RU2776024C1 - Method for passive cooldown of reactor plant with reactor under pressure - Google Patents

Abstract

FIELD: nuclear power industry.

SUBSTANCE: invention is aimed at an increase in the safety of nuclear hull research reactors and low-power reactors by using passive heat removal systems. A method for passive cooldown of a hull reactor includes placement of a reactor vessel with heat carrier circulation paths leading to the reactor core and diverting from the reactor core, as well as a neutron reflector in a pool with water, provision of a reactor plant with passive-action valves of natural circulation, providing safe heat removal from the reactor core and radiation channels in the reflector during the reactor cooldown in case of the absence of forced circulation. Pool water is used as the main heat absorber during the reactor cooldown.

EFFECT: increase in the safety and reliability of a system for cooldown of hull research reactors and low-power reactors.

5 cl, 5 dwg

Description

State of the art

The invention relates to systems for ensuring safe heat removal of residual energy release from the core of pressurized research reactors and low-power reactors.

Currently known installations usually have an emergency water injection system to prevent emptying of the reactor vessel with the core. There is also an emergency cooling system to remove residual power and cool the core. The emergency injection system usually includes high pressure pumps, medium pressure accumulators and low pressure pumps. The reactor emergency cooling system often uses a direct primary cooling system using special heat exchangers for final cooling. The water-filled pressurized accumulators are connected to the reactor's primary cooling circuit through shut-off valves sensitive to a lower primary pressure set point. The water filling the accumulators is under nitrogen pressure. However, the devices have a number of disadvantages. In such a system, there is no certainty that the injection of water from the accumulators for emergency core cooling occurs at the most favorable moment. Moreover, the injection of water into the primary circuit usually ends with the injection of nitrogen into it, which is used to increase the water pressure in the accumulators, so this method of emergency cooling carries the risks of gas entering the core and overheating of the fuel elements.

Known thermal heterogeneous reactor MIR.M1 with a moderator and a reflector of metallic beryllium. According to its design features, it is a channel and is placed in a pool of water. Such a design solution made it possible to combine the main advantages of pool and channel reactors, which made it possible to cool the channels with fuel assemblies and experimental channels with the coolant of the pool cooling circuit (CPB). However, in case of possible drying of the working fuel assemblies, for example, when gas is injected from the pressure compensator, the cooling of the outer surface of the channels by the FSC water is insufficient, and tubular aluminum fuel assemblies overheat and deform, which leads to the release of fission products into the primary circuit and fission gas products into the special ventilation system.

Known passive system of emergency cooling (patent US 20180261343 A1) reactor with a housing in a protective shell, immersed in the pool. In emergency situations, the water of the reactor pool is used to cool down the reactor, and the circulation of the cooling coolant through the reactor vessel is carried out due to natural convection. The disadvantage of this design is the complexity of the design of heat exchange equipment in the reactor pressure vessel and the likelihood of failure of the valves in the cooldown circuit, which makes the use of this method of core cooling insufficiently reliable, and dangerous if the valves are opened unauthorized.

Canadian patent CA 1070860 A describes a nuclear facility comprising a pressurized water pressure vessel (PWR) nuclear reactor, referred to as a fundamentally safe reactor. In accordance with this patent, the reactor vessel containing the core is made of steel and insulated from the outside. The reactor vessel, in the upper and lower parts of which systems of hydraulic seals are built, is immersed in a pool of water, which has its own vessel. The reactor vessel has an outlet pipe in the upper part for water, which passes through the core, is heated and, using an appropriate pipeline, is removed from the pool to the heat exchanger. From the heat exchanger, water is fed back through the corresponding return pipe to the inlet pipe located under the core in the reactor pressure vessel. A circulation pump is installed on the return pipe of the primary circuit. The reactor core, two branch pipes, a supply pipe and a return pipe with a circulation pump installed on it, as well as a heat exchanger form the first circuit of the reactor.

In the aforementioned Canadian patent, fundamental safety is ensured by the fact that the water in the pool is under pressure and a connection device is provided that, in the event of an accident, ensures the free flow of water from the pool into the lower connection on one side, as well as a connection device that ensures the free flow of water from the upper branch pipe to the pool on the other side. A possible accident can be expressed in the fact that if the primary circuit pump fails, this will lead to an increase in the temperature inside the reactor.

