Helium circulating drying system for spent fuel storage tank

Abstract

The utility model relates to a helium circulating drying system for a spent fuel storage tank, which is characterized in that a first cooler is additionally arranged between the spent fuel storage tank and a second cooler, so that a tube pass inlet and a tube pass outlet of the first cooler are connected in series in a cooling process tube section; and a shell pass inlet and a shell pass outlet of the first cooler are connected with the gas buffer tank and the spent fuel storage tank respectively, so that cooled and steam-water separated helium serves as a cooling medium to participate in a helium cooling process, the load of equipment of the system is reduced, energy is effectively utilized, and energy consumption is reduced. Two parallel helium flow direction pipelines are designed after steam-water separation, the helium flow direction is switched through monitoring of a first dew-point instrument and linkage control of a first three-way valve, the moisture in helium is reduced to a stable limit value through a primary cooling and drying process, and then the moisture in helium is deeply removed through an adsorption drying process. And the spent fuel storage tank is efficiently dried step by step, so that the service life of a drying adsorbent is effectively prolonged.

Description

Technical Field

[0001] This utility model relates to the field of gas purification technology, specifically to a helium circulation drying system for spent fuel storage tanks. Background Technology

[0002] In recent years, my country's nuclear power industry has developed rapidly. Currently, the number of nuclear power units under construction and the installed capacity have become the world's largest. In nuclear power plants that have been put into use, a large amount of spent fuel discharged from the reactor is stored in fixed pools. Over time, the existing spent fuel pools can no longer meet the needs of spent fuel storage and must be temporarily stored or transferred through dry spent fuel storage tanks.

[0003] When storing spent fuel in dry-type spent fuel storage tanks, the tank must be in a helium atmosphere and the internal water content must be less than a specified value. After the spent fuel is transferred from the water pool to the storage tank, the liquid water inside must first be drained, and then the tank must be continuously purged and dried with helium until the water content inside the tank meets the requirements for storing spent fuel.

[0004] For example, CN117711653A discloses an integrated operating system suitable for the dry storage process of spent fuel. The system uses a vacuum pump to remove moisture from the inside of the spent fuel storage tank and maintain a certain vacuum level. Then, helium gas at a certain pressure is introduced into the storage tank to meet the requirements of spent fuel storage. In this method, the drying rate is relatively slow as the vacuum level increases during the vacuum drying process, which affects efficiency. At the same time, the storage tank and fuel rods need to withstand high vacuum levels, which brings certain safety hazards.

[0005] To address the aforementioned technical deficiencies, CN116182514A discloses a helium circulation drying device system and method suitable for spent fuel sealed containers. This method uses a helium circulation drying device and an automatic control system to allow helium to circulate through the spent fuel storage tank and the helium drying device under a slightly positive pressure, thereby achieving drying of the spent fuel storage tank and helium protection. Although this method can effectively dry the spent fuel storage tank, it has high energy consumption during system operation due to unreasonable process design. Utility Model Content

[0006] To address the aforementioned problems, this invention proposes a helium circulation drying system for spent fuel storage tanks, which uses cooled and vapor-water separated helium as a cooling medium in the helium cooling process, thereby reducing the load on the system equipment.

[0007] To achieve the above objectives, the following technical solution is adopted: a helium circulation drying system for spent fuel storage tanks, comprising a spent fuel storage tank, a first cooler, a second cooler, a vapor-water separator, an adsorption dryer assembly, a gas buffer tank, a gas booster pump, and a gas heater.

[0008] The spent fuel storage tank, the first cooler, the second cooler, the steam-water separator, and the gas buffer tank are connected in sequence. The connection points of the first cooler and the second cooler in this series connection are both the tube-side inlet and outlet.

[0009] The gas buffer tank is connected to the shell-side inlet of the first cooler via a gas booster pump, and the shell-side outlet of the first cooler is connected back to the spent fuel storage tank via a gas heater.

[0010] The shell-side inlet of the second cooler serves as the coolant inlet, and the shell-side outlet serves as the coolant outlet.

[0011] A first dew point meter is installed at the exhaust port of the steam-water separator, and a first three-way valve is installed in the pipe section between the first dew point meter and the steam-water separator.

