A molten fuel in-vessel retention passive emergency cooling system and method for a marine nuclear power platform

Abstract

The application relates to a molten substance in-vessel retention passive emergency cooling system and method for a marine nuclear power platform, the passive emergency cooling system comprising an emergency cooling channel, a bottom cooling channel, a water diversion pipeline, a water taking pipeline, a water discharging pipeline and an exhaust pipeline, the water diversion pipeline, the water taking pipeline, the water discharging pipeline and the exhaust pipeline being communicated with the emergency cooling channel, the bottom cooling channel and seawater to form a natural circulation channel. The passive emergency cooling system of the application adopts double-layer bottom sealing modification on a reactor pressure vessel and a marine nuclear power platform bottom to form a seawater emergency cooling channel and a bottom cooling channel; the passive emergency cooling system utilizes a series of passive methods to be put into operation in a passive mode under a severe scene of power interruption after a serious accident of the marine nuclear power platform, safely and reliably leads out the heat of a reactor core molten substance, and ensures long-term cooling of the reactor core.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of passive emergency cooling technology for offshore nuclear power platform, and particularly relates to a molten in-vessel retention passive emergency cooling system and method for offshore nuclear power platform. BACKGROUND

[0002] With the deepening of the development of marine resources in China, the demand for stable, reliable and large-capacity offshore power and heat supply is increasingly urgent. Because the energy density of nuclear fuel is much higher than that of traditional fossil energy, offshore nuclear power platform can provide long-term and reliable sufficient electricity and heat for remote islands and offshore oil and gas development, and has good market prospects.

[0003] The external marine environment faced by offshore nuclear power platform is more complex than that of onshore nuclear power plant, and the risk of nuclear accident is theoretically higher than that of onshore nuclear power plant. In addition, offshore nuclear power platform may be deployed in remote sea areas, and the accident rescue is much more difficult than ordinary nuclear power plants. After a nuclear accident, if the primary coolant is lost, the core may be exposed and heated and melted due to decay heat, and the core melt will accumulate under the reactor pressure vessel head due to gravity. At this time, if there is no emergency heat conduction measure, the molten material will continue to melt through the lower head, causing the reactor pressure vessel to fail, leading to the risk of releasing a large amount of radioactive material to the containment, even to the environment, causing marine environmental pollution and international disputes.

[0004] At present, the measures to prevent the reactor pressure vessel from failing in the third generation nuclear power plant mainly include: (1) discharging the residual heat of the core by charging and discharging water in the secondary side of the steam generator; (2) discharging the residual heat of the core by using the pressure relief valve of the pressurizer; (3) cooling the pressure vessel by flooding the pit, which generally needs to set a large water tank as a cooling water source.

[0005] Due to the limited space of offshore nuclear power platform, it is difficult to set sufficient severe accident mitigation measures as in nuclear power plants. Therefore, the severe accident mitigation of offshore nuclear power platform is more difficult. SUMMARY

[0006] Therefore, the present application provides a molten in-vessel retention passive emergency cooling system and method for offshore nuclear power platform. In a severe accident, the passive emergency cooling system is used to introduce seawater into the containment and flood the outer wall of the reactor pressure vessel, so as to ensure that the core melt is retained inside the reactor pressure vessel, and to achieve long-term cooling of the core and effective discharge of heat in the reactor pressure vessel by passive means, thereby preventing the reactor pressure vessel barrier from being damaged, so as to achieve the purpose of severe accident mitigation.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions.

[0008] In a first aspect, the present application provides a molten material in-vessel retention passive emergency cooling system for a marine nuclear power platform, comprising an emergency cooling channel, a bottom cooling channel, a water diversion pipeline, a water intake pipeline, a water discharge pipeline and an exhaust pipeline, the water diversion pipeline, the water intake pipeline, the water discharge pipeline and the exhaust pipeline connecting the emergency cooling channel and the bottom cooling channel with seawater to form a natural circulation channel; wherein,

[0009] The emergency cooling channel is formed by a shielding water tank (or a primary shielding water tank) surrounding the reactor pressure vessel and a support structure of the reactor pressure vessel;

[0010] The bottom cooling channel is formed by setting a double-bottom coaming in a double-bottom of the platform below the reactor pressure vessel to enclose a closed space;

[0011] The water diversion pipeline is between the bottom cooling channel and the emergency cooling channel, and the water intake pipeline connects seawater with the water diversion pipeline through a sea valve tank;

[0012] An exhaust pipeline is arranged at the top of the emergency cooling channel, and the exhaust pipeline is communicated with the exhaust pipeline and the water discharge pipeline, respectively.

