RU2721384C1 - Nuclear power plant emergency cooling system - Google Patents

Abstract

FIELD: nuclear physics and equipment.

SUBSTANCE: invention relates to emergency cooling system of nuclear power plant and inner volume of anti-accident cover. System comprises sprinklers arranged inside sealed anti-accident shell, and a recess for collection of heat carrier in the floor of an anti-accident shell, at least one pump connected to the recess by means of a suction pipeline with a heat exchanger and a shutoff valve. Also, there are injection pipelines connecting the pumps with sprinkler nozzles and nuclear power plant reactor, wherein in the recess a vertical shaft is installed, in the upper part of which there is a reactor, and in lower part – melt localization device, around lower part of shaft there is a water collector connected to pumps by suction pipelines passing through valve chambers. In chambers there are cutoff valves, and in wall of lower part of well there are holes for heat carrier supply to device of melt localization.

EFFECT: increased safety of NPP due to application of melt localization device without considerable increase of reactor building height and provision of possibility to cool melt localization device in passive mode, as well as due to possibility of heat carrier filtration and safe arrangement of pipeline shutoff valves.

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Description

Technical field

The invention relates to the field of nuclear energy and is intended for use in nuclear power plants (NPPs) with a melt localization device (ULR).

State of the art

At all modern nuclear power plants, the tight enclosure of the reactor installation (RU) is in the form of an emergency shell.

In this case, the emergency shell is made in the form of a set of elements of the NPP unit, including building structures, which, fencing the space around the reactor, prevent the spread of radioactive substances and ionizing radiation into the environment in quantities exceeding the established limits. These requirements are currently directly established by various standards in the field of atomic energy use (General provisions for ensuring the safety of atomic power plants. Federal norms and rules in the field of atomic energy use. NP-001-15. M: FBI STC NRS, 2016, p. 56).

To remove heat from the switchgear during design basis accidents with rupture of the coolant circuit of the switchgear, modern nuclear power plants have an emergency cooling system, which usually includes a system that removes heat and prevents pressure buildup in the internal volume of the emergency shell, which is often achieved by spraying the coolant in the internal volume of the emergency shell through the nozzles (nozzles) of this system. Such nozzles are called sprinkler nozzles, and the part of the emergency cooling system that provides the coolant to the sprinkler nozzles is called the sprinkler system.

In this case, the coolant is collected with its further supply through pipelines to the switchgear and to the sprinkler nozzles.

Known technical solutions (Margulova T.Kh. Nuclear power plants:

Textbook for high schools. - 3rd ed., Revised. and add. - M .: Higher school, 1978, p. 360 with silt.), In which to collect the coolant falling on the floor of the sealed enclosure, in case of accidents with rupture of the coolant circuit of the switchgear, a sump tank is used, in which the emergency coolant reserve is also stored. Thus, the emergency supply of coolant is returned to its place of storage. In the event of an accident, the coolant is supplied to the switchgear and to the sprinkler nozzles by pumps from the pit tank, drains onto the floor of the emergency shell and flows by gravity back to the pit tank, which is located below the floor of the emergency shell in the foundation plate, after which the process is repeated. The disadvantage of this solution is that the long-term storage of the coolant in the pit tank requires the fulfillment of additional requirements for its design, because it is part of the emergency containment containment circuit. In addition, it is necessary to constantly maintain and monitor the quality of the coolant in the pit tank during the entire life of the nuclear power plant, which requires the installation of additional equipment, maintenance of this equipment and, therefore, additional operating costs.

The closest technical solution to the proposed one is a power plant (patent RU 2102800 C1, IPC G21C 15/18, priority 15.08.1996, publ. 01.20.1998), containing a water reactor installed in the emergency (protective) shell, connected by circulation pipelines for hot and cooled coolant to the steam generator, sprinkler system, fuel storage pool with emergency coolant reserve, pit, check valve and emergency and / or normal cooling system, consisting of a heat exchanger and a cooling pump, the suction pipe of which is connected through the shutoff valves to the drain pipe of the fuel storage pool, the pit and the circulation pipe for the hot coolant, and the discharge pipe is connected with a non-return valve, the power plant is equipped with two jet pumps of higher and lower capacity, the inlet sections of the nozzles (or nozzles) of which are interconnected and connected to the image to the discharge valve of the cooling pump discharge pipe, the suction nozzles of both jet pumps are connected via non-return valves to the suction pipe of the cooling pump, while the jet pump diffuser is connected to the circulation pipes for hot and cooled coolant, and the jet pump diffuser of lower capacity is connected to the inlet pipe for fuel storage pool.

