A passive spent fuel water tank cooling makeup water and waste heat utilization system

Abstract

This invention belongs to the technical field of nuclear facility safety equipment, and relates to a passive spent fuel pool cooling and replenishment system and waste heat utilization system. The system includes a spent fuel pool, a cooling pool, a spent fuel decay waste heat cooling system, a waste heat utilization system, and a passive replenishment system. The spent fuel pool is filled with coolant to cool the spent fuel assemblies, and the cooling pool is located above the spent fuel pool. The spent fuel decay waste heat cooling system relies on natural circulation to remove the decay waste heat generated by the spent fuel assemblies within the spent fuel pool. The waste heat utilization system is used to convert and utilize the decay waste heat energy of the spent fuel assemblies. The passive replenishment system ensures timely replenishment of the spent fuel pool under both normal and accident conditions. The system proposed in this invention can passively replenish the spent fuel pool under normal and accident conditions during power loss accidents, and solves the problem of low economic efficiency associated with spent fuel pools.

Description

Technical Field

[0001] This invention belongs to the field of nuclear facility safety equipment and relates to a passive spent fuel pool cooling water replenishment and waste heat utilization system. Background Technology

[0002] Spent fuel unloaded from nuclear power plant and nuclear-powered ship reactors carries high levels of radioactivity and needs to be submerged in water pools for extended periods. This allows for the removal of decay heat and radioactive shielding via powered cooling water. Currently, centrifugal pumps are commonly used for cooling spent fuel pools, but this approach faces two main problems. First, in the event of a plant-wide power outage, the power supply system will fail, and the failure of the powered system will prevent the timely removal of residual heat from the spent fuel assemblies. This can lead to a drop in the spent fuel pool level due to evaporation or leakage, exposing the spent fuel assemblies and causing heat transfer deterioration, resulting in a significant risk of radioactive leakage. Second, the decay heat from the spent fuel pools is not effectively utilized by the powered system and is instead directed to rivers, the ocean, or the air, resulting in energy waste.

[0003] Therefore, it is necessary to provide a passive spent fuel water tank cooling water replenishment and waste heat utilization system, so as to achieve normal and emergency water replenishment of the spent fuel water tank in the event of power failure, and solve the problem of low economic efficiency of spent fuel water tanks. Summary of the Invention

[0004] In order to overcome the problems existing in the prior art, the present invention proposes a passive spent fuel water tank cooling water replenishment and waste heat utilization system, which can passively achieve water replenishment of spent fuel water tank under normal and emergency conditions in the event of power failure, and solve the problem of low economic efficiency of spent fuel water tank.

[0005] The technical solution of this invention to solve the above problems is: a passive spent fuel water tank cooling water replenishment and waste heat utilization system, which is special in that:

[0006] It includes a spent fuel water pool, a cooling water pool, a spent fuel decay waste heat cooling system, a waste heat utilization system, and a passive water replenishment system; the spent fuel water pool is filled with coolant to cool the spent fuel assemblies, and the cooling water pool is located above the spent fuel water pool.

[0007] The spent fuel decay waste heat cooling system relies on natural circulation to remove the decay waste heat generated by the spent fuel assemblies in the spent fuel pool; the waste heat utilization system is used to realize the conversion and utilization of the decay waste heat energy of the spent fuel assemblies; the passive water replenishment system is used to ensure timely water replenishment of the spent fuel pool under normal system operation and accident conditions.

[0008] Furthermore, the aforementioned spent fuel decay waste heat cooling system includes at least one set of cooling loops.

[0009] The cooling circuit includes a waste heat venting device, a heat exchanger, an uplift pipeline, and a downlift pipeline. The waste heat venting device is located in a spent fuel water tank, and the heat exchanger is located in a cooling water tank. The waste heat venting device and the heat exchanger are connected via the uplift pipeline and the downlift pipeline. The waste heat venting device contains a low-boiling-point working fluid, which flows within a natural circulation channel formed by the waste heat venting device, the uplift pipeline, the heat exchanger, and the downlift pipeline.