The device for connecting the lower connection to the water in the pool is an air seal or even an open pipe, into which, under normal operating conditions, no flow enters due to the appropriate selection of pressures, as explained below. The device for connecting the upper pipe to the water in the pool is a bell of gas or compressed steam installed in the upper part of a relatively high chamber, also filled with gas or steam. The height of said chamber must be such that the appropriate level of the liquid contained in the basin provides a pressure equal to the pressure drop of the water circulating in the reactor circuit. Thus, the lower nozzle of the reactor and the surrounding water in the pool are under the same pressure, i.e. there is no pressure difference between the two volumes, despite the fact that the two volumes communicate freely, the level of fluid flow between them is zero because the fluids in them are at the same pressure.

In case of failure of the circulation pump, the pressure drop between the lower and upper pipes disappears, the pressure in the upper pipe increases and the water from the reactor is pushed into the chamber filled with gas, and from it into the pool. At the same time, water from the pool enters the lower branch pipe and from it enters the core area. The water from the reactor is thus replaced by water from the pool, which is colder. It has already been mentioned above that the reactor pressure vessel is insulated. In addition, the water in the pool contains boric acid in such a way that, when it enters the reactor core, it gradually stops the reaction.

The volume of water in the pool is relatively large, which, in the event of a failure of the primary circuit pump, ensures a sufficiently large number of hours of operation of the reactor without overheating the core above a predetermined safe level.

From a purely technical point of view of operation, a fundamentally safe reactor of the type described above, which is the subject of Canadian patent CA 1070860 A, has the disadvantage that, in the case of using a high temperature reactor, its design is too complicated. Indeed, the pressure of the liquid in the pool must be higher than the pressure corresponding to the saturation temperature of the liquid leaving the core area, so either the amount of water in the pool is limited, then the shutdown of the reactor will be ensured, but cooling of the core is achieved only for a short time. , or the amount of water in the pool will be large, then a complex structure of reinforced concrete is required to ensure the retention of liquid under pressure. Therefore, this method of cooling leads, rather, to an increase in the risk of creating an emergency situation, rather than to an increase in the reliability of heat removal of the residual power.

Closest to the claimed invention in terms of the largest number of matching essential features, the method of passive cooling of a research reactor with a forced circulation loop through the core was chosen as a prototype for a safe pool-vessel type reactor (patent CN 100578683 C). Pressurized water-cooled reactor plant, includes a cylindrical vessel with an active zone located in a pool of water, a first forced cooling circuit with a pump, shut-off and control valves and a main heat exchanger that removes heat from the primary circuit, located in the room at a mark above the water level in pool, as well as a cooldown heat exchanger located directly in the pool and removing the heat of the residual energy release to the pool water, circulation through which is carried out by an auxiliary pump. In the event of failure of the auxiliary pump, when the reactor core cools down, hydraulically adjustable valves open on the outlet and inlet pipes of the reactor vessel, thereby ensuring the mass transfer of the coolant between the vessel and the pool due to natural circulation (EC).

The prototype and the claimed invention have the following similar essential features in the cooling method. The method for cooling down a reactor plant under pressure with a forced circulation loop through the core in the reactor vessel includes placing the reactor vessel with inlet and outlet nozzles in a pool of water, wherein the reactor inlet and outlet nozzles are equipped with EC valves that open when forced circulation through the core is disturbed and form path of natural coolant circulation through the core and the reactor pool.

However, a significant disadvantage of such a cooling system is the method of opening the EC valves using hydraulics, which can lead to valve failures during their opening and possible personnel errors when controlling the valves. A serious failure that reduces the safety of the reactor can be either a situation with an erroneous or unintentional opening of the EC valve when the reactor is operating at power, or a failure or jamming of the valve when a signal to open is given, so this cooldown method cannot be classified as a highly reliable method in terms of safety indicators.

This disadvantage is due to the fact that any active systems for influencing the cooling and cooling systems of the active zones of reactor plants bear the risk of failure or false operation, which leads to a decrease in the safety of reactor plants.

