RU2810654C1 - Truss console of melt localization device (options) - Google Patents

Abstract

FIELD: nuclear industry.

SUBSTANCE: melt localization devices (hereinafter referred to as MLDs), equipped with a vessel for receiving and distributing the melt. The truss console of the melt localization device contains a power frame consisting of parallel and radial power ribs, outer, middle and inner shells, an upper power plate and a lower power plate forming external parallel and internal parallel sectors, and radial sectors placed between them. Additionally, it contains a manifold, as well as external radial sectors, first and second branch pipes passing through the outer power shell and intended for connecting the manifold with pipelines. The distance from the first pipe to one end of the manifold is less than the distance from the second pipe to the other end of this manifold. Sprinkling devices are located in some internal radial sectors and connected to distribution pipes. The outer parallel first sector and the inner parallel first sector are made empty, and the remaining outer and inner parallel and radial sectors are filled with protective concrete.

EFFECT: improving the reliability of the melt localization device.

3 cl, 6 dwg

Description

The invention relates to melt localization devices (hereinafter referred to as MLD), equipped with a vessel for receiving and distributing the melt, in particular, to mechanisms that ensure the preservation of the structural integrity of the MLL in the event of severe accidents.

The greatest radiation hazard is posed by accidents with core melting, which can occur with multiple failures of core cooling systems.

In such accidents, the core melt - corium, melting the internal reactor structures and the reactor vessel, flows beyond its boundaries, and due to the residual heat generation remaining in it, it can disrupt the integrity of the sealed shell of the nuclear power plant - the last barrier to the release of radioactive products into the environment.

To eliminate this, it is necessary to localize the core melt (corium) that has leaked from the reactor vessel and ensure its continuous cooling until complete crystallization. This function is performed by a melt localization device, which prevents damage to the sealed shell of a nuclear power plant and thereby protects the population and the environment from radiation exposure during severe accidents of nuclear reactors.

Known HLR designs intended for localization and cooling of the melt, as a rule, contain the following main elements: a guide apparatus mounted on a special support element - a console truss, a housing filled with sacrificial materials. In addition, various communication systems are connected to the HLR (instrument sensors, corium irrigation channels, channels for steam removal, etc.), ensuring the functioning of the HLR in the conditions of a severe accident.

The console truss protects the housing and internal communications of the ULR from destruction from the corium and is a support for the guide plate, which transmits static and dynamic impacts to the console truss, secured in the reactor shaft. The cantilever truss also ensures the operability of the guide plate in the event of its destruction.

A well-known truss-console [1, 2, 3, 4] ULR, containing parallel and radial power ribs, outer, middle and inner shells, an upper power plate and a lower power plate, forming internal and external sectors in which pipe covers are made, providing connection of instrumentation and control sensors, corium irrigation channels (collector with distribution pipelines), providing supply of cooling water from external sources, which flows through the irrigation channels through a console truss from above to the corium, channels for steam removal, ensuring steam removal from the sub-reactor room of the concrete shaft into the containment zone at the stage of corium cooling in the ULR housing, channels for air supply, providing air supply for cooling the guide plate during normal operation.

The disadvantage of the cantilever truss is that it cannot withstand the beyond-design thermal load that occurs in the absence of cooling of the free surface of the core melt (melt mirror) inside the ULR housing. For the load-bearing elements of the cantilever truss and the fastening elements of the cantilever truss in the reactor shaft, these effects are especially destructive during prolonged exposure to high temperatures on the cantilever truss.

The technical result of the claimed invention is to increase the reliability of the melt localization device.

The problems to be solved by the claimed invention are the following:

- ensuring, in case of beyond design basis accidents, the supply of water to the space inside the HLR housing to reduce the temperature of the vapor-gas mixture and provide convective cooling of the HLR equipment located above the melt surface;

- ensuring, in case of beyond design basis accidents, the supply of water to the surface of the melt to reduce the impact of thermal radiation from the side of the melt mirror on the above equipment of the HLR and to stop the release of aerosols.

The problem is solved by implementing the following embodiments of the invention.

Option 1.