[0012] The gas-water separator and the gas buffer tank are connected in parallel to the adsorption dryer group. The air inlet pipe section of the adsorption dryer group is connected to the first three-way valve, and the exhaust pipe section of the adsorption dryer group is connected to the air inlet end of the gas buffer tank.

[0013] Furthermore, the outlet of the gas-water separator is connected to a water storage tank.

[0014] Furthermore, both the first and second coolers are stainless steel shell-and-tube coolers.

[0015] Furthermore, the coolant in the second cooler is an aqueous solution of ethylene glycol at -10°C.

[0016] Furthermore, the adsorption dryer group is composed of a first adsorption dryer and a second adsorption dryer connected in parallel. The inlet ends of the first and second adsorption dryers are equipped with second three-way valves and connected to the first three-way valve. The outlet ends of the first and second adsorption dryers are connected to the gas buffer tank through filters.

[0017] Furthermore, a second dew point meter is installed between the gas buffer tank and the gas booster pump.

[0018] Furthermore, the first adsorption dryer and the second adsorption dryer are the same adsorption dryer.

[0019] The beneficial effects of this utility model are:

[0020] Compared with existing technologies, after high-temperature helium escapes from the spent fuel storage tank, it can first be pre-cooled by the first cooler and then enters the second cooler. The advantage of this design is that it reduces the cooling load of the second cooler. At the same time, the heat exchange medium of the first cooler is helium pressurized by a gas booster pump. This part of the helium is preheated by the first cooler and then enters the gas heater, which can reduce the load of the gas heater, thereby achieving efficient energy utilization and reducing the energy consumption of the device.

[0021] After gas-water separation, two parallel helium flow lines are designed. The flow direction of helium is switched by monitoring the first dew point meter and interlocking with the first three-way valve. The advantage of this process design is that it makes full use of the primary cooling and drying process to reduce the moisture in the helium to a stable limit value. Then, the moisture in the helium is further removed by the adsorption drying process, which efficiently achieves the gradual drying of the spent fuel storage tank, thereby effectively extending the service life of the drying adsorbent. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of this utility model.

[0023] As shown in the figure: 1. Spent fuel storage tank; 2. First cooler; 3. Second cooler; 4. Gas-water separator; 6. Gas buffer tank; 7. Gas booster pump; 8. Gas heater; 9. Water storage tank; 10. First dew point meter; 11. First three-way valve; 12. Second three-way valve; 13. Filter; 14. Second dew point meter; 300. Coolant inlet; 301. Coolant outlet; 500. First adsorption dryer; 501. Second adsorption dryer. Detailed Implementation

[0024] Example 1

[0025] The following description, in conjunction with the accompanying drawings, further illustrates the points, such as... Figure 1 As shown, a helium circulating drying system for spent fuel storage tanks is provided, including a spent fuel storage tank 1, a first cooler 2, a second cooler 3, a vapor-water separator 4, an adsorption dryer assembly 5, a gas buffer tank 6, a gas booster pump 7, and a gas heater 8.

[0026] The spent fuel storage tank 1 is connected to the tube-side inlet of the first cooler 2, the tube-side outlet of the first cooler 2 is connected to the tube-side inlet of the second cooler 2, the tube-side outlet of the second cooler 3 is connected to the steam-water separator 4, the steam-water separator 4 is connected to the gas buffer tank 6, and the liquid outlet of the steam-water separator 4 is connected to the water storage tank 9. A first dew point meter 10 is installed at the exhaust port of the steam-water separator 4, and a first three-way valve 11 is installed on the pipe section between the first dew point meter 10 and the steam-water separator 4.

[0027] The gas-water separator 4 and the gas buffer tank 6 are connected in parallel to the adsorption dryer group 5. The air inlet pipe section of the adsorption dryer group 5 is connected to the first three-way valve 11, and the exhaust pipe section of the adsorption dryer group 5 is connected to the air inlet end of the gas buffer tank 6.

[0028] Gas buffer tank 6 is connected to the shell-side inlet of first cooler 2 via gas booster pump 7, and shell-side outlet of first cooler 2 is connected back to spent fuel storage tank 1 via gas heater 8.

[0029] The shell-side inlet of the second cooler 3 serves as the coolant inlet 300, and the shell-side outlet of the second cooler 3 serves as the coolant outlet 301. The coolant inlet 300 and the coolant outlet 301 are connected to an external refrigeration unit, and the refrigerant in the refrigeration unit is an aqueous solution of ethylene glycol.