[0013] The passive emergency cooling system provided by the present application adopts sealing modification of the reactor pressure vessel and the double-bottom of the marine nuclear power platform bottom (i.e., the double-bottom of the platform below the reactor pressure vessel, including a platform upper plate and a platform bottom outer plate) to form a seawater emergency cooling channel and a bottom cooling channel. The passive emergency cooling system can be put into operation in a non-active manner under the working condition of a serious accident of the marine nuclear power platform, and ensures long-term cooling of the reactor core.

[0014] As an optional implementation, the shielding water tank and the support structure are sealed on the side close to the reactor pressure vessel in the emergency cooling channel to form a closed space, which can be used to fill seawater after an accident.

[0015] As an optional implementation, the height of the closed space is higher than the highest position of the core assembly in the reactor pressure vessel. This arrangement can ensure that seawater can submerge the main heat source of the reactor pressure vessel after an accident, and effectively remove the heat of the core.

[0016] As an optional implementation, the interface of the water diversion pipeline is arranged at the top of the bottom cooling channel to ensure that seawater can completely submerge the double-bottom and empty the gas between the double-bottom, thereby improving the heat transfer efficiency; after seawater fills the bottom cooling channel, seawater is injected into the emergency cooling channel through the water diversion pipeline.

[0017] As an optional embodiment, the valve of the water intake pipeline (for example, the valve 5) is arranged outside the shielding water tank to reduce the radioactive irradiation of the valve by the nuclear reactor and facilitate equipment maintenance.

[0018] As an optional embodiment, the valve of the water intake pipeline is a pneumatic ball valve (for example, the pneumatic ball valves 6 and 7 shown in FIG. 1). Figure 1

[0019] As an optional embodiment, the valve of the water intake pipeline is at least two (for example, the pneumatic ball valves 6 and 7 shown in FIG. 1). Figure 1

[0020] As an optional embodiment, the sea valve tank is arranged in the bottom platform of the side cabin.

[0021] In the present application, after an accident, the sea water is introduced into the bottom cooling channel through the sea valve tank, and the air is discharged and filled with sea water; the sea water in the emergency cooling channel can conduct heat to the bottom cooling channel through the steel structure (for example, the upper plate of the platform) below the reactor pressure vessel, and then conduct the heat to the sea water through the bottom outer plate of the platform.

[0022] As an optional embodiment, the top of the sea valve tank is provided with a sea valve.

[0023] As an optional embodiment, the bottom of the sea valve tank is provided with a suction grille.

[0024] As an optional embodiment, the outlet of the exhaust pipeline is higher than the water level.

[0025] In the present application, the exhaust pipeline is used to discharge the gas affecting the heat transfer effect, which can ensure that the sea water completely floods the cooling channel (for example, the emergency cooling channel). The combination of the water intake pipeline and the water discharge pipeline can form a natural circulation channel for emergency cooling.

[0026] As an optional embodiment, the water intake pipeline is further provided with a containment water inlet isolation valve.

[0027] As an optional embodiment, the discharge pipeline is provided with a containment discharge isolation valve.

[0028] As an optional embodiment, the water discharge pipeline is provided with a side sea valve (for example, a side sea ball valve).

[0029] As an optional embodiment, the exhaust pipeline is provided with a side exhaust valve (for example, a side exhaust ball valve).

[0030] ​​The application provides a non-active emergency cooling system for a marine nuclear power platform, which is used for introducing seawater into and submerging the outer wall of a reactor pressure vessel under a severe accident condition of the marine nuclear power platform, using multiple non-active methods to guide the heat of molten material in the reactor pressure vessel out, ensuring long-term cooling of a reactor core and preventing the destruction of a boundary barrier of the reactor pressure vessel, and effectively preventing the failure of a containment barrier.

