Safety condenser and nuclear reactor comprising same

Abstract

The invention relates to a safety condenser (25) intended to be connected to a steam generating component (14, 7 ') in a water-cooled nuclear reactor (3, 120), comprising:-a heat exchanger (26) partially arranged in a pool (30) containing a cooling fluid, the heat exchanger (26) comprising a bundle of parallel heat exchanger tubes (52) extending in a vertical direction between a lower tube sheet (60) and an upper tube sheet (58), each heat exchanger tube (52) is intended for receiving a downward flow of steam from a steam generating component (14, 7 '), the heat exchanger comprising an inlet (72) intended for receiving the steam generated in the steam generating component (7', 14) and an outlet (70) intended for receiving the steam generated in the steam generating component (7 ', 14). A heat exchanger (26) configured for cooling the steam by heat exchange with a cooling fluid contained in the pool (30) to produce a condensate, and an outlet configured for returning the condensate to the steam generating component; and-a cooling capacity regulator (100) configured for controlling the cooling capacity of the safety condenser (26) by regulating the height of condensate in the heat exchanger tubes, wherein the heat exchanger (26) further comprises a lower end dome (56) connected to the lower tube sheet (60) and comprising an outlet (70) intended to be connected to the steam generating component (7 ', 14) and an upper end dome (54) connected to the upper tube sheet (58) and comprising an inlet (72) intended to be connected to an outlet tube (92) of the steam generating component (7', 14), the lower end dome (56) and the upper end dome (54) being located outside the pool (30).

Description

Technical Field

[0001] The present invention relates to a safety condenser intended to be connected to a steam generator in a nuclear reactor.

[0002] Furthermore, the present invention relates to a nuclear reactor. Background Art

[0003] US4,765,946 discloses a safety condenser intended to be connected to a steam generator in a nuclear reactor, the safety condenser including a heat exchanger arranged in a pool containing a cooling fluid, the heat exchanger including a bundle of parallel heat exchanger tubes.

[0004] WO93 / 04481 discloses a safety condenser intended to be connected to a steam generator in a nuclear reactor, the safety condenser including a heat exchanger arranged in a pool containing a cooling fluid, the heat exchanger including a bundle of heat exchanger tubes.

[0005] WO93 / 04480 discloses a safety condenser intended to be connected to a steam generator in a nuclear reactor, the safety condenser including a heat exchanger, the heat exchanger including a bundle of heat exchanger tubes. Summary of the Invention

[0006] An object of the present invention is to provide a safety condenser for a steam generator having a heat exchange capacity that can be easily adjusted as needed.

[0007] According to one aspect, there is provided a safety condenser intended to be connected to a steam generating component in a water-cooled nuclear reactor, including:

[0008] - a heat exchanger partially arranged in a pool containing a cooling fluid, the heat exchanger including a bundle of parallel heat exchanger tubes, the heat exchanger tubes extending vertically between a lower tube sheet and an upper tube sheet, each heat exchanger tube being intended to receive a downward steam flow from the steam generating component, the heat exchanger including an inlet and an outlet, the inlet being intended to receive steam generated in the steam generating component, the heat exchanger being configured to cool the steam by heat exchange with the cooling fluid contained in the pool to produce condensate, the outlet being configured to return the condensate to the steam generating component; and

[0009] - a cooling capacity regulator configured to control the cooling capacity of the safety condenser by adjusting the height of the condensate in the heat exchanger tubes, wherein

[0010] The heat exchanger further includes a lower end dome and an upper end dome, the lower end dome being connected to the lower tube sheet and including an outlet intended to be connected to the steam generating component, and the upper end dome being connected to the upper tube sheet and including an inlet intended to be connected to the outlet pipe of the steam generating component.

[0011] The lower end dome and the upper end dome are located outside the pool.

[0012] Further embodiments may relate to one or more of the following features that can be combined in any technically feasible combination:

[0013] · The lower end dome and the upper end dome have a hemispherical shape;

[0014] · The pool is arranged in a housing having a first opening in the cover and a second opening in the bottom, the first opening and the second opening being vertically aligned with each other, wherein the heat exchanger extends through the first opening and the second opening.