In accordance with the first option, the truss-cantilever of the melt localization device contains a load-bearing frame consisting of parallel and radial load-bearing ribs (1), (2), outer, middle and inner shells (3), (4), (5), upper force plate (6) and lower force plate (7), forming external parallel first, second, third and fourth sectors (8), (9), (10), (11), internal parallel first, second, third and fourth sectors (12), (13), (14), (15) and radial sectors (16) placed between them in such a way that the parallel first external and first internal sectors (8), (12) lie on the same Cartesian axis with the parallel third external and third internal sectors (10), (14) and perpendicular to the axis on which parallel second external and second internal sectors (9), (13) lie, as well as parallel fourth external and fourth internal sectors (11), (15), according to the invention, additionally contains a manifold (17) FIG. 1, extending from the radial ribs of the outer radial sectors (16a), (16b), adjacent to the first parallel outer sector (8), through the outer parallel second, third and fourth sectors (9), (10), (11), and also outer radial sectors (16), first and second pipes (18a), (18b) FIG. 1, passing through the external power shell (3) and intended for connecting the manifold (17) with pipelines (19), the distance from the first nozzle (18a) to one end of the manifold (17) is less than the distance from the second nozzle (18b) to the other end of the specified collector (17), distribution pipes (20) fig. 2, fig. 3, connected from below to the collector (17) and passing from it through the middle power shell (4), spray devices (21) FIG. 2, fig. 3 located in some internal radial sectors and connected to the distribution pipes (20), while the external parallel first sector (8) and the internal parallel first sector (12) are made empty, and the remaining external and internal parallel and radial sectors are filled with protective concrete (22 ).

Additionally, in the cantilever truss, according to the invention, on the outer side of the outer power shell (3) there are support legs (23) with anchor ribs (24), which makes it possible to increase the reliability of fastening the cantilever truss to the reactor shaft.

In accordance with the first option, an essential feature of the claimed invention is the use of a manifold (17) with branch pipes (18), (20), pipelines (19), and spray devices (21) connected to it in the console truss, which allows the formation of a single water cooling circuit , which, due to the hydrostatic supply of cooling water from external systems, ensures its redistribution within a single manifold (17) regardless of the difference in cooling water flow rates in each of the nozzles (18), provides effective water, steam-water and steam-gas cooling of the console farm, guide plate, thermal protection of the housing flange and the melt mirror during the localization of the melt in the ULR housing, preventing overheating of the console truss and guide plate, ensuring their strength and resistance to external influences in conditions of direct exposure to thermal radiation from the melt mirror and improving the outflow of heat from hot areas of the load-bearing frame and protective concrete of the cantilever truss during prolonged heating.

In addition, if the water supply valves fail, the water cooling circuit formed by the manifold (17) of FIG. 1 with pipes connected to it (18) FIG. 1, (20) fig. 2, pipelines (19) FIG. 1, spray devices (21) FIG. 1, allows for efficient water cooling of the melt mirror with water coming from the nozzles (18) into the manifold (17), through which the water is redistributed into the nozzles (20) of FIG. 2, fig. 3, of which through the spray devices (21) FIG. 2, fig. 3, it directly or indirectly enters the vapor-gas environment located above the melt mirror.

In addition, the water cooling circuit, formed by the manifold (17) with pipes (18), (20), pipelines (19), and spray devices (21) connected to it, ensures a reduction and equalization of the temperature of the console truss, the guide plate and flange of the ULR housing, reducing the temperature of the slag cap and crust located on the surface of the melt, reducing the temperature of the vapor-gas environment located above the surface of the melt, which leads to cooling of the bottom of the nuclear reactor vessel and the surrounding elements of the reactor shaft equipment.

In addition, the water cooling circuit formed by the manifold (17) with pipes (18), (20), pipelines (19), and spray devices (21) connected to it provides additional cooling of the console truss due to heat flows through the truss elements - console and along protective concrete to the elements forming the specified contour.

Option 2.