[0031] In a second aspect, the application provides a molten material in-vessel retention non-active emergency cooling method for a marine nuclear power platform, which is implemented by using the non-active emergency cooling system, and the non-active emergency cooling method comprises the following steps:

[0032] 1) The bottom cooling channel, the emergency cooling channel and the external atmosphere space are communicated through the exhaust pipeline;

[0033] 2) The seawater enters the bottom cooling channel through the water intake pipeline, and then enters the emergency cooling channel through the water guide pipeline;

[0034] 3) The seawater enters the emergency cooling channel through the water intake pipeline and the water guide pipeline, and submerges the reactor pressure vessel;

[0035] 4) The water intake pipeline, the emergency cooling channel and the exhaust pipeline are communicated to form a natural circulation channel.

[0036] In the application, under a standby condition (i.e., when the marine nuclear power platform is normally running), the non-active emergency cooling system is in a standby state, specifically, the emergency cooling channel, the bottom cooling channel, the water intake pipeline and the exhaust pipeline are in a standby state, the valves in the non-active emergency cooling system are in a closed state, and the emergency cooling channel and the bottom cooling channel are in a sealed state. Under a severe accident condition (i.e., when a severe accident occurs in the marine nuclear power platform), the non-active emergency cooling method is used for emergency treatment. For example, when it is judged that the reactor core may be destroyed and the heat of the core cannot be effectively discharged, a series of valves on the water intake pipeline, the water discharge pipeline and the exhaust pipeline are opened, seawater is quickly injected into the bottom cooling channel and the emergency cooling channel, and finally the cooling channel is completely submerged, so that the heat of the core molten material is safely and reliably guided out.

[0037] As an optional implementation manner, in the step 1), the side exhaust valve, the containment discharge isolation valve, the containment bottom pneumatic ball valve and the containment water inlet isolation valve are opened, so that the bottom cooling channel, the emergency cooling channel and the external atmosphere space are communicated.

[0038] As an optional implementation manner, in the step 2), the sea valve is opened, seawater is sucked into the sea valve box from the bottom of the sea valve grid, flows through the containment water inlet isolation valve into the bottom cooling channel.

[0039] As an optional implementation manner, in the step 3), the containment bottom pneumatic ball valve is opened, the seawater of the sea valve box is injected into the emergency cooling channel, the gas in the emergency cooling channel is discharged, and the reactor pressure vessel is submerged.

[0040] As an optional implementation manner, in the step 4), the side sea valve is opened, the drain pipeline, the emergency cooling channel and the water intake pipeline are communicated, and the natural circulation channel is formed.

[0041] In the application, in the standby working condition, that is, when the marine nuclear power platform is normally operated, the emergency cooling channel of the reactor pressure vessel, the bottom cooling channel and the water intake and exhaust pipeline are in the standby state, the pneumatic valves are in the closed state, and the emergency cooling channel and the bottom cooling channel are in the closed state. In the severe accident working condition, that is, when it is judged that the reactor core may be melted down and the heat of the core cannot be effectively discharged, a series of valves on the water intake, drainage and exhaust pipelines are opened, seawater is rapidly injected into the bottom cooling channel and the emergency cooling channel, and finally the cooling channel is completely submerged, so that the heat of the core melt is safely and reliably discharged.

[0042] In the application, in the early stage of the accident, seawater directly enters the emergency cooling channel through the sea valve, the containment water inlet isolation valve and the containment bottom pneumatic ball valve, is heated and warmed by the reactor pressure vessel, and then flows upward due to the smaller density of the seawater, is discharged through the containment discharge isolation valve and the side sea valve, and is discharged to the side, so that natural circulation flow is formed. In the late stage of the accident, the decay heat in the reactor pressure vessel decreases, and the natural circulation flow decreases or is interrupted. The heat of the emergency cooling channel is conducted to the steel plate at the bottom of the containment through convection, and then is conducted to the seawater in the bottom cooling channel. The platform bottom outer plate is directly contacted with the external seawater, and the heat of the bottom cooling channel is dissipated to the seawater. In the early stage of the accident, part of the heat in the reactor pressure vessel can also be transmitted to the seawater through the platform bottom outer plate 12, but the natural circulation heat transfer is the main flow.

[0043] In the application, the above technical features can be freely combined to form new technical solutions without conflict.

