JP7182521B2 - Reactor system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nuclear reactor system having a reactor melt holding apparatus for holding reactor melt (fuel debris) containing melted fuel in a reactor vessel.

In a nuclear reactor system, assuming a loss of heat removal source in the core, a loss of coolant due to damage to the reactor vessel, and a scram failure event when the coolant flow rate decreases or when the power increases, the fuel in the core melts, Reactor melts (fuel debris) containing molten fuel can fall to the bottom of the reactor vessel.

In order to prevent the falling fuel debris from thermally damaging the bottom of the reactor vessel and releasing radioactive materials outside the reactor vessel, the fuel debris that has fallen to the bottom of the reactor vessel is A nuclear reactor system has been proposed that has a reactor melt holding device that holds at the .

Japanese Patent Application Laid-Open No. 2014-157029 (Patent Document 1) is a background art of this technical field.

This Patent Document 1 describes a reactor vessel that houses a core and holds a reactor coolant, and a molten fuel holding device that holds melted fuel that melts in the core and falls from the core in the event of an accident. A nuclear reactor system comprising: Patent Document 1 describes a molten fuel holding device that is installed inside the reactor vessel and below the core, and has a plate-like receiving pan that spreads in the horizontal direction. It is described that it has a protruding part that protrudes upwards, a recess in the upper surface, and a through hole that penetrates vertically (see abstract).

JP 2014-157029 A

Patent Literature 1 describes a nuclear reactor system provided with a molten fuel holding device that holds molten fuel falling from the core in the event of an accident and has a plate-shaped receiving pan extending horizontally.

However, in Patent Document 1, the fuel debris deposited on the molten fuel holding device (reactor melt holding device) is not sufficiently cooled, the reactor melt holding device melts, and the fuel debris is released into the reactor vessel. There is no mention of the possibility of falling to the bottom of the

In other words, in the reactor system described in Patent Document 1, there is a possibility that the volume (amount) of fuel debris falling per unit area (fixed area) will be large (large), and the thickness of the fuel debris that can be cooled In order to achieve this, it is necessary to increase the diameter of the reactor melt holding device, which may lead to an increase in the size of the reactor vessel, which may worsen economic efficiency.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a nuclear reactor system having a reactor melt holding device that is excellent in cooling efficiency without increasing the diameter of the reactor melt holding device.

In order to solve the above problems, the nuclear reactor system of the present invention comprises a reactor vessel filled with a coolant, and a core portion installed in the reactor vessel and having a plurality of control rod guide tubes through which control rods are guided. and a reactor melt holding device for holding the reactor melt that falls from the core, wherein the reactor melt holding device includes a plurality of reactor melts installed in the radial direction of the reactor vessel. A plurality of reactor melt holding containers are installed with a gap between adjacent reactor melt holding containers . characterized by having a shroud in which a coolant inlet is formed .

According to the present invention, it is possible to provide a nuclear reactor system having a reactor melt holding device with excellent cooling efficiency without increasing the diameter of the reactor melt holding device.

Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a cross-sectional elevational view for explaining the nuclear reactor system described in Example 1. FIG. FIG. 2 is a cross-sectional view of the nuclear reactor system described in Example 1, viewed from line AA shown in FIG. 1; FIG. 2 is a cross-sectional elevational view of the nuclear reactor system described in Example 1, which explains the reactor system at the time of core damage. FIG. 4 is a cross-sectional elevational view for explaining the nuclear reactor system described in Example 2;

Embodiments of the present invention will be described below with reference to the drawings. In addition, substantially the same or similar configurations are denoted by the same reference numerals, and the description may be omitted if the description is redundant.

First, the nuclear reactor system described in Example 1 will be described.

FIG. 1 is a cross-sectional elevational view illustrating the nuclear reactor system described in Example 1. FIG.

The nuclear reactor system described in this embodiment has a reactor vessel 1 and a core section 2 at the center of the reactor vessel 1 .

The core section 2 generates heat due to nuclear fission reaction, and the output is controlled by the output control device 3 . The interior of the reactor vessel 1 is substantially filled with the coolant 4, and with the core internals 5 as a boundary, the core upper part becomes the hot pool 6 and the core lower part becomes the cold pool 7.