[0010] Furthermore, the aforementioned waste heat utilization system includes at least one set of waste heat utilization lines;

[0011] The waste heat utilization line includes a steam turbine and a generator; the steam turbine is connected to the riser pipeline, and the output end of the steam turbine is connected to the generator.

[0012] Furthermore, the aforementioned passive water supply system includes at least one conventional water supply line and at least one emergency water supply line.

[0013] The conventional water replenishment line includes an intermediate water tank and a receiving water tank. The intermediate water tank is connected to the spent fuel water pool through a water injection pipeline with a check valve. The cooling water pool is connected to the top of the intermediate water tank through a water injection pipeline with a conventional water replenishment isolation valve. The receiving water tank is connected to the intermediate water tank through an overflow port.

[0014] The emergency water replenishment line includes a boron replenishment tank. The cooling water pool is connected to the top of the spent fuel water pool via a water injection pipeline with an emergency water replenishment isolation valve at its bottom. The boron replenishment tank is connected to the upper end of the emergency water replenishment isolation valve via a pipeline with a boron replenishment isolation valve. The boron replenishment tank is located above the spent fuel water pool and contains a boric acid solution of a certain concentration.

[0015] Furthermore, a pressure sensor is installed in the aforementioned spent fuel water tank, located on the lower side wall of the tank. The pressure sensor collects pressure signals to control the operation of the isolation valves in the conventional water supply line and the emergency water supply line.

[0016] Furthermore, the two ends of the aforementioned rising pipeline are respectively connected to the outlet of the waste heat exhauster and the inlet of the steam turbine, the two ends of the descending pipeline are respectively connected to the outlet of the heat exchanger and the inlet of the waste heat exhauster, the outlet of the steam turbine is connected to the inlet of the heat exchanger, and the cooling circuit of the spent fuel decay waste heat cooling system is a closed cooling circuit.

[0017] Furthermore, the aforementioned passive spent fuel water pool cooling water replenishment and waste heat utilization system also includes an equipment room and a spent fuel water pool building, with the steam turbine located in the equipment room, which is located above the spent fuel water pool.

[0018] Furthermore, the aforementioned passive spent fuel water pool cooling water replenishment and waste heat utilization system also includes the low-power energy-saving lighting system, wherein the steam turbine is connected to the generator through a gear transmission mechanism, and the generator supplies power to the low-power energy-saving lighting system.

[0019] Furthermore, the aforementioned steam turbine and generator are located within the equipment room, while the low-power energy-saving lighting system is located within the spent fuel water tank plant.

[0020] Furthermore, the height of the receiving tank is lower than the height of the intermediate tank, and the height of the intermediate tank is not lower than the height of the spent fuel pool. The intermediate tank, the receiving tank, and the spent fuel pool are all located in the same atmospheric environment.

[0021] Advantages of this invention:

[0022] The passive cooling water supply and waste heat utilization system for spent fuel pools of the present invention comprises a spent fuel decay waste heat cooling system, a waste heat utilization system, and a passive water supply system. The spent fuel decay waste heat system and the waste heat utilization system are coupled through a steam turbine, simultaneously enabling the timely extraction and utilization of decay waste heat. The passive water supply system addresses both normal operation and emergency conditions of the spent fuel pool, providing water level control and radioactive shielding, thus enhancing the inherent safety of the system. Therefore, the passive cooling water supply and waste heat utilization system for spent fuel pools of the present invention, combined with the passive technology characteristic of requiring no external power, possesses high safety and reliability, a simple structure, and is easy to maintain, effectively improving the system's economy and safety. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the passive spent fuel water pool cooling water replenishment and waste heat utilization system of the present invention.