In accordance with the second option, the truss-cantilever of the melt localization device contains a load-bearing frame consisting of parallel and radial load-bearing ribs (1), (2), outer, middle and inner shells (3), (4), (5), upper force plate (6) and lower force plate (7), forming external parallel first, second, third and fourth sectors (8), (9), (10), (11), internal parallel first, second, third and fourth sectors (12), (13), (14), (15) and radial sectors (16) placed between them in such a way that the parallel first external and first internal sectors (8), (12) lie on the same Cartesian axis with the parallel third external and third internal sectors (10), (14) and perpendicular to the axis on which parallel second external and second internal sectors (9), (13) lie, as well as parallel fourth external and fourth internal sectors (11), (15), according to the invention, further comprises a first manifold (17a) of FIG. 4, extending from the radial edge of the outer radial sector (16a) adjacent to the first parallel outer sector (8), through the outer second parallel sector (9), to the radial edge of the outer radial sector (16b) adjacent to the third parallel outer sector (10 ), the first pipe (18a) Fig. 5, passing through the outer power shell (3) and intended for connection with the first pipeline (19a) of FIG. 5 in such a way that the distance from the first pipe (18a) to one end of the first manifold (17a) is less than the distance to its other end, the second manifold (17b) of FIG. 4, extending from the radial edge of the outer radial sector (16b) adjacent to the first parallel outer sector (8), through the outer fourth parallel sector (11), to the radial edge of the outer radial sector (16d) adjacent to the third parallel outer sector (10 ), second pipe (18b) Fig. 5, passing through the outer power shell (3) and intended for connection with the second pipeline (19b) FIG. 5 in such a way that the distance from the second pipe (18b) to one end of the second collector (17b) is less than the distance to its other end, the distribution pipes (20) of FIG. 2, fig. 3, connected from below to the first and second collectors (17a), (17b) and passing from them through the middle power shell (4), spray devices (21) FIG. 2, fig. 3, located in some internal radial sectors and connected to the distribution pipes (20), external parallel first and third sectors (8), (10), internal parallel first and third sectors (12), (14) are made empty, and the rest are external and the internal parallel and radial sectors are filled with protective concrete (22).

Additionally, in the cantilever truss, according to the invention, on the outside of the outer power shell (3) there are support legs (23) with anchor ribs (24), which makes it possible to increase the reliability of fastening the cantilever truss to the reactor shaft.

In accordance with the second option, an essential feature of the claimed invention is the use of the first collector (17a) of FIG. in the cantilever truss. 4 with the first pipe (18a) FIG. 5 connected to the first pipeline (19a) of FIG. 5 such that the distance from the first pipe (18a) to one end of the first manifold (17a) is less than the distance to its other end, and the use of the second manifold (17b) of FIG. 4 with the second pipe (18b) FIG. 5, connected to the second pipeline (19b) of FIG. 5 in such a way that the distance from the second branch pipe (18b) to one end of the second manifold (17b) is less than the distance to its other end. Branch pipes (20) of Fig. are connected to the first (17a) and second (17b) independent collectors. 2, fig. 3, with spray devices (21) FIG. 2, fig. 3, which allows the formation of two independent water cooling circuits, which, due to the hydrostatic supply of cooling water from external systems, provide independent from each other effective water, steam-water and steam-gas cooling of the console farm, guide plate, thermal protection of the housing flange and the melt mirror during the localization process melt in the ULR body, preventing overheating of the cantilever truss and guide plate, ensuring their strength and resistance to external influences under conditions of direct exposure to thermal radiation from the melt mirror and improving the outflow of heat from hot areas of the load-bearing frame and protective concrete of the cantilever truss during prolonged heating .

In addition, if the water supply valves fail, the water cooling circuit formed by the collectors (17a) and (17b) of FIG. 5 with pipes (18a), (18b) connected to it; FIG. 5 and pipes (20) Fig. 2, fig. 3, pipelines (19a), (19b) FIG. 5, spray devices (21) FIG. 2, fig. 3, allows for effective water cooling of the melt mirror with water coming from the nozzles (18a), (18b) into the collectors (17a), (17b), through which the water is redistributed into the nozzles (20), from which through the spraying devices (21), it directly or indirectly enters the vapor-gas environment located above the melt mirror.

In addition, the water cooling circuit formed by collectors (17a), (17b) with pipes (18a), (18b), (20) connected to them, pipelines (19a), (19b), spray devices (21), ensures a decrease and equalization of the temperature of the cantilever truss, the guide plate and the flange of the ULR housing, a decrease in the temperature of the slag cap and crust located on the surface of the melt, a decrease in the temperature of the vapor-gas environment located above the surface of the melt, which leads to cooling of the bottom of the nuclear reactor vessel and its surrounding elements reactor shaft equipment.

In addition, the water cooling circuit formed by collectors (17a), (17b) with pipes (18a), (18b), (20) connected to it, pipelines (19a), (19b), spray devices (21), provides additional cooling of the cantilever truss due to heat flows through the elements of the cantilever truss and through the protective concrete to the elements forming the specified contour.

In fig. 1 shows a melt localization device with a cantilever truss, made in accordance with the claimed invention.

In fig. 2a shows a cantilever truss (without an upper power plate) of a melt localization device with elements of a water cooling circuit, made in accordance with the claimed invention.

In fig. Figure 2b shows part of the cantilever truss with the upper power plate.

In fig. Figure 3 shows a sectional view of part of the cantilever truss (without the upper load plate), made in accordance with the claimed invention.

In fig. Figure 4 shows a top view of a console farm with two collectors.