The emergency cooling system of such a power plant makes it possible to collect the coolant falling on the floor of the containment shell during accidents with a coolant leak and for any other reason, as well as long-term cooling of the switchgear and the internal volume of the emergency shell. At the same time, it is proposed to use the pit only for collecting liquid resulting from accidents with a primary circuit leak, and the necessary emergency coolant supply is in the holding pool.

The salient features of this technical solution are:

Размещение вне противоаварийной оболочки отсекающих вентилей системы аварийного охлаждения.

Placement of shut-off valves of the emergency cooling system outside the emergency shell.

Наличие приямка нижней части противоаварийной оболочки для сбора жидкости, охлаждающей реактор и внутренний объем противоаварийной оболочки при авариях с разрывом конура теплоносителя РУ.

The presence of a pit of the lower part of the emergency shell for collecting liquid cooling the reactor and the internal volume of the emergency shell during accidents with rupture of the coolant circuit of the reactor fluid.

The disadvantage of this technical solution is that:

- shut-off valves are located outside the emergency shell, which, if the emergency cooling system piping breaks outside the emergency shell, can lead to the loss of all coolant entering the pit, despite the presence of shut-off valves, and, as a result, a design basis accident can turn into a serious accident with the melting of the reactor core;

- the possibility of installation under the ULR reactor is not provided, therefore, the installation of the ULR would entail a significant increase in the height of the reactor building, which would reduce its stability, especially with regard to seismic effects;

- there are no devices for cleaning the coolant coming from the pit into the emergency cooling system and into the sprinkler system.

The objective of the present invention is to develop an emergency cooling system for a nuclear power plant and the internal volume of the emergency shell, which allows for increased safety of nuclear power plants by using a melt localization device without significantly increasing the height of the reactor building and providing the possibility of cooling the melt localization device in passive mode.

The technical result of the present invention is to increase the safety of nuclear power plants through the use of a melt localization device without significantly increasing the height of the reactor building and providing the possibility of cooling the melt localization device in passive mode, as well as by the possibility of filtering the coolant and the safe placement of shut-off valves for pipelines.

The technical result is achieved by the fact that in the known emergency cooling system of a nuclear power plant containing a sealing circuit, sprinkler nozzles located inside a sealed emergency shell, and a recess for collecting coolant in the floor of the emergency shell, at least one pump connected to the recess by a suction pipe with a heat exchanger and shut-off valve installed in it, and discharge pipelines connecting the pumps to the sprinkler nozzles and the reactor of a nuclear power plant, a vertical shaft is additionally installed in the recess, in the upper part of which there is a reactor, and in the lower part, a melt localization device, around the lower part of the shaft a water collector is located, connected to the pumps by suction pipelines passing through at least one valve chamber, in which shut-off valves are located, and at least one hole is made in the wall of the lower part of the shaft with the possibility of Tew of coolant to the melt localization device.

It is rational to equip the system with a reservoir with a coolant supply connected to the suction pipe.

It is preferable to use a spent nuclear fuel storage pool as a reservoir with a coolant reserve.

It is preferable to perform valve chambers with access from above through the mines from a level above the maximum possible level of coolant.

It is recommended to equip the catchment with filtering devices integrated into a single whole by a collector connected to the suction pipelines.

Brief Description of the Drawings

The invention is illustrated by drawings, where:

in FIG. 1 shows an emergency cooling system for a nuclear power plant in a preferred embodiment in a situation of maximum coolant level in an accident.

in FIG. 2 is a sectional view illustrating an arrangement of an emergency cooling system of a nuclear power plant in one embodiment of the invention.

in FIG. 3 is a sectional view of the emergency cooling system of a nuclear power plant in section 1-1 shown in FIG. 2.