[0015] · The lower end dome and the upper end dome are located outside the housing;

[0016] · The lower tube sheet is connected to a support frame, the outer diameter of the support frame being greater than the diameter of the second opening, and in particular, the outer diameter of the support frame being less than the diameter of the first opening;

[0017] · The safety condenser further includes a sealing device between the upper end dome and the housing, wherein the sealing device includes an axial compensator that enables the upper end of the heat exchanger to axially move relative to the housing along the longitudinal axis of the heat exchanger;

[0018] · A shielding baffle is arranged spaced apart from the heat exchanger tubes and / or the axial compensator;

[0019] · The safety condenser further includes a sealing support, wherein the outer diameter of the sealing support has a diameter larger than the first opening, and the axial compensator is fixed to the sealing support;

[0020] · The first opening has a stepped inner boundary, and the sealing support has a stepped outer boundary that at least partially complements the step of the inner boundary of the first opening;

[0021] · The cooling capacity regulator includes at least one valve, in particular a plurality of valves connected in parallel, wherein the at least one valve is arranged in a return line between the outlet and the steam generating component;

[0022] · The bundle of heat exchanger tubes is at least partially surrounded by a flow skirt, in particular, the flow skirt covers at least 50% of the length of the bundle of heat exchanger tubes; and / or

[0023] · The heat exchanger tubes are straight tubes.

[0024] According to another aspect, a water-cooled nuclear reactor is provided, which includes a safety condenser according to the embodiments disclosed herein.

[0025] Additional embodiments may relate to one or more of the following features that can be combined in any technically feasible combination:

[0026] · The steam generating component is a steam generator of a pressurized water reactor or a reactor pressure vessel of a boiling water reactor.

[0027] · The water-cooled nuclear reactor further includes a steam generating component, wherein the inlet of the heat exchanger is connected to the outlet pipe of the steam generating component, and the outlet of the heat exchanger is connected to the steam generating component.

[0028] · The water-cooled nuclear reactor further includes a passive pressure pulse emitter, which is adapted to emit a hydraulic pulse to at least one return line valve when the water level in the steam generating component drops below a predetermined liquid level.

[0029] · The nuclear reactor uses light water as the primary cooling medium. Description of the Drawings

[0030] Additional advantages, features, aspects and details are apparent from the dependent claims, the description and the drawings.

[0031] The drawings relate to embodiments of the present invention and are described below:

[0032] Figure 1 A nuclear power plant with a pressurized water reactor is schematically shown;

[0033] Figure 2 A safety condenser according to an embodiment is schematically shown;

[0034] Figure 3 The connection between the safety condenser and the steam generator of the pressurized water reactor is schematically shown;

[0035] Figure 4 The structure and function of the passive pressure pulse emitter (PPPT) are schematically shown; and

[0036] Figure 5 The connection between the safety condenser and the reactor pressure vessel of the boiling water reactor is schematically shown. Detailed implementation manner

[0037] Figure 1 A simplified schematic overview of a nuclear power plant 1 having a nuclear reactor in the form of a pressurized water reactor (PWR) 3 is provided. The PWR 3 includes a reactor core 5 having a reactor pressure vessel (RPV) 7. During operation, the heat generated by the reactor core 5 within the reactor pressure vessel 7 is transferred by a primary coolant medium (such as water), which circulates in a primary cooling loop 10 under the driving force of a reactor coolant pump (RCP) 12 or - in the case of operation in an emergency power mode - under natural circulation (convection). The primary cooling loop includes one or more steam generators 14, where the heat of the primary coolant medium is transferred to a secondary coolant medium circulating in a secondary cooling loop 16, thereby causing the secondary coolant medium to evaporate. The primary coolant medium is then redirected to the reactor core 5 again by the RCP 12. The secondary cooling loop 16 is used for a water-steam cycle.

[0038] In the secondary cooling loop 16, the steam is directed to one or more turbines 18, and the turbines 18 drive a generator 20 accordingly to generate electricity. The steam is further directed from the turbines 18 to a condenser 22, where the steam is cooled and condensed. Then, it is pumped back to one or more steam generators 14 by a second pump 24, particularly via a return line. The second pump 24 is also referred to as a condensate pump.

[0039] In addition, at least one safety condenser 25 is provided, and the safety condenser 25 includes a heat exchanger 26, particularly a straight-tube heat exchanger 26. The safety condenser 25 described below is connected to the steam generating components in a water-cooled nuclear reactor. In the case of a pressurized water reactor, the safety condenser 25 is connected to the steam generator 14.

