Reactor destroying and melting prevention technology for pressurized water nuclear reactor

Abstract

A pressurized water nuclear reactor destroying and melting prevention technology is composed of seven devices (see Figure 1 to Figure 10). 1, the starting controller is equipment for starting the whole technical system by an ultrahigh temperature signal before a reactor core is destroyed and molten; 2, a high-pressure cold air shutdown catapult is power equipment for emergency shutdown and starting of early-stage heat dissipation of a reactor core; and 3, the large-capacity tubular water tank is a water source for the whole heat dissipation process of the reactor core. And 4, the coolant pressurizing tank is used for pressurizing part of high-pressure cold water during emergency shutdown so that the high-pressure cold water quickly flows through the reactor core to finish early-stage heat dissipation. And the emergency water outlet valve is an outlet through which water flowing through the reactor core flows out of the pressure container after the reactor is shut down emergently. And the emergency water inlet valve 6 is a water inlet through which water in the tubular water tank flows into the pressure container after emergency shutdown. The natural circulation waste heat dissipation water inlet valve 7 is a water inlet for achieving convection waste heat dissipation inside and outside the pressure container. The seven devices are automatically connected and organically combined into a whole in the whole process from emergency shutdown to waste heat dissipation, and extra intervention and interference are not needed at all.

Description

Technical Field

[0002] "Double-defense technology" belongs to the field of nuclear reactor safety technology. Background Art

[0003] In order to prevent nuclear melt accidents, especially nuclear destruction accidents, the safety system of nuclear reactors must do the following under any circumstances when the core temperature rises to a level that threatens its safety: 1. Shut down the reactor in time; 2. Dissipate heat from the core in a timely and rapid manner to quickly reduce its temperature back to a safe range; 3. Establish an effective, reliable and long-lasting coolant convection natural circulation process for core residual heat dissipation, without the need for human intervention. The probability of a large-scale leakage accident in a third-generation pressurized water nuclear reactor (represented by Hualong One and AP-1000) is about 1×10 -8 / reactor-year, that is to say, when encountering extreme accident situations, its safety equipment has defects. For example, 1. Due to factors such as incorrect operation, serious spraying of rods and the introduction of positive reactor into the reactor, the core temperature rises rapidly, the structure deforms, and the safety control rod gets stuck when it falls. If the reactor cannot be stopped, a reactor destruction accident will occur. 2. After normal shutdown, the reactor enters the natural circulation process to dissipate residual heat. The heat dissipation inside and outside the pressure vessel is carried out by heat conduction through the pressure vessel shell (possibly with an insulation layer), and the heat dissipation efficiency is low. If the coolant in the pressure vessel is lost at this time and the core is exposed, the coolant cannot be replenished and the core will be melted. The present invention is a safety technology that solves the problem of preventing reactor destruction and melt accidents in pressurized water nuclear reactors under any circumstances. Summary of the invention

[0004] The "two-defense technology" consists of seven devices: a start-up controller, a high-pressure cold gas shutdown ejector, a large-capacity tubular water tank, a coolant booster tank, an emergency water outlet valve, an emergency water inlet valve, and a natural circulation waste heat dissipation water inlet valve. (See Figure 1 )

[0005] (I) Principle structure of 7 devices:

[0006] 1. Start the controller (see Figure 2 ), which consists of a starting power supply, a starting switch and a core temperature receiver. Under the control of the core temperature, when the reactor is forced to shut down in an emergency, it provides starting power to the high-pressure cooling gas solenoid valve of the shutdown ejector.

[0007] 2. High-pressure cold gas shutdown ejector (see Figure 3 ), consists of a high-pressure cold gas bottle, a high-pressure cold gas solenoid valve, a high-pressure cold gas duct, an ejector cylinder, an ejection tube, an ejection rotating pressure rod and an ejector fixing bracket. It is the power equipment for opening the emergency water outlet valve and the emergency water inlet valve when the reactor is shut down, and provides pressurized cold gas to the coolant booster tank.

