A passive residual heat removal system for a fuel salt discharge tank

Abstract

The application relates to a kind of passive residual heat removal systems of fuel salt discharge tank, heat transfer working medium is solid at room temperature and is liquid after heating, the passive residual heat removal system includes fuel salt discharge tank, salt discharge pipe, natural circulation loop, air cooler and circulation maintaining heat exchange device, fuel salt discharge tank is communicated with nuclear reactor core by salt discharge pipe, fuel salt discharge tank is communicated with air cooler and circulation maintaining heat exchange device respectively by natural circulation loop;Wherein, circulation maintaining heat exchange device is in thermal contact with molten salt reactor main loop pipeline, to compensate the heat loss of passive residual heat removal system by the heat energy of normal working loop.According to the passive residual heat removal system of the application, heat transfer working medium is not water, in the normal operation of reactor, it is standby state, maintain natural circulation fluid in molten liquid state and slowly natural circulation, once accident occurs, the fuel salt of reactor core is discharged into discharge tank, and the natural circulation fluid of molten liquid state can quickly establish natural circulation to remove decay heat.

Description

TECHNICAL FIELD

[0001] The present application relates to molten salt reactor thermal management, and more particularly to a passive residual heat removal system for a fuel salt drain tank. BACKGROUND

[0002] As the fourth generation nuclear reactor, molten salt reactor is the only liquid fuel nuclear reactor. Compared with other reactor types, molten salt reactor has good inherent safety, nuclear proliferation resistance and economy.

[0003] After the reactor accident, even if the emergency shutdown, there is still decay heat generated, and this part of residual heat is still considerable in a considerable period of time, which needs to be carried out to the final heat sink through the specially set residual heat removal system. Otherwise, the cumulative heat in the reactor may cause temperature rise, which may lead to failure of the reactor safety barrier, causing radioactive release and causing serious nuclear safety accidents.

[0004] The residual heat removal system is divided into active residual heat removal system and passive residual heat removal system, the difference between the two is that the active residual heat removal system must rely on external power or external action, while the passive residual heat removal system does not need external action and is completely driven by natural phenomena. Therefore, only the passive residual heat removal system can fundamentally solve the safety of the nuclear reactor in the event of an accident.

[0005] As early as the 1960s, the United States Oak Ridge National Laboratory (ORNL) used a passive heat exchange method in the design of the MSRE salt discharge tank. See R.C. Robertson and S.E. Beall's MSRE Design and Operation Report published by the U.S. Atomic Energy Commission in 1965. The working principle of MSRE is that the cooling water at the bottom of the steam drum flows into the inlet pipe through the inlet of the jacketed heat exchange element and flows downward, turns upward at the bottom of the jacket and enters the annular cavity, and is heated to boiling. The steam enters the upper part of the steam drum along the annular cavity and flows to the condenser along the steam pipeline. The condensed water returns to the steam drum under the action of gravity and enters the inlet pipe, forming a closed natural circulation. The existing passive residual heat removal technology, such as the passive residual heat removal system and experimental device and heat exchange device for molten salt reactor disclosed in CN201310286718.7, CN201610899803.4, CN201710566887.4 and CN202011538069.1, all use the above-mentioned MSRE scheme for passive heat exchange, and the heat transfer medium is water. In the case of water shortage, the above-mentioned existing technical solutions cannot solve the problem of residual heat removal. SUMMARY

[0006] In order to solve the problems caused by using water as the heat transfer medium in the prior art, the application provides a non-active residual heat removal system of a fuel salt drain tank.

[0007] The non-active residual heat removal system of the fuel salt drain tank according to the application, whose heat transfer medium is solid at room temperature and liquid after heating, comprises a fuel salt drain tank, a salt drain pipe, a natural circulation loop, an air cooler and a circulation maintaining heat exchange device, the fuel salt drain tank is communicated with a nuclear reactor core through the salt drain pipe, and the fuel salt drain tank is communicated with the air cooler and the circulation maintaining heat exchange device through the natural circulation loop; wherein the circulation maintaining heat exchange device is in thermal contact with a main loop pipeline of a molten salt reactor, so as to compensate the heat loss of the non-active residual heat removal system by the heat energy of a normal working loop.