[0024] Among them: 1-Spent fuel water pool, 2-Equipment room, 3-Cooling water pool, 4-Intermediate water tank, 5-Receiving water tank, 6-Boron replenishment storage tank, 100-Spent fuel assembly, 101-Waste heat exhauster, 102-Heat exchanger, 201-Steam turbine, 202-Generator, 203-Low power energy-saving lighting system, 300-Pressure sensor, 301-Check valve, 302-Conventional water replenishment isolation valve, 303-Boron replenishment isolation valve, 304-Emergency water replenishment isolation valve. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0026] Please see Figure 1 The passive spent fuel water tank cooling and replenishment system proposed in this invention is used to passively remove the decay waste heat generated by the spent fuel assembly 100 in the spent fuel water tank 1 to the cooling water tank 3 in a timely manner; at the same time, the decay waste heat can be converted and utilized by the waste heat utilization system to supply the low-power energy-saving lighting system 203; and the spent fuel water tank 1 can also be replenished passively under normal system operation and emergency conditions. Due to the combination of natural circulation cooling and passive water replenishment, the system can meet and maintain the long-term operation requirements of the spent fuel water tank 1.

[0027] like Figure 1 As shown, the spent fuel assembly 100 is submerged in a spent fuel water tank 1 within the plant, which is filled with cooling water to absorb the decay heat of the spent fuel assembly 100. To remove the decay heat from the spent fuel assembly 100, the provided spent fuel decay heat system includes at least one cooling loop. The cooling loop includes a waste heat exhauster 101, a heat exchanger 102, and riser and downcomer lines. The lower end of the cooling loop is placed in the spent fuel water tank 1, and the upper end is placed in a cooling water tank 3, which is positioned at a certain height above the spent fuel water tank 1 to ensure sufficient natural circulation driving force for the cooling loop.

[0028] Specifically, the waste heat exhauster 101 in the cooling circuit is located in the spent fuel water tank 1, the heat exchanger 102 is located in the cooling water tank 3, and the turbine 201 is located in the equipment room 2. The equipment room 2 is located above the spent fuel water tank and next to the cooling water tank 3. One end of the riser in the cooling circuit is connected to the outlet of the waste heat exhauster 101, and the other end is connected to the inlet of the heat exchanger 102; one end of the downcomer is connected to the outlet of the heat exchanger 102, and the other end is connected to the inlet of the waste heat exhauster 101. The cooling circuit composed of the waste heat exhauster 101, the heat exchanger 102, and the riser and downcomer forms a natural circulation channel. The outlet of the waste heat exhauster 101 is higher than the inlet, and the outlet of the heat exchanger 102 is lower than the inlet.

[0029] Preferably, the waste heat venting device 101 located in the spent fuel water tank 1 contains a low-boiling-point working fluid. During operation of the cooling circuit, the low-boiling-point working fluid in the waste heat venting device 101 absorbs the decay waste heat generated by the spent fuel assembly 100 through the coolant in the spent fuel water tank 1. Once the working fluid reaches its boiling point, it forms vapor and flows upwards. The vapor enters the heat exchanger 102 in the cooling water tank 3 via a riser pipe, where it condenses into a liquid. Due to its increased density, the liquid working fluid returns to the waste heat venting device 101 through the outlet of the heat exchanger 102 under gravity. Because the low-boiling-point working fluid forms a natural circulation flow within the cooling circuit using gravity and density differences, the timely removal of decay waste heat from the spent fuel water tank 1 can be achieved without relying on an external power source.

[0030] As attached Figure 1 As shown, to improve the efficiency of waste heat energy conversion and utilization in spent fuel water tank 1, a waste heat utilization subsystem including at least one set of waste heat utilization lines is provided. The waste heat utilization system consists of a steam turbine 201, a generator 202, and a low-power energy-saving lighting system 203. The steam turbine 201 and generator 202 are located in equipment room 2; the steam turbine 201 is connected to the riser line in the cooling circuit, and the inlet of the steam turbine 201 is connected to the outlet of the waste heat exhaust device 101 via the riser line; the outlet of the steam turbine 201 is connected to the inlet of the heat exchanger 102. The low-power energy-saving lighting system 203 is located in the building where the spent fuel water tank is located. The low-power energy-saving lighting system 203 can be located on the ceiling above the spent fuel water tank 1 or on the walls surrounding the spent fuel water tank 1. One end of the generator 202 is connected to the steam turbine 201 via a gear transmission mechanism, and the other end is connected to the low-power energy-saving lighting system 203 via an electric wire.

