D / W from the opening on the upper D / W floor surface.
[0005] In the event of a LOCA (Low-Level Collision) in a nuclear power plant, the cooling system described above is expected to suppress overheating by injecting water into the reactor pressure vessel and allowing it to flow out into the upper D / W (Dead Water Works). This water is then retained on the upper D / W floor without flowing out into the lower D / W through openings in the upper D / W floor.
[0006] On the other hand, from the perspective of detecting leaks in the upper drywall, it is necessary to quickly transfer leaked water from the upper drywall floor to the sump tank in the lower drywall floor. [Means for solving the problem]
[0007] The reactor containment vessel according to the above embodiment houses a reactor pressure vessel, and divides the internal space into a drywell and a suppression chamber by a diaphragm floor and a reactor pressure vessel pedestal, with the space above the diaphragm floor being the upper drywell and the space below the reactor pressure vessel, surrounded circumferentially by the reactor pressure vessel pedestal, being the lower drywell, the upper drywell and the lower drywell being connected to the suppression chamber by a vent pipe, and a drywell communication hole being provided to equalize the pressure in the upper drywell and the lower drywell, characterized in that the opening end of the drywell communication hole is positioned at a height above the water level in the upper drywell during an accident, so that water injected into the upper drywell during an accident is retained on the upper drywell floor. [Effects of the Invention]
[0008] In an embodiment of the present invention, the reactor containment vessel allows for the filling of the upper drywell floor with water in the event of an accident. [Brief explanation of the drawing]
[0009] [Figure 1] A schematic longitudinal cross-sectional view of the reactor containment vessel according to Example 1. [Figure 2] A schematic longitudinal cross-sectional view of the reactor containment vessel according to Example 2. [Figure 3] Enlarged longitudinal cross-sectional view of the main part of the reactor containment vessel according to Example 3. [Modes for carrying out the invention]
[0010] The reactor containment vessel according to the present invention will be described below with reference to the drawings.
[0011] (Example 1) Figure 1 shows a schematic longitudinal cross-sectional view of a reactor containment vessel according to Embodiment 1. In Figure 1, the reactor containment vessel 1 consists of a reactor pressure vessel 12, a drywell (D / W) housing piping and the like connected thereto, and a suppression chamber 5 that stores pool water 16 to absorb the energy of steam released into the D / W in the event of an accident via a vent pipe 6.
[0012] This D / W and suppression chamber 5 are separated by the reactor pressure vessel pedestal 14 and the diaphragm floor 13.
[0013] Furthermore, the drywell (D / W) is divided into an upper drywell (hereinafter abbreviated as upper D / W) 2 that houses the main steam piping, etc., and a lower drywell (hereinafter abbreviated as lower D / W) 4 that houses the control rod drive mechanism (not shown), etc., and the upper D / W 2 and lower D / W 4 are connected by a D / W communication hole 3.
[0014] Under normal circumstances, drain generated by valves or the like installed in the piping connected to the reactor pressure vessel 12 is routed over the diaphragm floor 13 in the upper D / W2 and led to the drain sump tank 8 via drain pipe 10 routed from the drain side channel 7 through the D / W communication hole 3 into the lower D / W4.
[0015] When an accident such as a LOCA occurs, the drain valve 11 disposed in the drain pipe 10 is closed to block the drain guided from the drain pipe 10 to the drain sump tank 8. Then, water is injected into the upper D / W2 to raise the opening 3a of the D / W communication hole 3, which is an opening on the floor surface of the upper D / W2, to a height above the water filling level H in the upper D / W2. Thus, when water is injected into the upper D / W2, water can be held up to the level H on the floor surface of the upper D / W2 without flowing into the lower D / W4 from the opening end 3a of the floor surface of the upper D / W2.
[0016] (Example 2) Hereinafter, Example 2 will be described with reference to FIG. 2. FIG. 2 is a schematic longitudinal sectional view of a reactor containment vessel according to Example 2. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the configuration of those parts is omitted.
[0017] Regarding the reactor containment vessel 1a in FIG. 2, when an accident such as a LOCA occurs, the D / W communication hole 3 is raised to a height H above the water filling level H1 in the upper D / W2, and the opening end 6a of the vent pipe 6 is set at a position H1 lower than the opening end 3a of the communication hole 3. Thus, when the water filling level in the upper D / W2 reaches a certain height H1 or more, the water filling water in the upper D / W2 flows from the upper D / W2 into the pressure suppression chamber 5 through the vent pipe 6.
[0018] In this Example 2, although the D / W communication hole 3 and the vent pipe 6 are shown as an example where they are alternately and individually installed in the reactor pressure vessel pedestal 14, it is needless to say that it can also be applied when the vent pipe 6 is disposed below the D / W communication hole 3 as shown in FIG. 1.
[0019] (Example 3) Hereinafter, Example 3 will be described with reference to FIG. 3. FIG. 3 is an enlarged longitudinal sectional view of a main part of a reactor containment vessel according to Example 3. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the configuration of those parts is omitted.
[0020] Figure 3 shows a method for detecting leakage water in the upper D / W2 considering the water filling of the upper D / W2 in Practical Example 3.
