WO2017067095A1

WO2017067095A1 - Core catcher

Info

Publication number: WO2017067095A1
Application number: PCT/CN2016/070208
Authority: WO
Inventors: 卢冬华; 梁振辉; 徐海岩; 张利
Original assignee: 中广核研究院有限公司; 中国广核集团有限公司; 中国广核电力股份有限公司
Priority date: 2015-10-23
Filing date: 2016-01-06
Publication date: 2017-04-27
Also published as: CN205104239U

Abstract

A core catcher, comprising a shell (110), a cooling channel (120), and a spacer grid (130). The cooling channel (120) comprises a horizontal channel (121) and multiple rod-like vertical channels (122) that are communicated with the horizontal channel (121). The horizontal channel (121) is provided at the bottom of the shell (110) and is communicated with a coolant inlet (111). The vertical channels (122) are disposed in the shell (110) and extend toward the top of the shell (110); melt filling channels are formed among adjacent vertical channels (122). The spacer grid (130) is fitted around each of the vertical channels (122) and is fixed on the inner wall of the shell (110); flow-through holes (132) communicated with the melt filling channels are formed on the spacer grid (130). The core catcher conducts away heat by means of saturated boiling of a coolant, has a simply structure and a small size, requires low costs, and has a good cooling effect. Meanwhile, the rod-like structural design of vertical channels (122) greatly increases the heat exchange area, reduces the risk of uneven stress around the channels, and increases the strength of the vertical channels (122). The number of the vertical channels (122) is also flexible and adjustable, thereby providing good adaptability.

Description

Core trap

Technical field

The utility model relates to the field of nuclear power plant safety equipment, in particular to a device for externally cooling and solidifying a core melt in the case of a serious reactor accident.

Background technique

Today, nuclear power has become an important energy component of many countries in the world. However, nuclear power has a very high use value, and it may also cause great harm. In the process of using nuclear power, if a major accident such as a nuclear leak occurs due to improper protection, it will bring the environment around the nuclear power plant and even the whole humanity. Extremely serious nuclear pollution disaster.

In the current nuclear power plant, the structure of the nuclear reactor is to form a reactor cavity in the containment, and a pressure vessel is arranged in the stack. When a serious accident occurs in the reactor, the melt of the core will melt through the pressure vessel casing, and an extremely serious nuclear accident may occur. In order to prevent the leakage of the core melt, the current conventional practice is to use a core melt external cooling and solidification device (also called a core trap), the following are common:

One is to provide an expansion chamber on the outer side of the pressure vessel, and a cooling water channel is arranged below the expansion chamber. After the core melt is fused through the lower head, the molten material flows into the expansion chamber, and the molten material is processed by the large-area plane of the expansion chamber. Cooling, the cooling water in the cooling water channel cools the melt to prevent the expansion chamber from being fused. However, this structure uses a large flat surface to level the melt to increase the cooling area of the melt and accelerate the cooling rate of the melt. However, such a design means occupying a large area under the containment and Space, and thus higher cost, also increases the difficulty of design.

Another way is to provide a barrel-shaped collector under the pressure vessel, a meltable sacrificial material is arranged in the collector, a cooling water channel is arranged outside the collector, and the molten material flows into the collector and interacts with the sacrificial material disposed therein. The melt is gradually cooled during the process of melting the sacrificial material. Due to the shape limitation of the collector, only the wall of the collector is taken away to remove the decay heat of the melt, and the heat transfer area is small, resulting in a small amount of heat transfer, especially after the central melt is collected and cooled.

Another way is to provide a collector under the pressure vessel, a cooling water channel is arranged outside the collector, a concrete bottom plate is arranged inside the collector, and a nozzle is arranged at the bottom of the collector, and the upper end of the nozzle extends into the concrete of the pile cavity The bottom plate and the lower end of the nozzle extend into the cooling water channel. After the molten material enters the collector, it first interacts with the concrete floor to cause the concrete to ablate. The concrete floor serves as a sacrificial material to reduce the temperature of the core melt to a certain extent; when the melt melts the upper end of the nozzle, The cooling water in the cooling water channel is injected through the nozzle, so that the bottom of the molten material is injected with water, and the molten material can be rapidly cooled. However, when the molten material is in direct contact with the cooling water, a large amount of steam is generated instantaneously, which may cause the pressure of the safety shell to rise instantaneously to cause damage, and even a steam explosion may occur, thereby causing serious consequences.