[0031] Preferably, when the spent fuel assembly 100, which generates decay heat, is stored in the spent fuel pool 1, the cooling circuit operates normally in a passive manner. The low-boiling-point working fluid in the waste heat exhauster 101 absorbs heat and becomes gas, then enters the turbine 201 through a riser. The gas continuously entering the turbine 201 drives the turbine to generate mechanical work. The turbine 201 drives the generator 202 to generate electricity through a gear transmission mechanism. The generator 202, in operation, provides sufficient and reliable power to the low-power energy-saving lighting system 203. The low-power energy-saving lighting system 203 can be used as auxiliary lighting for the spent fuel pool plant, thereby saving on the plant's electricity needs. Therefore, the waste heat utilization system can effectively utilize the previously wasted decay heat of spent fuel.

[0032] As attached Figure 1As shown, the passive water replenishment subsystem includes at least one conventional water replenishment line and at least one emergency water replenishment line to enable timely water replenishment of the spent fuel pool during normal operation and in case of an accident. When the spent fuel pool 1 contains spent fuel assemblies 100 that generate decay heat, the liquid level in the spent fuel pool will drop due to decay heat, natural evaporation, leakage, and other reasons. Therefore, the spent fuel pool needs to be replenished with water in a timely manner before the spent fuel water level falls below the minimum designed operating level.

[0033] Specifically, the water replenishment system includes two operating modes: regular water replenishment and emergency water replenishment. The cooling water pool 3 and boron replenishment storage tank 6 used for water replenishment are placed above the spent fuel water pool 1 and are directly injected through gravity and the principle of communicating vessels to achieve passive water replenishment.

[0034] Specifically, the conventional water supply line consists of an intermediate water tank 4, a receiving water tank 5, a cooling water pool 3, a check valve 301, a conventional water supply isolation valve 302, a pressure sensor 300, a spent fuel water pool 1, and an injection pipeline. The intermediate water tank 4 is connected to the spent fuel water pool 1 via a bottom water supply line, which consists of an injection pipeline and a check valve 301 located on the pipeline. Optionally, to ensure water supply flow and to handle pipeline valve failures, at least three independent parallel bottom water supply lines should be installed. The cooling water pool 3 is connected to the upper part of the intermediate water tank 4 via a bottom water supply line, which consists of an injection pipeline and a conventional water supply isolation valve 302 located on the pipeline. The receiving water tank 5 and the intermediate water tank 4 operate via an overflow mechanism. The pressure sensor 300 is located on the lower side wall of the spent fuel water tank 1. The pressure sensor 300 collects pressure signals to control the opening of the conventional water replenishment isolation valve 302, the boron replenishment isolation valve 303, and the emergency water replenishment isolation valve 304.

[0035] Preferably, the intermediate water tank 4 and the receiving water tank 5 are located within the same spent fuel water pool building. The height of the receiving water tank 5 is lower than the height of the intermediate water tank 4, and the height of the intermediate water tank 4 is not lower than the height of the spent fuel water pool 1. The intermediate water tank 4, the receiving water tank 5, and the spent fuel water pool 1 are all located in the same atmospheric environment.

[0036] The working principle of the conventional water supply line is as follows:

