RU152416U1 - EMERGENCY HEAT REMOVAL SYSTEM - Google Patents

Abstract

1. An emergency heat removal system containing a direct-flow steam generator connected by steam and water branches with a water storage tank, a water heat exchanger, an air heat exchanger, characterized in that the air heat exchanger is connected by a supply branch to the steam volume of the water storage tank, a branch with a water volume of the latter, moreover, the outlet end of the steam branch is located below the level of the water volume of the water storage tank; in addition, a shut-off valve is installed on the water branch between the water storage tank and the water heat exchanger, which is configured to connect a throttling element in parallel to it. The system according to claim 1, characterized in that a circulation pump is placed between the once-through steam generator and the water heat exchanger. An emergency heat removal system containing a once-through steam generator connected by steam and water branches with a water storage tank, a water heat exchanger, an air heat exchanger, characterized in that the air heat exchanger is connected by a supply branch to the steam volume of the water storage tank, a branch with a water volume of the latter, and the outlet the end of the steam branch is located below the level of the water volume of the water storage tank, in addition, the direct-flow steam generator is connected to the second circuit so that the supply pipeline of the second circuit is connected to the water branch of the steam generator, and the outlet pipeline of the second circuit is connected to the steam branch, while the water storage tank is hydraulically connected with the second circuit of the once-through steam generator. 4. The system according to claim 3, characterized in that between the once-through steam generator and the water heat exchanger p�

Description

The proposed technical solution relates to the field of nuclear energy and can be used in emergency cooldown systems of nuclear reactors without the consumption of external energy sources.

A known system of passive heat removal (SPOT) of nuclear installations, in which the removal of residual heat is carried out into the air through an air heat exchanger and an intermediate circuit connected to the steam generator in parallel with the second circuit. (Patent RU No. 20022320 of 05.16.1991, according to CL G21C 15/18). Moreover, during the normal operation of a nuclear installation to prevent freezing of the pipe system of the air heat exchanger due to the ingress of cold air through leaks, a natural circulation in the intermediate circuit is organized.

This system cannot be used for nuclear installations with a once-through steam generator due to the large hydraulic resistance of the once-through steam generator at a nominal flow rate of feed water. As a result of the high resistance, the pressure of the feed pump exceeds the driving pressure of the natural circulation of the intermediate circuit, which does not allow for leakage through the intermediate circuit during operation of the feed pump. In addition, the air heat exchanger has large dimensions.

A known system of passive heat removal from the steam generators of nuclear installations, in which the removal of residual heat is carried out through an intermediate circuit into the atmospheric air due to the evaporation of water reserves. (Patent RU No. 2050025 dated 05/14/1992 according to class G21C 15/18). The heat removal from the intermediate circuit is organized through a heat exchanger, which is several times smaller than an air heat exchanger due to the high heat transfer efficiency. The system is upstream and there are no losses through the intermediate circuit.

The disadvantage of such a system is the limited operating time. The time reserve of such a system is determined by the volume of stored water.

A known emergency cooldown system for nuclear reactors (see, for example, patent RU No. 52245 dated July 12, 2005 according to class G21C 15/18), in which the removal of residual heat from the core is carried out through an intermediate circuit with an air heat exchanger. The overpressure in the intermediate circuit is maintained by means of a compensating gas cylinder, and the residual heat is removed sequentially through a water heat exchanger, then through an air heat exchanger. Freezing of the air heat exchanger in standby mode is prevented by drainage from the side of the intermediate circuit.

The disadvantage of this system is the limited temperature range of the primary circuit. The system works efficiently in a two-phase mode (steam-water) of the intermediate circuit circulation. When the temperature of the primary circuit decreases, the system goes into single-phase circulation mode. In this case, the gas available in the intermediate circuit is collected in the upper part of the circuit and breaks the circulation, completely stopping heat dissipation.

The closest technical solution is a system containing a direct-flow steam generator having steam and water branches, a water supply capacity, a water heat exchanger, an air heat exchanger connected in parallel with the system steam branch, having a heat transfer surface that allows the removal of residual heat after exhausting water reserves for evaporation, which allows significantly reduce the size of the air heat exchanger and the volume of water reserves, ensure stable heat removal in the passive mode from the direct-flow rogeneratora unlimited time in the first loop wide range of temperatures and provide heat dissipation in the event of failure of the air heat exchanger (Patent RU №109898 from 27.10.2011 to cl. G21C 15/18).

