A passive residual heat removal system based on sea-cooled unlimited time heat pipe reactor

Abstract

The present invention discloses a passive residual heat removal system for a sea-cooled, time-indefinite heat pipe reactor, comprising a reactor core, a heat pipe, a main heat exchanger, and a passive residual heat removal heat exchanger. The heat pipe is equipped with a coolant medium, and the evaporation section of the heat pipe extends into the reactor core and is connected to the reactor core; the condensation section of the heat pipe passes through the passive residual heat removal heat exchanger and the main heat exchanger and is connected to the passive residual heat removal heat exchanger and the main heat exchanger; the cold source inlet of the passive residual heat removal heat exchanger is connected to the outlet of the water inlet pipeline; and the cold source outlet of the passive residual heat removal heat exchanger is connected to the inlet of the water outlet pipeline. The beneficial effects of the present invention are as follows: after the reactor is shut down, the system relies on the heat pipe evaporation section to transfer heat to the heat pipe condensation section, and the heat pipe condensation section transfers heat to the seawater side of the passive residual heat removal system through the residual heat removal heat exchanger. A natural circulation flow is formed by the height difference and density difference between the seawater inlet and the seawater outlet, thereby realizing time-indefinite passive residual heat removal.

Description

Technical Field

[0001] The present invention relates to the field of reactor safety technology, and in particular to a passive residual heat removal system based on a sea-cooled unlimited-time heat pipe reactor. Background Art

[0002] The heat pipe reactor is a novel reactor device that utilizes the two-phase natural circulation of alkali metals within heat pipes to transfer heat from the reactor core to the energy conversion system. It is widely applicable in small-scale UUV equipment and small nuclear power platforms. Heat pipes within the reactor provide a new and unique method for cooling the core. Through phase changes within the working fluid, the high latent heat of vaporization and condensation, and capillary suction, heat is transferred from the evaporation section of the reactor to the condensation section outside the pressure vessel through continuous isothermal vapor / liquid flow.

[0003] Like traditional pressurized water reactors, heat pipe reactors utilize heat generated by nuclear fission as their energy source. After a heat pipe reactor is shut down, although the core power is reduced to zero, fission fragments and other decay products still generate a significant amount of residual heat. Without effective measures, this heat will gradually accumulate, causing temperatures and pressures within the reactor to continue to rise. This poses the risk of compromising the integrity of the reactor's pressure boundary, exposing the core to melt, and potentially leaking radioactive material.

[0004] Therefore, it is necessary to design a residual heat removal system that can smoothly remove the residual heat from the core without relying on external power supply and human intervention after a total power loss accident. Summary of the Invention

[0005] The purpose of the present invention is to provide a safe and reliable passive residual heat removal system based on sea-cooling unlimited time heat pipe reactor to address the deficiencies of the existing technology.

[0006] The technical solution adopted by the present invention is: a passive waste heat removal system based on a sea-cooled unlimited time heat pipe reactor, comprising a reactor core, a heat pipe, a main heat exchanger and a passive waste heat removal heat exchanger, wherein the heat pipe is filled with a coolant working medium, and the evaporation section of the heat pipe extends into the reactor core and is connected to the reactor core; the condensation section of the heat pipe passes through the passive waste heat removal heat exchanger and the main heat exchanger, and is connected to the passive waste heat removal heat exchanger and the main heat exchanger; the cold source inlet of the passive waste heat removal heat exchanger is connected to the outlet of the water inlet pipeline, and the inlet of the water inlet pipeline (that is, the seawater inlet) is connected to seawater; the cold source outlet of the passive waste heat removal heat exchanger is connected to the inlet of the water outlet pipeline, and the outlet of the water outlet pipeline (that is, the seawater outlet) is connected to seawater; valves are arranged on each pipeline.

[0007] According to the above solution, a cold section isolation valve and a cold section check valve are sequentially arranged along the fluid flow direction on the water inlet pipeline.