In FIG. 1, 2, 3 the following notation is given:

1 - reactor;

2 - device localization of the melt;

3 - mine;

4 - holes in the shaft wall;

5 - a catchment basin;

6 - valve chambers

7 - walls of the shaft of the valve chambers;

8 - blocks of filter modules;

9 - collector;

10 - contour sealing the emergency shell;

11 - suction piping with shut-off valves;

12 - the floor of the emergency shell;

13 - emergency cover;

14 - sprinkler nozzles;

15 - pump;

16 - heat exchanger;

17 - exposure pool.

The reactor 1 is located in the shaft 3 in the emergency shell 13.

Under the reactor 1 in the shaft 3 is a device for the localization of the melt 2.

Here, in the emergency shell 13 is an emergency cooling system.

Under the reactor 1 in the emergency shell 13, a recess is made in which a shaft 3 is vertically mounted, in the upper part of which there is a reactor 1, and in the lower part, a melt localization device 2.

Around the bottom of the shaft 3 there is a catchment 5 and two separate valve chambers 6 with suction pipes with shut-off valves 11. As shown in FIG. 1, the valve chambers 6 are not filled with coolant in any accident, since access to them is from above through the mines from a level above the maximum possible emergency level of the coolant.

The water collector 5 preferably comprises filtering module blocks 8 and a manifold 9 connected by a suction pipe 11 to a pump 15 supplying a heat carrier to the sprinkler nozzles 14. The suction pipes 11 with shut-off valves are connected to heat exchangers 16 for cooling the heat carrier.

In one embodiment of the invention, the water collector 5 and at least two valve chambers 6 are located around the shaft 3 so that the wall of the shaft 3 of the reactor 1 is at the same time the inner wall of the water collector 5 and the valve chambers 6 and separates them, as shown in FIG. 2. The use of two or more valve chambers 6 increases the reliability of the emergency cooling system by ensuring the operation of the system in case of failure of one of the suction pipelines 11. In this case, the shut-off valves in the corresponding valve chamber 6 are closed, continuing the flow of coolant through the suction pipelines that have remained operational 11. Currently, in the used emergency cooling systems, the suction pipelines and pumps are duplicated, while the sprinkler system is divided into two independent channels, which when using the claimed emergency cooling system also requires the use of two valve chambers 6.

On the floor of the sump 5, in a preferred embodiment, blocks of filter modules 8 are installed, and in the valve chambers 6 shut-off valves and suction pipes 11 connecting the manifold 9 to the pumps 15. In the preferred embodiment, the shaft 3 has openings 4 connecting the premises of the sump 5 with the inside of the shaft reactor 3, where a melt localization device 2 is installed.

The emergency cooling system preferably comprises at least one reservoir with a coolant connected to the suction pipe 11 with shut-off valves, configured to supply coolant to the reactor 1 and to the sprinkler nozzles 14 for cooling the nuclear power plant in the event of an accident. In a preferred embodiment, a spent fuel pool 17 is used as one of these tanks.

The sealing circuit of the emergency shell 10 extends inside the walls of the catchment 5 and valve chambers 6.

The level of the walls of the shafts of the valve chambers 7 and the level of the upper edge of the melt localization device 2, as shown in FIG. 1, exceed the maximum level of the coolant inlet of the lower part of the emergency shell in any accident, therefore, the coolant cannot get into the valve chambers 6 and the melt localization device 2. In case of accidents, the coolant is outside the melt localization device 2 and cools it in passive mode in case of a severe accident.

Preferred Embodiment

The description and accompanying drawings are illustrations of the invention, which should not be construed as limiting its scope.

Various specific details are described in order to facilitate a comprehensive understanding of the invention. However, in some cases, well-known or traditionally used parts are not described so as not to clutter up the description.

Unless otherwise specified, all technical and scientific terms used in the present description have the meanings that are accepted among specialists in the field of technology to which the present invention relates.