Coolant 4 heated by core 2 flows into hot pool 6 , is cooled by heat exchanger 8 , and flows out to cold pool 7 . The coolant 4 in the cold pool 7 is supplied to the core section 2 by the pump 9 via the coolant retention section 10 installed below the core section 2 . Thus, the coolant 4 circulates through the core section 2 , the hot pool 6 , the heat exchanger 8 , the cold pool 7 , the pump 9 , the coolant retention section 10 and the core section 2 .

In addition, sodium is supplied to the heat exchanger 8, and in the heat exchanger 8, heat is exchanged between the coolant 4 to be heated and the supplied sodium.

A plurality of control rod guide tubes 13 through which control rods are guided are installed in the core section 2 .

In addition, below the coolant retention part 10 (below the core part 2), in the unlikely event that the fuel in the core part 2 melts, reactor molten material (fuel debris) containing the melted fuel will be deposited in the core part. 2 to the bottom of the reactor vessel 1, a reactor melt holding device is installed in the reactor vessel 1 to hold (capture) fuel debris.

This reactor melt holding device has a plurality of reactor melt holding containers 11 installed in the radial direction (horizontal direction) of the reactor vessel 1 .

A plurality of reactor melt holding containers 11 are installed with gaps between adjacent reactor melt holding containers 11 . By forming this gap, the coolant 4 flows (rises) through this gap, and the cooling efficiency of the reactor melt container 11 is improved.

The reactor melt holding apparatus also has an umbrella structure 14 . This umbrella-shaped structure 14 is installed above the reactor melt holding vessel 11 and between the adjacent reactor melt holding vessels 11 . The umbrella-shaped structure 14 supplies the coolant 4 flowing through the gap to the upper side of the reactor melt holding vessel 11, and furthermore, the cooling efficiency of the reactor melt holding vessel 11 is improved. In addition, the umbrella-like structure 14 traps fuel debris falling through the gaps to reduce fuel debris falling to the bottom of the reactor vessel 1 .

Note that the reactor melt holding device (reactor melt holding vessel 11 and umbrella-like structure 14) described in this embodiment does not necessarily capture 100% of falling fuel debris. A few percent of fuel debris falling to the bottom of the reactor vessel 1 is allowed. Even if several percent of fuel debris falls to the bottom of the reactor vessel 1, the nuclear reactor melt holding device described in this embodiment diffuses and accumulates, that is, per unit area (fixed area) , based on the knowledge that the accumulated fuel debris will not increase in volume and the bottom of the reactor vessel 1 will not be damaged.

In addition, the coolant 4 flowing out from the heat exchanger 8 to the cold pool 7 flows out to the cold pool 7 via the pipe 17 . The end of this pipe 17 is installed below the bottom (lower part) of the reactor melt holding vessel 11 . Thereby, the cooling efficiency of the reactor molten material holding container 11 is further improved.

In addition, it is preferable that the reactor melt container 11 has a height b longer than its diameter a. Thereby, the cooling efficiency of the reactor molten material holding container 11 is further improved.

Moreover, it is preferable that the reactor melt storage containers 11 are installed directly below (immediately below) the control rod guide tubes 13 in correspondence with each other. In other words, it is preferable that the position where the reactor melt holding container 11 is installed is a position corresponding to directly below (directly below) the control rod guide tube 13 . One prescribed (one bundle) of control rod guide tubes 13 corresponds to one prescribed nuclear reactor melt holding vessel 11 . As a result, falling fuel debris (atomized fuel debris) can be captured efficiently.

Further, it is preferable that the bottom surface (bottom portion) of the reactor melt holding container 11 is hemispherical. As a result, the pressure loss of the coolant 4 rising around the reactor melt container 11 is reduced, and the cooling efficiency is improved. Also, the thermal stress of the reactor melt container 11 is reduced (relaxed).

Moreover, it is preferable that each of the reactor melt holding containers 11 is provided with a structure for taking out, such as a handle. When removing the fuel debris from the reactor vessel 1 , the reactor melt holding container 11 can be taken out of the reactor vessel 1 individually.

