Auxiliary cooling system and method for fast reactor

Abstract

Provided is an auxiliary cooling system and method for a fast reactor. The auxiliary cooling system includes: a main container; a partition, an ascending channel is formed between the partition and the wall of the main container; a heat shielding layer, the heat shielding layer is arranged on the side of the partition away from the main container, and a descending channel is formed between the heat shielding layer and the partition; an overflow hole, the overflow hole is arranged on the partition, and is used to connect the ascending channel and the descending channel; a first throttling device, the first throttling device is arranged on the grid header, and the coolant in the grid header can enter the ascending channel through the first throttling device; and a second throttling device, the second throttling device is arranged at the outlet of the descending channel, and is used to supply cooling to the parts to be cooled. Through the auxiliary cooling system and method, the natural frequency of liquid sloshing in the annular area of ​​the ascending channel and the descending channel is avoided from the natural frequency of the equipment structure, so as to prevent flow-induced vibration.

Description

Technical Field

[0001] The present disclosure relates to the field of reactor technology, and in particular to an auxiliary cooling system and method for a fast reactor. Background Art

[0002] In order to reduce the temperature of the main container and pump support bearing parts of the fast reactor and avoid creep design, a main container cooling and pump support cooling auxiliary system is set up. That is, concentric cylinders are passed through one side of the main container and pump support to form rising and falling channels for the coolant. Since the ring areas of the rising and falling channels are filled with sodium liquid coolant, the free liquid surface will shake during an earthquake. If the natural frequency of the shaking is the same or close to the natural frequency of the equipment structure, flow-induced vibration is likely to occur. Summary of the invention

[0003] In one aspect, an auxiliary cooling system for a fast reactor is provided, comprising: a main container; a partition, an ascending channel is formed between the partition and the wall of the main container; a heat shielding layer, the heat shielding layer is arranged on a side of the partition away from the main container, and a descending channel is formed between the heat shielding layer and the partition; an overflow hole, the overflow hole is arranged on the partition, and is used to connect the ascending channel and the descending channel; a first throttling device, the first throttling device is arranged on the grid header, and the coolant in the grid header can enter the ascending channel through the first throttling device; and a second throttling device, the second throttling device is arranged at the outlet of the descending channel, and is used to supply cold to the parts to be cooled.

[0004] On the other hand, an auxiliary cooling method for a fast reactor is provided. Based on the above-mentioned auxiliary cooling system, the auxiliary cooling method includes: controlling the coolant temperature in the ascending channel and the overflow hole to be lower than 420°C; and controlling the temperature difference between the outlet coolant temperature of the descending channel and the inlet coolant temperature of the ascending channel to be no more than 47°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Other objects and advantages of the present disclosure will be apparent from the following description of the present disclosure with reference to the accompanying drawings, and will help to have a comprehensive understanding of the present disclosure.

[0006] Figure 1 It is a schematic structural diagram of an auxiliary cooling system for a fast reactor according to an embodiment of the present disclosure.

[0007] Figure 2 It is a schematic diagram of an application scenario of an auxiliary cooling system for a fast reactor according to an embodiment of the present disclosure.

[0008] Figure 3 yes Figure 2 Schematic diagram of the enlarged structure of part A.

[0009] Figure 4 yes Figure 2 Schematic diagram of the enlarged structure of part B.

[0010] Figure 5 yes Figure 2 Schematic diagram of the enlarged structure of part C.

[0011] In the figure, 1, main container; 11, grid plate header; 12, pump support; 13, intermediate heat exchanger support; 14, support plate; 2, partition; 21, overflow hole; 3, heat shielding layer; 4, ascending channel; 5, descending channel; 6, first throttling device; 7, second throttling device; 8, third throttling device.