Therefore, it is necessary to provide a passive core trap having a simple structure, a small volume, a good heat transfer effect, and a low cost to solve the above-mentioned deficiencies of the prior art.

Utility model content

The utility model aims to provide a core trap with simple structure, small volume, good heat transfer effect and low cost.

In order to achieve the above object, the technical solution of the present invention is to provide a core trap comprising a casing, a cooling passage and a positioning grid; the casing is disposed under the pressure vessel, and the casing is a hollow structure and a top opening, a bottom of the casing is provided with a coolant inlet, and an upper end of the casing is further provided with a coolant outlet; the cooling passage comprises a horizontal passage and a plurality of the pipelines communicating with the horizontal passage a rod-shaped vertical passage disposed at a bottom of the housing and in communication with the coolant inlet, the vertical passage being received within the housing and extending toward a top of the housing Forming a melt filling passage between the adjacent vertical passages; the positioning grid is sleeved outside the vertical passage and fixed to an inner wall of the casing, and the positioning grid is opened and connected The melt fills the flow orifice of the passage.

Preferably, the bottom end of the vertical channel is in communication with the horizontal channel, and the top end of the vertical channel is provided with a conical top cap, and the top cap is open to communicate with the vertical channel And a venting opening of the hollow structure of the housing.

Preferably, a bottom surface of the top cap is larger than a cross-sectional area of the vertical passage, the vent hole is formed on a bottom surface of the top hat, and the vent hole is located at a bottom edge of the top hat Between the outer edges of the vertical channels.

Preferably, a bottom plate is disposed in the housing, and the horizontal passage is formed between the bottom plate and the bottom surface of the housing, and the side wall of the vertical passage is fixed to the bottom plate.

Preferably, the side wall of the vertical passage comprises a steel pipe and a high temperature resistant layer disposed outside the steel pipe.

Preferably, the plurality of vertical channels are arranged in a square or a triangle.

Preferably, the positioning grid is provided with a mounting hole corresponding to the vertical passage, and the mounting hole is sleeved outside the side wall of the vertical passage.

Preferably, the positioning grid comprises a steel sheet layer and a ceramic layer disposed above the steel sheet layer.

Preferably, the inner wall surface of the casing is covered with a ceramic heat insulation layer.

Preferably, the coolant inlet communicates with the bottom of the refueling water tank provided outside the casing through the first pipe, and the refueling water tank is located higher than the horizontal channel.

Preferably, the coolant outlet communicates with the top of the refueling water tank disposed outside the casing through the second conduit, and the second conduit extends below the coolant level in the refueling water tank.

Preferably, the core trap further includes a flow guiding structure disposed between the pressure vessel and the casing, and the flow guiding structure and the hollow structure of the casing In communication, the core melt is introduced into the housing.

Preferably, the flow guiding structure comprises a straight pipe section, a inclined section and a horizontal section which are sequentially connected, the upper end of the straight pipe section is covered at a lower end of the pressure vessel, and the horizontal section is provided with a through hole.

Compared with the prior art, due to the core trap of the present invention, the rod-like structure design of the vertical passage is on the one hand The heat exchange area is greatly increased, and on the other hand, the risk of uneven circumferential force is reduced, in particular, the risk of damage of the high temperature resistant material layer caused by the uneven thermal stress of the corner is greatly reduced, and the vertical channel is increased. Strength; and the rod-shaped vertical channel is fixed by the positioning grid, which enhances its stability and reduces the possibility of instantaneously punching part of the vertical passage by the falling of the core melt. In addition, the number of vertical rod-shaped channels can be adjusted according to actual needs, thereby flexibly changing the heat exchange area per unit volume, so as to flexibly adapt to the needs of different power reactors, thereby ensuring that the core melt is cooled and solidified in a certain period of time, The structure is simple, the occupied area and space are small, and the cooling speed is moderate, so that the safety in the process of cooling and solidifying the core melt is further improved, and the cost of the core trap is low. Furthermore, since the heat transfer area is changed on a unit basis, it is not necessary to perform a modeling experiment of the entire apparatus, which simplifies the experimental verification research process.