Next, the nuclear reactor system described in the first embodiment, viewed from line AA shown in FIG. 1, will be described.

FIG. 2 is a cross-sectional view of the nuclear reactor system described in Example 1, viewed from line AA shown in FIG.

In the nuclear reactor system described in this embodiment, a plurality of (seven in this embodiment) reactor melt holding containers 11 are installed in the horizontal direction of the reactor vessel 1 in a zigzag pattern.

In this embodiment, one in the center and six reactor melt storage containers 11 around this one are installed in a hexagonal structure.

Moreover, these seven nuclear reactor molten material holding containers 11 are installed with gaps formed between adjacent nuclear reactor molten material holding containers 11 . As a result, each reactor melt holding container 11 comes into contact with the coolant 4, and the cooling efficiency of each reactor melt holding container 11 is improved.

Also, in this embodiment, a plurality of (six in this embodiment) umbrella-shaped structures 14 are installed. The umbrella-shaped structure 14 is installed in a gap formed between the adjacent reactor melt holding containers 11, and straddles a plurality of (three in this embodiment) reactor melt holding containers 11. is installed as follows. As a result, the coolant 4 flowing through the gap can be efficiently supplied to the upper side of the reactor molten material holding vessel 11, and the fuel debris falling through the gap can also be efficiently captured, thereby closing the gap. Falling fuel debris can be reduced.

It should be noted that the diameter a of the reactor melt container 11 is preferably two to three times the diameter of the control rod guide tube 13 . For example, when the diameter of the control rod guide tube 13 is 10 cm, the diameter a of the reactor melt holding vessel 11 is 20 cm to 30 cm. As a result, fuel debris can be captured efficiently.

Next, the nuclear reactor system described in the first embodiment, which is a nuclear reactor system at the time of core damage, will be described.

FIG. 3 is a cross-sectional elevational view of the nuclear reactor system described in Example 1 and explaining the nuclear reactor system at the time of core damage.

Here, it is assumed that the core section 2 is damaged in an unlikely event.

When the core 2 is damaged, the fuel in the core 2 melts, and the fuel debris 12 containing the melted fuel penetrates the coolant reservoir 10 and falls to the bottom of the reactor vessel 1 . At this time, the fuel debris 12 flows out from the control rod guide pipes 13 installed to protrude into the cold pool 7 and falls to the bottom of the reactor vessel 1 . At this time, the fuel debris 12 interacts with the coolant 4 and is atomized to about several millimeters (about 0.5 mm to 5.0 mm).

In this embodiment, such atomized fuel debris 12 is captured by a reactor melt holding vessel 11 of a reactor melt holding apparatus installed in the reactor vessel 1 .

A plurality of reactor melt holding containers 11 are installed in the horizontal direction, and since gaps are formed between the adjacent reactor melt holding containers 11, the coolant 4 flows (rises) through these gaps. and efficiently cools the reactor melt holding container 11 that has captured the fuel debris 12 .

The coolant 4 heated by the reactor melt container 11 is cooled by the heat exchanger 8 and supplied to the bottom (lower part) of the reactor melt container 11 .

By doing so, even if the pump 9 fails, the reactor melt holding vessel 11 can be cooled. This is because the difference in height between the heat exchanger 8 and the reactor melt container 11 generates a natural circulation force.

Thus, in the reactor system described in this embodiment, a plurality of reactor melt holding vessels 11 are installed in the horizontal direction, and gaps are formed between adjacent reactor melt holding vessels 11. . As a result, this gap can be used as a flow path for the coolant 4, the cooling area of each reactor melt holding container 11 is increased, the thickness of the fuel debris 12 that can be cooled is increased, and the horizontal A compact reactor melt holding apparatus can be provided. This reactor melt holding device can stably hold and cool high-temperature fuel debris.

In addition, in a small nuclear reactor system in which the core part 2 is not flat (no spread), the volume of fuel debris falling per unit area (constant area) is large, so the thickness of the fuel debris that can be cooled is set to For this purpose, it is necessary to increase the diameter of the device for holding the molten material of the nuclear reactor, which causes the problem of increasing the size of the reactor vessel 1 . However, since the nuclear reactor system described in this embodiment can solve such problems, it is particularly effective for small nuclear reactor systems.