The inventive method of passive cooldown of a pressurized vessel reactor makes it possible to eliminate these drawbacks and, with a significant simplification of the design, to provide the required safety indicators with an increase in the allowable power of the reactor, which determines the magnitude of the residual energy release.

As an additional system for cooling down a reactor plant during a long-term shutdown, the proposed method provides for the use of a pool cooling circuit (COC), the operation of which is similar to the operation of a similar circuit in the MIR.M1 reactors and in the nominal mode provides cooling of the reflector blocks and experimental channels (cells) installed in them with irradiation devices, and after the reactor shutdown and the formation of a natural circulation loop in the core through the pool, the operation of the BER allows you to maintain the temperature of the water in the pool at a low level, which reduces evaporation and release of radioactive gases from the water surface.

The purpose of the proposed method is to increase the reliability of the method of passive cooldown of the pressure vessel reactor by using passive valves that are triggered by the action of gravitational forces when the hydraulic parameters and pressure in the primary cooling circuit of the reactor change, as well as the use of a passive valve in the COB, which ensures the formation of a natural circulation path of the coolant through neutron reflector blocks and irradiation channels (cells) located in the reflector, in case of failure of the forced circulation of the BER.

The essence of the invention

The invention is aimed at creating an efficient system for safe heat removal of residual energy release from the core of pressure vessel-type nuclear reactors, including research reactors, as well as heat removal from experimental channels (cells) in the neutron reflector of research reactors, completely built on passive operating principles and having an increased level of reliability operation in case of probable emergency situations with violation of forced circulation.

This goal is achieved by the fact that in the method of passive cooldown of a pressure vessel reactor using pool water as a thermal energy accumulator, in addition to passive EC valves on the inlet and outlet branch pipes of the reactor vessel located in the pool under the water level, it is provided that, in order to switch to to the mode of opening the shutters of natural circulation valves in emergency situations with violation of the circulation of the coolant in the primary circuit, valves are installed in the pressure compensator tank located in the upper part of the reactor pool and connected to the inlet and outlet tracts, which open when the pressure drop between the tracts and create a bypass channel coolant circulation between them, as well as a gas outlet channel from the pressure compensator, which ensures a decrease in pressure in the reactor cooling circuit and the supply of cold water from the pressure compensator to the reactor pressure vessel for core cooling. The passive principle of valve operation is based on the ratio of the resulting force of the pressure drop acting on the EC damper damper and the force of gravity acting on the damper.

In addition, in research reactors, to improve the efficiency of the system for safe heat removal from neutron reflector units and from training devices (DU) in the reflector, including the OS with fissile material (for example, when producing Mo-99 fragmentation from enriched uranium), under the neutron reflector , located in the pool around the reactor vessel at the level of the core, a reduced pressure chamber is formed by pumping the coolant into the pool cooling circuit (CPB), while ensuring the downward circulation of the coolant through the reflector with the cells with OS installed in it. A possible emergency situation with the cessation of forced circulation in the FCC when the reactor is running leads to a sharp deterioration in heat removal from the OS with a high energy release in the experimental cells. Therefore, after stopping the forced circulation of the CVD, it is required to organize intensive heat removal from the cells of the reflector, which is carried out by switching to natural circulation, provided by installing a EC disk valve on the side wall of the reduced pressure chamber. The valve is a metal disc pressed against the wall by the hydrostatic pressure of the liquid column in the pool in the presence of vacuum in the chamber, i.e. during the operation of COB. In the event of CBF operation stoppage, the disk freely hanging on the cables moves away from the wall under its own weight, forming an annular slot through which the coolant can be naturally circulated through the neutron reflector and OS in the cells of the reflector, thereby ensuring sufficient heat removal, even if the CBF has stopped working, and the reactor continues to operate at the nominal power level.

Thus, the inventive method of cooldown of a vessel reactor using passive valves provides not only a safe mode of heat removal from the core of research reactors and low-power power reactors, but also allows heat to be removed from OS with a high energy release installed in reflector cells of high-power research reactors at any modes of operation of cooling systems, including emergency situations.