The disadvantage of this system is the need to place a water heat exchanger located in the tank with a supply of evaporated water above the steam generator, in order to organize natural circulation. This complicates the design, construction, maintenance, operation and implementation of accident management measures. During the ship's execution of this system, the center of mass of the vessel (floating nuclear power plant, nuclear icebreaker, etc.) rises, which affects its stability and seaworthiness.

The technical task is to create a system that simultaneously allows for stable heat removal for unlimited time and constant circulation of the coolant through the air heat exchanger, preventing its freezing.

The solution of this problem allows to increase the reliability of the system and provide emergency heat removal from a nuclear reactor for a long time.

The problem is solved in that in an emergency heat removal system comprising a direct-flow steam generator connected by a steam and water branches with a water supply tank, a water heat exchanger, an air heat exchanger with a supply branch is connected to a steam volume of a water supply tank, a branch branch with a water volume of the latter, and the output end the steam branch is located below the level of the water volume of the water storage tank, in addition, a shut-off valve is installed on the water branch between the water storage tank and the heat exchanger The parallel connection of the throttle element to it, or the steam generator is connected to the second circuit so that the inlet pipe of the second circuit is connected to the water branch of the steam generator and the secondary circuit is connected to the steam branch, while the water supply capacity is hydraulically connected to the second circuit of the direct-flow steam generator.

The emergency cooling system can be equipped with a circulation pump, which is located between the direct-flow steam generator and the water heat exchanger.

The inclusion of a circulation pump in the system allows to increase the flow rate along the intermediate circuit, which contributes to the intensification of the heat removal process and increase its duration by combining the passive and active process in a single intermediate circuit.

The essence of the technical solution is illustrated by drawings, where:

In FIG. 1 schematically shows an emergency heat removal system using a throttle element (option 1);

In FIG. 2 schematically shows an emergency heat removal system using a throttle element and a circulation pump (option 1);

In FIG. 3 schematically shows an emergency heat removal system using the ability to remove condensate from a water supply tank, (option 2);

In FIG. 4 schematically shows an emergency heat removal system using the possibility of condensate drainage and a circulation pump (option 2).

Two variants of the emergency heat removal system are proposed, where one technical problem is solved and the same result is achieved.

In the first embodiment, the system consists of a once-through steam generator 1, a water supply tank 2, an air heat exchanger 3, a water heat exchanger 4. shut-off valve 5 and a throttle element 6.

The direct-flow steam generator 1 is connected by a steam branch 7 with a water supply capacity 2, the outlet end of the steam branch is located below the level of the water volume of the latter. A water branch 8, the steam generator 1 is connected through a water heat exchanger 4 with a capacity of the water supply 2. On the water branch 8 between the water supply capacity 2 and the water heat exchanger 4 there is a shut-off valve 5, in parallel with which the throttle element 6 is connected.

The air heat exchanger 3 by the supply branch 9 is connected to the steam cavity of the water supply tank 2, and the discharge branch 10 with its water volume.

On the water branch 8 between the water heat exchanger 4 and the once-through steam generator 1 can be installed a circulation pump 11, which is designed to complement the passive mode of heat removal by active circulation. When completely de-energized, cooling will occur only due to natural circulation.

In the second embodiment, the system consists of a once-through steam generator 1, a water supply tank 2, an air heat exchanger 3, a water heat exchanger 4 and is connected to the second circuit. The system is connected by a water branch 8 to the pipeline of the second circuit 12, intended for supplying feed water to the steam generator 1, and a steam branch 7 to the pipe 13, intended to drain the feed water from the steam generator 1. The capacity of the water supply 2 is connected to the second circuit by a pipe 15, on which stop valves 16 are installed. By connecting the water supply tank 2 to the second circuit, the water level in the latter is maintained.

The direct-flow steam generator 1 is connected by a steam branch 7 with a water supply capacity 2, the outlet end of the steam branch is located below the level of the water volume of the latter. A water branch 8, the steam generator 1 is connected through a water heat exchanger 4 with a reservoir capacity of water 2.

The air heat exchanger 3 by the supply branch 9 is connected to the steam cavity of the water supply tank 2, and the discharge branch 10 with its water volume.