[0044] The application brings the following beneficial effects:

[0045] (1) The application provides a molten in-vessel retention passive emergency cooling system for a marine nuclear power platform, which utilizes a series of passive methods to safely and reliably guide out the heat of a reactor core melt under a severe accident after power interruption in a harsh scene; specifically, sea water level difference is utilized to passively introduce emergency cooling sea water to submerge the outer wall of a reactor pressure vessel; natural circulation is utilized to passively transport a large amount of heat accumulated in the reactor pressure vessel to sea water outside a hull in an early stage of an accident, so that the reactor pressure vessel can be rapidly cooled and depressurized after the severe accident, and the integrity of a second barrier can be maintained; heat conduction and heat convection are utilized to passively transfer reactor decay heat to the bottom plate outside the platform in a late stage of the accident, and the heat of the reactor core can be reliably guided out to the sea water for a long time.

[0046] (2) The application provides a molten in-vessel retention passive emergency cooling system for a marine nuclear power platform, which efficiently utilizes the original space and structure of the marine nuclear power platform, utilizes the existing shielding water tank and support structure, double-bottom structure, sea valve box and other structures and equipment, and only needs to newly add limited sealing coaming, pipelines and valves to realize the scheme, so that resource occupation is small and space utilization is high.

[0047] (3) The application provides a molten in-vessel retention passive emergency cooling system for a marine nuclear power platform, emergency cooling sea water only submerges a limited space between the outer wall of the reactor pressure vessel and the shielding water tank, does not enter the containment, does not damage important equipment inside the containment, and is convenient for rescue disposal and emergency decontamination in a late stage of the accident. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 A structure diagram of a molten in-vessel retention passive emergency cooling system for a marine nuclear power platform according to the application is shown.

[0049] In the figure, 1 is a reactor pressure vessel, 2 is an intake grid, 3 is a sea valve box, 4 is a sea valve, 5 is a containment inlet isolation valve, 6 is a containment bottom pneumatic ball valve, 7 is a containment bottom pneumatic ball valve, 8 is a containment discharge isolation valve, 9 is a hull side sea valve, 10 is a hull side exhaust ball valve, 11 is a double-bottom coaming, and 12 is a platform bottom plate. DETAILED DESCRIPTION

[0050] To make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below in combination with the embodiments of the application and the drawings. Obviously, the described embodiments are some embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0051] Embodiment 1

[0052] A molten fuel in-vessel retention passive emergency cooling system for a marine nuclear power platform, as shown in the figure, comprising an emergency cooling channel, a bottom cooling channel, a water intake pipeline, a water intake pipeline, a water discharge pipeline and an exhaust pipeline, the water intake pipeline, the water intake pipeline, the water discharge pipeline and the exhaust pipeline are connected with the emergency cooling channel and the bottom cooling channel and the seawater, forming a natural circulation channel. Specifically, Figure 1

[0053] The emergency cooling channel is formed by the shielding water tank (or primary shielding water tank) surrounding the reactor pressure vessel 1 and the support structure of the reactor pressure vessel 1. In the emergency cooling channel, the side of the shielding water tank and the support structure close to the reactor pressure vessel 1 is sealed to form a closed space which can be used to fill seawater after an accident. The height of the closed space is higher than the highest part of the core assembly in the reactor pressure vessel 1, so as to ensure that seawater can submerge the main heat source of the reactor pressure vessel 1 after an accident, and effectively remove the heat of the core.

[0054] The bottom cooling channel is formed by surrounding the double-bottom plate (including the upper plate (not marked in the figure) and the bottom outer plate 12) of the platform below the reactor pressure vessel 1 with a double-bottom coaming 11 to form a closed space.

[0055] The water intake pipeline is located between the bottom cooling channel and the emergency cooling channel, and the interface is arranged at the top of the bottom cooling channel, and the safety shell bottom pneumatic ball valve 6 and 7 arranged outside the shielding water tank are arranged on the water intake pipeline.

[0056] The water intake pipeline connects the seawater with the water intake pipeline through the sea valve box 3 and the safety shell water inlet isolation valve 5 arranged thereon, wherein the sea valve box 3 is arranged in the bottom platform of the side cabin, and the top of the sea valve box 3 is provided with a sea valve 4, and the bottom is provided with a bottom suction grille.