In fig. 5a shows a part of a cantilever truss with two collectors with the installation location of one of the pipes in the first collector.

In fig. Figure 5b shows a part of a cantilever truss with two collectors with the installation location of one of the pipes in the second collector.

In fig. 6 shows a general view of the melt localization device.

As shown in FIG. 1-6, the melt localization device contains a guide plate (25) installed under the nuclear reactor body (26) and supported by a cantilever truss (27). Under the console truss (27) there is a housing (28) of the ULR with a filler (29) for receiving and distributing the melt. In the upper part of the housing (28) of the ULR there is a flange (30) equipped with thermal protection (31). The filler (29) consists of several cassettes (32) stacked on top of each other, each of which contains one central and several peripheral holes (33). In the area between the upper cassette (32) and the flange (30) of the housing (28) of the LLR, along the perimeter of the housing (28) of the LLR, water supply valves (34) are located. The cantilever truss (27) contains a power frame, which consists of radial power ribs (2) (Fig. 2, 3), parallel power ribs (1), an external power shell (3), an internal power shell (4), a middle power shell shell (5), upper force plate (6) (Fig. 1), lower force plate (7). Inside the console farm (27), a water cooling circuit is formed, consisting of a manifold (17) (Fig. 2) with pipes (18), (20), pipelines (19), and spray devices (21) connected to it. On the outer side of the outer power shell (16) there are support legs (23) (Fig. 4) with anchor ribs (24).

The truss console of the melt localization device operates as follows.

As a result of direct interaction with the core melt and under the influence of thermal radiation from the side of the melt mirror, a temperature gradient is established inside the cantilever truss (27), which leads to heat flows through the elements of the power frame of the cantilever truss (27). Improved heat transfer from hot areas of the load-bearing frame and protective concrete (22) during prolonged heating is ensured by a water cooling circuit formed from a collector (17) with pipes (18), (20), pipelines (19), and spray devices connected to it (21), which performs its functions in the following modes:

- mode 1 - in case of beyond design basis accidents in case of failure to open the water supply valves (34), but after completion of the following processes: cessation of the flow of core melt from the nuclear reactor vessel (26) into the filler (29), dissolution of the bulk of the filler (29) in the melt , completion of the inversion of the oxide and metal components of the melt in the housing (28) of the ULR;

- mode 2 - in case of beyond design basis accidents after opening the water supply valves (34) at the stage of cooling the core melt in the reactor vessel (28) in the mode of convective heat and mass transfer of the vapor-droplet medium between the reactor shaft (35) and the internal volume of the reactor vessel (28) in position conditions the level of cooling water in the reactor shaft (35) is below the level of the water supply valves (34);

- mode 3 - in case of beyond design basis accidents after the opening of the water supply valves (34) at the stage of cooling the core melt in the reactor vessel (28) in the mode of supply of cooling water from the reactor shaft (35) to the internal volume of the reactor vessel (28) under level conditions cooling water in the reactor shaft (35) above the level of the water supply valves (34).

In mode 1, in conditions of a beyond design basis accident, when the water supply valves (34) fail to open, but after the flow of the core melt from the nuclear reactor vessel (26) into the filler (29) has stopped, the bulk of the filler (29) has dissolved in the melt, and the inversion has been completed oxide and metal components of the melt in the housing (28) of the ULR, the following processes occur. After the formation of a melt mirror in the housing (28) of the ULR, radiant heat flows begin to exert a thermal effect on the equipment of the system for localizing and cooling the melt of the nuclear reactor core. Radiant heat flows from the side of the melt mirror heat the thermal protection (31) of the flange (30) of the housing (28) of the ULR and the console truss (27). The vapor-gas environment located above the melt mirror heats up and rises up to the bottom of the nuclear reactor housing (26). Heating of the vapor-gas environment occurs not only from the melt mirror, but also from the thermal protection (31) of the flange (30) of the housing (28) of the ULR, the console truss (27) and the guide plate (25). The heat generated by the core melt increases the speed of convective flows of the vapor-gas mixture between the guide plate (25) and the nuclear reactor housing (26). Under the influence of convective heat flows, the lower power plate (7) of the console truss (27) heats up and heat exchange processes in the spray devices (21) increase. The vapor-gas mixture, heated in the spraying devices (21), enters the manifold (17) through the distribution pipes (20) in Fig. 1, fig. 5. Connected to the water manifold (17) are pipes (18) FIG. 1, fig. 5 are cut off from external water supply systems, therefore the vapor-gas mixture, circulating in the collector (17) and distribution pipes (20), equalizes its temperature in accordance with the temperature of the walls of the collector (17) and distribution pipes (20), which transfer heat through a layer of protective concrete (22) to the lower power plate (7), cooled by water or a steam-water mixture circulating in the reactor shaft (35).

