Reactor passive residual heat removal system based on variable heat conduction pipe

Abstract

The invention discloses a reactor passive residual heat removal system based on variable heat conduction pipes, the system comprises a reactor core, the variable heat conduction pipes arranged in a staggered manner, a heat pipe non-condensable gas section is externally connected with a reactor shell, under an accident condition, the temperature of the reactor core rises, and non-condensable gas extension condensation sections of the variable heat conduction pipes are compressed; and the waste heat of the reactor core is conducted to the shell through the extended condensation section and is finally dissipated to the environment heat trap through the shell. The device completely depends on passive heat transfer, is high in safety and stability, and can operate normally even under the condition of an isolated network; meanwhile, due to the design of extending the non-condensable gas section of the heat pipe, an extra residual row radiator does not need to be used any more, the mass of equipment is greatly reduced, and the space of the equipment is saved; the variable heat conduction pipes arranged in a staggered manner can ensure that waste heat of the reactor core is uniformly discharged, and the temperature of the reactor core is prevented from being too high; and the reactor is simple to operate and maintain and suitable for a heat pipe reactor in an underwater environment.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor safety systems, and in particular to a reactor passive residual heat removal system based on a variable thermal conductivity heat pipe. Background Art

[0002] The heat pipe reactor is a new type of reactor. It uses high-temperature heat pipes as the basic heat transfer element to extract the heat from the core. It has the advantages of passive, high reliability, simple system and compact structure. The working principle of the heat pipe reactor is that the fission energy generated by the reactor is transferred to the evaporation section of the metal heat pipe arranged in the core. The evaporation section of the heat pipe absorbs heat to produce steam. The steam condenses in the condensation section after passing through the adiabatic section of the heat pipe. Then the condensed liquid metal returns to the evaporation section of the heat pipe under the action of capillary force or gravity, forming a complete thermal cycle. The condensation section of the core heat pipe is directly connected to the thermoelectric and thermodynamic conversion system, which directly converts the heat from the heat pipe into electrical energy. The remaining waste heat is discharged to the final heat sink through the heat pipe through radiation heat exchange or other heat extraction methods. The heat pipe reactor has good application prospects in deep sea and deep space exploration, star surface bases and other fields. Due to its advantages of passiveness, long life and high reliability, the heat pipe reactor has become a research hotspot in the field of space and underwater nuclear reactors.

[0003] In a heat sink loss accident, the residual heat removal system removes the residual heat from the core to effectively control the temperature of the core and prevent further damage. However, in heat pipe reactors, residual heat removal usually encounters some difficulties, mainly including the following aspects: 1. External water sources, such as seawater, cannot directly contact the reactor core. Otherwise, it may not only cause the radioactive materials in the reactor to leak and spread to the external environment, causing serious safety and environmental problems, but also the corrosiveness of seawater may cause damage to the structure inside the reactor, further exacerbating safety hazards. 2. If cooling is only carried out on the periphery of the reactor, the center of the core may be locally overheated due to the difficulty in heat removal. This may cause some core components to melt, seriously affecting the normal operation and safety of the reactor. 3. For underwater power units, due to limited space resources in the cabin, it is difficult to carry large diesel engines or large battery packs. 4. The dedicated residual heat removal system has a large mass, which will increase the difficulty and cost of using underwater power units.

[0004] Traditional nuclear power plant waste heat removal systems are highly dependent on external electricity. Once the external power is lost, the system will not be able to effectively cool and remove the core waste heat, which may lead to nuclear safety accidents. Although the passive waste heat removal system of the third-generation nuclear power plant does not rely on external electricity, its complex circuit equipment structure, large system volume, and difficulty in operation and maintenance make it unsuitable for application scenarios with limited space such as underwater unmanned submersibles. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a reactor passive residual heat removal system based on variable heat conduction heat pipes, which includes a core, staggered variable heat conduction heat pipes, and the non-condensable gas section of the heat pipe is externally connected to the reactor shell, which greatly reduces the weight of the equipment and saves equipment space; there are no boiling, corrosive and other problems, and the reliability is high; it is suitable for underwater heat pipe reactors with a capacity of 100 kW to 10 MW. The system relies entirely on passive heat transfer, does not require additional energy, and can operate in an isolated grid for a long time.

[0006] The present invention provides a reactor passive residual heat removal system based on a variable thermal conductivity heat pipe, characterized in that the system comprises: a reactor core, a variable thermal conductivity heat pipe, an insulation layer, a heat exchanger, an insulation sleeve, and a heat dissipation shell.

