A passive, separate heat pipe spent fuel pool cooling system

Abstract

The application relates to a spent fuel pool cooling system of a passive separated heat pipe, belonging to the technical field of spent fuel pool design of nuclear power plants. The system comprises a heat end heat exchanger and a cold end condenser. The heat end heat exchanger is arranged on the two side wall surface areas of the spent fuel pool in the spent fuel plant house according to a set form. The cold end condenser is arranged in an air cooling tower outside the spent fuel plant house. The heat end heat exchanger and the cold end condenser are correspondingly connected through an ascending pipeline and a descending pipeline, and the external environment is used as a final heat sink, so that passive cooling of the spent fuel pool area is realized. The system provided by the application can enhance two-phase heat exchange by using a low-pressure heat pipe, and improve the safety performance and economy of the spent pool cooling system.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power plant spent fuel pool design technology, specifically a passively decoupled heat pipe spent fuel pool cooling system. Background Technology

[0002] The heat pipe principle was proposed by R.S. Gaugler of General Motors in Ohio, USA, in 1944, and has been developed for nearly 80 years. Heat pipes have excellent heat exchange performance; for the same cross-sectional area, a heat pipe's heat exchange capacity is more than 3000 times that of a copper pipe. In daily life, heat pipe technology is commonly used in computer CPU cooling, new energy-saving air conditioners, solar water heaters, and many other areas. In industrial applications, heat pipe technology is often used in boiler waste heat recovery systems, aerospace, and internal combustion engine cooling systems. In 1974, the Alaska Pipeline in the United States used 112,000 heat pipes to solve the permafrost problem. In 2006, the Qinghai-Tibet Railway opened, and multiple individual heat pipes were also used on both sides of the tracks. These heat pipes range in length from a few meters to tens of meters, totaling 18,200 pipes, with an actual service life of over 17 years.

[0003] In the field of nuclear energy, patent ZL201210491112.2 proposes a spent fuel pool cooling and purification system, which is a cooling system suspended on the wall of the spent fuel pool; AREVA has proposed a spent fuel pool cooling system design for the Goesgen-Daeniken nuclear power plant, which suspends split heat pipes on the wall of the spent fuel pool, and has carried out preliminary experimental verification for this; patent CN204029398U proposes a passive spent fuel pool cooling system, which realizes the passive removal of spent fuel decay heat based on the principle of split heat pipes. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a passively separable heat pipe-based spent fuel water tank cooling system. This system enhances two-phase heat exchange and improves the safety and economy of the spent fuel tank cooling system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A passively isolated heat pipe-based spent fuel water pool cooling system includes a hot-end heat exchanger and a cold-end condenser. The hot-end heat exchanger is arranged in a predetermined manner on both sides of the spent fuel water pool within the spent fuel plant, and the cold-end condenser is arranged in an air-cooled tower outside the spent fuel plant. The hot-end heat exchanger and the cold-end condenser are connected to each other via rising and falling pipes, respectively, using the external environment as the final heat sink to achieve passive cooling of the spent fuel water pool area.

[0007] Furthermore, in the passively detachable heat pipe spent fuel pool cooling system described above, the hot-end heat exchanger includes multiple individual heat pipe heat exchangers, each of which includes a vertical tube bundle, a top gas collection chamber, and a bottom water distribution chamber. The top gas collection chamber has a steam outlet, and the bottom water distribution chamber has a water inlet.

[0008] Furthermore, in the passively detachable heat pipe spent fuel pool cooling system described above, the cold-end condenser includes multiple individual condensers, the number of which is consistent with the number of individual heat pipe heat exchangers; each individual condenser has a steam inlet and a water outlet, its steam inlet being connected to the steam outlet of an individual heat pipe heat exchanger via the rising pipe, and its water outlet being connected to the water inlet of the individual heat pipe heat exchanger via the falling pipe.

[0009] Furthermore, in the passively detachable heat pipe spent fuel pool cooling system described above, the pipes of the cooling system are filled with pure water as the cooling working fluid and are in a near-vacuum state with an absolute pressure of less than 300 Pa.

[0010] Furthermore, in the passively detachable heat pipe spent fuel pool cooling system described above, the single-unit condenser is a tube-fin heat exchanger, and the angle of the single-unit condenser can be adjusted within the range of 0-30° to increase heat exchange.