[0008] According to the above solution, a hot section check valve and a hot section isolation valve are sequentially arranged along the fluid flow direction on the water outlet pipeline.

[0009] According to the above solution, the water inlet pipe is connected to the water outlet pipe.

[0010] According to the above solution, the inlet of the water inlet pipe extends out of the bulkhead on one side of the ship and is connected to the seawater outside the bulkhead.

[0011] According to the above solution, the outlet of the water outlet pipe extends out of the bulkhead on the other side of the ship and is connected to the seawater outside the bulkhead.

[0012] According to the above solution, the reactor core is arranged in a pressure vessel, and the evaporation section of the heat pipe passes through the pressure vessel and is connected to the reactor core.

[0013] According to the above solution, the passive waste heat removal heat exchanger has a built-in partition to form a dual-flow heat exchanger, and the cold source flows in a dual-flow manner in the passive waste heat removal heat exchanger.

[0014] The beneficial effects of the present invention are as follows: 1. The present invention adopts an isolation valve based on "fail-safety". After the accident of total power loss, the isolation valve will automatically open; after the reactor is shut down, the system relies on the heat pipe evaporation section to transfer heat to the heat pipe condensation section, and the heat pipe condensation section transfers heat to the seawater side of the passive residual heat removal system through the residual heat removal heat exchanger, relying on the height difference and density difference between the seawater inlet and the seawater outlet to form a natural circulation flow. At this time, the natural circulation driving force is equal to the resistance of the seawater flowing in the pipe, without relying on external energy and operating personnel, realizing unlimited passive residual heat removal, maintaining the temperature and pressure in the core within the normal range, effectively avoiding the core meltdown accident, and improving the safety and reliability of the offshore power plant. 2. Relying on the internal circulation characteristics of the heat pipe under different operating conditions of reactor power operation and residual heat removal to achieve heat transfer and residual heat extraction, heat pipe sharing is realized, and the system pipeline structure is reduced. The system is simple, safe, stable and reliable. 3. The present invention does not require a waste heat discharge water tank, which reduces the overall resource occupancy of the power unit. It has a compact and efficient structure and realizes passive waste heat discharge without time limit and low noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of a specific embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of the working principle of the heat pipe when the reactor is running and this embodiment is not put into operation.

[0017] Figure 3 This is a schematic diagram of the working principle of the heat pipe when the reactor is running and this embodiment is put into operation.

[0018] Among them: 1 - reactor core, 2 - heat pipe, 3 - main heat exchanger, 4 - passive residual heat removal heat exchanger, 5 - partition, 6 - bulkhead, 7 - seawater, 8 - cold section isolation valve, 9 - hot section isolation valve, 10 - pressure vessel, 11 - cold section check valve, 12 - hot section check valve, 13 - seawater inlet, 14 - seawater outlet. DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1 The passive waste heat removal system of a sea-cooled, time-indefinite heat pipe reactor shown in the figure includes a reactor core 1, a heat pipe 2, a main heat exchanger 3, and a passive waste heat removal heat exchanger 4. The heat pipe 2 contains a coolant working medium, and the evaporation section of the heat pipe 2 extends into the reactor core 1 and is connected to the reactor core 1; the condensation section of the heat pipe 2 passes through the passive waste heat removal heat exchanger 4 and the main heat exchanger 3 and is connected to the passive waste heat removal heat exchanger 4 and the main heat exchanger 3; the cold source inlet of the passive waste heat removal heat exchanger 4 is connected to the outlet of the water inlet pipeline, and the inlet of the water inlet pipeline (that is, the seawater inlet 13) is connected to the seawater 7; the cold source outlet of the passive waste heat removal heat exchanger 4 is connected to the inlet of the water outlet pipeline, and the outlet of the water outlet pipeline (that is, the seawater outlet 14) is connected to the seawater 7; valves are arranged on each pipeline.

