Safety container cooling system

Abstract

Safety container cooling system (10) comprising a sealed safety container (12) of a nuclear facility, - with a heat exchanger for heat transfer between a medium to be cooled and a cooling medium, - with first means to extract the medium to be cooled from the safety vessel (12) in a first cooling circuit and supply it to the heat exchanger and, after it has flowed through the heat exchanger, return it to the safety vessel (12), wherein the first means comprise a first pumping device (38) to pump the medium, now cooled by the heat exchanger, back into the safety vessel (12), - with second means to supply the recoolant from a coolant reservoir to the heat exchanger and to return it to the coolant reservoir after it has passed through the heat exchanger, wherein the second means comprise a second pumping device located outside the safety vessel (12) to set the recoolant in motion, wherein the second means comprise a turbine (40) which is driven by the flow of the cooling medium, wherein the first pump device (38) is coupled to the turbine (40) in such a way that it is driven by it, characterized by the fact that the first pumping device (38) and the turbine (40) are arranged outside the safety container (12), that the heat exchanger is a condenser (30) arranged outside the safety container (12), that the first means have a withdrawal device (24) in the safety container (12) for withdrawing the medium to be cooled from the safety container (12), which has a steam component and an air component, and at least the steam component is directed to the condenser (30), that the steam component is condensed to water by the condenser (30), that the water is pumped back into the safety container (12) as a cooled medium by the first pumping device (38).

Description

[0001] The invention relates to a containment vessel cooling system comprising a sealed containment vessel of a nuclear facility, a heat exchanger for heat transfer between a medium to be cooled and a cooling medium, first means for extracting the medium to be cooled from the containment vessel in a first cooling circuit and supplying it to the heat exchanger, and returning it to the containment vessel after it has passed through the heat exchanger, wherein the first means comprise a first pumping device for pumping the medium, now cooled by the heat exchanger, back into the containment vessel, and second means for supplying the cooling medium from a coolant reservoir to the heat exchanger and returning it to the coolant reservoir after it has passed through the heat exchanger, wherein the second means comprise a second pumping device located outside the containment vessel to circulate the cooling medium.wherein the second means comprise a turbine which is driven by the flow of the cooling medium, and wherein the first pumping device is coupled to the turbine in such a way that it is driven by it.

[0002] It is generally known that nuclear facilities implement numerous precautions to protect the environment from potential damage in the event of an accident. An accident can be accompanied by increased temperatures within a nuclear reactor if the reactor's safety cooling systems fail. In such cases, the heat energy generated by the reactor, such as decay power, is not sufficiently dissipated, and the reactor can overheat.

[0003] To ensure maximum safety even in the event of an accident, a nuclear reactor is surrounded by a hermetically sealed containment structure. This prevents any radioactive materials that might escape from the reactor core from reaching the environment in the event of an accident, instead keeping them contained within the containment structure. A coolant collection area, or reactor sump, is usually located within the containment structure. In the event of an accident, for example, radioactively contaminated cooling water leaking from a cooling system is collected in this area, cooled as needed, and then returned to the cooling system, the reactor core, or other systems.There are also protection concepts in which a nuclear reactor is located in a cooling medium collection area, which is flooded with cooling water in the event of an accident to achieve increased cooling, whereby the radioactively contaminated cooling water accumulating in the cooling medium collection area must also be cooled.

[0004] German patent application DE 19942199 A1 discloses a device and a method for pressure relief and passive replenishment of coolant in a pressure vessel, thus enabling the replenishment of coolant losses. Another containment protection system is disclosed in patent DE 102012213614 B3. A device for emergency cooling of a plant for external processes is disclosed in DE 102011107284 A1, as is a heat dissipation system for a nuclear power plant in DE 102012213489 A1. Furthermore, a system for pressure relief of a safety container is disclosed in JP 2014 106106 A.

[0005] In the event of an accident, the heat energy generated by the nuclear reactor or another heat source in the containment vessel or its cooling medium collection area, in the form of heated and subsequently cooled medium, must be dissipated to the outside. If this does not occur, increased steam formation could create a dangerous overpressure in the containment vessel. If this pressure exceeds a critical level, it would have to be released directly from the containment vessel into the environment to prevent containment vessel failure.

[0006] To ensure adequate cooling, appropriate cooling systems are provided, typically including a heat exchanger. This ensures that radioactively contaminated materials remain within the containment vessel and are not released into the environment. On the primary side of such a heat exchanger, the heated medium to be cooled flows through a cooling circuit; in the event of an incident, this would typically be radioactively contaminated water. The secondary side of such a heat exchanger carries a coolant that absorbs thermal energy from the heated medium, thus cooling it, but without coming into direct contact with it, preventing contamination. The uncontaminated coolant then transfers the absorbed thermal energy to a heat sink outside the containment vessel.