During the first supply of water from external systems to the nozzles (18), water is mixed with steam, resulting in rapid condensation of the steam and a sharp drop in local pressure inside the nozzle (18). Steam from the manifold (17) begins to flow into the nozzle (18), increasing the pressure in it, which leads to a decrease in the flow of water entering the nozzle (18), up to a temporary cessation of flow.

From the pipe (18), cooling water begins to flow into the manifold (17), filled with a vapor-gas mixture. Moving along the collector (17), the water flow condenses steam and accelerates, forming a shock wave front. Two fronts, moving from one point in the collector (17) in opposite directions towards each other, will meet on the opposite side of said collector (17). The result of the meeting is a water hammer in accordance with the interference pattern of interaction. A more complex picture is observed when water simultaneously enters the collector (17) from two or more pipes (18). To reduce the amplitude of self-oscillations and reduce their destructive power, the following measures were taken:

- in option 1 FIG. 1 collector (17) is open, which eliminates direct head-on collision of shock waves moving towards each other and softens the subsequent head-on collision of reflected shock waves when moving in the opposite direction;

- in option 2 fig. 4, 5, collectors (17a), (17b) are open, which eliminates direct head-on collision of shock waves moving towards each other and softens the subsequent head-on collision of reflected shock waves when moving in the opposite direction;

- in option 1 FIG. 1 pipes (18a), (18b) are cut asymmetrically into the collector (17), relative to the location of its end walls, for which the radial ribs of the outer radial sectors (16a), (16b) are used, so that the distance from one end wall to the first nozzle (18a) is not equal to the distance from the other end wall to the second nozzle (18b). Thus, for each of the receiving pipes (18a) and (18b), the distance to the end walls of the collector (17) will be different. This allows for a spatial displacement of the maximum impact impacts relative to the position of the nozzles (18a) and (18b);

- in option 2 fig. 4, 5 pipes (18a), (18b) cut asymmetrically into the collectors (17a), (17b) relative to the location of the end walls of the collectors (17a), (17b), for which the radial ribs of the outer radial sectors (16a), (16b) are used ), (16c), (16d), such that the distance from one end wall to the first pipe (18a) is not equal to the distance from it to the other end wall, and the distance from one end wall to the second pipe (18b) is not equal to the distance from it to the other end wall. Thus, for each of the receiving pipes (18a) and (18b), the distance to the end walls of the collectors (17a), (17b) will be different. This allows for a spatial displacement of the maximum impact impacts relative to the position of the nozzle (18a) in the manifold (17a) and relative to the position of the nozzle (186) in the manifold (17b);

- inside the cantilever truss (27), the elements (17), (18), (20), (21), forming the water cooling circuit, are filled with protective concrete (22) on the outside, ensuring their integrity during hydraulic shocks and vibrations;

- in option 1 FIG. 1 distribution pipes (20) are embedded from below into the collector (17), which reduces the flow of vapor-gas mixture into the collector (17) during the movement of shock waves and ensures the removal of water through the distribution pipes (20), which leads to the weakening of shock condensation waves and damping or significant weakening of self-oscillations of cooling water inside the collector (17).

- in option 2 fig. 4, 5, the distribution pipes (20) are cut into the collectors (17a), (17b) from below, which reduces the flow of steam-gas mixture into the collectors (17a), (17b) during the movement of shock waves and ensures the removal of water through the distribution pipes (20), which leads to a weakening of shock condensation waves and damping or significant weakening of self-oscillations of cooling water inside the collector (17).

From the collector (17) in option 1 and from the collectors (17a), (17b) in option 2, cooling water flows into the distribution pipes (20), located radially with approximately the same azimuthal step. The initial supply of cooling water is accompanied by boiling and temporary blocking of the water flow in the distribution pipes (20), but as the walls of the distribution pipes (20) cool and the vapor-gas mixture located inside the distribution pipes (20) cools, the cooling water flow stabilizes and becomes stable.