The graphic representation of the passive cooldown method is presented in the form of coolant circulation schemes in the cooling systems at different stages of the research reactor cooldown, the vessel of which and the neutron reflector are located in the pool. On FIG. 1 shows a diagram of the normal circulation of the coolant in the primary circuit and the cooling circuit of the pool. On FIG. Figure 2 shows the flow diagram during the transition to natural circulation in the primary circuit through the pressure compensator tank in case of violation of forced circulation and the remaining increased pressure in the primary circuit. The pool cooling circuit is operating normally. On FIG. 3 shows the scheme of coolant flows during the transition to natural circulation in the primary circuit with a decrease in pressure in it. The coolant flow passes through the EC valves installed on the coolant circulation paths leading to the core and leaving the core, as well as through the EC valve installed in the pressure compensator vessel. The pool cooling circuit is operating normally. On FIG. 4 shows the transition to the scheme of evaporative cooling of water in the pool circulating through the core and the neutron reflector in case of failure of all forced cooling systems as a result, for example, of a complete blackout, pump breakdowns, breaks in circulation pipelines, unauthorized closing of valves, etc.

On FIG. Figure 5 shows a diagram of the cooling down of a low power power reactor. Since the coolant circulating in the primary cooling circuit has a high temperature (over 300°C), direct contact of the elements of the coolant circulation path with the pool water is highly undesirable. Therefore, the reactor vessel is made in the form of a Field tube and is enclosed in a heat-insulating casing with a gas (air) layer. The branch pipes of the circulation pipelines are located in the upper part of the reactor vessel and also do not have direct contact with the pool water. The pressure compensator, through which circulation of the hot coolant is minimal during normal operation of the reactor, is located in the reactor pool, as well as natural circulation valves on stagnant sections of pipelines connected to the coolant circulation paths leading to the core (lower part of the reactor pressure vessel) and draining from the core .

On the diagrams, the numbers indicate:

1 - Pool of the reactor plant;

2 - Reactor plant housing;

3 - The active zone of the reactor plant;

4 - Neutron reflector of the reactor plant with irradiation cells;

5 - Equipment room for the primary cooling circuit of the reactor;

6 - Circulation pump of the first reactor cooling circuit;

7 - Shut-off and control valves of the primary cooling circuit of the reactor;

8 - Heat exchanger (steam generator) of the primary cooling circuit of the reactor;

9 - Circulation pipelines of the first reactor cooling circuit;

10 - Drainage line from the primary circuit room;

11 - Coolant circulation path leading to the core;

12 - Coolant circulation path from the core;

13 - Primary circuit pressure compensator;

14 - EC valve in the pressure compensator, triggered by the pressure difference between the inlet and outlet pipes;

15 - EC valve stem in the pressure compensator;

16 - Ball valve for water of the EC valve in the pressure compensator;

17 - Ball valve for gas of the EC valve in the pressure compensator;

18 - Damper spring of the EC valve in the pressure compensator;

19 - Gas purge from the primary circuit pressure compensator to special ventilation;

20 - Safety valve against excess pressure in the primary circuit;

21 - EC valve, triggered by a decrease in pressure in the primary circuit;

22 - Ball damper of the EC valve, triggered by a decrease in pressure in the primary circuit;

23 - Damper spring of the EC valve, which was triggered by a decrease in pressure in the primary circuit;

24 - Reduced pressure chamber under the neutron reflector;

25 - Equipment room for the pool cooling circuit;

26 - Circulation pump of the pool cooling circuit;

27 - Shutoff and control valves of the pool cooling circuit;

28 - Heat exchanger of the pool cooling circuit;

29 - Circulation pipelines of the pool cooling circuit;

30 - Outlet pipeline of the pool cooling circuit from the low pressure chamber under the neutron reflector;

31 - Pipeline of the pool cooling circuit for returning the cooled coolant to the reactor pool;

32 - Drainage line from the pool cooling circuit room;

33 - EC valve, triggered by pressure increase in the low pressure chamber under the neutron reflector;

34 - Disc valve of the EC valve, triggered by an increase in pressure in the low pressure chamber under the neutron reflector;

35 - Cable suspension of the EC damper disc, triggered by an increase in pressure in the low pressure chamber under the neutron reflector;

36 - Cables for closing the EC valves, triggered by a pressure drop in the core and EC valves, triggered by a decrease in pressure in the primary circuit;