[0008] 3. Large capacity tubular water tank (see Figure 4), which is composed of large-diameter round or rectangular steel pipes arranged vertically side by side or stacked horizontally outside the steel jacket lining the containment, and cast in the prestressed concrete structure of the containment. The water in the water tank is the source of coolant for the early heat dissipation of the core and the later residual heat dissipation after the emergency shutdown.

[0009] 4. Coolant booster tank (see Figure 5 ), which consists of a tank body fixed on the top of the containment and connected to a tubular water tank, a tank body vent hole, a vent buoyancy plug composed of a cone plug float and a connecting rod, a float support net, a high-pressure cold air inlet and a high-pressure cold air duct. It is used to meet the needs of rapid core heat dissipation after emergency shutdown.

[0010] 5. Emergency water outlet valve (see Figure 6 ), which consists of a valve body, a valve, a valve gasket, a sealing spring and a valve conversion push rod. It is installed outside the outlet of the primary pressure vessel and is the outlet for the coolant flowing through the core to flow out of the primary circuit after emergency shutdown.

[0011] 6. Emergency water inlet valve (see Figure 7 ), which consists of a valve body, a valve, a valve gasket, a valve conversion push rod, a push rod sealing ring and a sealing spring. Installed outside the water inlet of the primary pressure vessel, it is the inlet for the pressurized coolant to flow into the core for heat dissipation during emergency shutdown.

[0012] 7. Natural circulation heat dissipation water inlet valve (see Figure 8 ), consists of a water inlet valve body located at the center of the bottom of the pressure vessel, a conical valve with a push rod, a valve sealing gasket, a sealing spring, an ejector cylinder, an ejection piston with a push rod, a high-pressure cold air bottle, a high-pressure cold air solenoid valve, a solenoid valve starting power supply, a starting switch, a float, a float upper shaft, a high-pressure cold air duct and a waterproof connecting circuit wire, which uses the convection of coolant inside and outside the pressure vessel to dissipate the residual heat of the core.

[0013] (II) The process of starting the “two-defense technology”. Under normal working conditions, there are 7 equipment states: A, start the controller, the start switch is disconnected, B, the ejector is stopped, the ejection tube is in the upper part of the ejection tube body, C, the emergency water outlet valve is closed, D, the emergency water inlet valve is closed, E, the large-capacity tubular water tank is filled with water. F, the water level in the coolant booster tank is in the middle and upper part, the float is completely immersed in water, its buoyancy is pushed upward through the connecting rod, and the buoyancy plug blocks the vent hole, G, the natural circulation heat dissipation water inlet valve is closed, the float stops at the bottom, and the start switch is disconnected.

[0014] 1. Emergency ejection shutdown and early core cooling process (see Fig. 9), regardless of the reason, when the core temperature rises to the point where there is a threat of destruction and melting of the reactor, the core temperature receiver receives the core ultra-high temperature signal and immediately turns on the start switch. The high-pressure cold air solenoid valve is energized and started, and the high-pressure cold air in the high-pressure cold air bottle enters the shutdown catapult. The ejection tube instantly presses the safety control rod downward into the core with strong pressure (regardless of whether the core is deformed), so as to achieve timely shutdown and complete the following at the same time: A. Part of the high-pressure cold air enters the coolant booster tank through the duct to boost the coolant. B. By turning the pressure rod, the emergency water outlet valve is pressed outward by 90°, and the high-temperature coolant sprays into the pressure vessel pit from the outlet. C. By turning the pressure rod, the emergency water inlet valve is pressed outward by 90°, and the pressurized coolant flows through the core at high speed, causing it to quickly drop to a safe temperature. As the water in the tubular water tank flows through the core and into the pressure vessel pit, the cold air pressure in the booster tank and tubular water tank gradually decreases. When it drops to the same atmospheric pressure as outside the tank, the float loses the buoyancy of the water. Under the action of gravity, the buoyancy plug float falls on the support net, the vent opens, and air enters the booster tank and tubular water tank. The coolant continues to flow through the core by gravity to dissipate heat until all the water in the water tank flows into the pressure vessel pit.