[0008] In a preferred embodiment, the fuel salt drain tank has a natural circulation inlet and a natural circulation outlet, the natural circulation loop has a first natural circulation loop hot section, a second natural circulation loop hot section and a natural circulation loop cold section, and the air cooler has an air cooler primary side inlet and an air cooler primary side outlet, wherein two ends of the first natural circulation loop hot section are connected with the natural circulation outlet and the circulation maintaining heat exchange device respectively, two ends of the second natural circulation loop hot section are connected with the circulation maintaining heat exchange device and the air cooler primary side inlet respectively, and two ends of the natural circulation loop cold section are connected with the air cooler primary side outlet and the natural circulation inlet respectively, thereby forming the natural circulation loop.

[0009] In a preferred embodiment, in the natural circulation loop, the driving force of the natural circulation fluid flow is the height difference H1 between the center of the fuel salt drain tank and the center of the air cooler and the height difference H2 between the center of the circulation maintaining heat exchange device and the center of the air cooler.

[0010] In a preferred embodiment, the fuel salt drain tank comprises a plurality of fuel salt drain tank heat exchange elements, an upper tube sheet, a lower tube sheet, a side wall, an upper head, a lower head, a lower chamber and an upper chamber, wherein the upper tube sheet and the lower tube sheet are spaced apart from each other to accommodate the core fuel salt therebetween, the fuel salt drain tank heat exchange elements are installed in the side wall through the upper tube sheet and the lower tube sheet, the lower head is connected with the side wall to define the lower chamber below the lower tube sheet, the upper head is connected with the side wall to define the upper chamber above the upper tube sheet, the lower chamber and the upper chamber are communicated through the fuel salt drain tank heat exchange elements to accommodate the natural circulation fluid therein, and the core fuel salt and the natural circulation fluid exchange heat through the fuel salt drain tank heat exchange elements in the fuel salt drain tank.

[0011] In a preferred embodiment, the fuel salt drain tank further has a gas exhaust port communicated with the fuel salt inlet, the position of the gas exhaust port on the side wall is close to the upper tube sheet, and the liquid level of the core fuel salt filled between the upper tube sheet and the lower tube sheet does not submerge the gas exhaust port.

[0012] In a preferred embodiment, the circulation maintaining heat exchange device includes a plurality of circulation maintaining heat exchange device heat exchange elements, which are tightly fixed around the main loop pipeline of the molten salt reactor to achieve thermal contact.

[0013] The passive waste heat removal system for the fuel salt drain tank of the present invention uses a non-water heat transfer medium. During normal reactor operation, the primary circuit operates normally, and the heat energy transferred by the primary circuit circulates through a heat exchanger to compensate for heat losses in the passive waste heat removal system, maintaining its standby state. During this time, the natural circulating fluid is in a molten liquid state and circulates slowly, avoiding the need for additional heating devices. The reactor's thermal energy compensates for heat losses in the passive waste heat removal system during standby, preventing the natural circulating fluid from freezing and clogging. The natural circulation is powered by hydrogen. In the event of an accident, after the core fuel salt is drained into the fuel salt drain tank, the molten liquid natural circulating fluid can quickly build up decay heat, enabling the passive heat removal function to immediately operate. The natural circulation is powered by hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of a molten salt reactor cooling system with a fuel salt discharge tank according to a preferred embodiment of the present invention.

[0015] Figure 2 yes Figure 1 Schematic diagram of the fuel salt discharge tank.

[0016] Figure 3 yes Figure 1 Schematic diagram of the structure of the circulation and heat exchange device.