[0037] A pressure sensor 300 located in the spent fuel water tank 1 collects pressure information at the measurement point in real time. During normal operation, when the liquid level in the spent fuel water tank 1 falls below the designed minimum operating level, the pressure sensor 300 controls the opening of the conventional water replenishment isolation valve 302. Cooling water in the cooling water tank 3 enters the intermediate water tank 4 through the water injection pipeline at the bottom of the tank. Due to the communicating vessel principle, the cooling water in the intermediate water tank 4 enters the spent fuel water tank 1 through multiple interconnected water injection lines at the bottom, replenishing the spent fuel water tank 1 in a timely manner. At the same time, excess cooling water in the intermediate water tank 4 flows into the receiving water tank 5 through the overflow port. Multiple batches of cooling water collected in the receiving water tank 5 can be actively returned to the cooling water tank 3 for use. When the spent fuel water tank 1 is replenished with sufficient cooling water, i.e., when the water level reaches the designed maximum operating level, the pressure sensor 300 closes the conventional water replenishment isolation valve 302 on the water injection pipeline, ending the water replenishment process. The conventional water replenishment lines can prevent small fluctuations in the liquid level of the spent fuel water tank.

[0038] Specifically, the emergency water replenishment line consists of a cooling water tank 3, a boron replenishment storage tank 6, a boron replenishment isolation valve 303, an emergency water replenishment isolation valve 304, and a water injection pipeline. The cooling water tank 3 is connected to the upper part of the spent fuel water tank 1 via a water injection line at its bottom. The water injection line consists of a water injection pipeline and an emergency water replenishment isolation valve 304 located on the pipeline. The boron replenishment storage tank 6 is located beside the cooling water tank 3 and is connected to the upper end of the emergency water replenishment isolation valve 304 at the bottom of the cooling water tank via a water injection pipeline with a boron replenishment isolation valve 303 at its bottom. The boron replenishment storage tank 6 contains a boric acid solution of a certain concentration.

[0039] The working principle of the emergency water supply line is as follows:

[0040] Pressure sensor 300, located within spent fuel water pool 1, collects pressure information at measurement points in real time. In the event of an accident, the cooling water level in spent fuel water pool 1 drops significantly, posing a risk of exposure and radioactive leakage to spent fuel assembly 100. Pressure sensor 300 controls the opening of emergency water replenishment isolation valve 304, allowing cooling water from the cooling water pool to directly enter the spent fuel water pool below through the injection pipeline. This timely replenishment of a large amount of cooling water to spent fuel water pool 1 effectively mitigates the risks of exposure and radioactive leakage to spent fuel assembly 100. Simultaneously, pressure sensor 300 controls the opening of boron replenishment isolation valve 303, allowing boric acid solution from boron replenishment tank 6 to mix with cooling water through boron replenishment isolation valve 303 and emergency water replenishment isolation valve 304 before entering spent fuel water pool 1, ensuring the coolant's radioactive shielding effect. Once the spent fuel water tank 1 is replenished with sufficient cooling water, i.e., when the water level reaches the designed maximum operating level, the pressure sensor 300 closes the boron replenishment isolation valve 303 and the emergency water replenishment isolation valve 304 on the water injection pipeline, ending the emergency water replenishment. Optionally, the aforementioned emergency water replenishment pipeline can have multiple rows, and there can be multiple isolation valves on the pipelines. The emergency water replenishment lines enable the replenishment of the spent fuel water tank under accident conditions.

[0041] As can be seen above, the passive water replenishment system, consisting of conventional water replenishment lines and emergency water replenishment lines, can replenish water to the pool where the liquid level has dropped in a timely manner, ensuring that the liquid level of the spent fuel pool remains within the normal operating design parameters.

[0042] In summary, the passive spent fuel water tank cooling and replenishment system and waste heat utilization system provided by this invention includes a spent fuel decay waste heat cooling system, a waste heat utilization system, and a passive water replenishment system. By employing passive technology while leveraging the existing characteristics of active systems that are safe, reliable, mature, and efficient, it can fully guarantee the cooling and replenishment of the spent fuel water tank under normal operating conditions and accident conditions. At the same time, it can fully and effectively utilize the waste heat from spent fuel assembly decay for necessary auxiliary lighting. In the context of diverse technical systems, the spent fuel water tank cooling and replenishment system and waste heat utilization system has outstanding safety and economy.