[0015] 2. Natural circulation heat dissipation process (see Fig.10 ), after the emergency ejection to stop the reactor, the coolant in the large-capacity tubular water tank flows through the core to dissipate heat and then flows into the pressure vessel pit. When the water surface in the pit is above a certain depth of the emergency water outlet valve, the float floats up under the action of buoyancy, the top start switch is turned on, the high-pressure cold air solenoid valve is energized, the valve opens, and the high-pressure cold air in the high-pressure cold air bottle enters the ejector action piston upward through the push rod with strong pressure, pushing the natural circulation water inlet valve into the pressure vessel, opening the coolant convection channel inside and outside the pressure vessel, and the core waste heat causes the coolant to heat up, forming a natural circulation convection waste heat dissipation process, which does not require any human intervention or active energy intervention until the core waste heat is completely dissipated. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The overall principle structure diagram of the "two-defense technology". The diagram shows the relationship between the positions of the seven devices and their status before startup.

[0018] In the figure

[0019] Pressure Vessels Start the controller Core temperature measuring device High pressure cold air bottle High pressure air conditioning solenoid valve Ejection tube Catapult cylinder Catapult bracket Safety control rod Emergency water outlet valve Emergency water inlet valve Large capacity tubular water tank Coolant booster tank Conical waste heat dissipation water inlet valve Steam generator Voltage Regulator Main pump Containment steel lining Containment Pressure vessel fixing seat Pressure vessel pit Emergency water inlet valve transmission lever Emergency water outlet valve transmission lever Natural circulation water inlet valve ejection mechanism.

[0020] Figure 2 , start controller principle circuit diagram

[0021] In the figure

[0022] Core temperature signal receiver Start control switch Start the power supply High pressure air conditioning solenoid valve coil Circuit connecting wire

[0023] Figure 3 , Sectional view of the principle structure of the high-pressure cold gas shutdown catapult and the position and connection relationship of each component

[0024] In the figure

[0025] High pressure cold air bottle High pressure air conditioning solenoid valve Shutdown ejection tube Catapult cylinder Catapult bracket Safety control rod Pressure Vessels Emergency water outlet valve transmission lever Emergency water inlet valve transmission lever High pressure cooling air duct High pressure cold air duct to booster tank wire

[0026] Figure 4 , Cross-section view of a large capacity tubular water tank

[0027] In the figure

[0028] Tubular water tank Coolant booster tank Concrete containment Containment steel lining Water pipe to emergency water inlet valve

[0029] Figure 5 , coolant boost tank cross-section

[0030] In the figure

[0031] Booster tank body Buoyancy plug and float rod Buoyancy plug (dashed line) Falling float plug Tubular water tank Containment Containment steel lining Float Ventilation holes Float support net Normal level High pressure cold air boost duct

[0032] Figure 6 , Schematic diagram of the emergency water outlet valve

[0033] In the figure

[0034] Valve conversion push rod Open the front valve Sealing spring Valve body Connection bolt hole Valve position after opening (dashed line) Valve gasket

[0035] Figure 7 , Schematic diagram of the emergency water inlet valve

[0036] In the figure

[0037] Valve body Valve conversion push rod Open the front valve After opening the valve (dashed line) Sealing spring Ejector seal is broken Gasket Connection bolt hole

[0038] Figure 8 , core heat dissipation principle diagram after ejection shutdown

[0039] In the figure

[0040] Core temperature measuring device Start the controller High pressure cold air bottle High pressure air conditioning solenoid valve Catapult cylinder Ejection tube Safety control rod Pressure Vessels Emergency water inlet valve opening transmission lever After opening the emergency water inlet valve Emergency water outlet valve opens and turns the pressure lever Emergency water outlet valve after opening High pressure cooling air duct Coolant booster tank Pressurized high-pressure cold air duct

[0041] Fig. 9 , natural circulation heat dissipation water inlet valve and opening mechanism principle structure section view marked in the figure