To prevent reverse circulation through the system in the mode of steam generation on the water branch 8 between the water heat exchanger 4 and the steam generator 1 is a check valve 14.

On pipelines 12 and 13 installed shutoff valves.

The air heat exchanger 3 is placed in the duct 17, equipped with gate valves 18.

The emergency heat removal system operates as follows.

Initially, the emergency heat removal system is connected to a once-through steam generator 1 in steam, water with the shut-off valve 5 closed and is in standby mode. Gate valves 18 are closed.

In the first embodiment, to prevent freezing of the air heat exchanger 3, the flow rate through the system circuit is maintained due to the throttle element 6 connected in parallel to the shutoff valve 5. Steam from the steam generator 1 rises along the steam branch 7 into a container with a supply of water 2, where it partially condenses, and partially through the supply branch 9 enters the air heat exchanger 3, cools and returns to the tank with a supply of water 2. Water from the tank with a supply of water 2 through the throttle element 6, the water heat exchanger 4 enters pa ogenerator 1.

In the event of an emergency, the system starts up by opening the gate valves 18 and the shutoff valve 5. The system develops natural circulation through the air heat exchanger 3 and the water heat exchanger 4 due to the difference in the density of steam (steam-water mixture) generated in the steam generator 1 and entering the water supply tank 2 and condensate at the outlet of the air heat exchanger 3.

Natural circulation through the water heat exchanger 4 occurs due to the difference in the weight of the coolant on the lifting and lowering section of the water branch 8 of the circuit. Heat is removed to the final absorber from the air heat exchanger 3 and the water heat exchanger 4 in parallel.

In the second embodiment, to prevent freezing of the air heat exchanger 3, the flow rate through the system loop is maintained by adjusting the water level in the water storage tank 2 by draining the steam-water mixture into the second circuit. Similarly to the first option, steam from the steam generator 1 rises along the steam branch 7 into a container with a supply of water 2, where it partially condenses, and partially through a supply branch 9 enters an air heat exchanger 3, cools and returns to a container with a supply of water 2. To prevent overfilling of the container with a supply of water 2, water or steam-water mixture through the pipeline 15 through the stop valves 16 is discharged into the second circuit.

When an emergency occurs, the system starts up by opening the slide gate valves 18 and closing the shut-off devices on the pipelines 12 and 13. Further, the situation develops as in the first embodiment.

In the event of an emergency not related to a complete blackout, the presence of a circulation pump in the system allows heat to be removed from the reactor to a cold state.

The proposed solution allows you to use a water heat exchanger as efficiently as possible, to provide reliable heat removal for an unlimited time in a wide temperature range of the primary circuit, to reduce the size of air and water heat exchangers.

In addition, it allows to provide heat removal even in the event of termination of heat removal from the water heat exchanger, since air and water heat exchangers operate independently, which allows providing a reserve of time for restoration of heat removal from the water heat exchanger or taking necessary measures to manage the accident.

Therefore, the reliability of the system and the reactor installation as a whole is increased.

Claims (4)

1. An emergency heat removal system comprising a direct-flow steam generator connected by a steam and water branches to a water supply tank, a water heat exchanger, an air heat exchanger, characterized in that the air heat exchanger by a supply branch is connected to a steam volume of a water supply tank, a branch branch to the water volume of the latter, moreover, the outlet end of the steam branch is located below the level of the water volume of the water supply tank, in addition, on the water branch between the water supply tank and the water heat exchanger are installed a valve which is adapted to the parallel connection thereto throttling element. 2. The system according to claim 1, characterized in that a circulation pump is located between the direct-flow steam generator and the water heat exchanger. 3. An emergency heat removal system comprising a direct-flow steam generator connected by a steam and water branches to a water supply tank, a water heat exchanger, an air heat exchanger, characterized in that the air heat exchanger by a supply branch is connected to a steam volume of the water supply tank, a branch branch to the water volume of the latter, moreover, the outlet end of the steam branch is located below the level of the water volume of the water storage tank, in addition, the direct-flow steam generator is connected to the second circuit so that to the water branch of the steam generator a supply pipe of the second circuit is connected to the torus, and a discharge pipe of the second circuit is connected to the steam branch, while the water storage capacity is hydraulically connected to the second circuit of the once-through steam generator. 4. The system according to p. 3, characterized in that between the direct-flow steam generator and the water heat exchanger is placed a circulation pump.

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