[0021] Preferably, a cold section isolation valve 8 and a cold section check valve 11 are sequentially arranged on the water inlet pipeline along the fluid flow direction.

[0022] Preferably, a hot section check valve 12 and a hot section isolation valve 9 are sequentially arranged on the water outlet pipeline along the fluid flow direction.

[0023] In the present invention, the cold section isolation valve 8 and the hot section isolation valve 9 are automatically opened after the total power loss accident.

[0024] Preferably, the water inlet pipe is connected to the water outlet pipe.

[0025] Preferably, the inlet of the water inlet pipe extends out of a bulkhead 6 on one side of the ship and is connected to the seawater 7 outside the bulkhead 6 .

[0026] Preferably, the outlet of the water outlet pipe extends out of the bulkhead 6 on the other side of the ship and is connected to the seawater 7 outside the bulkhead 6.

[0027] Preferably, the reactor core 1 is disposed in a pressure vessel 10 , and the evaporation section of the heat pipe 2 passes through the pressure vessel 10 and is connected to the reactor core.

[0028] Preferably, the passive waste heat removal heat exchanger 4 has a built-in partition 5 to form a dual-flow heat exchanger. The cold source flows in a dual-flow manner in the passive waste heat removal heat exchanger 4, and the heat exchange is more sufficient and uniform.

[0029] In this embodiment, there are multiple groups of heat pipes 2 that are evenly spaced apart. The heat pipes 2 have a common existing structure, including a tube shell, a liquid wick, and end covers.

[0030] In this embodiment, the coolant medium built into the heat pipe 2 is an alkali metal medium; the cooling medium of the passive waste heat discharge heat exchanger 4 , ie, the cold source, is seawater 7 .

[0031] During the design process of the present invention, the passive waste heat removal heat exchanger 4 can be arranged at the upper or lower part of the main heat exchanger 3 according to the overall layout of the ship's power plant. When the passive waste heat removal heat exchanger 4 is arranged at the upper part of the main heat exchanger 3, the steam diffuses to the central gap and flows to the condensation section through the adiabatic area, that is, the steam flows through the condensation section of the heat pipe 2 at the main heat exchanger 3 and continues to diffuse forward to the condensation section connected to the passive waste heat removal heat exchanger 4, and the heat is transferred to the passive waste heat removal system. When the passive waste heat removal heat exchanger 4 is arranged at the lower part of the main heat exchanger 3, the steam diffuses directly to the condensation section, that is, the steam first diffuses to the condensation section of the heat pipe 2 connected to the passive waste heat removal heat exchanger 4, and the heat is transferred to the passive waste heat removal system, and the steam is completely condensed in this section.

[0032] The passive waste heat removal heat exchanger 4 is arranged outside the pressure vessel 10, which can effectively reduce the volume of the pressure vessel 10; the number of cold source inlets and cold source outlets of the passive waste heat removal heat exchanger 4 can be configured according to actual conditions to ensure that the natural circulation flow matches the waste heat required to be removed by the system, thereby realizing an unlimited cooling function.

[0033] The relevant parameters in the present invention satisfy the following formula:

[0034] mCΔT=hAΔt (1),

[0035] p

[0036] In formula (1), m is the total mass flow rate of the working fluid in the heat pipe 2, kg / s; ΔT is the temperature difference between the inlet end and the condensation end of the heat pipe 2, °C; C p is the average specific heat capacity of the inlet and condensation ends of the heat pipe 2, J / (kg·℃); h is the convective heat transfer coefficient, J / (m 2 ·s·℃); A is the convection heat transfer area, m 2 ; Δt is the difference between the average wall temperature of the contact part between the heat pipe 2 and the waste heat discharge heat exchanger 4 and the temperature of the cooling medium in the waste heat discharge heat exchanger 4, ℃.

[0037] The total heat exchange Q1 of the heat pipe 2 is equal to the heat Q2 carried away by convection heat transfer between the coolant medium (alkali metal medium) in the heat pipe 2 and the heat pipe 2, Q1 = mCpΔT, Q2 = hAΔt.

