RU2740786C1 - System for passive heat removal of reactor plant - Google Patents

Abstract

FIELD: heat exchange.

SUBSTANCE: invention relates to a system of heat removal from a reactor plant, in particular, in systems of emergency cooling of active zones of nuclear reactors without consumption of external energy sources. System includes steam generator with steam and water branches, steam-water injector, heat exchanger located below steam generator and cooled by final heat absorber, water storage tank installed above steam generator and connected by water branch with cut-off valve arranged on it to steam generator, supplying branch to supply pipeline of heat exchanger, and its upper volume is connected by additional branch to steam branch of steam generator, starting reservoir arranged above steam-water injector and upper part connected by supplying branch to supply pipeline of heat exchanger. At that, steam generator water line is connected to water storage capacity side surface in point at level corresponding to horizontal level of steam-water injector arrangement, and additional branch of water storage capacity is connected to steam branch of steam generator in point of connection of steam branch to input into steam-water injector.

EFFECT: technical result of the passive heat removal system is increase in the level of reliability and duration of discharge of residual heat emissions supplied to the steam generator after the heat exchanger in passive mode for an unlimited period of time in the absence of external power sources and higher safety of the reactor plant operation.

4 cl, 2 dwg

Description

The invention relates to the field of nuclear power, is intended to remove heat from a reactor facility, in particular, in systems for emergency cooling of the cores of nuclear reactors without consuming external energy sources.

A known system (Patent RU No. 2037893 dated 06/19/1995), which contains a heat exchanger and a coolant circulation circuit of a nuclear power plant, in parallel to which a jet pump is connected in the form of an injector-condenser. The inlet of the jet pump through the injected medium is connected to the outlet of the heat exchanger, the inlet of which is connected to the heat source - the water volume of the steam generator. A non-return valve is installed on the outlet pipeline of the jet pump, between which a condensation module is placed and the jet pump, with the help of which the system is started. Water from a heat source (steam generator or reactor) enters the heat exchanger, is cooled in it due to the evaporation of make-up water, and is supplied to the nozzle of the injected stream of the jet pump. The disadvantage of such a system is the limited time of its operation by the volume of the evaporated feed water reserves. In addition, since the condensation module fills up completely during the first start-up, it is not possible to restart the system and continue to remove heat if the circulation is interrupted.

The closest technical solution is an emergency heat removal system under the patent RU No. 186261 dated 01/15/2019, which contains:

- a once-through steam generator, the steam branch of which is equipped with a shut-off valve and connected to a steam-water injector, and the water branch, also with a shut-off valve, is connected to the bottom of the water storage tank;

- a water storage tank located above the once-through steam generator, the upper part of which is connected by an additional branch with a steam branch, and the lower part is divided by a partition into two sections: a water storage section connected to a water branch, and a section of a stable water level, which are combined in the upper part of the volume water storage capacity;

- a steam-water injector located at the level of the upper edge of the partition of the water storage tank,

- a heat exchanger connected by an inlet pipeline equipped with a check valve to the outlet of the steam-water injector, and by the outlet pipeline to the inlet of the steam-water injector,

- a start-up tank located above the steam-water injector and connected by a supply branch with a section of the supply pipe of the heat exchanger between the steam-water injector and a check valve and an outlet branch with a supply branch of the water storage tank

The disadvantage of this system is that in the presence of steam flow in the steam branch, the steam pressure in the water storage tank will be higher than the pressure in the mixing chamber of the steam-water injector by the value of the hydraulic resistance of the section of the steam branch from the point of connection of the additional branch to the steam-water injector. Since the water storage tank and the mixing chamber of the steam-water injector are communicating vessels, there will be a flow of water from the water storage tank to the steam-water injector, the volume of the mixing chamber of the steam-water injector and the pipeline following it will overflow, which will make it difficult for steam to pass into the starting tank and start work. steam-water injector in cyclic modes of system operation.

In addition, with a significant hydraulic resistance of the section of the steam branch from the steam generator to the connection point of the additional branch in the phase of starting the system, it is possible for water from the steam generator to enter the water storage tank, its overflow with an increase in the water level and, accordingly, the overflow of water in the volume of the steam-water injector, which, by analogy with the previous will make it difficult to start the system.

The technical result of the passive heat removal system (PHRS) is to increase the reliability of the removal of residual heat supplied to the steam generator in the passive mode for an unlimited time in the absence of external energy sources and to increase the safety of the reactor plant.

To achieve the technical result, the proposed composition of the passive heat removal system contains:

- a steam generator with a steam branch, with a shut-off valve located on it,

- a heat exchanger connected by an inlet pipeline equipped with a check valve with the outlet of the steam-water injector, and the outlet pipeline with the inlet of the steam-water injector,

- a water storage tank installed above the steam generator and connected to it by a water branch with a shut-off valve placed on it and a check valve installed above it, a supply branch to the supply pipe of the heat exchanger, and its upper volume is connected by an additional branch to the steam branch of the steam generator at the point of steam connection branches to the steam-water injector, and the water branch of the steam generator is connected to the side surface of the water storage tank at a point at a level corresponding to the horizontal level of the steam-water injector,

- a start-up tank located above the steam-water injector and connected by an inlet branch with a section of the supply pipe of the heat exchanger between the steam-water injector and a check valve and a discharge branch with a supply branch of the water storage tank.