[0007] Depending on the type of incident, such cooling systems must be highly efficient and capable of transporting large quantities of heat from the cooling medium collection area of ​​a containment vessel to the outside, even over extended periods. According to current technology, it is common practice to use electric motor-driven pumps to force a flow of the medium to be cooled through the cooling circuit. This results in an increased heat flow rate through the heat exchanger and thus an increased cooling effect. In this design, the electric motors for the pumps are located inside the containment vessel.

[0008] Patent document DE 102017008254 A1 discloses a containment vessel cooling system comprising a reactor sump in which, during operation, a pump driven by a turbine is positioned below the surface of the medium to be cooled, i.e., completely enclosed by the medium within the reactor sump. This reduces the risk of pump cavitation and thus increases reliability. Patent document DE 102019004244 B3 discloses an arrangement of a pump with a drive turbine for the aforementioned containment vessel cooling system, and DE 102018009260 A1 discloses a suitable embodiment of a pump for such an arrangement.

[0009] Patent document DE 102017008253 B3 describes another safety container cooling system in which cooling water is supplied from outside the safety container to a heat exchanger inside the safety container and, after absorbing heat, is discharged from the safety container, thus cooling the entire safety container. Furthermore, another safety container cooling system is described in JP 2013 096928 A.

[0010] Furthermore, a safety container cooling system disclosed in patent document DE 102021002515 B3 improves the cooling system by having a pump driven by a turbine located below the surface of the medium to be cooled, and receiving the cooling medium via a pipeline from a cooling medium collection area, so that the inlet height to the pump is increased and cavitation of the pump is avoided accordingly.

[0011] A common feature of all the aforementioned concepts for heat removal from the containment vessel is that they require a cooling water collection area or reactor sump that is accessible and functional in every operating condition and in the event of a malfunction.

[0012] Based on this state of the art, the object of the invention is to provide a safety container cooling system that operates independently of a cooling water collection area and is simultaneously suitable for long-term heat dissipation.

[0013] The problem is solved by a safety vessel cooling system of the type mentioned above. This system is characterized in that the first pumping device and the turbine are arranged outside the safety vessel, that the heat exchanger is a condenser arranged outside the safety vessel, that the first means have a suction device in the safety vessel for extracting the medium to be cooled from the safety vessel, which has a vapor component and an air component, and that the medium to be cooled is fed to the condenser, that the vapor component is condensed to water by the condenser, and that the water is pumped back into the safety vessel as a cooled medium by the first pumping device.

[0014] A fundamental aspect of the invention is that, instead of extracting water from a sump in the containment vessel as before, steam is extracted from the containment vessel above the sump. This steam is then condensed back into water in a condenser before being pumped back into the containment vessel. This allows the extraction point to be advantageously located almost anywhere in the wall or ceiling of the containment vessel, as long as it is above the level of the cooling medium. A further advantage arises from the arrangement of the components of the first cooling circuit, which can be located primarily outside the containment vessel, for example, within the reactor building. This ensures comparatively easy access to the components. Furthermore, it allows for greater flexibility in the arrangement of the system components.Furthermore, a turbine is provided to drive the first pumping device, which is driven by the recooling water from the recooling circuit, i.e., by the resources of the second cooling circuit. This ensures the long-term operation of the safety vessel cooling system, as the first pumping device is not powered by an electric motor that would be inoperable during a power outage.

[0015] A further development of the safety vessel cooling system is characterized by the fact that the first components include an inlet device within the safety vessel for the recirculated cooled medium, which is connected to the fourth pipeline. This allows the cooled medium to be directed to a specific location within the safety vessel and used there selectively. This might be the case, for example, if a particular area within the safety vessel has a particularly high temperature due to its design. The inlet device could also be, for instance, a section of pipe that returns the water to the pump sump.

[0016] A particularly advantageous embodiment of the safety vessel cooling system provides that the water from the condenser is first routed to a condensate collection tank and can then be pumped out by the first pumping device. Firstly, a condensate collection tank enables continuous operation of the first pumping device. Secondly, it ensures that only water without gas is supplied to the first pumping device, which is advantageous for its operation, for example, to prevent a predetermined water supply level to the first pumping device from falling below a certain level.

[0017] A particular advantage of the safety container cooling system according to the invention arises when the first means have a connection element to which an exhaust air filter system of the safety container is connected. The exhaust air filter system for the safety container is a separate system, specifically for the safety container cooling system. Alternatively, the connection element can also be connected to an existing exhaust air filter system of the safety container, since such a system is present in any case for safety reasons. The connection of the safety container cooling system to the exhaust air filter system according to the invention combines the two systems and creates an additional advantage, for example, by allowing the portion of air already extracted from the safety container to be routed through the filters of the exhaust air filter system, and thus purified air is released into the environment while simultaneously reducing the pressure in the safety container.