[0012] It should be noted that, for the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the sizes of structures or regions may be enlarged or reduced, that is, these drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0014] Unless otherwise defined, the technical terms or scientific terms used in this disclosure should be understood by ordinary technicians in the field. "First", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprising" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0015] In this document, unless otherwise specified, directional terms such as "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship based on the drawings, and are only for the convenience of describing the present disclosure, and do not indicate or imply that the device, element or component referred to must have a specific orientation, be constructed or operate in a specific orientation. It should be understood that when the absolute position of the described object changes, the relative positional relationship they represent may also change accordingly. Therefore, these directional terms should not be understood as limiting the present disclosure.

[0016] The embodiment of the present disclosure provides an auxiliary cooling system and method for a fast reactor. The auxiliary cooling system includes: a main container 1; a partition 2, wherein an ascending channel 4 is formed between the partition 2 and the wall of the main container 1; a heat shielding layer 3, wherein the heat shielding layer 3 is arranged on the side of the partition 2 away from the main container 1, and a descending channel 5 is formed between the heat shielding layer 3 and the partition 2; an overflow hole 21, wherein the overflow hole 21 is arranged on the partition 2, and is used to connect the ascending channel 4 and the descending channel 5; a first throttling device 6, wherein the first throttling device 6 is arranged on the grid header 11, and the coolant in the grid header 11 can enter the ascending channel 4 through the first throttling device 6; and a second throttling device 7, wherein the second throttling device 7 is arranged at the outlet of the descending channel 5, and is used to supply cooling to the parts to be cooled. Through the structural design of the auxiliary cooling system, the ascending channel 4 and the descending channel 5 of the coolant are formed between the wall of the main container 1 and the partition 2 and the heat shielding layer 3, and the main container 1 and other parts to be cooled can be cooled and lowered at the same time. At the same time, due to the shielding effect of the heat shielding layer 3 and the partition 2, the natural frequency of the coolant sloshing in the annular area of ​​the ascending channel 4 and the descending channel 5 can be avoided from the natural frequency of the fast reactor equipment structure, preventing flow-induced vibration.

[0017] It should be noted that the cooling liquid in the embodiment of the present disclosure is sodium liquid as an example, that is, sodium liquid is used as a coolant. However, it should not be understood that sodium liquid is the only choice of cooling liquid in the embodiment of the present disclosure. The cooling liquid in the embodiment of the present disclosure can also be selected as any other type of cooling liquid based on the conventional knowledge of those skilled in the art.

[0018] Figure 1 It is a schematic structural diagram of an auxiliary cooling system for a fast reactor according to an embodiment of the present disclosure. Figure 2 It is a schematic diagram of an application scenario of an auxiliary cooling system for a fast reactor according to an embodiment of the present disclosure. Figure 3 yes Figure 2 Schematic diagram of the enlarged structure of part A. Figure 4 yes Figure 2 Schematic diagram of the enlarged structure of part B. Figure 5 yes Figure 2 Schematic diagram of the enlarged structure of part C.

[0019] like Figures 1 to 5As shown, the ascending channel 4 and the descending channel 5 are formed between the inner wall of the main container 1, the partition 2 and the heat shielding layer 3, and the bottom inlet of the ascending channel 4 is connected to the sodium liquid cold pool through the first throttling device 6 arranged on the grid header 11. Under the action of the circulating pump, the sodium liquid in the cold pool can enter the ascending channel 4 from the bottom of the ascending channel 4 and rise along the ascending channel 4. In this process, the sodium liquid will exchange heat with the wall of the main container 1 to cool the main container 1. When the sodium liquid in the ascending channel 4 rises to the height of the overflow hole 21, it will enter the descending channel 5 through the overflow hole 21. The sodium liquid in the descending channel 5 is transported to the part to be cooled through the second throttling device 7 to cool the part to be cooled, and the sodium liquid flowing out through the second throttling device 7 finally flows back into the sodium liquid cold pool. Through the above process, the circulating cooling process of the sodium liquid is realized.

