RU2504031C1 - Device to remove excessive thermal energy from inner volume of nuclear power plant containment - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: device to remove excessive thermal energy from an inner volume of a nuclear power plant containment comprises three heat exchangers connected to each other with a system of light-boiling coolant, and the heat exchangers are mounted one above another. The lower heat exchanger is arranged in a reservoir for water strengthened from inside the containment in the middle part 7 of the side wall 8. The middle heat exchanger is fixed inside the containment in the upper part 20 of the side wall 8. The upper heat exchanger is fixed on the outer surface 31 of the wall of the containment dome. At the same time the system of light-boiling coolant is equipped with valves 48 and 47 with a bellows servodrive, which are installed accordingly on the inlet section 40 of the first heat exchanger, and on the inlet section 38 of the third heat exchanger.

EFFECT: efficient passive removal of excessive heat released by equipment.

7 cl, 5 dwg

Description

The invention relates to the field of nuclear energy, namely, to increase the safe operation of nuclear power plants and can be used in the unlikely emergency situation when a partial or complete disconnection of active energy sources occurs and it is required to passively remove excess thermal energy into the atmosphere from the internal volume of the containment and from the cooled water in the holding pool, which is constantly heated by the residual thermal energy of spent nuclear fuel.

A known system for the passive removal of excess thermal energy into the atmosphere from the internal volume of the protective shell of a nuclear power plant containing, internal and external heat exchangers filled with low-boiling liquid, is interconnected by tubes passed through the side wall of the protective shell. (USSR author's certificate No. 1829697, IPC: G21C 9/00 priority of 05/08/1991).

This system provides a passive removal of excess thermal energy into the atmosphere from superheated air of the internal volume of the containment in the event of an accident with the loss of electric power sources at a nuclear power plant (NPP). At the same time, the analyzed invention does not provide for the removal of excess thermal energy from water in the holding pool, where spent nuclear fuel is stored.

The closest technical solution to the proposed one is a device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant, containing three heat exchangers interconnected by a system of low-boiling coolant, one of which is installed in a water tank located inside the protective shell and valves. (RF patent No. 2030801, IPC: G21C 13/10, G21C 15/18 priority from 09/09/1992).

If necessary, this device provides a passive removal of excess thermal energy into the atmosphere only from the tank with water in which the equipment to be cooled is placed, air cooling in the volume of the protective shell is carried out by means of a sprinkler active system by means of a pump.

Over the 70-year period of operation of nuclear power plants and nuclear power plants, it was noted that the most common emergency situations are systems and equipment related to providing power to equipment groups: electric motor-pump, electric motor-fan, electric motor-compressor, and so on because of “failures” for general reasons. " But this equipment is necessary because of the increase in the specific loads on the equipment, the specific capacities of nuclear power plants and the convenience of managing power equipment: automatically, remotely and at the workplace.

One of the technical causes of the accident at the Fukushima-1 nuclear power plant was a failure for common reasons - the disappearance of electrical emergency power. But this is only an emergency; longer the emergency has developed into an accident. The power plant was designed in the USA in 1960 with requirements that satisfy the level of their knowledge at that time. Currently, the accumulated level of knowledge and operating experience is higher and at the same time others - higher capabilities of scientific departments, technological capabilities of industrial enterprises - manufacturers and operating organizations.

Based on the accumulated: level of knowledge, industrial experience in manufacturing equipment, operating circuits and equipment traces, operating experience and new regulatory requirements for design, manufacture and operation, it is recommended to develop and implement emergency passive systems in order to reduce and possibly eliminate the “human factor” . It is difficult to imagine a similar emergency situation at our nuclear power plants.

The objective of this invention is to reduce the influence of the "human factor", namely, if necessary, passively remove excess thermal energy from under the sealed part of the protective shell of a nuclear power plant, both from its air volume and simultaneously from the tank where spent nuclear fuel is stored under water , both in normal operating conditions, and in emergency situations, and during accidents.