[0043] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1.A passive spent fuel pool cooling, makeup and waste heat utilization system, comprising: a spent fuel pool, a cooling pool, a spent fuel decay heat cooling system, a waste heat utilization system and a passive makeup system; the cooling pool is located above the spent fuel pool; the spent fuel decay heat cooling system relies on natural circulation to remove the decay heat generated by the spent fuel assemblies in the spent fuel pool; the waste heat utilization system is used to realize the conversion and utilization of the decay heat energy of the spent fuel assemblies; the passive makeup system is used to ensure that the spent fuel pool is timely supplied with water under normal operation and accident conditions; the waste heat utilization system comprises at least one waste heat utilization circuit, the waste heat utilization circuit comprises a steam turbine connected to the spent fuel decay heat cooling system; the passive makeup system comprises at least one emergency makeup circuit and at least one regular makeup circuit, the emergency makeup circuit comprises a water injection pipeline and an emergency makeup isolation valve, and the regular makeup circuit comprises an intermediate tank, a receiving tank and a water injection pipeline with a check valve; the intermediate tank is connected to the spent fuel pool through a water injection pipeline with a check valve, the cooling pool is connected to the upper part of the intermediate tank through a water injection pipeline with a regular makeup isolation valve, and the receiving tank is connected to the intermediate tank through an overflow port; the emergency makeup circuit comprises a boron makeup tank, the cooling pool is connected to the upper part of the spent fuel pool through a water injection pipeline with an emergency makeup isolation valve at the bottom, the boron makeup tank is connected to the upper end of the emergency makeup isolation valve through a pipeline with a boron makeup isolation valve, the boron makeup tank is located above the spent fuel pool, the height of the receiving tank is lower than the height of the intermediate tank, and the height of the intermediate tank is not lower than the height of the spent fuel pool. 2.The passive spent fuel pool cooling, makeup and waste heat utilization system according to claim 1, wherein: the spent fuel decay heat cooling system comprises at least one cooling loop; the cooling loop comprises a waste heat remover, a heat exchanger, an ascending pipeline and a descending pipeline, the waste heat remover is located in the spent fuel pool, the heat exchanger is located in the cooling pool, and the waste heat remover and the heat exchanger are connected through the ascending pipeline and the descending pipeline. 3.The passive spent fuel pool cooling, makeup and waste heat utilization system according to claim 2, wherein: the waste heat utilization circuit comprises a generator, and the output end of the steam turbine is connected to the generator. 4.The passive spent fuel pool cooling, makeup and waste heat utilization system according to claim 3, wherein: a pressure sensor is arranged in the spent fuel pool, and the pressure sensor collects pressure signals to control the actions of the isolation valves in the regular makeup circuit and the emergency makeup circuit. 5.The passive spent fuel pool cooling, makeup and waste heat utilization system according to claim 2, wherein: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Two ends of the ascending pipeline are connected with the outlet of the waste heat remover and the inlet of the steam turbine respectively, two ends of the descending pipeline are connected with the outlet of the heat exchanger and the inlet of the waste heat remover respectively, the outlet of the steam turbine is connected with the inlet of the heat exchanger, and the cooling loop of the spent fuel decay heat cooling system is a closed cooling loop. 6.The non-powered spent fuel pool cooling, makeup and waste heat utilization system according to claim 3, characterized in that: It further comprises a device room and a spent fuel pool plant, the steam turbine is located in the device room, and the device room is located above the spent fuel pool. 7.The non-powered spent fuel pool cooling, makeup and waste heat utilization system according to claim 6, characterized in that: It further comprises a low-power energy-saving lighting system, the steam turbine is connected with the generator through a gear transmission mechanism, and the generator supplies power to the low-power energy-saving lighting system. 8.The non-powered spent fuel pool cooling, makeup and waste heat utilization system according to claim 7, characterized in that: The steam turbine and the generator are located in the device room, and the low-power energy-saving lighting system is located in the spent fuel pool plant. 9.The non-powered spent fuel pool cooling, makeup and waste heat utilization system according to claim 3, characterized in that: The intermediate water tank, the receiving water tank and the spent fuel pool are in the same atmospheric environment.

Images