[0020] In addition, since the sodium liquid is used to cool the main container 1 when it is in the ascending channel 4, the sodium liquid can be used to cool the part to be cooled only after it enters the descending channel 5. Therefore, the main container 1 and the part to be cooled can be cooled separately by controlling the liquid level of the sodium liquid. That is, the flow rate of the sodium liquid in the ascending channel 4 can be controlled so that the liquid level of the sodium liquid does not exceed the installation height of the overflow hole 21, and the sodium liquid is used to cool the main container 1. When the liquid level of the sodium liquid exceeds the installation height of the overflow hole 21, the sodium liquid can enter the descending channel 5 and flow out from the bottom outlet of the descending channel 4, and is used to cool the part to be cooled.

[0021] In some exemplary embodiments, a plurality of overflow holes 21 are provided on the partition 2 between the ascending channel 4 and the descending channel 5. The plurality of overflow holes 21 are all located in a first plane, and the plurality of overflow holes 21 are evenly spaced and arranged on the partition 2. The first plane is perpendicular to the flow direction of the coolant in the ascending channel 4 and is also perpendicular to the flow direction of the coolant in the descending channel 5. Figure 2 , the first plane is perpendicular to the central axis of the main container 1. By providing a plurality of overflow holes 21, the flow rate of the sodium liquid from the ascending channel 4 into the descending channel 5 can be increased, the continuity of the sodium liquid flow can be ensured, water hammer can be prevented, and temperature oscillation can be avoided.

[0022] Optionally, in the embodiment of the present disclosure, the overflow hole 21 may be a circular hole or a rectangular hole. The size and number of the overflow holes 21 should ensure the continuity of the sodium liquid flow after overflow and the continuity of the flow beams between adjacent overflow holes 21, prevent water hammer and avoid temperature oscillation.

[0023] It should be noted that the shape of the overflow hole 21 is not limited to a circular hole or a rectangular hole. On the premise of satisfying the above functions, those skilled in the art can select any other shape of the overflow hole 21. At the same time, the number and size of the overflow holes 21 are not specifically limited in the embodiments of the present disclosure.

[0024] The above expressions "circular hole" and "rectangular hole" mean that the cross section is circular or rectangular.

[0025] Optional, see Figure 3 , the first throttling device 6 includes a labyrinth throttling device. When the auxiliary cooling system is used to cool the main container 1 and the part to be cooled, sodium is taken from the cold pool, and after passing through the first throttling device 6, it reaches a predetermined coolant level to cool the main container 1 and the part to be cooled respectively.

[0026] Optionally, the second throttling device 7 includes an orifice plate throttling element or a small hole throttling element. The second throttling device 7 is arranged at the bottom outlet of the descending channel 5, which can ensure the free liquid level height of the descending channel 5 and prevent the outlet position of the descending channel 5 from having a waterfall.

[0027] In the embodiment of the present disclosure, a third throttling device 8 is further included, and the third throttling device 8 is arranged at the bottom of the descending channel 5. The to-be-cooled part includes a first cooling portion and a second cooling portion, and the first cooling portion and the second cooling portion are separated by a support plate 14. Figure 4 and Figure 5 The first cooling part is the part where the part to be cooled is located above the support plate 14, and the second cooling part is the part where the part to be cooled is located below the support plate 14. The second throttling device 7 is arranged on the upper side of the support plate 14, and is used to supply cooling to at least a part of the first cooling part; the third throttling device 8 is arranged on the lower side of the support plate 14, and is used to supply cooling to at least a part of the second cooling part. By arranging the third throttling device 8, the sodium liquid flowing out of the descending channel 5 can reach different positions in the fast reactor respectively, so as to cool different parts of the same equipment or multiple different equipment.

[0028] Furthermore, the third throttling device 8 includes an orifice plate throttling element or a small hole throttling element. It should be noted that the type of the third throttling device 8 is not limited to the above type, as long as it can play a throttling role.

[0029] It should be noted that the number of the first throttling device 6, the second throttling device 7, and the third throttling device 8 and their passable cross-sections should be such that no cavitation occurs in each hole. In addition, the structure of each throttling device should ensure that the auxiliary cooling system forms a turbulent flow condition within all flow variation ranges, so as to ensure that the fluid resistance coefficient of each throttling device remains unchanged, thereby making the pressure drop of the fluid unchanged and the fluid flow more stable.