[0011] Furthermore, in the passively isolated heat pipe spent fuel pool cooling system described above, the height of the air-cooled tower ensures that it can form a chimney effect, carrying away the heat released by the cold-end condenser through natural air intake.

[0012] Furthermore, in the passively isolated heat pipe spent fuel pool cooling system described above, the bottom of the air-cooled tower is equipped with an active fan for forced circulation to enhance heat exchange under energized conditions.

[0013] Furthermore, in the passively disconnectable heat pipe spent fuel water pool cooling system described above, a vacuum maintenance system is installed on the rising pipe located outside the boundary of the spent fuel plant. The vacuum maintenance system includes a vacuum maintenance isolation valve and a vacuum pump connected in series, which are used to restore the vacuum level of the cooling system by activating the vacuum maintenance system when the vacuum level of the cooling system drops to a set threshold.

[0014] Furthermore, the passively disconnected heat pipe spent fuel water pool cooling system described above has a water replenishment system installed on the downcomer pipe located outside the boundary of the spent fuel plant. The water replenishment system includes a water replenishment isolation valve and a water replenishment tank, and replenishes the cooling fluid lost during the long-term operation of the cooling system through the water replenishment system.

[0015] Furthermore, in the passively disconnectable heat pipe spent fuel water pool cooling system described above, an ascending section isolation valve and a descending section isolation valve are respectively installed on the ascending pipe and the descending pipe located outside the boundary of the spent fuel plant.

[0016] The passive containment heat removal system described in this invention has the following significant technical advantages:

[0017] 1. The hot end adopts multiple individual heat pipe heat exchangers, each independent of the others and without affecting each other. The failure of a single one will not affect the overall operation, resulting in a long cooling system life and a high safety factor.

[0018] 2. In addition to natural ventilation cooling, the cold end also has an additional fan, following the principle of passive cooling and increasing the cooling capacity;

[0019] 3. The cooling system's pipes are in a near-vacuum state with an absolute pressure of less than 300 Pa. The low-pressure heat pipes can enhance two-phase heat exchange and improve the safety and economy of the waste pool cooling system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a spent fuel water tank cooling system with a passively disconnectable heat pipe provided in an embodiment of the present invention;

[0021] Figure 2 for Figure 1 A top view of the system structure;

[0022] Figure 3 A and C represent the front view, top view, and side view of the hot-end heat exchanger, respectively.

[0023] In the diagram: 1-Hot end heat exchanger; 2-Spent fuel water pool; 3-Fuel element placement area; 4-Spent fuel plant boundary; 5-Vacuum maintenance isolation valve; 6-Vacuum pump; 7-Makeup water isolation valve; 8-Makeup water tank; 9-Cooling tower support; 10-Fan; 11-Air-cooled tower; 12-Cold end condenser; 13-Rising section isolation valve; 14-Descending section isolation valve; 15-Rising pipe; 16-Descending pipe; 17-Descending section temperature measuring point; 18-Rising section temperature measuring point; 19-Water pool temperature measuring point; 20-Differential pressure measuring point. Detailed Implementation

[0024] The present invention will now be further described with reference to specific embodiments and the accompanying drawings.

[0025] This invention provides a passively separable heat pipe-based spent fuel pool cooling system. The system uses low-pressure heat pipes to enhance two-phase heat exchange, thereby improving the safety and economy of the spent fuel pool cooling system.

[0026] Figure 1This diagram illustrates a passively disconnectable heat pipe-based spent fuel water tank cooling system according to an embodiment of the present invention. Figure 2 The diagram shows a top view of the cooling system, which mainly consists of a hot-end heat exchanger 1, a cold-end condenser 12, an ascending pipe 15, a descending pipe 16, an air-cooled tower 11, and supporting facilities. The hot-end heat exchanger 1 is arranged in a predetermined manner on both sides of the spent fuel water pool 2 inside the spent fuel plant to efficiently cool the spent fuel water pool 2 area. The cold-end condenser 12 is arranged inside the air-cooled tower 11 outside the spent fuel plant, using the external environment as the final heat sink to achieve passive cooling. The hot-end heat exchanger 1 and the cold-end condenser 12 are connected to each other through the ascending pipe 15 and the descending pipe 16, respectively.