DRAWINGS

1 is a schematic view showing the structure of a core trap of the present invention.

Figure 2 is a schematic view of the cooling passages of Figure 1 in a triangular arrangement.

Figure 3 is a schematic view of the cooling passages of Figure 1 in a square arrangement.

4 is a schematic structural view of a tubular body of the vertical passage of FIG. 1.

Figure 5 is a partial cross-sectional view of Figure 4 .

Figure 6 is a partially enlarged schematic view of the positioning grid of Figure 1.

Figure 7 is a plan view of the steel sheet layer of the spacer grid of Figure 6.

Figure 8 is a top plan view of the ceramic layer of the spacer grid of Figure 6.

Figure 9 is a partially enlarged schematic view of the housing of Figure 1.

Figure 10 is a schematic view showing the state of use of the core trap of the present invention.

Figure 11 is a schematic view of the cooling process of the core trap of the present invention.

Figure 12 is a second schematic diagram of the cooling process of the core trap of the present invention.

Figure 13 is a third schematic diagram of the cooling process of the core trap of the present invention.

Figure 14 is a fourth schematic diagram of the cooling process of the core trap of the present invention.

detailed description

Embodiments of the present invention will now be described with reference to the drawings, in which like reference numerals represent like elements.

As shown in FIG. 1 , the core trap 100 provided by the present invention includes a housing 110 , a cooling passage 120 , a positioning grid 130 , and a refueling water tank 140 . The housing 110 is disposed under the pressure vessel 200, and the cooling passage 120 and the positioning grid 130 are disposed in the housing 110, and the positioning grid 130 is fixed to the inner wall of the housing 110, and the refueling water tank 140 is disposed in the housing. The outside of the 110 is in communication with the housing 110.

Specifically, the housing 110 has a hollow structure and is open at the top. The bottom of the housing 110 is provided with a coolant inlet 111. The side wall of the upper end of the housing 110 is provided with a coolant outlet 112 through which the core melt passes. The top opening flows into the interior of the housing 110. The refueling water tank 140 is disposed at one side of the casing 110 and has a coolant therein, the refueling water tank 140 is located higher than the coolant inlet 111; the bottom of the refueling water tank 140 is connected to the coolant inlet 111 through the first duct 141. a second pipe 142 is disposed at a top of the refueling water tank 140. One end of the second pipe 142 extends below the coolant level in the refueling water tank 140, and the other end of the second pipe 142 communicates with the coolant outlet 112. A valve 143 is provided on a pipe 141. Thus, the coolant in the refueling tank 140 can be passively injected into the coolant inlet 111, and the coolant vaporized by the heat exchange in the casing 110 can be discharged into the refueling tank 140 through the second conduit 142 for condensation.

Of course, the coolant outlet 112 can also be connected elsewhere for condensation, a technique well known to those skilled in the art.

With continued reference to FIG. 1, the cooling passage 120 includes a horizontal passage 121 and a plurality of rod-shaped vertical passages 122 communicating with the horizontal passage 121. The horizontal passage 121 is disposed at the bottom of the housing 110 and with the coolant inlet 111. The vertical channel 122 is received in the housing 110 and extends toward the top of the housing 110. The positioning frame 130 is sleeved outside the vertical channel 122 and fixed to the inner wall of the housing 110 to enhance the vertical channel 122. Stability. Moreover, a melt filling passage 123 is formed between the adjacent vertical passages 122, and the melt filling passage 123 is evenly distributed, which can ensure uniform flow of the core melt and ensure the cooling speed, thereby ensuring the core melt in a certain period of time. Achieve cooling and solidification. Since the vertical passage 122 of the rod-like structure is employed, uniform cooling around the vertical passage 122 can be achieved, the stress is greatly reduced, and reliability is increased. At the same time, since the area of the cooling passage 120 is large, the cooling speed is fast.

As shown in FIG. 1-3, a bottom plate 124 is disposed in the housing 110, and a horizontal passage 121 is formed between the bottom plate 124 and the bottom surface of the housing 110. The bottom end of each side wall of each vertical channel 122 is fixed to the bottom plate 124, and a plurality of rod-shaped vertical channels 122 are arranged in a square or a triangle. Among them, the plurality of vertical channels 122 arranged in a triangle shape are relatively compact, and can provide relatively more cooling channels, as shown in FIG. The vertical channels 122 arranged in a square shape can make the flow resistance of the core melt less, and the area ratio of the melt overflow holes 132 (described later) in the positioning grid 130 can be relatively large, and the core melt can be relatively large. It can be quickly passed through the positioning grid 130 and spread evenly into the melt filling channel 123, as shown in FIG.