[0007] The variable heat conduction heat pipe is an inflatable heat pipe composed of a pipe wall, a liquid wick, a steam chamber and a non-condensable gas section. Non-condensable gas is filled inside to adjust the length of the working section. The inner layer of the pipe wall is provided with a liquid wick, the non-condensable gas section constitutes the non-condensable gas section, and the steam chamber constitutes the evaporation section.

[0008] The variable thermal conductivity pipe passes through the insulation layer, the evaporation section at one end of the variable thermal conductivity pipe is inserted in the core, the condensation section of the variable thermal conductivity pipe is inserted in the heat pipe heat exchanger, the variable thermal conductivity pipe is arranged in a staggered manner, and the non-condensable gas section extended at the other end of the variable thermal conductivity pipe is wrapped with insulation material, and the non-condensable gas section is annularly embedded in the heat dissipation shell to prevent heat loss too quickly and the shell temperature is too high. The shell and seawater complete natural convection cooling.

[0009] Furthermore, the core is a heat pipe cooled solid state reactor core.

[0010] Furthermore, the variable thermal conductivity heat pipe is a part of the heat pipe inserted into the core and is arranged in a staggered manner to ensure that the residual heat of the core can be discharged normally.

[0011] The beneficial effects of the present invention are as follows: the reactor passive residual heat removal system based on variable thermal conductivity heat pipes disclosed in the present invention completely relies on passive heat transfer and can operate in an isolated grid for a long time; the equipment is simplified, light in weight, and compact in size, and can be used for nuclear power plants with strict requirements on weight and volume, and is suitable for underwater heat pipe reactors of kilowatt to tens of megawatts. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a passive waste heat removal system for flushing heat pipes with seawater in the prior art;

[0013] Figure 2 It is a front view of the reactor passive residual heat removal system based on the variable thermal conductivity heat pipe of the present invention;

[0014] Figure 3 This is a schematic diagram of the variable thermal conductivity heat pipe under normal working conditions according to an embodiment of the present invention;

[0015] Figure 4 This is a schematic diagram of the variable thermal conductivity heat pipe in an accident condition according to an embodiment of the present invention;

[0016] Figure 5 It is a side view of the reactor passive residual heat removal system based on the variable thermal conductivity heat pipe of the present invention;

[0017] In the figure: 1. core, 2. heat pipe, 3. insulation layer, 4. heat exchanger, 5. valve, 6. variable thermal conductivity tube, 7. non-condensable gas section, 8. insulation sleeve, 9. shell, 10. pipe wall, 11. liquid absorption core, 12. steam chamber, 13. non-condensable gas section. DETAILED DESCRIPTION

[0018] The passive residual heat removal system of the existing underwater unmanned submersible heat pipe reactor passively removes the core residual heat by introducing seawater to flush the heat pipe, such as Figure 1 As shown, it is composed of a core 1, a heat pipe 2, a shell and tube heat exchanger 3, a heat pipe heat exchanger 4 and a valve 5. Under accident conditions, the valve 5 is opened to introduce seawater to impact the heat-insulating honeycomb briquette-like insulation layer 3 and take away the residual heat of the core. In the early stage of use of this heat exchanger, seawater will produce violent local boiling when it contacts the wall surface of hundreds of degrees Celsius. In addition, seawater is corrosive and easily corrodes materials. At the same time, the discharge of seawater after the heat exchange is completed is also a problem.

[0019] Example 1

[0020] Figure 2 The present invention provides a reactor passive residual heat removal system based on a variable thermal conductivity pipe, characterized in that the system comprises: a reactor core 1, a variable thermal conductivity pipe 6, an insulation layer 3, a heat exchanger 4, an insulation sleeve 8, and a heat dissipation shell 9.

[0021] The variable heat conduction heat pipe 6 is an inflatable heat pipe composed of a pipe wall 10, a liquid wick 11, a steam chamber 12 and a non-condensable gas section 13. Non-condensable gas is filled inside to adjust the length of the working section. The inner layer of the pipe wall 10 is provided with a liquid wick 11, the non-condensable gas section 13 constitutes the non-condensable gas section 7, and the steam chamber 12 constitutes the evaporation section.

