RU2732857C1 - System for passive heat removal of reactor plant - Google Patents

Abstract

FIELD: nuclear energy.

SUBSTANCE: system for passive heat removal of reactor plant includes straight-flow steam generator with steam branch, steam-water injector, heat exchanger located below straight-flow steam generator and connected by supply pipeline with output of steam-water injector, and a discharge pipeline to the inlet of the steam-water injector, a water storage capacity installed above the straight-flow steam generator and connected to it by a water branch with a shut-off valve placed on it, and a starting reservoir. In the passive heat removal system above the water reserve capacity the compensating capacity is installed. Upper volume of vessel is connected to steam branch of straight-flow steam generator with cutoff valve installed on it. Discharge branch of container is located on side surface. On the supply pipeline of the heat exchanger there installed is a check valve, the starter tank is located above the steam-water injector and is connected to the supply pipeline of the heat exchanger, and the branching branch is connected to the supplying branch of the compensating capacity.

EFFECT: invention allows improving reliability of heat removal supplied to steam generator residual heat release in passive mode.

3 cl, 2 dwg

Description

The invention relates to the field of nuclear energy, in particular, to remove heat from a reactor plant and can be used in systems for emergency cooling of the cores of nuclear reactors without consuming external energy sources.

Known system according to the patent RU No. 2037893 from 19.06.1995), which contains a heat exchanger and a circulation circuit of the coolant 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 the emergency heat removal system, for which the patent RU No. 150816 dated 06/03/2014 was issued. The system contains a once-through steam generator, the steam and water branches of which are connected to the water storage tank, the upper part of which is connected to the heat exchanger by the supply pipeline, the steam branch is connected to the water storage tank below the level of the water volume, and a jet pump is installed on the supply pipeline section, which is connected at the inlet with a water storage tank, and at the outlet with a heat exchanger, which is connected by a discharge pipeline equipped with a check valve, to the lower part of the water storage tank, in addition, the jet pump is connected at the inlet by an additional branch with a discharge pipeline located between the check valve and the lower part of the water storage tank , and between the outlet of the jet pump and the heat exchanger, a starting tank equipped with a starting valve is connected.

The disadvantage of this system is that the opening of the shut-off and start-up valves must occur simultaneously, since if the start-up valve opens later, then it is not known after what period of time or by what signal. But with the simultaneous opening of these valves, water is first displaced from the water seal into the water storage tank and only then the hot steam-water mixture enters and the water storage tank and its steam volume begin to warm up.

However, with the simultaneous opening of the starting valve due to the pressure difference in the water storage tank and the starting tank, an unheated medium will flow into the starting tank through the jet pump through two parallel branches: one through the supply pipe of the heat exchanger and the other consisting in series of a section connected to the water supply tank the outlet pipeline and an additional (bypass) branch. Since the temperature of the incoming media is the same, condensation of steam in the jet pump will be impossible, and the driving head of circulation in the system will not arise.

In the case of opening the start valve after the water storage tank warms up (it is not known by what signal), media (water and steam) will also enter the jet pump through the same branches and at the same temperature, i.e. steam condensation will also be impossible, since water circulation through the heat exchanger in the absence of a driving pressure does not yet occur and cold water does not yet enter the jet pump through an additional (bypass) line.

In addition, it is known that jet pumps have a limited range of operating parameters and are switched off with a significant decrease in steam flow and pressure. Meanwhile, in the emergency heat removal system, as the power of residual heat release decreases, the steam capacity of the steam generator and the steam pressure significantly decrease. This causes the jet pump to stop working. However, since the starting tank will be completely filled with water during the first start-up and long-term operation thereafter, the secondary start of circulation in the system after the increase in steam pressure and emergency heat removal will be impossible.

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

The technical result is achieved by the fact that in the composition of the passive heat removal system containing a direct-flow steam generator with a steam branch, a steam-water injector, a heat exchanger located below the direct-flow steam generator and connected by a supply pipeline to the outlet of a steam-water injector, and a discharge pipeline to the inlet of a steam-water injector, a water storage capacity set above of a once-through steam generator and a water branch connected to it with a shut-off valve placed on it and a start-up tank a compensating tank installed above the water storage tank is introduced, which is connected by a supply branch to the supply pipe of the heat exchanger, its upper volume is connected by a steam branch to the steam branch of a once-through steam generator with an installed on it shut-off valve, and the outlet branch of the compensating tank is located on the side surface at a level corresponding to the installation level of the steam-water injector, and is connected to the water storage tank, as well as to the supply pipes A non-return valve is installed on the heat exchanger line, and the starting tank is located above the steam-water injector and is connected to the upper part of the heat exchanger inlet pipeline, and the outlet branch is connected to the compensating tank inlet branch.

The direct-flow steam generator and the compensating tank and the water storage tank located above it create a natural water circulation path through the direct-flow steam generator. Another circulation path, including a steam-water injector and a heat exchanger and connected to the compensation tank, has a constant water level in the compensation tank.

Installation of the steam-water injector at the same level with the water level in the compensating tank ensures the presence of water in the mixing chamber of the steam-water injector (as in communicating vessels), promotes condensation of the incoming steam and creates conditions for reliable initial and subsequent start-up of the steam-water injector.

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 compensating tank.

The installation of a check valve on the supply line of the heat exchanger prevents water from the compensating tank from the compensating 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 compensating tank and thereby free up the volume of the starting tank for subsequent starts of the steam-water injector.