In actual use, the arrangement can be comprehensively considered according to the core size and the cooling rate of the melt, and the number of the rod-shaped vertical channels 122 can be selected as needed, so that the heat exchange area per unit volume can be flexibly changed, so that The heat transfer area can be increased or decreased according to the number of geometrical requirements to flexibly adapt to the needs of different power reactors, so as to ensure that the core melt can be cooled and solidified in a certain period of time, and has the advantages of simple structure and moderate cooling speed. In addition, since the heat transfer area is changed on a unit basis, it is not necessary to perform the modeling experiment of the entire apparatus like EPR and VVER, and the experimental verification research process is simplified.

As shown in FIG. 1 and FIG. 4-5, a plurality of tubular bodies 125 having a hollow rod-like structure are fixed on the bottom plate 124. The hollow structure of each tubular body 125 forms a vertical passage 122, and each vertical passage 122 is combined with The horizontal passages 121 are in communication, and a melt filling passage 123 is formed between the outer walls of the tubular body 125. The top end of each tubular body 125 is covered with a conical top cap 126. The top cap 126 is provided with a venting opening 127 communicating with the vertical passage 122 and the interior of the housing 110. Specifically, the bottom surface of the top cap 126 is larger than the cross-sectional area of the tubular body 125, the vent hole 127 is formed on the bottom surface of the top cap 126, and the vent hole 127 is located between the bottom edge of the top cap 126 and the outer edge of the tubular body 125. Sealing the top of the vertical passage 122 by the conical top cap 126 prevents core melt from falling into the vertical passage 122 while facilitating the fall of the core melt, while the vapor in the vertical passage 122 can be passed The air holes 127 are discharged to the inside of the casing 110, and are discharged to the refueling water tank 140 through the coolant outlet 112.

With continued reference to FIG. 5, the sidewall of the tubular body 125 includes a steel tube 1251 and a high temperature resistant layer 1252 that is coated over the outer portion of the steel tube 1251. The high temperature resistant layer 1252 is preferably a ceramic layer. Thus, when the core melt flows into the melt filling passage 123, the heat thereof is sequentially transmitted to the coolant in the vertical passage 122 through the ceramic layer and the steel pipe 1251, and the ceramic layer can protect the steel pipe 1251 from the steel pipe 1251 and the core melt. Direct contact causes damage; and the ceramic layer slows down the heat transfer process, avoids rapid cooling of the core melt and generates a large amount of steam, which causes overpressure of the containment and ensures that the core melt is cooled and solidified in a certain period of time. At the same time, due to the rod-shaped design of the vertical passage 122, the heat exchange area can be greatly increased, and the problem of uneven circumferential force of the pipe body 125 is improved, and in particular, the high temperature resistant layer which may be caused by uneven thermal stress of the corner is greatly reduced. The risk of 1252 damage increases the strength of the vertical channel 122.

Of course, the high temperature resistant layer 1252 is not limited to the ceramic layer, and may be other layers of high temperature resistant materials.

As shown in FIG. 1 and FIG. 6-8, the positioning grid 130 is respectively provided with a mounting hole 131 and a through hole 132. The position and the number of the mounting holes 131 correspond to the tube body 125 forming the vertical channel 122. During installation, the mounting hole 131 of the positioning grid 130 is sleeved outside the tubular body 125, and the positioning grid 130 is fixed to the inner wall of the housing 110 and is disposed adjacent to the top cap 126 (see FIG. 1). By fixing the vertical passage 122 by the positioning frame 130, the stability thereof is enhanced, and the impact on the rod-shaped vertical passage 122 when the core melt falls is alleviated, and the falling of the core melt is instantaneously washed to the partial vertical passage 122. The possibility.