[0042] Pressure Vessels Conical valve with push rod Water inlet valve body High pressure cooling air duct Valve gasket Sealing spring Ejection piston with ejector rod Catapult cylinder Start the power supply Start switch Float upper shaft Float Circuit wire High pressure air conditioning solenoid valve High pressure cold air bottle

[0043] Fig.10 , natural circulation heat dissipation water inlet valve ejection open heat dissipation diagram marked in the figure

[0044] Pressure Vessels Conical valve with push rod Water inlet valve body Pressure vessel lying pit water surface Pressure vessel support Convection Coolant Ejector piston with ejector rod Catapult cylinder Start the power supply Start switch Float upper shaft Float Circuit wire High pressure air conditioning solenoid valve High pressure cold air bottle High pressure cooling air duct DETAILED DESCRIPTION

[0045] The "two-defense technology" is a principle and structural invention. The specific structure and parameters of the seven devices of the "two-defense technology" must be matched and designed according to the actual situation of the specific pressurized water nuclear reactor. The preferred method is that the "two-defense technology" consists of the principle structure of seven devices: 1. The start controller is the device for starting the "two-defense technology". It is controlled by the core temperature and consists of a start power supply, a start switch and a core temperature receiver. 2. The high-pressure cold gas shutdown catapult consists of a catapult cylinder, a catapult cylinder, a catapult fixing frame, two pressure rods for catapult rotation, a high-pressure cold gas bottle, a high-pressure cold gas solenoid valve, and a high-pressure cold gas duct. 3. A large-capacity tubular water tank consists of a large-diameter steel pipe cast in the reinforced concrete of the containment. 4. The coolant booster tank consists of a tank body, a vent on the top of the tank body, a float, a buoyancy plug with a connecting rod, a float support net, a high-pressure cold gas inlet and a high-pressure cold gas duct.

[0046] 5. Emergency water outlet valve, consisting of valve body, valve, valve gasket, sealing spring and valve push rod. 6. Emergency water inlet valve, consisting of valve body, valve, valve gasket, valve push rod, push rod sealing ring and sealing spring. 7. Natural circulation waste heat dissipation water inlet valve, consisting of valve body located at the bottom center of pressure vessel, conical valve with push rod, valve gasket, sealing spring, high pressure cold air bottle, high pressure cold air solenoid valve, high pressure cold air conduit, starting power supply, float starting switch, float, float upper floating shaft, waterproof circuit connecting wire, high pressure cold air ejector cylinder and ejection piston with push rod.

Claims

1. The technology of pressurized water nuclear reactor anti-destruction and melt belongs to the field of nuclear safety, and its characteristics are It consists of 7 principle equipments in organic combination:

1. Start controller, which consists of start power supply, start control switch, core temperature receiver and connection circuit; 2. High-pressure cold air shutdown catapult, which consists of catapult cylinder, catapult tube, catapult bracket, catapult rotating pressure rod, high-pressure cold air bottle, high-pressure cold air solenoid valve and high-pressure cold air connecting duct; 3. Large-capacity tubular water tank, which consists of large-diameter steel pipes cast in reinforced concrete of containment; 4. Coolant booster tank, which consists of tank body, vent, vent buoyancy plug with connecting rod and float, float support net and booster cold air inlet and a high-pressure cold air duct; 5. The emergency water outlet valve is composed of a valve body, a valve, a valve gasket, a sealing spring and a valve push rod; 6. The emergency water inlet valve is composed of a valve, a valve body, a valve gasket, a valve sealing spring, a valve push rod and a push rod sealing ring; 7. The natural circulation waste heat dissipation water inlet valve is composed of a conical valve with a push rod, a valve body located in the center of the bottom of the pressure vessel, a valve gasket, a sealing spring, a high-pressure cold air bottle, a high-pressure cold air solenoid valve, a high-pressure cold air duct, a starting power supply, a float, a starting switch, a float upper shaft and a waterproof circuit wire.

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