The steam generator and the water storage tank located above it, connected by the steam and water branches, create a natural steam and water circulation path through the steam generator.

The circulation path, including a steam-water injector, a heat exchanger, supply and outlet pipelines of the heat exchanger and connected to the water storage tank, has a constant water level in the water storage tank.

Installation of shut-off valves on the steam and water branches of the steam generator disconnects the system from the steam generator and, when they are opened in an emergency, contributes to the simultaneous start of the steam-water injector and the beginning of circulation through the heat exchanger without the need to warm up the system and the water storage tank.

The installation of a check valve on the supply line of the heat exchanger prevents water from the water supply tank from the water supply tank through its supply line to the pressure pipe of the steam-water injector at start-up.

Installation of the starting tank above the steam-water injector allows the accumulated condensate to be drained from it into the water storage tank and thereby free up the volume of the starting tank for subsequent starts of the steam-water injector.

Connecting the water branch of the steam generator to the side surface of the water storage tank, which determines the water level in the water storage tank, at a point at a level corresponding to the horizontal level of the steam-water injector, thereby ensures the presence of water at the same level in the mixing chamber of the steam-water injector (as in communicating vessels ), which contributes to the condensation of steam entering the mixing chamber and creates conditions for reliable initial and subsequent start-ups of the steam-water injector.

The connection of an additional branch to the steam branch of the steam generator at the point of connection of the steam branch to the steam-water injector ensures, even in the presence of steam movement along the steam branch, equal pressure of the vapor medium in the water storage tank and in the mixing chamber of the steam-water injector. This ensures that the water levels in them are equal, which contributes to the condensation of steam in the mixing chamber and the start of the operation of the steam-water injector.

Installing a non-return valve on the steam generator water branch above the shut-off valve prevents water from the steam generator from entering the water storage tank.

The passive heat removal system can be equipped with a check valve located on the outlet branch of the start-up tank, which prevents water from entering the start-up tank from the water storage tank with an increase in steam pressure and, thereby, eliminates the decrease in the volume of the start-up tank required to start the system.

The implementation of the starting tank with the possibility of external cooling will increase the efficiency of condensation of the steam entering it, reduce the pressure in the starting tank and improve the conditions for successive repeated starts of circulation in the system.

The proposed system of passive heat removal from the reactor plant allows both reliable natural circulation of water through the steam generator and forced circulation of water with the removal of heat from residual heat for an unlimited time to the final absorber through a heat exchanger located below the steam generator and cooled as the final heat absorber by water from an external reservoir. or sea water (for floating reactor installations), the reserves of which are unlimited.

The essence of the technical solution is illustrated by drawings:

fig. 1 is a schematic diagram of a passive heat removal system (PHRS) of a reactor plant.

fig. 2 is a diagram of the PHRS of the reactor plant with check valves on the water branch of the steam generator and on the outlet branch of the starting tank.

The system (Fig. 1) consists of a steam generator 1, a heat exchanger 4 located below the steam generator 1, a water storage tank 3 located above the steam generator 1, a steam-water injector 5, the horizontal axis of which corresponds to the water level line in the water storage tank 3, and a starting tank 15 located above the steam-water injector 5.

The steam generator 1 is connected by a steam branch 2 with a shut-off valve 10 installed on it and a steam-water injector 5.

The steam-water injector 5 is connected at the outlet by a supply pipeline 6, with a check valve 16 installed on it, with a heat exchanger 4. The heat exchanger 4 is connected by a discharge pipeline 7 with a steam-water injector 5 at the inlet.

The lower part of the water storage tank 3 is connected by the supply line 8 with the supply line of the heat exchanger 6, the upper volume of the water supply tank 3 is connected by an additional line 14 to the steam line 2 at the point of connection of the steam line 2 to the steam-water injector 5, and the water line 9 with the cutoff placed on it valve 11 is connected to the side surface of the storage tank 3 at the level corresponding to the horizontal level of the steam-water injector 5.

A check valve 17 (Fig. 2) is installed on the water branch 9 with an excess over the cut-off valve 11.

The upper part of the volume of the starting tank 15 is connected by a branch 12 to a pipeline 6 between the outlet of the steam-water injector 5 and a check valve 16, and the lower part of the volume is connected by a branch 13 with a check valve 18 installed on it (Fig. 2) to a branch 8.

The passive heat removal system works as follows.

Initially, the passive heat removal system is in a standby state and is disconnected from the steam generator 1 by closed shut-off valves 10 and 11.

The system is filled with condensate up to the level of connection of branch 9 to the side of the water storage tank 3. The pressure in the system is lower than the pressure in the steam generator 1.

At the moment the system is put into operation, the steam generator 1 is connected to the system by opening the shut-off valves 10 and 11. Steam from the steam generator enters the system via branch 2, the pressure in the system increases and approaches the pressure in the steam generator.