As a non-limiting example of the implementation of the method of passive cooldown of a pressure vessel reactor, the operation of the system for removing residual heat from a pressure vessel reactor located in a pool is considered. In the example shown, valves of a special design (Fig. 1, pos. 14, 21 and 34) are used as passive valves, in which, for example, metal balls are used as a damper (Fig. 2, pos. 16 or Fig. 3, pos. 22) forming a ball-cone seal in the raised (cocked) state and kept in this state from falling to the lower position by the pressure drop across the damper flap. This pressure differential creates an upward force that presses the ball of the flapper tightly against the tapered surface of the valve body, sealing it. The pressure drop across the ball dampers of the valves in the nominal mode of operation of the reactor is determined either by the difference between the hydrostatic pressure in the reactor pool (Fig. 1, item 1) and the pressure in the nozzle on which the valve is installed (Fig. 1, item 11, 12), or the pressure difference between the sections of the inlet and outlet pipes, to which a pressure compensator is connected with a double valve for water and gas located in it (Fig. 1, pos. 14-18).

Any violation of operational parameters for coolant flow in the primary circuit (Fig. 1, pos. 6, 7, 8, 9, 11, 12), leading to a decrease in forced circulation through the core, causes a decrease in pressure drop across the core and at the EC valve (Fig. 2, pos. 14-18) installed in the pressure compensator (Fig. 2, pos. 13). A decrease in the flow through the core can be caused, for example, by a breakdown or blackout of the circulation pump (Fig. 1, item 3), unintentional closing of the valve (Fig. 1, item 7) or a rupture of the circulation pipeline (Fig. 1, item 9 , 11, 12). In the latter case, if a rupture of the circulation pipelines occurs in the primary circuit equipment room (Fig. 1, item 5), or in the CSC equipment room (Fig. 1, item 25), water from the rooms lined with stainless steel sheet returns through the drain pipelines (Fig. 1, item 10 or item 32) back to the reactor pool, so the water level in the pool does not decrease in emergency situations with depressurization, which is an important safety factor for the reactor plant.

Due to the decrease in pressure drop across the EC valve (Fig. 2, item 13) in the pressure compensator (Fig. 2, item 13), there is a decrease in pressure pressing the ball valve (Fig. 2, item 16) to the seating surface of the valve body, and when a certain value of the pressure drop is reached, the ball valve lowers under its own weight, thereby opening the passage of the coolant along the bypass line between the inlet and outlet pipes, and, at the same time, through the stem (Fig. 2, item 15) opens the ball valve (Fig. 2, item 17) of the gas line, thereby forming a channel for the exit of compressed gas from the compensator into the special ventilation system (Fig. 2, item 19). For the spherical design of the valve damper in the pressure compensator, the solution to the problem of ensuring the required operation mode of the EC valve is achieved by fulfilling the relation

where

- зависимость перепада давления на байпасной линии между подводящим (Фиг. 2, поз. 11) и отводящим (Фиг. 2, поз. 12) патрубками от расхода теплоносителя в первом контуре, кг/см²;

- dependence of the pressure drop on the bypass line between the inlet (Fig. 2, item 11) and outlet (Fig. 2, item 12) branch pipes on the coolant flow in the primary circuit, kg/cm ² ;

- площадь проходного сечения посадочного отверстия шаровой заслонки клапана ЕЦ (Фиг. 2, поз. 14) в компенсаторе давления, см²;

- the area of the passage section of the landing hole of the ball valve of the EC valve (Fig. 2, pos. 14) in the pressure compensator, cm ² ;

- масса шаровой заслонки (Фиг. 2, поз. 16) на клапане ЕЦ в компенсаторе давления, кг.

- mass of the ball valve (Fig. 2, item 16) on the EC valve in the pressure compensator, kg.

The dynamic shock when the ball valve falls in the pressure compensator is softened by a damper spring (Fig. 2, item 18).

In the first seconds after the opening of the EC valve in the pressure compensator, relatively cold water is supplied from the compensator to the core after a short period of time due to the relatively short length of the supply pipeline to the reactor, which facilitates the task of cooling the core at the initial, most dangerous stage of the development of an emergency. when the level of residual energy release in the core is still very high.