[0057] The exhaust pipeline is arranged at the top of the emergency cooling channel, and the safety shell exhaust isolation valve 8 is arranged on the exhaust pipeline; the exhaust pipeline is communicated with the exhaust pipeline and the water discharge pipeline respectively, the side exhaust ball valve 10 is arranged on the exhaust pipeline, and the outlet of the exhaust pipeline is higher than the water level, which is used for exhausting the gas affecting the heat transfer effect, and can ensure that the seawater completely submerges the cooling channel (for example, the emergency cooling channel). The side sea ball valve is arranged on the water discharge pipeline.

[0058] The combination of the exhaust pipeline and the water discharge pipeline can form a natural circulation channel for emergency cooling.

[0059] ​The non-active emergency cooling system provided by the embodiment is used for introducing seawater into and flooding the outer wall of the reactor pressure vessel 1 under the severe accident condition of the marine nuclear power platform, using various non-active methods to guide the heat of the molten material in the reactor pressure vessel 1 out, ensuring long-term cooling of the core and preventing the destruction of the reactor pressure vessel 1 boundary barrier, and effectively preventing the failure of the containment barrier.

[0060] Embodiment 2

[0061] The embodiment provides a molten material in-vessel retention non-active emergency cooling method for a marine nuclear power platform, which is implemented by using the molten material in-vessel retention non-active emergency cooling system for a marine nuclear power platform in the embodiment 1.

[0062] The initial state of the non-active emergency cooling system is that the reactor pressure vessel 1 is in a normal operating state, and the sea valve 4, the containment water inlet isolation 5, the containment bottom pneumatic ball valve 6, the containment bottom pneumatic ball valve 7, the containment discharge isolation valve 8, the side sea ball valve 9 and the side exhaust ball valve 10 are in a closed state.

[0063] When a severe accident occurs in the marine nuclear power platform, the core in the reactor pressure vessel 1 is melted, which causes the temperature and pressure in the reactor pressure vessel 1 to rise sharply, and reaches the set limit value, then the non-active emergency cooling system in the embodiment 1 is put into operation to cool the reactor pressure vessel 1, and the specific cooling method is as follows:

[0064] 1) opening the side exhaust ball valve 10, the containment discharge isolation valve 8, the containment bottom pneumatic ball valve 7, the containment water inlet isolation valve 5, so that the bottom cooling channel, the emergency cooling channel and the external atmosphere space are communicated;

[0065] 2) opening the sea valve 4 on the sea valve box 3, seawater enters the sea valve box 3 from the bottom suction grid 2, flows through the containment water inlet isolation valve 5 into the bottom cooling channel; seawater is injected into the bottom cooling channel to discharge the gas therein; after the seawater is filled, the seawater in the bottom cooling channel enters the emergency cooling channel through the containment bottom pneumatic ball valve 7;

[0066] 3) opening the containment bottom pneumatic ball valve 6, the seawater of the sea valve box is directly injected into the emergency cooling channel; after the seawater is injected into the emergency cooling channel, the gas therein is discharged, and the reactor pressure vessel 1 is gradually flooded;

[0067] 4) opening the side sea ball valve 9, so that the drainage pipeline (i.e., the side top seawater pipeline), the emergency cooling channel and the water intake pipeline are communicated, and a natural circulation channel is formed.

[0068] At the initial stage of the accident, seawater enters the emergency cooling channel directly through the sea valve 4, the containment water inlet isolation valve 5 and the containment bottom pneumatic ball valve 6. After the seawater is heated and warmed by the reactor pressure vessel 1, the density of the seawater becomes smaller, and the seawater flows upward and is discharged through the containment discharge isolation valve 8 and the side sea ball valve 9, and then is discharged to the side of the ship, thereby forming a natural circulation flow.

[0069] At the final stage of the accident, the decay heat in the reactor pressure vessel 1 decreases, and the natural circulation flow decreases or is interrupted. The heat of the emergency cooling channel is conducted to the steel plate at the bottom of the containment through convection, and then is conducted to the seawater in the bottom cooling channel. The platform bottom outer plate 12 is directly in contact with the external seawater, and the heat of the bottom cooling channel is dissipated to the seawater.

[0070] At the initial stage of the accident, part of the heat in the reactor pressure vessel 1 can also be transmitted to the seawater through the platform bottom outer plate 12, but the natural circulation heat transfer is the main flow.

[0071] Through the above approaches, the heat of the reactor core can be reliably and long-term discharged to the seawater, and the reactor losing power supply after the serious accident can be effectively and timely cooled.