[0018] In the safety container cooling system according to the invention, the condensate container is also integrated into the condenser. This allows for a particularly space-saving arrangement of the components of the first cooling circuit.

[0019] A particularly advantageous design variant of the safety tank cooling system is characterized by the fact that supplementary water is introduced directly into the safety tank via a separate inlet line, or via the separate inlet line into the fourth pipeline and then into the safety tank. A key principle of this design variant is to ensure that sufficient cooling water is always available for the primary cooling circuit. This allows supplementary water to be introduced directly into the safety tank as needed. Alternatively, it is also possible to feed the supplementary water into the fourth pipeline, in which case it also reaches the safety tank, for example, via the first pumping device and the fourth pipeline.In this way it is also possible to increase the level of the cooling medium as needed, for example to achieve a desired water coverage of radioactive substances that have leaked from a leak point and are then present on the bottom of the safety container.

[0020] Furthermore, it is advantageous to store a predetermined quantity of make-up water in a container outside the containment vessel or in a water reservoir, and to supply the make-up water to the containment vessel only as needed. If the make-up water is stored in the container, it is advantageously available immediately. The container can also be pressurized, eliminating the need for additional technical equipment to pump the make-up water into the containment vessel. The water can also be prepared with additives or inhibitors, for example, with boron. The advantage of a water reservoir is that virtually any quantity of make-up water can be provided.

[0021] Further advantageous design options can be found in the additional dependent claims.

[0022] The invention, further embodiments and further advantages will be described in more detail using the embodiment shown in the drawing.

[0023] It shows the Fig. 1. A schematic diagram of an exemplary safety container cooling system.

[0024] The Fig.Figure 1, the only figure, shows a schematic diagram of a containment vessel cooling system 10 according to the invention, which, in the illustrated variant, is suitable for long-term heat dissipation from heat generated in the containment vessel. Long-term heat dissipation is defined as a period of two weeks or more up to six months or more. A containment vessel 12 is shown, in which a reactor pressure vessel 14 of a nuclear reactor is arranged. The reactor pressure vessel 14 is intended to have a leakage point 16 through which the radioactively contaminated water and other radioactive substances escape. This is meant to symbolize a corresponding incident that necessitates long-term heat dissipation from the containment vessel 12. The containment vessel 12 is flooded with cooling water as the cooling medium 18, which collects in the lower region of the containment vessel 12 and is heated by radioactive substances.In this process, part of the cooling medium 18 transitions into a vapor state, which is symbolized by the clouds 20 in the safety container 12.

[0025] At a first point in the safety vessel 12 above a cooling medium level 22, a withdrawal device 24 is arranged, which in a simple embodiment is a free pipe end. Several arrows are shown in the figure near the clouds 20 to indicate the path of the steamer or gas-vapor mixture from the cooling water collection area to the withdrawal point 24. However, the withdrawal device 24 can also have a system of 2, 3, or more withdrawal points, which draw the medium to be cooled from the safety vessel 12 at several points and then combine it into a first pipe 28. This pipe is connected to the withdrawal device 24, through which the medium to be cooled is guided through a wall 26 of the safety vessel 12.The medium to be cooled, in particular steam and gaseous components of the air from the containment vessel 12, is then guided by the overpressure prevailing in the containment vessel 12 to a condenser 30 located outside the containment vessel 12 in a reactor building 13 and introduced into it, which has a lower pressure compared to the overpressure. In the condenser 30, the steam component of the medium to be cooled is condensed into water and is conveyed via a second pipe 32 to a condensate tank 34 in the reactor building 13, where it is collected. From the condensate tank 34, a third pipe 36 leads to an inlet of a first pump 38, which, in the example shown, is arranged on a common shaft with a turbine 40 that drives the first pump 38. The first pump 38 and the turbine 40 are also located in the reactor building 13.The first pump 38 extracts cooled medium, i.e., water, from the condensate tank 34 as needed and conveys it back into the containment vessel 12 via a fourth pipe 42 through a second point in the wall 26. In a simple embodiment, the cooled medium is conveyed as a free jet through the fourth pipe 42 into the containment vessel 12. However, an inlet device 43 can also be connected to the free end of the fourth pipe 42, which sprays or injects the cooled medium, for example, with a spray device, precisely onto specific areas requiring additional cooling. In the figure, the inlet device 43 is indicated as a pipe section that returns the cooled medium directly to the reactor sump.

[0026] The extraction device 24, the pipelines 28, 32, 36, 42, the condenser 30, the condensate tank 34 and the first pump device 38 are part of a first cooling circuit.