[0030] The adsorption dryer group 5 used in this embodiment is not limited to the number of adsorption dryers or the connection method between adsorption dryers. It can be a single adsorption dryer, two adsorption dryers connected in series, or adsorption dryers connected in parallel.

[0031] The first cooler 2 is used for the initial cooling of the high-temperature helium gas coming out of the spent fuel storage tank 1. The cooling medium is room-temperature dry helium gas pressurized by the gas booster pump 7.

[0032] The second cooler 3 is used to deeply cool the helium gas coming out of the first cooler 2. The cooling medium of this cooler is an aqueous solution of ethylene glycol at -10°C.

[0033] Gas-water separator 4 is used to separate moisture from helium gas.

[0034] Water storage tank 9 is used to store liquid water separated from helium gas.

[0035] Adsorption dryer group 5 is used to adsorb trace amounts of moisture in helium gas.

[0036] Gas buffer tank 6 is used to store helium after steam-water separation and drying, and to stabilize its pressure.

[0037] The gas booster pump 7 is used to send helium from the gas buffer tank 6 into the spent fuel storage tank 1, and is the power source for the helium circulation.

[0038] Gas heater 8 is used to increase the temperature of circulating helium, which helps to quickly remove moisture from the spent fuel storage tank 1.

[0039] In this embodiment,

[0040] Preferably, the first cooler 2 and the second cooler 3 are stainless steel shell-and-tube heat exchangers.

[0041] The preferred spent fuel storage tank has a volume of 4 cubic meters and is filled with spent fuel rods.

[0042] The preferred gas buffer tank 6 has a volume of 100L.

[0043] The preferred gas heater 8 has a tube-type structure and a power of 3.0KW.

[0044] Example 2

[0045] Based on the structure of the helium circulation drying system for spent fuel storage tanks proposed in Example 1, the adsorption dryer group 5 in this embodiment adopts a parallel structure of the first adsorption dryer 500 and the second adsorption dryer 501 as applied in Example 1. Specifically,

[0046] The first adsorption dryer 500 and the second adsorption dryer 501 are provided with a second three-way valve 12 at their inlet ends and are connected to the first three-way valve 11 through the second three-way valve 12. The outlet ends of the first adsorption dryer 500 and the second adsorption dryer 5011 are connected to the gas buffer tank 6 through the filter 13. A second dew point meter 14 is provided between the gas buffer tank 6 and the gas booster pump 7.

[0047] In this embodiment,

[0048] The first adsorption dryer 500 and the second adsorption dryer 501 are the same adsorption dryers. During operation, under the switching control of the second three-way valve 12, one is used for normal drying and adsorption, while the other is used for regeneration.

[0049] Filter 13 is made of stainless steel and is used to filter solid impurities.

[0050] The application and principle of this embodiment, and the helium circulation drying system for spent fuel storage tanks proposed in this embodiment, are described in accordance with... Figure 1 After connection is completed and airtightness is tested, the system is controlled by a PLC control system.

[0051] Dry helium gas, after passing through spent fuel storage tank 1, becomes high-temperature, high-humidity helium gas. It then enters the first cooler 2 for initial cooling, and subsequently enters the second cooler 3 for further cooling to -10°C, becoming low-temperature helium gas. This high-humidity, low-temperature helium gas enters the vapor-liquid separator 4 for vapor-liquid separation, after which most of the water becomes liquid and settles and is collected in the water storage tank 9. The dry helium gas leaves the vapor-liquid separator 4, and the first dew point meter 10 detects the water content of the helium gas at this point. Due to the high humidity value of the circulating helium gas measured at the beginning of system operation, this value is higher than normal. At this time, the control... The first three-way valve 11 is connected to the gas buffer tank 6. The helium after gas-water separation flows to the gas buffer tank 6. The function here is to store and ensure the pressure stability of the helium. After passing through the gas buffer tank 6, the helium is pressurized by the gas booster pump 7 and enters the shell side of the first cooler 2. Here, the helium acts as a heat exchange medium and exchanges heat with the humid and hot helium in the tube side of the first cooler 2. After being heated, it enters the gas heater 8 and is further heated to 80-100°C. After being dried at high temperature, it enters the spent fuel storage tank 1, which removes the internal moisture and completes the drying process of the spent fuel storage tank 1.