The release of compressed gas from the pressure compensator leads to a gradual decrease in pressure in the primary circuit, as a result of which the down pressure of the ball valves (Fig. 3, item 22) of the EC valves (Fig. 3, item 21) decreases, due to which the pressure drop across these ball valves become insufficient to keep them in the upper (closed) state and they fall down under their own weight, thereby opening a shortened natural circulation path through the core (Fig. 1, pos. 3) and the pool (Fig. 1, pos. one).

For a ball valve damper design, the solution to the problem of ensuring the required operation mode of the EC valve on the inlet and outlet pipes is achieved by fulfilling the relation

where

- зависимость перепада давления на отводящем (Фиг. 2, поз. 12) и подводящем (Фиг. 2, поз. 11) патрубках от расхода теплоносителя в первом контуре, кг/см²;

- dependence of the pressure drop on the outlet (Fig. 2, item 12) and inlet (Fig. 2, item 11) branch pipes on the coolant flow rate in the primary circuit, kg/cm ² ;

- площадь проходного сечения посадочного отверстия шаровой заслонки клапанов ЕЦ, установленных, соответственно, на отводящем и подводящем патрубках, см²;

- area of the passage section of the landing hole of the ball valve of the EC valves, installed, respectively, on the outlet and inlet pipes, cm ² ;

- масса шаровой заслонки на клапанах ЕЦ, установленных, соответственно, на отводящем и подводящем патрубках, кг.

- mass of the ball damper on the EC valves installed, respectively, on the outlet and inlet pipes, kg.

Thus, the selection of the mass of the ball damper and the area of the orifice of the landing hole provide the required mode and sequence of operation of the EC valves on the reactor branch pipes. The dynamic impact of falling ball valves (Fig. 3, pos. 22) is softened by damper springs (Fig. 3, pos. 23).

After opening all EC valves in the primary circuit, the coolant circulation through the core during its cooldown is carried out along a shortened path of the reactor pressure vessel - pool , thereby ensuring safe heat removal at any level of residual heat release from the reactor. In this case, the pool water acts as an accumulator of thermal energy, and if there is a need to keep the temperature of this water at a low level, then this can be ensured using the pool cooling circuit. Thus, the BER provides not only the specified mode of cooling of experimental cells with irradiation devices during normal operation of the reactor, but also acts as an effective system for removing the residual energy release of the reactor facility.

However, in order to justify a high level of safety and thermal reliability, it is necessary to consider a complete failure of forced cooling systems, including CBF. In this case, there is a risk of overheating of the irradiation devices in the reflector (Fig. 4, item 4), especially if it is loaded with OS with fissile material (for example, to produce Mo-99 fragmentation from enriched uranium). In this case, to ensure safe cooling of such devices, the body of the reduced pressure chamber under the reflector is equipped with EC valves with butterfly valves (Fig. 4, item 34), freely hanging on cables (Fig. 4, item 35). During normal operation of the CB, the cables holding the shutter deviate from the vertical plane by an angle α and the butterfly valves are tightly pressed against the hole in the body (Fig. 3, item 34) under the action of the hydrostatic pressure of water in the pool and the vacuum created when the coolant is pumped out of the reduced pressure chamber and seal the chamber from the side of its body, providing a given flow rate of the coolant through the reflector and the experimental irradiation cells located in it. When the circulation in the COB ceases to act on the disk damper, the forces pressing it against the seating surface of the housing, and under its own weight, it moves away from the hole on the supporting cables and takes a position in the vertical plane, thereby opening the passage for the coolant from the pool under the reflector.

For the disc design of the EC valve damper, the solution to the problem of ensuring the required mode of valve actuation in the reduced pressure chamber (LPC) under the neutron reflector is achieved by fulfilling the relation

where

- зависимость перепада давления на дисковой заслонке (Фиг. 3, поз. 34) от расхода в КОБ, кг/см²;

- dependence of the pressure drop across the butterfly valve (Fig. 3, pos. 34) on the flow rate in the COB, kg/cm ² ;

- площадь проходного сечения посадочного отверстия дисковой заслонки в камере пониженного давления под отражателем нейтронов, см²;

- area of the flow section of the landing hole of the disk damper in the chamber of reduced pressure under the neutron reflector, cm ² ;

- масса дисковой заслонки на клапане ЕЦ, установленном в камере пониженного давления под отражателем нейтронов, кг;

is the mass of the disc damper on the EC valve installed in the reduced pressure chamber under the neutron reflector, kg;

α is the angle of deviation of the cables holding the disc from the vertical plane when the EC valve is closed, installed in the reduced pressure chamber under the neutron reflector, rad.