[0030] In some exemplary embodiments, the partition 2 is a cylindrical structure, and the cylindrical structure is designed to facilitate cooperation with the wall surface of the main container 1. For example, when the cylindrical partition 2 is arranged in the main container 1, the ascending channel 4 between the partition 2 and the main container 1 is also annular. The heat shielding layer 3 is also a cylindrical structure, and the axis of the heat shielding layer 3 coincides with the axis of the partition 2. Therefore, the descending channel 5 formed between the partition 2 and the heat shielding layer 3 is also annular. By setting the ascending channel 4 and the descending channel 5 to be annular, the main container 1 and the part to be cooled can be cooled from multiple angles, which can improve the cooling efficiency and ensure the cooling effect.

[0031] Furthermore, the number of the heat shielding layers 3 is three, and the three heat shielding layers 3 are all cylindrical structures, and the axes of the three heat shielding layers 3 coincide. By providing three heat shielding layers 3, heat can be further shielded to prevent the higher temperature sodium liquid from transferring heat to the lower temperature sodium liquid in the descending channel 5, resulting in a reduction in the cooling efficiency of the main container 1.

[0032] It should be noted that the number of the heat shielding layers 3 is not limited to three layers. In actual application, the number of the heat shielding layers 3 can be reduced or increased according to installation requirements, which is not limited in the embodiments of the present disclosure.

[0033] In the embodiment of the present disclosure, the cooling member includes a pump support 12 and / or an intermediate heat exchanger support 13. Figure 2 The auxiliary cooling system of the embodiment of the present disclosure can be used for cooling the main container 1 of the reactor and the pump support 12 and / or the intermediate heat exchanger support 13. However, it should be understood that the auxiliary cooling system can also be used for other equipment that needs to be cooled in the fast reactor, which is not limited in the embodiment of the present disclosure.

[0034] The disclosed embodiment also provides an auxiliary cooling method for a fast reactor, which is based on the auxiliary cooling system described above. Specifically, the auxiliary cooling method includes: controlling the sodium temperature in the ascending channel 4 and the overflow hole 21 to be lower than 420°C, and controlling the temperature difference between the outlet sodium temperature of the descending channel 5 and the inlet sodium temperature of the ascending channel 4 to be no more than 47°C. This can avoid various problems caused by thermal shock, for example, the problem of alternating stress on the surface of the equipment caused by temperature changes when sodium of different temperatures is mixed.

[0035] In the embodiment of the present disclosure, the cooling of the main container 1 is taken as an example. By analyzing and calculating the wall temperature of the main container 1, the cooling outlet temperature of the main container 1, and the natural frequency of the liquid sloshing in the annular domain, all indicators meet the design requirements. At the same time, the flow velocity in the throttling device and the critical cavitation velocity are analyzed to prevent the coolant from cavitation in the throttling device. The specific structural scheme and analysis and calculation results are as follows:

[0036] The auxiliary cooling system for the main container 1 takes sodium from the grid header 11 and enters the ascending channel 4 through the labyrinth throttling device on the lower surface of the grid header 11. The ascending channel 4 is composed of the wall of the main container 1 and the radial partition 2 cylinder, and the descending channel 5 is composed of the radial partition 2 cylinder and three concentric heat shielding layer 3 cylinders. The throttling device at the bottom of the descending channel 5 adopts a perforated plate structure.

[0037] 1) Temperature calculation

[0038] The energy equation for cooling the main container 1 is:

[0039]

[0040] The first node is the main container 1, and the physical meaning is that the heat transferred from the ascending channel 4 to the main container 1 is equal to the heat dissipated by the main container 1 to the surroundings.