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

The execution of the starting tank with the possibility of external cooling increases the efficiency of condensation of the steam entering it, reduces the pressure in the starting tank and improves the conditions for successive repeated starts of circulation in the system.

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

FIG. 1 schematically shows the passive heat removal system of a reactor plant (PHRS).

FIG. 2 schematically shows the SPOT of a reactor plant with a check valve on the outlet branch of the starting tank.

The system (Fig. 1) consists of a direct-flow steam generator 1, a heat exchanger 4 located below the direct-flow steam generator 1, a compensating tank 3, located with an excess over the direct-flow steam generator 1 and a water reserve 13 located below the compensating tank 3 and above the direct-flow steam generator 1, a steam-water injector 5 located at the water level in the compensating tank 3 and the starting tank 15 located above the steam-water injector 5.

The once-through steam generator 1 is connected by a steam branch 2 with a shut-off valve 10 placed on it with a steam-water injector 5. The steam-water injector 5 is connected at the outlet by a supply pipeline 6 with a check valve 12 located on it with a heat exchanger 4. Heat exchanger 4 is connected by a discharge pipeline 7 to a steam-water injector 5 according to entrance.

The lower part of the water storage tank 13 is connected by a water branch 9 with a shut-off valve 11 placed on it with a direct-flow steam generator 1, and its upper part is connected by a branch branch 18 to the compensating tank 3 at the same level with the steam-water injector 5.

The lower part of the compensating tank 3 is connected by the supply line 8 with the supply line of the heat exchanger 6, the upper part of the compensating tank 3 is connected by the steam line 14 to the steam line 2.

The upper part of the starting tank 15 is connected by a branch 16 to the section of the pipeline 6 between the steam-water injector 5 and the check valve 12, and the lower part of the starting vessel 15 is connected by a branch 17, on which the check valve 19 is installed (Fig. 2), to the 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 once-through steam generator 1 by closed cut-off valves 10 and 11. The system is filled with condensate to the level of connection of the outlet branch 18 to the side of the compensating tank 3. The pressure in the system is lower than the pressure in the steam generator.

When the system is put into operation, the steam generator 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. Water begins to flow into the steam generator 1 from the water storage tank 13 through the water branch 9. Along the closed path, the water storage tank 13 - steam generator 1 - compensating tank 3, natural circulation occurs due to the difference in the density of the medium on the downward water branch 9 and the lifting steam branch 2 with heat removal from the steam generator into the system.

Steam from the once-through 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 compensating 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 water heat exchanger 4 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 compensating tank 3 and, along the branch 18, is poured into the water storage tank 13 to compensate for the loss of the water supply for vaporization.

At start-up, part of the steam along branch 16 passes into the starting tank 15 and condenses. Since the starting tank 15 is located above the steam-water injector 5 and the compensating tank 3, the formed condensate through the branch 17 and the branch 8 enters the compensating tank 3.

Since the movement of water in the system through the heat exchanger 4 is not regulated, at any moment of time the amount of heat entering the once-through 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 entering the once-through 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 in the reactor installation and, accordingly, the amount of heat supplied with coolant in a once-through steam generator 1.

Under such conditions, the amount of water supplied from the pressure of the steam-water injector 5 sequentially along branches 6, 8, 18 and 9 into the steam generator 1 exceeds the amount of water required for steam generation at the current power of the reactor plant. As a result, steam generation in the once-through 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 once-through steam generator 1, the steam-water injector 5, the compensating tank 3 and the starting tank 15 are aligned. If, at the same time, the level of condensate in the branch 17 and the starting tank 15 is higher than the water level in the compensating tank 3, then under the action of the leveling pressure, the water from the starting tank 15 will flow through the branches 17 and 8 into the water volume of the compensating tank 3 until the water levels in them equalize. In this case, the volume of the starting chamber 15 is freed from condensate.

Further, since the heat supply continues in the direct-flow steam generator 1, and the flow of water 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 compensating 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 circulation starts.

The circulation of water in the system, heat removal through the heat exchanger 4 and the flow of water into the steam generator 1 are resumed.

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 direct-flow 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 technical solution provides heat removal from the residual heat release of the reactor plant through a heat exchanger located below the direct-flow steam generator and cooled by the final absorber (sea water or water from an external reservoir), with an unlimited amount of which the process of heat removal in the presence of heat release can continue indefinitely until the complete cooling of the reactor plant ...

Claims (3)

1. The system of passive heat removal of the reactor plant, including a once-through steam generator with a steam branch, a steam-water injector, a heat exchanger located below the once-through steam generator and connected by a supply pipeline to the outlet of the steam-water injector, and by a discharge pipeline to the inlet of a steam-water injector, a water storage tank installed above the once-through steam generator and a water line connected to it with a shut-off valve placed on it, and a starting tank, characterized in that a compensating tank is installed in the passive heat removal system above the water storage tank, which is connected by a supply line to the supply line of the heat exchanger, its upper volume is connected to the steam line a direct-flow steam generator with a shut-off valve installed on it, and the outlet branch of the compensating tank is located on the side surface at a level corresponding to the installation level of the steam-water injector, and is connected to the water storage tank on the supply pipe A non-return valve is installed in the heat exchanger line, the start-up tank is located above the steam-water injector and its upper part is connected to the supply line of the heat exchanger, and the outlet branch is connected to the supply line of the compensating tank. 2. The system according to claim 1, characterized in that a check valve is installed on the discharge branch of the starting tank. 3. The system of claim. 1, characterized in that the starting capacity is made with the possibility of external cooling.

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