With the development of natural circulation through the core and the reflector with irradiation cells located in it, almost all the power of residual heat is used to heat the water in the pool. In this case, there are two main mechanisms of heat removal from this water - heat removal through the walls of the pool to the surrounding structures and heat removal by evaporation of water from the surface of the pool. Thermal radiation and heat removal from the air circulating above the surface of the pool can be neglected. However, these heat removal mechanisms are quite enough to maintain the temperature of the core and irradiation devices in an acceptable range, which, even in the presence of boiling on the surface of the fuel elements and OS, will not exceed the temperature value of ~115°C, determined by the saturation temperature of the water in the lower part of the pool. At the same time, depending on the volume of the pool, the maximum temperature in it will be reached in a few days, and then it will gradually decrease, taking into account the decrease in the level of residual energy release. Taking into account the most efficient heat removal mechanism, such as evaporation from the pool water surface, the average temperature in the pool will not exceed 85-90°C. The consequence of this mechanism of heat removal from the reactor being cooled down will be a gradual and slow decrease in the water level in the pool, but this decrease is easily compensated by fresh water replenishment.

Claims (5)

1. The method of passive cooling of a reactor plant with a pressure vessel located in the pool, in which valves with gates are used that open to form a natural coolant circulation loop through the core and the reactor pool, and connected to the ducts leading to the core and draining from the core coolant circulation, characterized in that the opening of the gates of the natural circulation valves is provided by gravitational forces when the pressure pressing the gate to the seat in the reactor cooling circuit decreases, and in order to switch to the mode of opening the gates of the natural circulation valves in the pressure compensator vessel located in the upper part of the reactor pool and connected to the inlet and outlet tracts, valves are installed that open when the pressure drop between the tracts decreases and create a coolant circulation channel between the inlet and outlet ducts and a gas outlet channel from the pressure compensator ion, which ensures a decrease in pressure in the reactor cooling circuit and the supply of cold water from the pressure compensator to the reactor pressure vessel to cool the core. 2. The method of passive cooling of the reactor plant according to claim 1, characterized in that the valves in the pressure compensator, which, when opened, create a coolant circulation channel between the inlet and outlet tracts and a gas outlet channel from the pressure compensator, are made in the form of a double valve of passive action, which works due to gravitational forces. 3. The method of passive cooling of the reactor plant according to claim 1 and / or 2, characterized in that the reactor vessel is made in the form of a Field tube and provides thermal insulation of the heated surfaces of the reactor plant coolant circulation path from the water in the pool, creating a gas gap using an external casing. 4. Method for passive cooling down of a reactor plant with a pressurized reactor vessel and a neutron reflector with irradiation cells located in the pool, in which valves with shutters are used that open to form a natural coolant circulation loop through the core and the reactor pool, and connected to the inlet to the core and to the coolant circulation paths from the core, characterized in that the opening of the gates of the natural circulation valves is provided by gravitational forces when the pressure pressing the gate to the seat in the reactor cooling circuit is reduced, and in order to switch to the mode of opening the gates of the natural circulation valves in the pressure compensator tank, located in the upper part of the reactor pool and connected to the inlet and outlet tracts, valves are installed that open when the pressure drop between the tracts decreases and create a coolant circulation channel between the inlet and outlet pipes acts and a channel for removing gas from the pressure compensator, which ensures a decrease in pressure in the reactor cooling circuit and the supply of cold water from the pressure compensator to the reactor pressure vessel for core cooling, and the design of the neutron reflector ensures the flow of coolant from the pool under the reflector into the reduced pressure chamber and then the coolant sent to the cooling circuit of the pool. 5. The method of passive cooling of the reactor plant according to claim 3, characterized in that the reduced pressure chamber is equipped with a natural circulation valve of passive action, the opening of which, when the forced circulation in the cooling circuit of the pool is stopped, ensures the development of natural circulation of the coolant through the reflector with irradiation cells.

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