[0072] The above is a preferred embodiment of the present application, but the present application should not be limited to the content disclosed in the embodiment and the drawings. It should be noted that, for ordinary skilled in the art, some improvements and refinements can be made to the above technical solutions without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A molten fuel in-vessel retention passive emergency cooling system for a marine nuclear power platform, characterized in that, The non-active emergency cooling system comprises an emergency cooling channel, a bottom cooling channel, a water diversion pipeline, a water intake pipeline, a water discharge pipeline and an exhaust pipeline, the water diversion pipeline, the water intake pipeline, the water discharge pipeline and the exhaust pipeline connect the emergency cooling channel and the bottom cooling channel with seawater to form a natural circulation channel; wherein, The emergency cooling channel is formed by a shielding water tank (or a primary shielding water tank) surrounding the reactor pressure vessel and a support structure of the reactor pressure vessel; The bottom cooling channel is formed by setting a double-layer bottom coaming in a double-layer bottom of a platform below the reactor pressure vessel to enclose a closed space; The water diversion pipeline is between the bottom cooling channel and the emergency cooling channel; the water intake pipeline connects seawater with the water diversion pipeline through a sea valve box; An exhaust pipeline is arranged at the top of the emergency cooling channel, and the exhaust pipeline is communicated with the exhaust pipeline and the water discharge pipeline respectively.

2. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 1, wherein In the emergency cooling channel, the side of the shielding water tank and the support structure close to the reactor pressure vessel is sealed to form a closed space.

3. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 2, wherein The height of the closed space is higher than the highest position of the core assembly in the reactor pressure vessel.

4. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 1, wherein The interface of the water diversion pipeline is arranged at the top of the bottom cooling channel; or / and A valve is arranged in the water diversion pipeline, and the valve of the water diversion pipeline is arranged outside the shielding water tank.

5. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 4, wherein The valve of the water diversion pipeline is a pneumatic ball valve; or / and The valve of the water diversion pipeline is at least two.

6. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 1, wherein The sea valve box is arranged in the bottom platform of the side cabin.

7. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 1 or 6, wherein The top of the sea valve box is provided with a sea valve, and the bottom is provided with a suction grille.

8. The molten core in-vessel retention non-active emergency cooling system for the marine nuclear power platform according to claim 1, wherein The outlet of the exhaust pipeline is higher than the water level of seawater; and / or The water intake pipeline is further provided with a containment water inlet isolation valve; the exhaust pipeline is provided with a containment exhaust isolation valve; the water discharge pipeline is provided with a side sea valve; and the exhaust pipeline is provided with a side exhaust valve.

9. A molten fuel in-vessel retention passive emergency cooling method for a marine nuclear power platform, characterized in that, The non-active emergency cooling method is implemented by using the non-active emergency cooling system according to any one of claims 1-8, and the non-active emergency cooling method comprises the following steps: 1) The bottom cooling channel, the emergency cooling channel and the external atmosphere space are communicated through the exhaust pipeline; 2) The seawater enters the bottom cooling channel through the water intake pipeline, and then enters the emergency cooling channel through the water guide pipeline; 3) The seawater enters the emergency cooling channel through the water intake pipeline and the water guide pipeline, and floods the reactor pressure vessel; 4) The drain pipeline, the emergency cooling channel and the water intake pipeline are communicated to form a natural circulation channel.

10. The molten core-in-containment passive emergency cooling method for the marine nuclear power platform according to claim 9, characterized in that, in the step 1), the side exhaust valve, the containment exhaust isolation valve, the containment bottom pneumatic ball valve and the containment water inlet isolation valve are opened to communicate the bottom cooling channel, the emergency cooling channel and the external atmosphere space; or / and in the step 2), the sea valve is opened, the seawater is sucked into the sea valve box from the bottom of the sea valve through the sea inlet grid, and then flows into the bottom cooling channel through the containment water inlet isolation valve; or / and in the step 3), the containment bottom pneumatic ball valve is opened to inject the seawater in the sea valve box into the emergency cooling channel, discharge the gas in the emergency cooling channel, and flood the reactor pressure vessel; or / and in the step 4), the side sea valve is opened to communicate the drain pipeline, the emergency cooling channel and the water intake pipeline to form a natural circulation channel. ​ ​ ​ ​

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