[0021] On the floor surface 15 of the upper D / W2, an inclination in the direction of the drainage side groove 7 installed on this floor surface 15 is formed. And in the lower D / W4, a drain sump tank 8 is provided. A leakage water detector 9 is installed in this drain sump tank 8. The drainage side groove 7 on the floor of the upper D / W2 and the drain sump tank 8 of the lower D / W4 are connected by a drain pipe 10. A drain valve 11 is installed in the drain pipe 10 inside the lower D / W4. This drain valve 11 is in the "open" state during normal times, and control is performed to make it "closed" when implementing water filling to the upper D / W2.
[0022] With the above configuration, during normal times, when leakage water occurs in the upper D / W2, the leakage water is collected from the drainage side groove 7 on the floor of the upper D / W2 to the drain sump tank 8 of the lower D / W4 through the drain pipe 10, and the presence or absence of leakage water is detected by the leakage water detector 9. In case of an accident such as LOCA, when implementing water filling to the upper D / W2, by closing the drain valve 11, the water injected into the upper D / W2 is not allowed to flow into the drain sump tank 8 of the lower D / W4 and is retained on the floor surface of the upper D / W2.
[0023] Regarding the type of this drain valve 11, an electric valve operable under environmental conditions during accidents such as LOCA is applied. Note that a melting valve in which the valve rod and valve body melt and perform a "closed" operation under certain high-temperature conditions may be adopted, or a pressure valve that performs a "closed" operation under certain pressure conditions can be used so that it can be operated as static equipment. Also, the operation of a two-way valve in which an electric valve and a melting valve, or an electric valve and a pressure valve are connected or combined is also possible.
[0024] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention.
[0025] These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention.
[0026] These embodiments and their variations are included within the scope and essence of the invention, as well as within the scope of the claims and its equivalents. [Explanation of Symbols]
[0027] 1…Reactor containment vessel 1a…Reactor containment vessel 2… Upper drywell (Upper D / W) 3...D / W communication hole 3a...Open end 4…Lower drywell (Lower D / W) 5… Suppression Chamber 6... Bent pipe 6a...Open end 7…Drainage ditch 8…Drain sump tank 9… Leakage detector 10... Drain piping 11…Drain valve 12…Reactor pressure vessel 13…Diaphragm floor 14… Reactor pressure vessel pedestal 15…Floor surface 16... Pool water H, H1…Hydrostatic water level
Claims
1. The reactor pressure vessel is housed within a structure that divides the internal space into a drywell and a suppression chamber by a diaphragm floor and a reactor pressure vessel pedestal. The space above the diaphragm floor is designated as the upper drywell, and the space below the reactor pressure vessel, circumferentially surrounded by the reactor pressure vessel pedestal, is designated as the lower drywell. In a reactor containment vessel in which the upper drywell and the lower drywell are connected to the suppression chamber by a vent pipe, and a drywell communication hole is provided to equalize the pressure between the upper drywell and the lower drywell, A reactor containment vessel characterized in that the opening end of the drywell communication hole is positioned at a height equal to or greater than the water level in the upper drywell during an accident, thereby ensuring that water injected into the upper drywell during an accident is retained on the upper drywell floor.
2. The reactor containment vessel according to claim 1, characterized in that the open end of the vent pipe is positioned higher than the upper drywell floor and lower than the open end of the drywell communication hole, so that after the water level in the upper drywell reaches a certain height or higher, the water in the upper drywell flows from the upper drywell into the suppression chamber.
3. The reactor pressure vessel is housed within a structure that divides the internal space into a drywell and a suppression chamber by a diaphragm floor and a reactor pressure vessel pedestal. The space above the diaphragm floor is designated as the upper drywell, and the space below the reactor pressure vessel, circumferentially surrounded by the reactor pressure vessel pedestal, is designated as the lower drywell. In a reactor containment vessel in which the upper drywell and the lower drywell are connected to the suppression chamber by a vent pipe, and drywell communication holes are provided to equalize the pressure between the upper drywell and the lower drywell, A reactor containment vessel characterized in that a drainage channel is installed on the diaphragm floor, water leaking into the upper drywell is guided from the drainage channel to the drain sump via a drain pipe, and a drain valve located in the drain pipe is closed when the upper drywell is filled with water in the event of an accident.
4. The reactor containment vessel according to claim 1, characterized in that a drainage channel is installed on the diaphragm floor, water leaking into the upper drywell in the event of an accident is guided from the drainage channel to the drain sump via a drain pipe, and a drain valve located in the drain pipe is closed when the upper drywell is filled with water.
5. The reactor containment vessel according to claim 2, characterized in that a drainage channel is installed on the diaphragm floor, water leaking into the upper drywell in the event of an accident is guided from the drainage channel to the drain sump via a drain pipe, and a drain valve located in the drain pipe is closed when the upper drywell is filled with water.
6. The reactor containment vessel according to any one of claims 3 to 5, characterized in that the drain valve is an electrically operated valve capable of operating under environmental conditions during a loss-of-cooling accident.
7. The reactor containment vessel according to any one of claims 3 to 5, characterized in that the drain valve is a molten valve that closes under certain high-temperature conditions.
8. The reactor containment vessel according to any one of claims 3 to 5, characterized in that the drain valve is a pressure valve that closes under certain pressure conditions.
9. The reactor containment vessel according to any one of claims 3 to 5, characterized in that the drain valve is a dual valve comprising an electric valve and a melting valve that closes under certain high-temperature conditions, or a dual valve comprising an electric valve and a pressure valve that closes under certain pressure conditions.