[0017] Figure 4 Schematic diagram of the structure of a fuel salt discharge tank of a molten salt reactor cooling system according to another preferred embodiment of the present invention. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0019] like Figure 1 As shown, the passive waste heat removal system for a fuel salt discharge tank according to a preferred embodiment of the present invention includes a fuel salt discharge tank 1, a natural circulation loop 2, an air cooler 3, a circulation-maintaining heat exchange device 4, and a salt discharge pipe 6. The fuel salt discharge tank 1 is connected to the nuclear reactor core (not shown) via the salt discharge pipe 6. The fuel salt discharge tank 1 is connected to the air cooler 3 and the circulation-maintaining heat exchange device 4 via the natural circulation loop 2, respectively. The circulation-maintaining heat exchange device 4 is in thermal contact with the main loop pipe 7 of the molten salt reactor. It should be understood that the various pipes and equipment in the molten salt reactor cooling system may be coated with heating and insulation devices.

[0020] The primary side of the air cooler 3 refers to the heat source side, and the secondary side refers to the heat load side (i.e., the cold side), and the primary side fluid transfers heat to the secondary side fluid through the partition wall heat exchange in the air cooler 3. For example, the tube-shell heat exchanger, if the heat source fluid goes in the tube, the tube is the primary side, and the tube is the secondary side. It can also be exchanged, and the heat source fluid goes outside the tube, and the tube is the primary side, and the tube is the secondary side. The difference depends on which side the heat source is on. Specifically, the natural circulation fluid in the natural circulation loop 2 exchanges heat with air in the air cooler 3. The natural circulation fluid can be a molten salt, or a liquid metal, a heat-conducting oil, etc. The air cooler 3 is placed in the air cooling tower 5, and the secondary side of the air cooler 3 exchanges heat by air natural convection to the atmosphere. It should be understood that the structure type of the air cooler 3 can be various, such as U-shaped tube type, spiral tube type, plate type, etc.

[0021] As shown in Figure 1 The fuel salt discharge tank 1 includes a fuel salt inlet 1-1, and both ends of the salt discharge pipe 6 are connected to the nuclear reactor core (not shown) and the fuel salt inlet 1-1, respectively, so as to discharge the fuel salt in the nuclear reactor core into the fuel salt discharge tank 1.

[0022] As shown in Figure 2 The fuel salt discharge tank 1 includes a plurality of fuel salt discharge tank heat exchange elements 1-4, an upper tube plate 1-8, a lower tube plate 1-9, and a side wall 1-12, wherein the fuel salt discharge tank heat exchange elements 1-4 are fixedly installed in the side wall 1-12 through the upper tube plate 1-8 and the lower tube plate 1-9 spaced apart from each other. The fuel salt discharge tank 1 also has a gas outlet 1-5 connected to the fuel salt inlet 1-1, which is connected to the gas path system (not shown, which fills the sinusoidal gas), and the position on the side wall 1-12 is close to the upper tube plate 1-8. When the core fuel salt is discharged from the nuclear reactor core, the core fuel salt fills between the upper tube plate 1-8 and the lower tube plate 1-9, and the liquid level reaches the fuel salt liquid level 8, without submerging the gas outlet 1-5. It should be understood that the fuel salt discharge tank heat exchange elements 1-4 can be straight tubes, longitudinal finned tubes, twisted tubes, serpentine tubes (or spiral tubes), etc.

[0023] As shown in Figure 2As shown, the fuel salt drain tank 1 includes a lower chamber 1-2, an upper chamber 1-3, an upper head 1-10 and a lower head 1-11, wherein the lower head 1-11 is connected with the side wall 1-12 to define the lower chamber 1-2 below the lower tube sheet 1-9, the upper head 1-10 is connected with the side wall 1-12 to define the upper chamber 1-3 above the upper tube sheet 1-8, and the lower chamber 1-2 and the upper chamber 1-3 are communicated through the fuel salt drain tank heat exchange element 1-4, so that the reactor core fuel salt and the natural circulation fluid exchange heat through the fuel salt drain tank heat exchange element 1-4 in the fuel salt drain tank 1. It should be understood that the shape of the upper head 1-10 and the lower head 1-11 is not limited, which can be an oval head, a flat head or other shapes.

[0024] As shown in Figure 3 , the circulation maintaining heat exchange device 4 includes a plurality of circulation maintaining heat exchange device heat exchange elements 4-1 which are fixedly arranged around the main loop pipe 7 to achieve thermal contact and exchange heat through thermal conduction, thermal radiation and contact conduction. It should be understood that the type of the circulation maintaining heat exchange device 4 can be various, such as a tube type, a spiral plate type, a spiral pipe type, a micro-channel plate type, etc., and the circulation maintaining heat exchange device 4 and the main loop pipe segment 7 where it is located can be integrated in structure to form a heat exchanger, such as a jacketed heat exchanger.