[0040] The heat exchanger 26 is connected at its first end via a filling line to the outlet 28 of at least one steam generator 14 in the secondary loop 16, and at its second end to the downcomer section 29 of the same steam generator. In one embodiment, the second end of the steam generator 14 is connected to the upper end of the downcomer section 29, particularly allowing mixing with the secondary-side feed water to reduce the thermal stress on the steam generator tube sheet or the return line connection nozzle. In one embodiment, the second end is connected to the return line of the secondary cooling loop 16, where the return line returns the condensed steam to the steam generator 14. The first end is the upper end in the drawing, and the second end is the lower end in the drawing.

[0041] Each safety condenser 25 having a heat exchanger 26 is provided to condense the steam generated in the steam generating component (in the case of a pressurized water reactor, in the steam generator 14) so as to remove heat from the decay circuit in the event of a failure of the feedwater supply to the steam generating component. Hereinafter, the details will be described with respect to a single safety condenser 26. As described above, more than one, in particular 2, 3, 4 or more safety condensers 26 can be used.

[0042] Regardless of the type of light water cooled nuclear reactor, the safety condenser 26 provides an additional heat sink for the reactor coolant (e.g., secondary coolant). For example, in the case of a station blackout that results in a total loss of feedwater supply, the safety condenser and its pool provide an additional heat sink for the decay heat still generated by the reactor core 5 after shutdown, thus avoiding a continuous level drop in the steam generator 14 of the PWR 3 or the reactor pressure vessel 7' of the boiling water reactor described below. Figure 5

[0043] Figure 2 and Figure 3 More details of the safety condenser 26 and its arrangement in the nuclear power plant 1 are shown. The heat exchanger 26 of the safety condenser 25 has a generally cylindrical shape. In one embodiment, the upper and lower ends of the heat exchanger 26 may have a dome shape. The large dome shape can facilitate inspection.

[0044] From Figure 2 It can be seen that the safety condenser 25 includes a heat exchanger 26 and a pool 30. The heat exchanger 26 is at least partially arranged in the pool 30. The pool 30 has dimensions such that it can operate for at least 72 h. In one example, the depth of the pool can be between 3 m and 6 m. For example, in the case of multiple safety condensers, each of them should be able to operate for at least 72 h.

[0045] The pool 30 is arranged within a housing 31. For example, the housing 31 is made of concrete.

[0046] In one embodiment, the housing 31 may have a lining 32, which is made of steel, for example, and is particularly arranged on the inner side of the housing 31 or covers the inner side of the housing 31. The housing 31 has a bottom 34 that limits the lower end of the pool 30.

[0047] In one embodiment, the bottom 34 is inclined towards the heat exchanger 26. In other words, the heat exchanger 26 is located at the deepest part of the pool 30. This improves the natural circulation of the water in the pool 30.

[0048] According to an embodiment that can be combined with other embodiments disclosed herein, the heat exchanger 26 extends through the pool 30. In the illustrated embodiment, the heat exchanger 26 extends vertically through the pool 30.​

[0049] The pool 30 is covered with a cover 36 at its upper end.

[0050] In one example, the heat exchanger 26 extends through the bottom 34 of the housing 31 and the cover 36. In one embodiment, the domed upper and lower ends of the heat exchanger 26 are arranged outside the housing 31, in particular allowing tube inspection without the need to empty the pool 30.

[0051] The housing 31 includes a first opening 38 in the cover 36 and a second opening 40 in the bottom 34. The first opening 38 and the second opening 40 are vertically aligned with each other. The diameter of the first opening 38 is larger than the diameter of the second opening 40. Additionally, according to one embodiment, the first opening 38 and the second opening 40 are circular.

[0052] According to an embodiment, when viewed from above, the housing 31 may have a generally rectangular shape, wherein each side wall 42 has a (horizontal) length of about 10 m to 20 m. In other embodiments, the pool or housing may have a circular horizontal cross-section.