When the NPP operates at power, there is no liquid in the catchment 5, and it is filled with coolant only in case of an accident.

The emergency cooling system delivers a solution of boric acid to the reactor circuit with a concentration sufficient to maintain subcriticality of the active zone of the nuclear power reactor 1 at all stages of the accident with the flow of the reactor coolant circuit.

At the initial stage of accidents with leaks of the coolant circuit of the switchgear, emergency stocks of coolant are used, in particular from the holding pool 17. After emergency stocks of coolant are received in catchment 5, organization of recirculation (up to 30 days) of coolant from catchment 5 is provided.

With increasing pressure and / or temperature in the internal volume of the emergency shell 13, the sprinkler nozzles 14 are automatically turned on. Then the sprayed coolant cools the internal volume of the emergency shell 13 and lowers the pressure in it, after which it flows by gravity into the catchment 5.

Recirculation of the coolant is as follows. After falling into the reactor 1 and in the internal volume of the emergency shell 13, the coolant flows onto the floor of the emergency shell 13, from where it flows by gravity into the water collector 5 located below the floor level 12 of the emergency shell. Then, through the blocks of filter modules 8, made with the possibility of cleaning the coolant from debris, the coolant enters the manifold 9, and from there to the suction pipes 11 with shut-off valves. Next, the coolant enters the heat exchangers 16, in which it is cooled, and by pumps 15 is again fed into the reactor 1 and, if necessary, to the sprinkler nozzles 14.

In addition, the coolant trapped in the water collector 5 through the openings 4 in the shaft wall enters the shaft 3 of the reactor 1, which allows cooling the melt 2 localization device from the outside in the passive mode during a severe accident with core melting, which further increases the safety of the nuclear power plant.

In the event of a breakdown in the pipelines of the emergency cooling system outside the emergency shell 12, the defective section can be shut off by one of the shut-off valves, which are located in each valve chamber 6, and the coolant will not be lost.

The technical and economic effect of the invention is as follows:

1. Improves the safety of nuclear power plants in general.

2. Increases the stability of the reactor building to capsize by reducing the height of the reactor building, which reduces the cost of the emergency shell and the reactor building as a whole by reducing the number of materials and the amount of work required for their construction.

3. The seismic resistance of the reactor building is increased by reducing the height of the reactor building.

4. The number of sealed elements of the emergency containment sealing circuit is reduced by installing the entire water collector in the sealed emergency containment shell. The cost of leaky structures, their installation, monitoring and maintenance is much lower than tight.

Industrial applicability

The emergency cooling system of a nuclear power plant can be used in nuclear power plants equipped with a melt localization device and can increase their safety in seismic impacts, design and severe accidents.

Claims (6)

1. The emergency cooling system of the nuclear power plant and the internal volume of the emergency shell, containing sprinkler nozzles located inside the sealed emergency shell, and a recess for collecting coolant in the floor of the emergency shell, at least one pump connected to the recess by a suction pipe with a heat exchanger installed in it and a shut-off valve, and discharge pipelines connecting the pumps to the sprinkler nozzles and the reactor of a nuclear power plant, characterized in that a vertical shaft is installed in the recess, in the upper part of which the reactor is located, and in the lower part, a melt localization device, a water collector is placed around the lower part of the shaft connected to the pumps by suction pipelines passing through at least one valve chamber in which shut-off valves are located, and at least one opening is made in the wall of the lower part of the shaft with the possibility of heat transfer Pure to the melt localization device. 2. The system according to p. 1, characterized in that it is equipped with a reservoir with a coolant supply connected to the suction pipe. 3. The system according to claim 2, characterized in that a spent fuel pool is used as a reservoir with a coolant reserve. 4. The system according to p. 1, characterized in that the discharge pipelines connecting the pumps and heat exchangers with the reactor of a nuclear power plant are equipped with check valves. 5. The system according to p. 1, characterized in that the valve chambers are made with access from above through the mines from a level above the maximum possible emergency coolant level. 6. The system according to claim 1, characterized in that the catchment is equipped with filtering devices integrated into a single collector connected to the suction pipelines.

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