The problem is achieved in that in the known device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant, containing three heat exchangers interconnected by a system of low-boiling coolant, one of which is installed in a water tank located inside the protective shell and valves, is new the fact that all heat exchangers are mounted one above the other, the first of which is located in the water tank is fixed in the middle of the side wall of the protective shell, Torah exchanger fastened inside the containment shell in the upper part of the side wall of the containment, and the third heat exchanger is mounted on the outer wall surface of the containment dome, wherein the servo valves are provided with bellows, and installed at the inlet portion of the first heat exchanger and the inlet portion of the third heat exchanger.

In addition, the water tank may be a holding pool for spent fuel nuclear fuel.

In addition, the first and second heat exchangers can be made in the form of flat sections located around the perimeter, respectively, of the water tank and the wall of the protective shell.

In addition, the panels of the first heat exchanger can rest on the bottom of the water tank on spring springs, and the upper part is attached to the wall of the tank through hinges.

In addition, the panels of the second heat exchanger can be freely suspended on the side wall of the containment.

In addition, the third heat exchanger can be mounted on the outer surface of the dome of the containment shell through hinges and sliding supports.

In addition, a valve with a bellows actuator installed in the inlet section of the first heat exchanger is adjusted to open at a lower pressure than a valve with a bellows actuator installed in the inlet section of the third heat exchanger.

The installation of all heat exchangers one above the other ensures that when the temperature of the low-boiling coolant in the first heat exchanger reaches 35 ° С, the natural circulation of the coolant in the system begins, namely the rise of the hot coolant and the lowering of the coolant.

The location of the water tank in the middle of the side wall of the containment is caused by the technology of reloading nuclear fuel.

The location of the second heat exchanger in the upper sealed part of the protective shell is caused by the fact that the upper part of the protective shell is the beginning of an ordered lowering flow of the water-vapor-gas mixture inside the protective shell during normal and non-standard operation. The upper arrangement of the third heat exchanger leads to increased natural circulation and increased removal of thermal energy from the first and second heat exchangers.

Mounting the third heat exchanger on the outer surface of the dome ensures a guaranteed return of thermal energy to the final absorber for ambient air, and in emergency cases for greater efficiency the heat exchanger can be watered from above with water.

The spent nuclear fuel discharged from the reactor has a sufficiently high residual energy release, which must be continuously removed for some time using cooled water, therefore it is placed in a water tank in the form of a pool for aging for a rather long time - the water tank under normal conditions is cooled under help active system.

Making the first and second heat exchangers flat creates an improved heat dissipation, and their location along the perimeter of the water tank and the wall of the containment shell allows you to place the maximum number of heat exchangers without cluttering the process volume.

The installation of the panels of the first heat exchanger in a water tank by means of spring springs and hinges provides compensation for the thermal expansion of the panels of the heat exchangers.

The suspension of the second heat exchanger allows you to compensate for the thermal expansion of its panels and pipelines.

The fastening of the third heat exchanger on the outer surface of the dome of the protective shell by means of hinges and sliding supports makes it possible to compensate for the expansion of the elements of the heat exchanger and the external power surface of the protective shell at different temperatures of the heat exchanger and the protective shell.

Different calibrations of the valve servomotors for opening provide a phased inclusion in the work of the first, second and third heat exchangers.

The following is a description of one of the many embodiments of the device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant, united by a single inventive concept, as shown in the following claims.

The invention is illustrated by drawings, where

figure 1 shows a tiered arrangement of heat exchangers;

figure 2 shows a cross section of the outer third heat exchanger;

figure 3 is a cross section of the pool of spent nuclear fuel with a view of the first heat exchanger;

figure 4 shows a cross section of the pool exposure;

5 shows a section of a valve with a bellows actuator;

A device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant consists of active and passive systems for removing excess thermal energy.

The active system for removing excess thermal energy contains heat exchangers made in the form of tubular panels 1, in which the circulation of the coolant is carried out by means of an electric pump 2.

The passive excess heat energy removal system consists of three heat exchangers interconnected by a closed hermetic circuit filled with a low-boiling coolant, for example, type C1 refrigerant approved for use by the International Agreement. The heat exchangers are arranged in tiers one above the other, the lower of which is the first, structurally made in the form of finned panels 3.