In the present invention, the positioning grid 130 includes a perforated steel sheet layer 130a and a ceramic layer 130b disposed above the steel sheet layer 130a. The purpose of the perforated steel plate layer 130a is to fix the steel pipe 1251 of the pipe body 125. The diameter of the mounting hole 131 formed in the steel plate layer 130a is slightly larger than the diameter of the steel pipe 1251, thereby facilitating the fixing, and the entire positioning grid 130 The steel plate layer 130a may be made of one piece of steel plate, or may be formed by arranging a plurality of steel plates and then welding, depending on the size of the core and the installation condition; in addition, the edge of the steel plate layer 130a is fixed to the casing. The inner wall of 110, thereby achieving the role of a fixed support. The ceramic layer 130b is overlaid on the steel sheet layer 130a. In this embodiment, the ceramic layer 130b is assembled from a small piece of ceramic for ease of fabrication, but not limited thereto. The ceramic layer 130b is mainly used to avoid direct contact between the core melt and the large area of the steel sheet layer 130a, so as not to cause damage to the steel sheet layer 130a.

Referring to FIG. 9, the inner wall surface of the housing 110 is covered with a ceramic heat insulation layer 110a. The ceramic heat insulation layer 110a may be assembled from a plurality of ceramic blocks, and the ceramic blocks may have the same shape. different. In this embodiment, the ceramic block of three different shapes and structures is mainly used to form the heat insulating layer 110a by tight fitting to prevent the casing 110 from directly contacting the core melt to cause damage.

Referring to FIG. 1 again, the core trap 100 further includes a flow guiding structure 150 disposed between the pressure vessel 200 and the housing 110 and communicating with the hollow structure of the housing 110. Used to introduce the core melt into the housing 110.

Specifically, the flow guiding structure 150 includes a straight pipe section 151, a slanting section 152 and a horizontal section 153 which are sequentially connected. The upper end of the straight pipe section 151 is covered at the lower end of the pressure vessel 200, and the horizontal section 153 is provided with a through hole 154, and the through hole 154 is The hollow structure of the housing 110 is in communication for introducing the core melt into the housing 110.

It can be understood that the core trap 100 also includes some conventional designs such as connecting pipes and foundation pits, and details are not described herein.

The working principle of the core trap 100 of the present invention will be described below with reference to Figs.

Referring first to Figure 11, there is no coolant in the horizontal channel 121 and the vertical channel 122 of the core trap 100 during normal operation of the system.

When a serious reactor accident occurs, the core melt 300 enters the interior of the casing 110 through the flow guiding structure 150, and the core melt 300 uniformly flows into the melt filling passage 123 through the overflow holes 132 on the positioning grid 130. , as shown in Figures 10 and 12.

At this time, the valve 143 on the first pipe 141 is opened, and the coolant in the refueling water tank 140 is automatically flowed into the horizontal passage 121 through the first pipe 141, and is gradually injected into the vertical passage 122 as shown in FIG. Then, the heat of the core melt is sequentially transmitted to the coolant (such as cooling water) in the vertical passage 122 through the high temperature resistant layer 1252 and the steel pipe 1251, and the coolant is heated to boil to form steam, and the steam passes through the top cap 126. The air vent 127 enters the interior of the housing 110 and enters the refueling water tank 140 through the coolant outlet 112 and the second conduit 142 for condensation. Through the vaporization of the coolant, the coolant is cooled in a saturated boiling manner, so that the refueling water tank 140, the horizontal passage 121, and the vertical passage 122 form a passive heat exchange circulation passage. After the heat exchange is completed, the solidification of the core melt 300 is achieved, as shown in FIG.