Steam from the steam generator 1 enters the steam-water injector 5 and moves through it into the starting tank 15. Since the steam-water injector 5 is located at the same level with the water level in the water storage tank 3, water is present in the mixing chamber of the steam-water injector 5. The incoming steam is mixed with water, condensed and an increased pressure of the mixed medium arises in the pressure chamber of the steam-water injector 5, which creates circulation of water through pipelines 6 and 7 through the heat exchanger 4.

The circulation of water through the heat exchanger 4 with heat removal to the external environment occurs due to the pressure difference in the pressure pipe of the steam-water injector against its mixing chamber. In this case, a part of the water consumption along the branch 8 enters the water storage tank 3 and flows through the water branch 9 to the steam generator 1 to compensate for the steam consumption for steam generation.

At startup, part of the steam along branch 12 passes into the starting tank 15 and condenses. Since the starting tank 15 is located above the steam-water injector 5 and the water storage tank 3, the resulting condensate through the outlet branch 13 and the branch 8 enters the water storage tank 3.

Since the movement of water in the system through the heat exchanger 4 is not regulated, then at any moment of time the amount of heat entering the steam generator 1 and the amount of heat removed through the heat exchanger 4 are not equal and the system cannot operate in a stationary mode, i.e. all processes are nonstationary and dynamic.

In the presence of effective circulation processes for each circulation path and heat removal through the heat exchanger 4, the amount of heat supplied to the steam generator 1 can be less than the amount of heat removed through the heat exchanger 4. Such conditions arise in the process of reducing the residual heat release in the reactor installation and, accordingly, the amount of heat supplied from coolant into the steam generator 1.

Under such conditions, the amount of water supplied from the pressure of the steam-water injector 5 sequentially along the branches 6, 8 and 9 into the steam generator 1 exceeds the amount of water required for vaporization at the current power of the reactor plant. As a result, steam generation in the steam generator 1 decreases, the steam pressure in the system decreases, the flow of steam through the steam branch 2 decreases until it stops, and the operation of the steam-water injector 5 is interrupted. The circulation of water through pipelines 6, 7 and 8 is stopped.

In this case, due to the lack of steam flow along the branch 2, the steam pressure in the steam generator 1, the steam-water injector 5, the water storage tanks 3 and the starting tank 15 are aligned. If, at the same time, the level of condensate in branch 13 and starting tank 15 is higher than the water level in water storage tank 3, then under the action of leveling pressure, water from starting tank 15 will flow through branches 13 and 8 into the water volume of water storage tank 3 until water levels in them. In this case, the volume of the starting tank 15 is freed from condensate.

Further, since the heat supply in the steam generator 1 continues, and the flow of water into the steam generator from the pressure of the steam-water injector 5 has ceased, vaporization in the steam generator 1 begins to increase, the steam output to the system increases, the steam pressure in the branch 2 and in the water storage tank 3 increases.

Steam begins to flow through branch 2 into the steam-water injector 5, through it into the starting tank 15 and the next start of the circulation of water in the system, heat removal through the heat exchanger 4 and the flow of water into the steam generator 1.

The process of heat removal will continue until the next decrease in the steam pressure in the system and the failure of the steam-water injector 5. all processes are repeated. In the presence of a continuous supply of heat to the steam generator 1, a cyclical operation of the system occurs without restrictions on the duration of operation and with a reliable removal of all heat supplied to the system through the heat exchanger 4.

The proposed solution allows the heat of residual heat to be removed through a heat exchanger located below the steam generator and cooled by the final absorber. In the presence of an unlimited amount of reserves of the final absorber (sea water or water from an external reservoir), the process of heat removal will continue in the presence of heat release for an unlimited time up to a state in which the power of heat release will be equal to heat loss to the environment.

Claims (4)

1. The system of passive heat removal of the reactor plant, including a steam generator with a steam branch with a shut-off valve located on it, connected to a steam-water injector, and with a water branch with a shut-off valve located on it, connected to a water storage tank, a steam-water injector, a heat exchanger located below steam generator and connected by a supply line to the outlet of the steam-water injector, and by the outlet pipeline at the inlet of the steam-water injector, a water storage tank installed above the steam generator with a supply line connected to the supply line of the heat exchanger and with an additional branch connecting its upper volume with the steam branch of the steam generator, starting a tank located above the steam-water injector and its upper part connected by a supply line to the supply line of the heat exchanger, and by a discharge line connected to the supply line of the water storage tank, a check valve installed on the supply line of the heat exchanger, characterized in that in The other branch of the steam generator is connected to the side surface of the water storage tank at a point at a level corresponding to the horizontal level of the steam-water injector, and an additional branch of the water storage tank is connected to the steam branch of the steam generator at the point where the steam branch is connected to the inlet to the steam-water injector. 2. The system of claim. 1, characterized in that the water branch of the steam generator is equipped with a check valve located above the shut-off valve. 3. The system according to claim 1, characterized in that a check valve is located on the discharge branch of the starting tank. 4. The system of claim. 1, characterized in that the starting capacity is made with the possibility of external cooling.

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