Tubular panels 1 of heat exchangers of an active system for removing excess heat energy and finned panels 3 of heat exchangers of a passive system for removing excess heat energy are installed in a water tank, which is a rectangular pool 4 of exposure to accommodate slipways 5 of spent fuel assemblies with burned out nuclear fuel that releases heat energy quite a long time.

The pool 4 is installed inside the hermetic layer 6 of the protective shell in the middle part 7 at the cylindrical side wall 8. The tubular panels 1 and finned panels 3 are located vertically, respectively, at the end wall 9 and along the side walls 10 and 11 of the holding pool 4, leaving the spent nuclear fuel free space in front of the gate 12 for slipways 5 of spent fuel nuclear fuel. Tubular panels 1 and finned panels 3 are mounted vertically on the bottom 13 of the pool 4 on the spring springs 14, with the top 15 and 16, the panels 1 and 3 are respectively attached to the walls 9, 10, 11 of the pool 4 by hinges 17 and 18. The pool 4 is closed by a power cover 19 serving as additional biological protection.

The second heat exchanger is installed inside the sealed layer 6 of the protective shell in the upper part 20 of the cylindrical side wall 8 and is structurally made in the form of panels 21 freely suspended on the brackets 22 vertically around the perimeter of the wall 8 of the protective shell.

The third heat exchanger is structurally made as a bundle of inclined finned tubes 23 with fin ribs placed in the honeycomb cells with distribution 24 and collecting 25 collectors. Between the levels of these collectors 24 and 25, a stabilizing collector 26 is installed, which allows holding the output ends of the tube bundle below the coolant level and eliminating pressure pulsation and heat transfer along the tube bundle. For drainage and recharge of the system of low-boiling coolant there is a device 27 connected to the system of low-boiling coolant through a valve 28 with a bellows actuator, which serves to maintain a constant level of refrigerant in the system of low-boiling coolant. The collecting manifold 25 and the stabilizing manifold 26 are interconnected by bypass 29 with a valve 30 for draining the finned tubes 23 of the third heat exchanger. The third heat exchanger is mounted on the surface 31 of the outer power layer 32 of the dome of the containment shell using hinges 33 and sliding bearings 34.

A closed hermetic circuit for a low-boiling coolant consists of a discharge pipe 35 for a heated coolant and a supply pipe 36 for a cooled coolant. The exhaust pipe 35 connects the outlet 37 of the panels 3 of the first heat exchanger to the input 38 of the distribution manifold 24 of the third heat exchanger, and the supply pipe 36 connects the output 39 of the collector 25 through the bypass 29 of the third heat exchanger to the input 40 of the panels 3 of the first heat exchanger. The outlet 35 and supply 36 pipelines are passed through the inner sealed layer 6 of the protective sheath using sealed penetrations 41 and 42, and through the outer power layer 32 of the sheath using sealed penetrations 43 and 44.

The panels 21 of the second heat exchanger are connected in parallel to the outlet 35 and supply 36 pipelines. The inlet 45 of the panels 21 is connected to the supply pipe 36, and their outlet 46 is connected to the outlet pipe 35. At the outlet 35 and supply 36 pipelines at the points of their connection, respectively, to the input 38 of the distribution manifold 24 of the third heat exchanger and to the input 40 of the panels 3 of the first heat exchanger valves 47 and 48 with bellows actuator.

Valves 47 and 48 with a bellows-type servo-actuator consist of: an airtight cover 51 of the guide cup 52 located in the sleeve-like body 49 in the corrugated rings 50, in which the stem 53 with the piston 54 at one end 55 is placed, a plate 56 for the seat saddle 57 at the other end 58, perforated guide 59 for the rod 53 and the inlet 60 and outlet 61 of the hole for the flow of low-boiling coolant, while an adjustable telescopic spring 63 is mounted between the piston 54 and the bottom 62 of the sleeve housing 49. The valve body is 49 47 and 48 are mounted on pipelines 35 and 36 along the flow path of the coolant at an obtuse angle with respect to the direction of flow of the coolant, so that the force of support of the coolant will be carried out under the plate 56 to squeeze it from the seat 57.