[0038] Factors affecting h in engineering design include the size of the heat pipe 2, the coolant flow rate of the passive waste heat removal heat exchanger 4, etc. It is necessary to calculate Q1=Q2 based on the heat balance and design the waste heat removal system and equipment parameters.

[0039] The present invention relies on the height difference and density difference between the seawater inlet 13 and the seawater outlet 14 to form a natural circulation flow. There is a height difference between the seawater inlet 13 and the seawater outlet 14 (the seawater inlet 13 and the seawater outlet 14 are both located below the water surface, wherein the depth of the seawater inlet 13 is greater than the depth of the seawater outlet 14). At this time, the natural circulation driving force is equal to the resistance of the seawater flowing in the pipe, wherein the natural circulation driving force = ρ 入口至出口平均值 gh-ρ 海水 gh,ρ 入口至出口平均值 The average density of the fluid between the seawater inlet 13 of the water inlet pipe and the seawater outlet 14 of the water outlet pipe (in kg / m 3 ), g is the acceleration due to gravity (unit is m / s 2 ), h is the height difference between the seawater inlet 13 and the seawater outlet 14 (in m), ρ 海水 is the density of the external seawater (in kg / m 3 ) The flow resistance of seawater in the pipeline includes local resistance and longitudinal resistance.

[0040] The working principle of the present invention is:

[0041] (1) The reactor is in operation and the passive residual heat removal system is not in operation.

[0042] During normal operation of the ship's power plant, the evaporation section of the heat pipe 2 is heated by the heat released by the reactor core 1. The alkali metal working fluid in the heat pipe 2 begins to boil and evaporate. The steam diffuses to the central gap and flows through the adiabatic section (the heat pipe section in contact with the passive waste heat removal heat exchanger 4) to the condensation section. The steam in the heat pipe 2 condenses in the condensation section, releasing latent heat of vaporization. The heat is transferred to the main heat exchanger 3 through the wall of the heat pipe 2. Figure 2 shown.

[0043] During the design process, the contact area between the condensing section of heat pipe 2 and the main heat exchanger 3 is ensured to be sufficiently large, and the heat exchange capacity of the main heat exchanger 3 is sufficiently strong to ensure that all steam generated in the evaporation section of heat pipe 2 is completely condensed in the condensing section in contact with the main heat exchanger 3. In this state, there is no need to activate the passive waste heat removal system; the system is in standby mode, and the cold section isolation valve 8 and the hot section isolation valve 9 are closed.

[0044] (2) Reactor shutdown and passive residual heat removal system operating status.

[0045] In the event of an accident where the active safety system cannot be effectively used and all power is lost, the evaporation section of the heat pipe 2 is heated by the heat released by the waste heat of the reactor core 1, and the alkali metal working fluid in the heat pipe 2 begins to boil and evaporate. The steam diffuses to the central gap and condenses through the condensation section of the heat pipe 2 connected to the waste heat discharge heat exchanger 4. The heat is transferred to the waste heat discharge heat exchanger 4. Figure 3 As shown. Since the main heat exchanger 3 is not operating at this time, steam condenses in the condensing section of the heat pipe 2 connected to the passive waste heat removal heat exchanger 4, transferring heat to the seawater 7. The baffle 5 built into the passive waste heat removal heat exchanger 4 enables a dual-flow of seawater in the passive waste heat removal heat exchanger 4, making the heat exchange more complete and uniform. The heated seawater flows out of the upper part of the bulkhead 6 along the outlet pipe, while the low-temperature seawater continues to flow into the passive waste heat removal heat exchanger 4 through the inlet pipe, achieving unlimited and long-term cooling. During the circulation process, the two isolation valves of the system remain open.