[0027] The condenser 30 is a heat exchanger. Accordingly, it has connections for linking it to a cooling circuit. The cooling circuit has a first cooling line 44, which pumps cooling water from a water reservoir outside the reactor building 13 to the turbine 40. The water reservoir can be, for example, a pond or a basin, from which the cooling water is pumped to the turbine 40 by means of a second pump, which is also located outside the reactor building 13, and drives the turbine. After passing through the turbine 40, the cooling water is conveyed via a second cooling line 46 to an inlet of the condenser 30, through which it flows, extracting heat from the vapor in the medium to be cooled, causing it to condense into water.On one outlet side of the condenser 30, the recooling water leaves the condenser and is returned to the water reservoir via a third recooling line 48. The direction of flow of the recooling water is indicated in the figure by corresponding arrows. Advantageously, the second pump is located outside the reactor building 13, so that the flow through the recooling circuit can be ensured by the second pump even from a location further away from the containment vessel 12 or the reactor building 13.

[0028] The first pipeline 28 has a connection element 50 located within the reactor building 13, to which a line 52 of a filter air system is connected. Further components of the filter air system, such as a molecular filter, are located outside the reactor building 13 and are not shown in the figure. The filter air system is thus fluidically connected to the containment vessel 12 via the line and the first pipeline 28, and its primary function is to prevent impermissibly high pressures within the containment vessel 12 by venting air through the filter air system. The filter air system, in turn, is responsible for filtering out all radioactive components in the air introduced into the filter air system before purified air is released into the environment.In the area around the connection element 50 and in the first pipeline 28 and the line 52, valves are shown which can be opened or closed depending on the need in the operation of the air filter system and / or the safety container cooling system. Reference symbol list 10 Safety container cooling system 12 safety containers 13 reactor buildings 14 reactor pressure vessels 16 Leakage points 18 medium to be cooled 20 clouds 22 Cooling medium levels 24 Extraction device 26 Wall 28 first pipeline 30 Capacitor 32 second pipeline 34 Condensate containers 36 third pipeline 38 first pump device 40 Turbine 42 fourth pipeline 43 Induction device 44 first cooling line 46 second cooling line 48 third cooling line 50 connection element 52 Line

Claims

A safety vessel cooling system (10) comprising a sealed safety vessel (12) of a nuclear facility, with a heat exchanger for heat transfer between a medium to be cooled and a recoolant, with first means for taking the medium to be cooled from the safety vessel (12) in a first cooling circuit and supplying it to the heat exchanger and returning it to the safety vessel (12) after it has flowed through the heat exchanger, wherein the first means comprise a first pumping device (38) for pumping the medium, now cooled by the heat exchanger, back into the safety vessel (12), with second means for supplying the recoolant from a coolant reservoir to the heat exchanger and returning it to the coolant reservoir after it has flowed through the heat exchanger, wherein the second means comprise a second pumping device located outside the safety vessel (12) to circulate the recoolant.wherein the second means comprise a turbine (40) which is driven by the flow of the recooling medium, wherein the first pumping device (38) is coupled to the turbine (40) in such a way that it is driven by it, characterized in that the first pumping device (38) and the turbine (40) are arranged outside the safety vessel (12), that the heat exchanger is a condenser (30) arranged outside the safety vessel (12), that the first means comprise a withdrawal device (24) in the safety vessel (12) for withdrawing the medium to be cooled from the safety vessel (12), which has a vapor component and an air component, and at least the vapor component is directed to the condenser (30), that the vapor component is condensed to water by the condenser (30), that the water is pumped back into the safety vessel (12) as a cooled medium by the first pumping device (38). Safety container cooling system (10) according to claim 1, characterized in that the first means have an inlet device (43) in the safety container (12) for the re-pumped cooled medium, which is connected to a fourth pipe (42). Safety container cooling system (10) according to claim 1 or 2, characterized in that the water from the condenser (30) is first directed to a condensate collection container (34) and can be pumped from there by the first pumping device (38). Safety container cooling system (10) according to one of the preceding claims, characterized in that the first means have a connection element (50) to which an exhaust air filter system of the safety container (12) is connected. Safety container cooling system (10) according to claim 3, characterized in that the condensate collection container (34) is integrated into the condenser (30). Safety container cooling system (10) according to claim 2, characterized in that additional water is introduced into the fourth pipeline (42) and then into the safety container (12) via the separate inlet line. Safety container cooling system (10) according to one of the preceding claims 1 to 5, characterized in that additional water is introduced directly into the safety container (12) via a separate inlet line. Safety container cooling system (10) according to claim 6 or 7, characterized in that a predetermined quantity of make-up water is stored in a container outside the safety container (12) or is stored in a water reservoir, and that the supply of make-up water to the safety container (12) is carried out as required.

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