[0025] As shown in Figure 1 and Figure 2 , the fuel salt drain tank 1 has a natural circulation inlet 1-6 and a natural circulation outlet 1-7, the natural circulation loop 2 has a first natural circulation loop hot section 2-1-1, a second natural circulation loop hot section 2-1-2 and a natural circulation loop cold section 2-2, and the air cooler 3 has an air cooler primary side inlet 3-1 and an air cooler primary side outlet 3-2, wherein the two ends of the first natural circulation loop hot section 2-1-1 are connected with the natural circulation outlet 1-7 and the circulation maintaining heat exchange device 4 respectively, the two ends of the second natural circulation loop hot section 2-1-2 are connected with the circulation maintaining heat exchange device 4 and the air cooler primary side inlet 3-1 respectively, and the two ends of the natural circulation loop cold section 2-2 are connected with the air cooler primary side outlet 3-2 and the natural circulation inlet 1-6 respectively, thereby forming a natural circulation loop. In the natural circulation loop, the driving force of the natural circulation fluid flow is the height difference H1 between the center of the fuel salt drain tank 1 and the center of the air cooler 3 and the height difference H2 between the center of the circulation maintaining heat exchange device 4 and the center of the air cooler 3, as shown in Figure 1 .

[0026] In the present embodiment, the natural circulation inlet 1-6 is arranged on the lower head 1-11, and the natural circulation loop cold section 2-2 enters the lower chamber 1-2 directly through the natural circulation inlet 1-6, as shown in Figure 2as shown. In another embodiment, the natural circulation inlet 1-6 is arranged on the upper head 1-10, and the natural circulation loop cold section 2-2 enters the lower chamber 1-2 via the natural circulation inlet 1-6, sequentially through the upper tube sheet 1-8 and the lower tube sheet 1-9, as shown. Figure 4

[0027] In the normal operation of the nuclear reactor, the main loop works normally to carry out the nuclear heat load. At the same time, the natural circulation fluid, after heat exchange through the circulation maintaining heat exchange device 4, has a temperature rise, a small density, and flows upward, sequentially through the second natural circulation loop hot section 2-1-2 and the air cooler primary side inlet 3-1, and after heat exchange in the air cooler 3 primary side, has a temperature drop, a large density, and flows downward, sequentially through the air cooler primary side outlet 3-2, the natural circulation loop cold section 2-2, the lower chamber 1-2, the fuel salt discharge tank heat exchange element 1-4, the upper chamber 1-3, and the first natural circulation loop hot section 2-1-1, and finally returns to the circulation maintaining heat exchange device 4, forming a circulation.

[0028] In the case of nuclear reactor shutdown and fuel salt discharging from the core, the fuel salt in the core of the nuclear reactor flows through the salt discharge pipe 6, and enters the fuel salt discharge tank 1 via the fuel salt inlet 1-1. At this time, the decay heat of the core fuel salt raises the temperature of the natural circulation fluid in the fuel salt discharge tank heat exchange element 1-4 through the heat exchange of the partition wall, has a small density, and flows upward into the upper chamber 1-3, sequentially through the first natural circulation loop hot section 2-1-1, the circulation maintaining heat exchange device 4, the second natural circulation loop hot section 2-1-2, and the air cooler primary side inlet 3-1 via the natural circulation outlet 1-7, and after heat exchange in the air cooler 3 primary side, has a temperature drop, a large density, and flows downward, sequentially through the air cooler primary side outlet 3-2 and the natural circulation loop cold section 2-2, and enters the lower chamber 1-2 via the natural circulation inlet 1-6, and finally returns to the fuel salt discharge tank heat exchange element 1-4, forming a natural circulation.