[0046] During the design process, ensure that the contact area between the condensing section of heat pipe 2 and the waste heat removal heat exchanger 4 is sufficiently large, that the seawater flow rate and temperature parameters are sufficient to remove the heat released by the waste heat of the reactor core 1, and that all steam generated in the evaporation section of heat pipe 2 is completely condensed in the condensing section in contact with the waste heat removal heat exchanger 4. Ensure that no steam medium is present in the downstream adiabatic section (the heat pipe section in contact with the main heat exchanger 3). The design process must ensure that the core decay heat removal requirements match the cooling capacity of the passive waste heat removal system. The cooling capacity of the passive waste heat removal system is related to factors such as the heat transfer efficiency of the heat pipe, the natural circulation flow rate, and the heat exchange efficiency of the heat pipe and waste heat removal heat exchangers.

[0047] The above description is only a preferred embodiment of the present invention, but the present invention should not be limited to the contents disclosed in the embodiment and the accompanying drawings. Therefore, any equivalent or modified implementation that does not depart from the spirit disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A passive residual heat removal system based on sea-cooled unlimited time heat pipe pile, characterized in that: The reactor comprises a reactor core, a heat pipe, a main heat exchanger and a passive waste heat removal heat exchanger. The heat pipe contains a coolant working medium. The evaporation section of the heat pipe extends into the reactor core and is connected to the reactor core. The condensation section of the heat pipe passes through the passive waste heat removal heat exchanger and the main heat exchanger and is connected to the passive waste heat removal heat exchanger and the main heat exchanger. The cold source inlet of the passive waste heat removal heat exchanger is connected to the outlet of the water inlet pipeline, and the inlet of the water inlet pipeline is connected to seawater. The cold source outlet of the passive waste heat removal heat exchanger is connected to the inlet of the water outlet pipeline, and the outlet of the water outlet pipeline is connected to seawater. Valves are arranged on each pipeline. The water inlet pipe is also connected to the water outlet pipe through a connecting pipe. The water inlet pipe, the water outlet pipe and the connecting pipe between the two are all located on the same side of the passive waste heat removal heat exchanger, and the three are located on the same straight line; the water inlet pipe is located below the water outlet pipe; The natural circulation flow is formed by relying on the height difference and density difference between the seawater inlet and the seawater outlet. There is a height difference between the seawater inlet and the seawater outlet. The seawater inlet and the seawater outlet are both located below the water surface, and the depth of the seawater inlet is greater than the depth of the seawater outlet.

2. The passive residual heat removal system based on sea-cooled unlimited time heat pipe stack according to claim 1, characterized in that: A cold section isolation valve and a cold section check valve are sequentially arranged along the fluid flow direction of the water inlet pipeline.

3. The passive residual heat removal system based on sea-cooled unlimited time heat pipe stack according to claim 1, characterized in that: A hot section check valve and a hot section isolation valve are sequentially arranged along the fluid flow direction of the water outlet pipeline.

4. The passive residual heat removal system based on sea-cooled unlimited time heat pipe stack according to claim 1, characterized in that: The inlet of the water inlet pipeline extends out of a bulkhead on one side of the ship and is communicated with the seawater outside the bulkhead.

5. The passive residual heat removal system based on sea-cooled unlimited time heat pipe reactor according to claim 1, characterized in that: The outlet of the water outlet pipe extends out of the bulkhead on the other side of the ship and is communicated with the seawater outside the bulkhead.

6. The passive residual heat removal system based on sea-cooled unlimited time heat pipe reactor according to claim 1, characterized in that: The reactor core is arranged in a pressure vessel, and the evaporation section of the heat pipe passes through the pressure vessel and is connected to the reactor core.

7. The passive residual heat removal system based on sea-cooled unlimited time heat pipe reactor according to claim 1 is characterized in that: The passive waste heat removal heat exchanger has a built-in partition to form a dual-flow heat exchanger, and the cold source flows in a dual-flow manner in the passive waste heat removal heat exchanger.

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