From the nozzles (20), first the steam-water mixture, and then the water, begin to flow into the spraying devices (21), in which, due to hydrodynamic turbulence, the cooling water is sprayed and its drop-jet free-flow (gravitational) downward movement occurs. The supply of cooling water from the water cooling circuit formed from the manifold (17) in option 1 and from the manifolds (17a), (17b) in option 2 with connected pipes (18), distribution pipes (20), pipelines (19), spray devices (21), on the melt surface, is accompanied by steam-water cooling of the slag cap and thin crust on the surface of the melt. The incoming water from the formed water cooling circuit quickly reduces the temperature of the vapor-gas environment above the melt mirror. The water-cooled crust above the melt surface stabilizes. The temperature of the thermal protection (31) of the flange (30) of the housing (28) of the ULR, the temperature of the console truss (27) and the guide plate (25) gradually decreases and is set close to the temperature of saturated steam. During this period, a water level appears on the melt crust. The mass of boiling water becomes less than the mass of water coming from the water cooling circuit into the internal space of the housing (28) of the ULR. This process ends with the formation of a water level inside the housing (28) of the ULR. Saturated steam from the housing (28) of the HLR rises upward and, having reached the internal space limited by the internal power shell (5) of the console truss (27), moves in two ways:

- the first path is inside the nuclear reactor housing (26) and then into the hermetic shell outside the reactor shaft (35);

- the second path is along the outer surface of the nuclear reactor housing (26) beyond the reactor shaft (35) into a sealed shell.

Having reached a sealed volume, the vapor-gas mixture expands and cools.

In mode 2, under conditions of a beyond design basis accident after the opening of the water supply valves (34) at the stage of cooling the core melt in the reactor vessel (28), in the mode of convective heat and mass transfer of the vapor-droplet medium between the reactor shaft (35) and the internal volume of the reactor vessel (28), under conditions position of the cooling water level in the reactor shaft (35) below the level of the water supply valves (34), the following processes occur. When the water supply valves (34) are triggered to open under conditions of a low water level in the reactor shaft (35), the cooling of the outer surface of the ULR housing (28) may be disrupted, leading to its overheating. To eliminate this phenomenon, it is necessary to increase the level of cooling water in the reactor shaft (35). For this purpose, cooling water from internal sources or from the outside of the sealed shell, for example, from fire engines, is supplied through pipes (18) to the manifold (17) in option 1 and to the manifolds (17a), (17b) in option 2, from where through the distribution pipes (20) and spraying devices (21), it enters the housing (28) of the ULR. The temperature inside the housing (28) of the LLR is stabilized, saturated steam from the housing (28) of the LLR rises up and, having reached the internal space limited by the internal power shell (5) of the console truss, moves in two ways:

- the first path is inside the nuclear reactor housing (26) and then into the hermetic shell outside the reactor shaft (35);

- the second path is along the outer surface of the nuclear reactor housing (26) beyond the reactor shaft (35) into a sealed shell.

As the melt mirror cools, the water level inside the LLR housing (28) gradually increases and reaches the water supply valves (34) located in the LLR housing (28). Through the previously activated water supply valves (34), cooling water flows into the reactor shaft (35), increasing the water level in it. This process continues until the water levels in the reactor shaft (35) and inside the reactor housing (28) are equalized.

In mode 3, in conditions of a beyond design basis accident after the opening of the water supply valves (34) at the stage of cooling the core melt in the reactor vessel (28), in the mode of cooling water flowing from the reactor shaft (35) into the internal volume of the reactor vessel (28) in position conditions the level of cooling water in the reactor shaft (35) is higher than the level of the water supply valves (34), the following processes occur. Steam-water cooling of the slag cap and thin crust on the surface of the melt begins. The incoming water from the water supply valves (34) quickly reduces the temperature of the vapor-gas environment above the melt surface. The water-cooled crust above the melt surface stabilizes. The temperature of the thermal protection (31) of the flange (30) of the housing (29) of the ULR, the temperature of the console truss (27) and the guide plate (25) gradually decreases and is set close to the temperature of saturated steam. During this period, a water level appears on the melt crust. The mass of boiling water becomes less than the mass of water coming from the reactor shaft (35) through the open water supply valves (34) into the internal space of the ULR housing (28). This process ends with leveling the water levels in the reactor shaft (35) and inside the ULR housing (28).

Saturated steam from the housing (28) of the HLR rises upward and, having reached the internal space limited by the internal power shell (5) of the console truss, moves in two ways:

- the first path is inside the nuclear reactor housing (26) and then into the hermetic shell outside the reactor shaft (35);

- the second path is along the outer surface of the nuclear reactor housing (26) beyond the reactor shaft (35) into a sealed shell.

With intense vaporization at the initial stage of cooling the surface of the melt after the actuation of the water supply valves (34) inside the housing (28) of the LLR, the pressure increases relative to the pressure of saturated steam in the shaft (35) of the reactor, generated by boiling water around the outer surface of the housing (28) of the LLR.