[0027] Figure 3 A schematic diagram of the hot-end heat exchanger 1 is shown. The hot-end heat exchanger 1 is located on the inner wall of the spent fuel water tank 2, above the fuel element placement area 3. The hot-end heat exchanger 1 comprises multiple individual heat pipe heat exchangers. Each individual heat pipe heat exchanger mainly consists of a vertical tube bundle, a top gas collection chamber, and a bottom water distribution chamber. The top gas collection chamber has a steam outlet, and the bottom water distribution chamber has a water inlet. The vertical tube bundle consists of straight tubes or shaped tubes, with a length ranging from 4000 to 7000 mm. The overall dimensions of the hot-end heat exchanger 1 are less than 350 mm × 1500 mm × 7000 mm. The multiple individual heat pipe heat exchangers operate independently and do not affect each other. Damage to a single heat pipe heat exchanger will not affect the overall operation, resulting in a long cooling system lifespan and a high safety factor.

[0028] The cold-end condenser 12 is located inside the air-cooled tower 11 outside the spent fuel plant. It is a tube-fin heat exchanger with a sufficiently large heat dissipation surface area to meet the heat dissipation requirements of the spent fuel water pool 2. The cold-end condenser 12 includes multiple individual condensers, the number of which matches the number of individual heat pipe heat exchangers. Each individual heat pipe heat exchanger is connected to each individual condenser in a one-to-one correspondence. Specifically, each individual condenser has a steam inlet and a water outlet. Its steam inlet is connected to the steam outlet of the individual heat pipe heat exchanger via a rising pipe 15, and its water outlet is connected to the water inlet of the individual heat pipe heat exchanger via a descending pipe 16. The angle of the individual condenser can be adjusted within the range of 0-30° to increase heat exchange.

[0029] The cooling system's piping is filled with pure water as the cooling medium and is in a near-vacuum state (absolute pressure less than 300 Pa), with external insulation measures installed on the piping. Low-pressure heat pipes enhance two-phase heat exchange, improving the safety and economy of the wastewater cooling system.

[0030] The air-cooled tower 11 is located outside the spent fuel plant, and its internal space can accommodate the cold-end condenser 12. The height of the air-cooled tower 11 ensures that it can form a certain chimney effect. A motorized fan 10 is installed at the bottom of the air-cooled tower 11. When there is electricity, heat exchange can be enhanced by forced circulation; when the fan 10 is not used, natural air intake can also remove heat.

[0031] A vacuum maintenance system and a water replenishment system are respectively installed on the rising pipe 15 and the falling pipe 16 located outside the boundary 4 of the waste heat treatment plant. The vacuum maintenance system mainly includes a vacuum maintenance isolation valve 5 and a vacuum pump 6 connected in series, with the vacuum maintenance isolation valve 5 connected to the rising pipe 15. The water replenishment system mainly includes a water replenishment isolation valve 7 and a water replenishment tank 8, with the water replenishment isolation valve 7 connected to the falling pipe 16. During long-term operation, when the vacuum level of the cooling system decreases, the vacuum maintenance system can be activated to restore the vacuum level of the cooling system. During this process, the lost cooling medium can be replenished through the water replenishment system.

[0032] In this embodiment, the diameter of the rising pipe 15 is not less than 100mm; the descending pipe 16 needs to not form a solid water column and has a diameter of not less than 60mm.

[0033] An ascending isolation valve 13 and a descending isolation valve 14 are respectively installed on the ascending pipe 15 and the descending pipe 16. The ascending isolation valve 13 and the descending isolation valve 14 are located outside the boundary 4 of the waste plant.

[0034] Temperature measuring point 18 is set on the rising section of the rising pipe 15, temperature measuring point 17 is set on the falling section of the falling pipe 16, and temperature measuring point 19 is set on the surface of the spent fuel water pool 2, which are used to monitor the temperature of the rising pipe 15, the falling pipe 16 and the spent fuel water pool 2 in real time.

[0035] A differential pressure measuring point is set on the hot end heat exchanger 1 to measure the differential pressure between the two ends of the hot end heat exchanger 1.