A device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant operates as follows. In the normal operation of a nuclear power plant, spent nuclear fuel fuel under water in the holding pool 4 continues to produce residual heat, which is constantly removed by the heat carrier, in this case, water to the tubular panels 1 of the heat exchanger of the active system for removing excess heat energy. In the tubular panels 1 of the heat exchanger, coolant is constantly forcibly pumped using an electric pump 2. It provides heat transfer, and maintaining a safe temperature of nuclear fuel. In this case, the passive excess heat energy removal system is in standby mode.

In the case of an unlikely accident, when a local or complete blackout of the power supply occurred at the station and the electric pump 2 of the active system for removing excess thermal energy stopped, and constant forced cooling with water, the residual heat of nuclear fuel ceased, then with an increase in the temperature of the cooling water, the system of passive removal of excess thermal energy. Heat removal occurs as follows. In the tank capacity of the spent nuclear fuel pool 4, the water and finned panels 3 of the first heat exchanger begin to heat up. The temperature of the low-boiling coolant located in the ribbed panels 3 starts to increase, respectively, and the pressure in the circuit of the low-boiling coolant begins to increase. Since the valve 48 with a bellows actuator is adjusted by means of an adjustable telescopic spring 63 to a lower pressure for opening the circulation circuit of the low-boiling coolant than the valve 47, when the temperature reaches 35 ° C, the force of the increased pressure of the low-boiling coolant affects the entire circuit and, having passed the outlet 61 and perforation guide 59 will begin to move the piston 54 by squeezing the plate 56 from the seat saddle 57, the coolant begins to circulate through the inlet 60 and outlet 61 By arranging low-boiling natural circulation of coolant 35 from a recovery and the feed conduits 36 between the panels 3 and 21 of the first and second heat exchangers. Excessive heat is removed into the containment. When the temperature reaches below the set, the valve 48 closes. If you want to continuously maintain a temperature close to the set temperature, the valve 48 may be partially open or with small vibrations to go to a neutral position. If the volume of the protective shell is not sufficient for receiving heat, the pressure in the circuit of the low-boiling coolant continues to increase until the opening pressure of the bellows of the valve 47 to the inlet 38 in the fin tubes 23 of the outdoor heat exchanger and the natural circulation of the low-boiling coolant begins to take place throughout the circuit, including the third a heat exchanger for removing heat into the atmosphere to the surrounding air.

The technical and economic effect consists in increasing the safety of a nuclear power plant by providing, in the case of unlikely electrical blackout of the entire nuclear power plant, to remove excess energy heat constantly emitted by the equipment passively.

Claims (7)

1. A device for removing excess thermal energy from the internal volume of the protective shell of a nuclear power plant, comprising three heat exchangers interconnected by a low-boiling coolant system, one of which is installed in a water tank located inside the protective shell, and valves, characterized in that all heat exchangers are mounted one above the other, the first of which, located in the water tank, is fixed in the middle part of the side wall of the protective shell, the second heat exchanger is fixed inside the protective cover Points in the upper part of the side wall of the containment, and the third heat exchanger is mounted on the outer wall surface of the containment dome, wherein the servo valves are provided with bellows and installed at the inlet portion of the first heat exchanger and the inlet portion of the third heat exchanger. 2. The device according to claim 1, characterized in that the water tank is a holding pool for spent fuel nuclear fuel. 3. The device according to claim 1, characterized in that the first and second heat exchangers are made in the form of panels located around the perimeter, respectively, of the water tank and the inner wall of the protective shell. 4. The device according to claim 1, characterized in that the panels of the first heat exchanger are mounted on the bottom of the water tank on spring springs and are attached to the wall of the tank by hinges at the top. 5. The device according to claim 1, characterized in that the panels of the second heat exchanger are freely suspended on the side wall of the protective shell. 6. The device according to claim 1, characterized in that the third heat exchanger is mounted on the outer surface of the dome of the protective shell by means of hinges and sliding supports. 7. The device according to claim 1, characterized in that the valve with a bellows actuator installed in the inlet section of the first heat exchanger is adjusted to open at a lower pressure than the valve with a bellows actuator installed in the inlet section of the third heat exchanger.

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