Because the core trap 100 of the present invention includes a housing 110, a cooling passage 120 disposed in the housing 110, and a positioning grid 130 for positioning the cooling passage 120; the cooling passage 120 includes a horizontal passage 121 and The horizontal channel 121 is connected to a plurality of rod-shaped vertical channels 122. The horizontal channel 121 is disposed at the bottom of the housing 110 and communicates with the coolant inlet 111. The vertical channel 122 is received in the housing 110 and facing the housing. The top of the 110 extends to form a melt filling passage 123 between the adjacent vertical passages 122. The positioning grid 130 is sleeved outside the vertical passage 122 and fixed to the inner wall of the housing 110, and the positioning grid 130 is opened. The overflow hole 132 that connects the melt filling passage 123. In the case of a serious accident, the core melts into the housing 110 and flows into the melt filling passage 123 through the overflow hole 132 in the positioning grid 130. The coolant flowing into the vertical passage 122 through the horizontal passage 121 is cooled and solidified by vaporization to the outside of the casing 110 to achieve cooling solidification of the core melt. Through the rod-shaped structure design of the vertical channel 122, on the one hand, the heat exchange area is greatly increased, on the other hand, the risk of uneven circumferential force is greatly reduced, and in particular, the resistance caused by the uneven thermal stress of the corner is greatly reduced. The risk of damage to the layer of high temperature material increases the strength of the vertical channel 122; in addition, the rod-shaped vertical channel 122 is fixed by the spacer grid 130, which enhances its stability and reduces the vertical passage of the core melt by instantaneously slamming The possibility of 122. Furthermore, the number of the rod-shaped vertical channels 122 can be adjusted according to actual needs, thereby flexibly changing the heat exchange area per unit volume, so as to flexibly adapt to the needs of different power reactors, thereby ensuring that the core melt can be cooled and solidified in a certain period of time. The utility model has the advantages of simple structure, small occupied area and small space, moderate cooling speed, further improved safety in the cooling and solidification process of the core melt, and the cost of the core trap 100 is low. Since the heat transfer area is changed on a unit basis, it is not necessary to carry out the modeling experiment of the entire device, which simplifies the experimental verification research process.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. Therefore, the equivalent changes made by the scope of the present invention remain within the scope of the present invention. .

Claims

A core trap characterized by: including

The housing is disposed under the pressure vessel, the casing has a hollow structure and is open at the top, the bottom of the casing is provided with a coolant inlet, and the upper end of the casing is further provided with a coolant outlet;

a cooling passage, the cooling passage including a horizontal passage and a plurality of rod-shaped vertical passages communicating with the horizontal passage, the horizontal passage being disposed at a bottom of the casing and communicating with the coolant inlet The vertical passage is received in the housing and extends toward the top of the housing, and a molten material filling passage is formed between the adjacent vertical passages;

Positioning the grid, the positioning grid is sleeved outside the vertical passage and fixed to the inner wall of the casing, and the positioning grid is provided with an overflow hole communicating with the molten material filling passage.
A core trap according to claim 1, wherein a bottom end of said vertical passage communicates with said horizontal passage, and a top end of said vertical passage is provided with a conical top hat. The top cap is provided with a vent hole communicating with the vertical passage and the hollow structure of the casing.
The core trap according to claim 2, wherein a bottom surface of the top cap is larger than a cross-sectional area of the vertical passage, and the vent hole is formed in a bottom surface of the top cap, and The vent is located between the bottom edge of the top cap and the outer edge of the vertical channel.
A core trap according to claim 1, wherein a bottom plate is disposed in said housing, said horizontal passage being formed between said bottom plate and said bottom surface of said housing, said side of said vertical passage The wall is fixed to the bottom plate.
A core trap according to claim 1 wherein the side walls of said vertical passageway comprise a steel tube and a refractory layer disposed outside said steel tube.
A core trap according to claim 1 wherein a plurality of said vertical channels are arranged in a square or a triangle.
The core trap according to claim 1, wherein the positioning grid is provided with a mounting hole corresponding to the vertical passage, and the mounting hole is sleeved in the vertical passage. Outside the side wall.
The core trap of claim 1 wherein said spacer grid comprises a steel sheet layer and a ceramic layer disposed over said steel sheet layer.
A core trap according to claim 1 wherein the inner wall of said housing is covered with a ceramic insulating layer.
A core trap according to claim 1, wherein said coolant inlet communicates with a bottom of a refueling water tank provided outside said casing through a first pipe, and said refueling water tank is positioned higher than The position of the horizontal channel.
A core trap according to claim 1 wherein said coolant outlet communicates with a top portion of a refueling water tank disposed outside said housing through a second conduit, and said second conduit extends into said Refill the coolant below the liquid level in the tank.
A core trap according to claim 1 further comprising a flow guiding structure disposed between said pressure vessel and said housing, said flow guiding structure and said The hollow structure of the housing is in communication for introducing the core melt into the housing.
A core trap according to claim 12, wherein said flow guiding structure comprises a straight pipe section, a slanted section and a horizontal section which are sequentially connected, and an upper end of said straight pipe section is coated at a lower end of said pressure vessel The horizontal section is provided with a through hole.