[0036] The system is in operation as follows: The system is a normally connected system. Once the temperature of the spent fuel water pool is higher than the system startup temperature, boiling phase change occurs in the hot end heat exchanger 1, generating steam. The steam rises along the rising pipe 15 to the cold end condenser 12, where it is condensed into water. The condensate returns to the bottom of the hot end heat exchanger 1 along the falling pipe 16, thus completing one cycle and completing the heat removal.

[0037] This invention provides a passive, split-type heat pipe cooling system for spent fuel water tanks. It mainly consists of split-type low-pressure heat pipes with cold and hot ends. By fully utilizing the wall gaps of the spent fuel water tank through rational planning, multiple individual split-type heat pipe heat exchangers are arranged for efficient cooling. This system can provide long-term passive cooling of the spent fuel water tank after an accident, ensuring the tank water temperature does not exceed 80°C. The system is passive, requiring no active equipment or power source. This invention reduces the possibility of dry burning of the spent fuel water tank after an accident, improving the safety and reliability of the spent fuel water tank.

[0038] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of the present invention should be defined by the appended claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A passively disconnectable heat pipe-based spent fuel water tank cooling system, characterized in that, The system includes a hot-end heat exchanger (1) and a cold-end condenser (12). The hot-end heat exchanger (1) is arranged in a set manner on both sides of the wall area of ​​the spent fuel water pool (2) in the spent fuel plant. The cold-end condenser (12) is arranged in the air-cooled tower (11) outside the spent fuel plant. The hot-end heat exchanger (1) and the cold-end condenser (12) are connected to each other through rising pipe (15) and falling pipe (16), respectively, using the external environment as the final heat sink to achieve passive cooling of the area of ​​the spent fuel water pool (2). The hot-end heat exchanger (1) includes multiple individual heat pipe heat exchangers. Each individual heat pipe heat exchanger includes a vertical tube bundle, a top gas collection chamber, and a bottom water distribution chamber. The top gas collection chamber has a steam outlet, and the bottom water distribution chamber has a water inlet. The cold-end condenser (12) includes multiple individual condensers, the number of which is the same as the number of individual heat pipe heat exchangers. Each individual condenser has a steam inlet and a water outlet. Its steam inlet is connected to the steam outlet of an individual heat pipe heat exchanger through the rising pipe (15), and its water outlet is connected to the water inlet of the individual heat pipe heat exchanger through the descending pipe (16). The cooling system's pipes are filled with pure water as the cooling medium and are in a near-vacuum state, with an absolute pressure of less than 300 Pa. A vacuum maintenance system is installed on the rising pipe (15) located outside the boundary (4) of the waste plant. The vacuum maintenance system includes a vacuum maintenance isolation valve (5) and a vacuum pump (6) connected in series. When the vacuum level of the cooling system drops to a set threshold, the vacuum maintenance system is activated to restore the vacuum level of the cooling system. A water replenishment system is installed on the downcomer pipe (16) located outside the boundary (4) of the cooling plant. The water replenishment system includes a water replenishment isolation valve (7) and a water replenishment tank (8) to replenish the cooling fluid lost by the cooling system during long-term operation.

2. The spent fuel water tank cooling system with a passively disconnectable heat pipe according to claim 1, characterized in that, The single-unit condenser is a tube-fin heat exchanger, and the angle of the single-unit condenser can be adjusted within the range of 0-30° to increase heat exchange.

3. The spent fuel water tank cooling system with a passively disconnectable heat pipe according to claim 1 or 2, characterized in that, The height of the air-cooled tower (11) ensures that it can form a chimney effect, carrying away the heat released by the cold-end condenser (12) through natural air intake.

4. The spent fuel water tank cooling system with a passively disconnectable heat pipe according to claim 1, characterized in that, The air-cooled tower (11) is equipped with a dynamic fan (10) at its bottom, which is used to enhance heat exchange through forced circulation under energized conditions.

5. The spent fuel water tank cooling system with a passively disconnectable heat pipe according to claim 1, characterized in that, An ascending section isolation valve (13) and a descending section isolation valve (14) are respectively installed on the ascending pipe (15) and the descending pipe (16) located outside the boundary (4) of the waste plant.

Images