[0041]

[0042] After simplification, we can get:

[0043]

[0044] δ1: Thickness of main container 1 [m]

[0045] λ1: Thermal conductivity of steel [W / (K·m)]

[0046] q: The amount of heat dissipated from the protective container through the insulation layer [W / (K·m 2 )]

[0047] h up: Heat exchange coefficient between the main container 1 and the coolant in the ascending channel 4 [W / (K·m 2 )]

[0048] A: Surface area of ​​main container 1

[0049] The second node is the ascending channel 4,

[0050]

[0051]

[0052] δ1: Thickness of main container 1 [m]

[0053] δ2: thickness of separator 2 [m]

[0054] λ: Thermal conductivity of steel [W / (K·m)]

[0055] h up : Heat exchange coefficient between main container 1 and ascending channel 4 [W / (K·m 2 )]

[0056] Mass flow rate [kg / s]

[0057] c p : Specific heat of Na [J / (kg·K)]

[0058] T inlet : Sodium temperature at the inlet of auxiliary cooling system of main container 1 [K]

[0059] The third node is the partition 2,

[0060]

[0061] h down :Heat transfer coefficient of sodium in descending channel 5 [W / (K·m 2 )]

[0062] δ3: Width of partition 2 [m]

[0063] The fourth node is the descending channel 5,

[0064]

[0065]

[0066] δ5; Thickness of thermal shielding layer 3 [m]

[0067] The fifth node is the heat shield layer 3. The thickness of the static sodium liquid is ignored in the one-dimensional calculation.

[0068]

[0069]

[0070] h Na : Heat exchange coefficient between the hot sodium pool outside the heat shielding layer 3 and the heat shielding layer 3 [W / (K·m 2 )]

[0071] Then we can write the matrix:

[0072]

[0073] By performing multiple sets of experiments to solve the above matrix, we can get the temperature of each node.

[0074]

[0075]

[0076] According to the calculation results, the wall temperature of the main container 1 and the cooling outlet temperature of the main container 1 are both lower than the design limit requirements.

[0077] 2) Analysis of natural frequency of liquid sloshing

[0078] From the perspective of shielding possible vibrations and preventing water hammer from occurring in such a long periphery of the ascending channel 4 and the descending channel 5, a large number of overflow holes 21 must be selected so that, except for the shorter initial parts of the ascending channel 4 and the descending channel 5, the flow of sodium is in the form of continuous liquid.

[0079] In order to ensure that flow-induced vibration does not occur around the openings of the fast reactor equipment, it is necessary to calculate the natural frequency, the sloshing frequency of the annular liquid:

[0080]

[0081] The constant related to the ratio of the inner and outer diameters of the ring = 1.841

[0082] a: Circumferential radius

[0083] H: Liquid level

[0084] By comparison, it can be seen that the natural frequency of liquid sloshing is much lower than the natural frequency of the structure (the natural frequency of the structure can be determined through modal calculation based on the size and constraint relationship of the structure), so flow-induced vibration can be avoided.

[0085] 3) Analysis of cavitation of throttling device

[0086] An important criterion for the throttling device is that cavitation does not occur in the narrow cross section where the final path cross section narrows during the liquid flow process. When the reactor is running at full power, the sodium temperature at the throttling device is 360°C, and the saturated vapor pressure of sodium at this time is about 18Pa. At the same time, the absolute pressure from the sodium in the throttling device to the bottom of the reactor under rated conditions is P1=0.5256MPa. The maximum flow rate limit is 34m / s, as follows:

[0087]

[0088]

[0089] Therefore, when the static pressure in the narrowest cross section drops to 18 Pa, cavitation will only occur if the sodium flow rate in the narrow cross section is greater than or equal to the flow rate v.

[0090] By controlling the flow rate in the throttling device to be lower than the critical flow rate of cavitation, cavitation can be prevented from occurring to the coolant in the throttling device.

[0091] The auxiliary cooling system and the auxiliary cooling method according to the embodiments of the present disclosure have at least one of the following technical effects:

[0092] 1) After the coolant passes through the first throttling device 6 at the inlet of the auxiliary cooling system, it can reach a predetermined coolant liquid level in the ascending channel 4 to cool the main container 1 and the part to be cooled respectively.