The reactor shaft (35) and the internal volume of the LLR housing (28) form a hydraulic circuit connected by hydraulic channels in the LLR housing (28).

The hydraulic circuit “reactor shaft (35) - internal volume of the ULR housing (28)” has negative feedback, leading to attenuation of pressure fluctuations during rapid vaporization on the surface of the melt inside the ULR housing (28). This hydraulic circuit works as follows. As soon as the pressure in the internal space of the ULR housing (28) becomes greater than the pressure in the reactor shaft (35), then the flow of water from the reactor shaft (35) through the water supply valves (34) into the internal space of the ULR housing (28) stops or becomes negative: water is pressed out by increased pressure from the housing (28) of the ULR into the reactor shaft (35). Vaporization on the surface of the melt is reduced, and steam through channels located inside the nuclear reactor vessel (26) and along the outer surface of the nuclear reactor vessel (26) enters a sealed shell outside the reactor shaft (35), equalizing the pressure inside and outside the vessel (28 ) ULR. The rate of pressure equalization is determined by the rate of steam evacuation through the channels inside the nuclear reactor vessel (26) and along the outer surface of the nuclear reactor vessel (26) into the sealed shell. If in these directions the evacuation of steam from the internal space of the housing (28) of the LLR is significantly hampered, then the pressure of saturated steam inside the housing (28) of the LLR will increase. Draining water from the reactor housing (28) will lead to a decrease in vapor formation above the surface of the melt, which will lead to a decrease in pressure in the hydraulic circuit “reactor shaft (35) - internal volume of the reactor housing (28). After equalizing the pressure in the reactor shaft (35) and inside the reactor housing (28), the water level inside the reactor housing (28) begins to rise again - water begins to flow from the reactor shaft (35) into the reactor housing (28), inside which the process of vaporization begins with an increase in pressure, this leads to the fact that the processes in the hydraulic circuit “reactor shaft (35) - internal volume of the reactor housing (28)” can be repeated cyclically several times until the cooling of the melt surface inside the reactor housing (28) is completed.

The supply of cooling water from the water cooling circuit into the housing (28) of the ULR somewhat accelerates the cooling of the equipment of the melt localization device located above the melt crust, but does not change the fundamental picture. Additional water increases the volume of water above the melt crust, but this additional volume is redistributed according to the law of equalization vessels through the flow sections of the opened water supply valves (34) between the reactor shaft (35) and the internal volume of the ULR housing (28). Consequently, the water level in the housing (28) of the ULR, taking into account the return of condensate from the sealed shell, will gradually increase:

- as water enters the LLR housing (28) from the water cooling circuit and vaporization decreases both above the melt crust and along the outer surface of the LLR housing (28) in the reactor shaft (35);

- as the residual energy releases decrease and the overall cooling of the melt.

This process can be slightly modified by the absence of return of condensate to the reactor shaft (35) from the sealed volume, which is possible in the absence of heat transfer from the sealed volume to the environment, but in principle the absence of returned condensate from the sealed volume cannot affect the process of cooling the melt within 24 hours of water entering the housing (28) of the ULR from the water cooling circuit, unless depressurization of the hermetic shell occurs with a subsequent drop in pressure to atmospheric pressure. But even in these conditions, when water is supplied from the water cooling circuit into the housing (28) of the ULR, the stability of cooling of the melt, both from the outer surface of the housing (28) of the ULR, and from the side of the melt crust, will be ensured, provided that the opening is triggered at least one water supply valve (34) and fulfilling the condition for equalizing water levels in the reactor shaft (35) and inside the ULR housing (28).

Elements of the load-bearing frame of the console truss (27), namely parallel load-bearing ribs (1), radial load-bearing ribs (2), outer, middle and inner load-bearing shells (3), (4), (5), as well as upper and lower power plates (6), (7) can be made of steel grade 09G2S.

The diameter of the internal power shell (5) is 5.1 m.

The diameter of the middle power shell (4) is 5.9 m.

The diameter of the external power shell (3) is 9.2 m.

The height of the cantilever truss (27) is 2 m.

Thus, the use of a melt localization device for the collector (17) in option 1 and collectors (17a), (17b) in option 2 with connected pipes (18), distribution pipes (20), pipelines (19), spraying devices in the console farm (21), forming a water cooling circuit, makes it possible to increase the reliability of the melt localization device by ensuring, during beyond design basis accidents, the supply of water into the space inside the HLC housing to reduce the temperature of the vapor-gas mixture and ensuring convective cooling of the HLR equipment located above the melt mirror, as well as ensuring accidents in the supply of water to the surface of the melt to reduce the impact of thermal radiation from the side of the melt mirror on the above equipment of the HLR and to stop the release of aerosols.