[0052] During the helium circulation drying process of the spent fuel storage tank 1, after the system has been running for a period of time, when the detection value of the first dew point meter 10 drops to a stable limit value, the flow direction of the helium is changed, and the first three-way valve 11 is connected to the adsorption dryer group 5. The helium is then passed through the adsorption dryer group 5 for deep drying. When the detection value of the first dew point meter 10 reaches the drying requirements of the spent fuel storage tank 1, the system operation can be stopped.

[0053] During the helium circulation drying process of the spent fuel storage tank 1, the first adsorption dryer 500 is responsible for adsorption drying, and the second adsorption dryer 501 is responsible for adsorbent regeneration. When the value detected by the second dew point meter 14 rises and exceeds the drying requirements of the spent fuel storage tank 1, it proves that the adsorbent in the first adsorption dryer 500 has reached saturation. At this time, the second three-way valve 12 is activated to switch to the second adsorption dryer 501 for adsorption drying. At this time, the first adsorption dryer 500 begins to regenerate. The above operations are alternated and cycled until the drying process of the spent fuel storage tank 1 is completed.

[0054] This utility model is not limited to this embodiment. Any equivalent concept or modification within the technical scope disclosed in this utility model shall be included in the protection scope of this utility model.

Claims

1. A helium circulation drying system for spent fuel storage tanks, characterized in that, It includes a spent fuel storage tank (1), a first cooler (2), a second cooler (3), a steam-water separator (4), an adsorption dryer group (5), a gas buffer tank (6), a gas booster pump (7), and a gas heater (8). The spent fuel storage tank (1), the first cooler (2), the second cooler (3), the steam-water separator (4), and the gas buffer tank (6) are connected in sequence. The connection points of the first cooler (2) and the second cooler (3) in this series connection are both the tube inlet and outlet. The gas buffer tank (6) is connected to the shell-side inlet of the first cooler (2) via a gas booster pump (7), and the shell-side outlet of the first cooler (2) is connected back to the spent fuel storage tank (1) via a gas heater (8). The shell-side inlet of the second cooler (3) serves as the coolant inlet (300), and the shell-side outlet of the second cooler (3) serves as the coolant outlet (301). A first dew point meter (10) is installed at the exhaust port of the steam-water separator (4), and a first three-way valve (11) is installed on the pipe section between the first dew point meter (10) and the steam-water separator (4). The gas-water separator (4) and the gas buffer tank (6) are connected in parallel to the adsorption dryer group (5). The air inlet pipe section of the adsorption dryer group (5) is connected to the first three-way valve (11), and the exhaust pipe section of the adsorption dryer group (5) is connected to the air inlet end of the gas buffer tank (6).

2. The helium circulating drying system for spent fuel storage tanks according to claim 1, characterized in that, The outlet of the gas-water separator (4) is connected to the water storage tank (9).

3. The helium circulating drying system for spent fuel storage tanks according to claim 2, characterized in that, The first cooler (2) and the second cooler (3) are both stainless steel shell-and-tube heat exchangers.

4. The helium circulating drying system for spent fuel storage tanks according to claim 3, characterized in that, The coolant in the second cooler (3) is an aqueous solution of ethylene glycol at -10°C.

5. The helium circulating drying system for spent fuel storage tanks according to any one of claims 1-4, characterized in that, The adsorption dryer group (5) is composed of a first adsorption dryer (500) and a second adsorption dryer (501) connected in parallel. The first adsorption dryer (500) and the second adsorption dryer (501) are provided with a second three-way valve (12) at their inlet ends and are connected to the first three-way valve (11) through the second three-way valve (12). The outlet ends of the first adsorption dryer (500) and the second adsorption dryer (501) are connected to the gas buffer tank (6) through a filter (13).

6. The helium circulating drying system for spent fuel storage tanks according to claim 5, characterized in that, A second dew point meter (14) is installed between the gas buffer tank (6) and the gas booster pump (7).

7. The helium circulating drying system for spent fuel storage tanks according to claim 6, characterized in that, The first adsorption dryer (500) and the second adsorption dryer (501) are the same adsorption dryer.

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