[0022] The variable heat conduction pipe 6 passes through the insulation layer 3, the evaporation section at one end of the variable heat conduction pipe 6 is inserted in the core 1, the condensation section of the variable heat conduction pipe 6 is inserted in the heat pipe heat exchanger 4, the variable heat conduction pipe 6 is arranged in a staggered manner, and the non-condensable gas section 7 extended at the other end of the variable heat conduction pipe 6 is wrapped with an insulation material 8, and the non-condensable gas section 7 is annularly embedded in the heat dissipation shell 9 to prevent heat from being lost too quickly and the shell temperature from being too high, and the shell and seawater complete natural convection cooling.

[0023] like Figure 3 As shown, under normal operating conditions, heat is transferred from the tube wall 10 to the liquid wick 11 and finally to the working fluid in the steam chamber 12. The non-condensable gas section 13 of the variable thermal conductivity heat pipe 6 will accumulate at the end of the heat pipe. According to the plane boundary theory, there will be no or little diffusion effect. The heat of the core 1 is transferred from the heat pipe 6 to the heat pipe heat exchanger 4. Due to the existence of the non-condensable gas section 7, there will be no or little heat leakage.

[0024] Under accident conditions, the temperature of the evaporation section increases, and the steam temperature increases accordingly. According to the partial pressure principle of saturated steam, the gas pressure in the evaporation section will increase, squeezing the non-condensable gas section at the same time. Figure 4 As shown, the working area of ​​the heat pipe will be extended at this time. After the reactor is shut down or under accident conditions, the heat exchanger 4 stops working, the core temperature rises, the non-condensable gas section of the variable heat conduction pipe is compressed, the evaporation section of the heat pipe is extended, and the heat is transferred to the insulation material 8 through the heat pipe, and then to the shell 9. The presence of the insulation material 8 prevents the heat from being transferred too quickly, and the temperature of the shell 9 is too high to exceed the design limit. The staggered variable heat conduction pipes 6 ensure the uniformity of the core residual heat discharge and prevent the temperature at the center of the core from being too high. The shell 9 is the shell of the underwater nuclear power device. The shell 9 is in direct contact with the seawater, and the last step of the heat dissipation process is completed through large-space natural convection with the seawater.

[0025] Furthermore, the core 1 is a heat pipe cooled solid-state reactor core.

[0026] Furthermore, the non-condensable gas section 7 is filled with helium.

[0027] Furthermore, the variable thermal conductivity heat pipe 6 is a part of the heat pipe inserted into the core 1 and is arranged in a staggered manner to ensure that the residual heat of the core can be discharged normally.

[0028] Under accident conditions, the core temperature rises, the non-condensable gas in the variable thermal conductivity tube is compressed to extend the working section, and the residual heat of the core is conducted to the outer shell through the extended working section, and finally dissipated to the environmental heat sink through the outer shell.

[0029] The present invention is described in detail above in combination with specific implementation methods and exemplary examples. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments; the above description cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, the technical solution of the present invention and its implementation methods may be subjected to a variety of equivalent substitutions, modifications or improvements, all of which fall within the scope of the present invention; the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A reactor passive residual heat removal system based on variable thermal conductivity heat pipe, characterized in that: The system comprises: a core (1), a variable heat conduction pipe (6), an insulation layer (3), a heat exchanger (4), an insulation sleeve (8), and a heat dissipation casing (9); The variable heat conduction heat pipe (6) is an inflatable heat pipe consisting of a pipe wall (10), a liquid wick (11), a steam chamber (12) and a non-condensable gas section (13); the inner layer of the pipe wall (10) is provided with the liquid wick (11), the non-condensable gas section (13) constitutes a non-condensable gas section (7), and the steam chamber (12) constitutes an evaporation section; The variable heat conduction pipe (6) passes through the insulation layer (3); the evaporation section at one end of the variable heat conduction pipe (6) is inserted into the core (1); the condensation section of the variable heat conduction pipe (6) is inserted into the heat pipe heat exchanger (4); the variable heat conduction pipe (6) is arranged in a staggered manner; the non-condensable gas section (7) extending from the other end of the variable heat conduction pipe (6) is wrapped with the insulation material (8); and the non-condensable gas section (7) is annularly embedded in the heat dissipation casing (9).

2. The reactor passive residual heat removal system based on variable thermal conductivity heat pipe according to claim 1 is characterized in that: The core (1) is a heat pipe cooled solid-state reactor core.

3. The reactor passive residual heat removal system based on variable thermal conductivity heat pipe according to claim 1, characterized in that: The non-condensable gas section (7) is filled with helium.

4. The reactor passive residual heat removal system based on variable thermal conductivity heat pipe according to claim 1, characterized in that: The variable thermal conductivity heat pipe (6) is a part of a heat pipe inserted into the core (1).

Images