[0093] 2) The second throttling device 7 and the third throttling device 8 are arranged at the bottom of the descending channel 5 to ensure the free liquid level height of the descending channel 5 and prevent the occurrence of waterfalls at the outlet hole of the descending channel 5.

[0094] 3) The plurality of overflow holes 21 between the ascending channel 4 and the descending channel 5 ensure the continuity of the sodium liquid flow after overflow and the continuity of the flow beams between adjacent overflow holes 21, thereby preventing water hammer and avoiding temperature oscillation.

[0095] 4) Under earthquake conditions, the natural frequency of liquid sloshing in the annular areas of the ascending channel 4 and the descending channel 5 in the auxiliary cooling system structure can be avoided from the natural frequency of the equipment structure, thereby preventing flow-induced vibration.

[0096] Although some embodiments according to the overall technical concept of the present disclosure have been shown and described, those skilled in the art will appreciate that changes may be made to these embodiments without departing from the principles and spirit of the overall technical concept of the present disclosure, and the scope of the present disclosure is defined by the claims and their equivalents.

Claims

1. An auxiliary cooling system for a fast reactor, characterized in that: include: main container; a partition, wherein an ascending channel is formed between the partition and the inner wall of the main container; A heat shielding layer, the heat shielding layer is arranged on a side of the partition away from the main container, and a descending channel is formed between the heat shielding layer and the partition; an overflow hole, the overflow hole being arranged on the partition plate and being used for connecting the ascending channel and the descending channel; a first throttling device, wherein the first throttling device is arranged on the grid header, and the coolant in the grid header can enter the ascending channel through the first throttling device; as well as a second throttling device, the second throttling device being arranged at the outlet of the descending channel and used for supplying cooling to the part to be cooled; a third throttling device, the third throttling device being arranged at the bottom of the descending channel; The second throttling device and the third throttling device are respectively configured to provide cooling to different positions of the part to be cooled; The second throttling device and the third throttling device are respectively arranged at the bottom of the descending channel and at different positions of the part to be cooled, and the overflow hole is arranged as follows: When the coolant cools the main container, the liquid level of the coolant does not exceed the height of the overflow hole; When the coolant cools the component to be cooled, the liquid level of the coolant exceeds the height of the overflow hole.

2. The auxiliary cooling system for a fast reactor according to claim 1, characterized in that: The partition is provided with a plurality of overflow holes, and the plurality of overflow holes are all located in a first plane, wherein the first plane is perpendicular to the flow direction of the coolant in the ascending channel.

3. The auxiliary cooling system for a fast reactor according to claim 1, characterized in that: The first throttling device comprises a labyrinth throttling element.

4. The auxiliary cooling system for a fast reactor according to claim 1, characterized in that: The second throttling device includes an orifice plate throttling element or a small hole throttling element.

5. The auxiliary cooling system for a fast reactor according to claim 1, characterized in that: The third throttling device includes an orifice type throttling element or a small hole type throttling element.

6. The auxiliary cooling system for a fast reactor according to claim 1, characterized in that: The partition plate and the heat shielding layer are both cylindrical structures, and the axes of the two coincide with each other.

7. The auxiliary cooling system for a fast reactor according to claim 6, characterized in that: The number of the heat shielding layers is three, and the axes of the three heat shielding layers coincide with each other.

8. The auxiliary cooling system for a fast reactor according to any one of claims 1 to 7, characterized in that: The parts to be cooled include pump supports and / or intermediate heat exchanger supports.

9. An auxiliary cooling method for a fast reactor, based on the auxiliary cooling system according to any one of claims 1 to 8, characterized in that: The auxiliary cooling method comprises: Controlling the coolant temperature in the ascending channel and the overflow hole to be lower than 420° C.; and The temperature difference between the outlet coolant temperature of the descending passage and the inlet coolant temperature of the ascending passage is controlled not to exceed 47°C.

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