Information sources:

1. RF Patent No. 2576517, IPC G21C 9/016, priority dated December 16, 2014;

2. RF Patent No. 2576516, IPC G21C 9/016, priority dated December 16, 2014;

3. RF Patent No. 2575878, IPC G21C 9/016, priority dated December 16, 2014;

4. Melt localization device for NPPs with VVER-1200, I.A. Sidorov, 7th MNTK “Ensuring the safety of NPPs with VVER”, OKB “GIDROPRESS”, Russia, May 17-20, 2011;

5. RF Patent No. 2742583, IPC G21C 9/016, priority dated 03/18/2020

Claims (3)

1. Truss-cantilever of the melt localization device, containing a load-bearing frame consisting of parallel and radial force ribs (1), (2), outer, middle and inner shells (3), (4), (5), upper force plate ( 6) and the lower force plate (7), forming external parallel first, second, third and fourth sectors (8), (9), (10), (11), internal parallel first, second, third and fourth sectors (12) , (13), (14), (15) and radial sectors (16) placed between them in such a way that the parallel first external and first internal sectors (8), (12) lie on the same Cartesian axis with the parallel third external and third internal sectors (10), (14) and perpendicular to the axis on which the parallel second external and second internal sectors (9), (13), as well as parallel fourth external and fourth internal sectors (11), (15), lie, differing in that , which additionally contains a manifold (17) extending from the radial ribs of the outer radial sectors (16a), (16b) adjacent to the first parallel outer sector (8), through the outer parallel second, third and fourth sectors (9), (10) , (11), as well as external radial sectors (16), first and second branch pipes (18a), (18b), passing through the outer power shell (3) and intended for connecting the manifold (17) with pipelines (19), distance from the first branch pipe (18a) to one end of the manifold (17) is less than the distance from the second branch pipe (18b) to the other end of the said manifold (17), distribution pipes (20), connected from below to the manifold (17) and passing from it through the middle power shell (4), spray devices (21) located in some internal radial sectors and connected to distribution pipes (20), while the external parallel first sector (8) and the internal parallel first sector (12) are made empty, and the remaining external and internal parallel and radial sectors are filled with protective concrete (22). 2. Truss-cantilever of the melt localization device, containing a load-bearing frame consisting of parallel and radial force ribs (1), (2), outer, middle and inner shells (3), (4), (5), upper force plate ( 6) and the lower force plate (7), forming external parallel first, second, third and fourth sectors (8), (9), (10), (11), internal parallel first, second, third and fourth sectors (12) , (13), (14), (15) and radial sectors (16) placed between them in such a way that the parallel first external and first internal sectors (8), (12) lie on the same Cartesian axis with the parallel third external and third internal sectors (10), (14) and perpendicular to the axis on which the parallel second external and second internal sectors (9), (13), as well as parallel fourth external and fourth internal sectors (11), (15), lie, differing in that which further comprises a first manifold (17a) extending from the radial edge of the outer radial sector (16a) adjacent to the first parallel outer sector (8), through the outer second parallel sector (9), to the radial edge of the outer radial sector (16b), adjacent to the third parallel outer sector (10), the first pipe (18a) passing through the outer power shell (3) and intended for connection with the first pipeline (19a) in such a way that the distance from the first pipe (18a) to one end of the first manifold (17a) is less than the distance to its other end, the second manifold (17b), extending from the radial edge of the outer radial sector (16b), adjacent to the first parallel outer sector (8), through the outer fourth parallel sector (11), to the radial edge of the outer radial sector (16g), adjacent to the third parallel outer sector (10), the second branch pipe (18b), passing through the external power shell (3) and intended for connection with the second pipeline (19b) in such a way that the distance from the second branch pipe (18b ) to one end of the second collector (17b) is less than the distance to its other end, distribution pipes (20), connected from below to the first and second collectors (17a), (17b) and passing from them through the middle power shell (4), spraying devices (21), located in some internal radial sectors and connected to distribution pipes (20), external parallel first and third sectors (8), (10), internal parallel first and third sectors (12), (14) are made empty, and the remaining external and internal parallel and radial sectors are filled with protective concrete (22). 3. Truss-cantilever of the melt localization device according to claim 1, characterized in that on the outer side of the outer power shell (3) support legs (23) with anchor ribs (24) are installed.

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