[0029] In the present application, the main loop fluid and the natural circulation fluid can be the same or different. The entire system does not use water, and is widely applicable to waterless areas. The passive residual heat removal system is in standby state during the normal operation of the nuclear reactor, does not need additional heating device heating, and uses the heat energy of the nuclear reactor to compensate for the heat loss of the passive residual heat removal system, prevents the overcooling freezing blockage of the heat transfer working medium, simplifies the system, and improves the inherent safety and economy. In the case of nuclear reactor shutdown and fuel salt discharging from the core, the fuel salt discharge tank is cooled by water, and completely relies on passive action to remove the decay heat.

[0030] ​The above merely describes preferred embodiments of the present application, and is not intended to limit the scope of the present application. The above-described embodiments of the present application can be variously changed. That is, simple, equivalent changes and modifications made in accordance with the content of the claims and the specification of the present application are intended to fall within the scope of the present application. The present application is not limited by the above-described embodiments.

Claims

1. A passive residual heat removal system for a fuel salt drain tank, characterized by, The heat transfer medium of the passive waste heat removal system is solid at room temperature and liquid after heating. The passive waste heat removal system includes a fuel salt discharge tank, a salt discharge pipe, a natural circulation loop, an air cooler and a circulation maintenance heat exchange device. The fuel salt discharge tank is connected to the nuclear reactor core through the salt discharge pipe, and the fuel salt discharge tank is connected to the air cooler and the circulation maintenance heat exchange device through the natural circulation loop. The circulation maintenance heat exchange device is in thermal contact with the main loop pipeline of the molten salt reactor to compensate for the heat loss of the passive waste heat removal system through the heat energy of the normal working loop.

2. The passive residual heat removal system according to claim 1, characterized by The fuel salt discharge tank has a natural circulation inlet and a natural circulation outlet, the natural circulation loop has a first natural circulation loop hot section, a second natural circulation loop hot section and a natural circulation loop cold section, and the air cooler has an air cooler primary side inlet and an air cooler primary side outlet, wherein the two ends of the first natural circulation loop hot section are respectively connected to the natural circulation outlet and the circulation maintaining heat exchange device, the two ends of the second natural circulation loop hot section are respectively connected to the circulation maintaining heat exchange device and the air cooler primary side inlet, and the two ends of the natural circulation loop cold section are respectively connected to the air cooler primary side outlet and the natural circulation inlet, forming a natural circulation loop.

3. The passive residual heat removal system according to claim 2, characterized in that: In the natural circulation loop, the power sources for the natural circulation fluid flow are the height difference H1 between the center of the fuel salt discharge tank and the center of the air cooler and the height difference H2 between the center of the circulation maintaining heat exchange device and the center of the air cooler.

4. The passive residual heat removal system in accordance with claim 1, characterized by, The fuel salt discharge tank includes a plurality of fuel salt discharge tank heat exchange elements, an upper tube sheet, a lower tube sheet, a side wall, an upper head, a lower head, a lower chamber and an upper chamber, wherein the upper tube sheet and the lower tube sheet are spaced apart from each other to accommodate the core fuel salt therebetween, the fuel salt discharge tank heat exchange elements are installed in the side wall through the upper tube sheet and the lower tube sheet, the lower head is connected to the side wall to define a lower chamber below the lower tube sheet, and the upper head is connected to the side wall to define an upper chamber above the upper tube sheet, the lower chamber and the upper chamber are connected through the fuel salt discharge tank heat exchange elements to accommodate natural circulation fluid therein, and the core fuel salt and the natural circulation fluid exchange heat in the fuel salt discharge tank through the fuel salt discharge tank heat exchange elements.

5. The passive residual heat removal system in accordance with claim 4, characterized by The fuel salt discharge tank also has an exhaust port connected to the fuel salt inlet. The exhaust port is located on the side wall close to the upper tube plate, and the liquid level of the core fuel salt filled between the upper tube plate and the lower tube plate does not submerge the exhaust port.

6. The passive residual heat removal system in accordance with claim 1, characterized by The circulation maintaining heat exchange device comprises a plurality of circulation maintaining heat exchange device heat exchange elements, which are tightly fixed around the main loop pipeline of the molten salt reactor to achieve thermal contact.

Images