Next, the nuclear reactor system described in Example 2 will be described.

FIG. 4 is a cross-sectional elevational view for explaining the nuclear reactor system described in Example 2. FIG.

The reactor system described in this example further has a shroud 16 as compared to the reactor system described in the first example. By installing the shroud 16 in this way, the inside of the shroud 16 becomes an upward flow, and the outside of the shroud 16 becomes a downward flow, thereby improving the cooling efficiency of the reactor molten material holding vessel 11 .

This shroud 16 houses the reactor melt holding apparatus therein. The shroud 16 is cylindrical in its lower portion and conical in its upper portion with a larger opening above than below. That is, the shroud 16 has a columnar structure at its lower portion and a conical structure at its upper portion. As a result, falling fuel debris (atomized fuel debris) can be captured efficiently.

A plurality of coolant inlets 15 are formed in the outer circumference of the shroud 16 . The coolant 4 flows into the shroud 16 from the coolant inlet 15 and flows out to the cold pool 7 from the opening at the top of the shroud 16 .

The coolant inlet 15 is installed below the bottom (lower portion) of the reactor melt container 11 . Thereby, the cooling efficiency of the reactor molten material holding container 11 is further improved.

Also, the conical structure of the shroud 16 is installed above the umbrella structure 14 . In other words, the shroud 16 is formed such that the diameter of the region above the nuclear reactor melt holding device (umbrella-like structure 14) installed therein increases upward. As a result, falling fuel debris can be efficiently captured, and fuel debris falling to the periphery of the reactor melt holding container 11 can also be captured.

In addition, the conical structure of the shroud 16 and the pipe 17 are installed by devising the respective installation positions so as not to interfere with each other.

In addition, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail and specificity in order to facilitate the understanding of the present invention, and are not necessarily limited to those having all the described components. Also, it is possible to replace part of the constituent elements of one embodiment with part of the constituent elements of another embodiment. It is also possible to add the constituent elements of another embodiment to the constituent elements of one embodiment. Moreover, it is also possible to add, delete, or replace a part of other constituent elements with respect to a part of the constituent elements of each embodiment.

DESCRIPTION OF SYMBOLS 1... Reactor vessel 2... Core part 3... Power control device 4... Coolant 5... Reactor internal structure 6... Hot pool 7... Cold pool 8... Heat exchanger 9... Pump 10... Coolant retention part 11... Reactor Molten material holding container 12 Fuel debris 13 Control rod guide tube 14 Umbrella-like structure 15 Coolant inlet 16 Shroud 17 Piping

Claims (7)

A reactor vessel filled with a coolant, a core portion installed in the reactor vessel and having a plurality of control rod guide tubes through which control rods are guided, and a reactor melt that falls from the core portion are held. a reactor melt holding device;
The reactor melt holding device has a plurality of reactor melt holding vessels installed in the radial direction of the reactor vessel, and the plurality of reactor melt holding vessels are adjacent to the reactor. It is installed with a gap formed between it and the melt holding container ,
A nuclear reactor system comprising a shroud in which a plurality of coolant inlets are formed on the periphery of the reactor melt holding device . 2. The nuclear reactor system according to claim 1, wherein said reactor melt holding vessels are installed directly below said control rod guide tubes in correspondence with each other. 2. The nuclear reactor system of claim 1, wherein each of said reactor melt holding vessels has a structure for removal from said reactor vessel. 2. The nuclear reactor system according to claim 1, wherein said reactor melt container has a hemispherical bottom. 2. The nuclear reactor system of claim 1, wherein said reactor melt holding vessel is longer in height than in diameter. 2. The nuclear reactor system according to claim 1, wherein said reactor melt holding device has an umbrella-like structure above a gap formed between adjacent said reactor melt holding containers. 2. The nuclear reactor system according to claim 1 , wherein said shroud increases in diameter upwardly in a region above a reactor melt holding device installed therein.

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