[0053] The housing 31 is provided with a third opening 44 in the cover 36, which is arranged for discharging steam outside the housing 31, for example via an exhaust chimney (not shown). Below the third opening 44 and above the nominal water level 46, the housing 31 is provided with an area 48 in which steam can be collected. The area 48 is defined by a grating plate 50 at its lower end and above the nominal water level 44. In one embodiment, the grating plate 50 may be made of austenitic steel. For example, the grating plate can be used as a platform from which descent into the pool can be obtained via a ladder for inspecting the safety condenser tube housing and other pool internal parts. In some embodiments that can be combined with other embodiments disclosed herein, a grating plate is provided for partially removing the water droplets entrained in the generated steam escaping from the pool. For this purpose, the grating plate 50 is positioned such that the steam generated by the water in the pool and escaping through the third opening 44 must pass through the grating plate 50.

[0054] The nominal water level 44 is the water level of the pool during the normal operation of the nuclear reactor (i.e., when the safety condenser 25 is not operating).

[0055] The heat exchanger 26 includes a plurality of parallel heat exchanger tubes 52 extending between an upper end dome 54 and a lower end dome 56. The heat exchanger tubes 52 form a bundle of parallel heat exchanger tubes 52. The bundle of parallel heat exchanger tubes has a generally circular shape in a plane orthogonal to the longitudinal axis X of the safety condenser. The diameter of the bundle of parallel heat exchanger tubes 52 is smaller than the diameters of the first opening 38 and the second opening 40. The upper end dome 54 and the lower end dome 56 are arranged outside and / or external to the pool 30 and / or the housing 31. According to an embodiment, the heat exchanger tubes 52 are straight tubes.

[0056] In the illustrated embodiment, the upper end dome 54 and the lower end dome 56 respectively have a hemispherical shape. The upper end dome 54 and the lower end dome 56 may also have other shapes, such as a cylindrical shape.

[0057] For example, the heat exchanger tubes 52 are straight tubes, especially when installed in the housing 31, especially extending in the vertical direction. The heat exchanger 26 may include 400 to 700 heat exchanger tubes 52, such as 500 to 600 heat exchanger tubes 52. The heat exchanger tubes 52 may have a nominal diameter between DN 30 and DN 50. In one embodiment, the length of the heat exchanger tubes 52 is between 4 m and 8 m, such as between 5 m and 7 m. The heat exchanger tubes 52 may be arranged at a square pitch. For example, the center distance between the heat exchanger tubes 52 may be between 40 mm and 100 mm.

[0058] The heat exchanger tubes 52 respectively extend into the end domes 52, 54 in an upper tube sheet 58 in the upper end dome 54 and a lower tube sheet 60 in the lower end dome 56. The heat exchanger tubes 52 respectively terminate in the upper tube sheet 58 and the lower tube sheet 60. The upper tube sheet 58 and the lower tube sheet 60 respectively have a circular shape in a plane orthogonal to the longitudinal axis X of the heat exchanger 26. The upper tube sheet 58 is arranged at the upper end of the heat exchanger tubes 52.

[0059] According to an embodiment, the upper tube sheet 58 and / or the lower tube sheet 60 are at least partially positioned outside the housing, especially allowing inspection of the welded seams under pressure loading. The tube sheet has a thickness (extension in the direction of the longitudinal axis X) between 0.4 m and 0.8 m.

[0060] The heat exchanger 26 further includes a support frame 62 for holding the heat exchanger tubes 52. The support frame 62 includes a plurality of tube support plates 63a and one or more tie rods 63b. For example, the support frame 62 may include 3 to 10 tube support plates, especially 4 to 7 tube support plates. The tube support plates 63a are spaced apart from each other, for example, at regular distances.

[0061] According to an embodiment, the tube support plate 63a has high water permeability. For example, the tube support plate 63a is provided with holes, in particular broached holes. The tube support plate 63a is adapted to maintain a regular pitch between the tubes 52 and limit tube vibration. The geometry of the holes in the tube support plate allows a longitudinal increase in the length of the straight tube bundle.

[0062] The tie rods 63b are connected to the upper tube sheet 58 and / or the lower tube sheet 60. In particular, the tie rods 63b support the tube support plate 63a, in particular maintaining a regular vertical pitch of the tube support plate 63a.

[0063] According to one embodiment, the bundle of heat exchanger tubes 52 is surrounded by a flow skirt 64. In one embodiment, the flow skirt 64 is formed of a circular steel plate. The flow skirt may also include vertical frames and / or longitudinal beams for stabilization.

[0064] In one example, the flow skirt 64 covers more than 50% of the length of the bundle of heat exchanger tubes 52.

[0065] According to an embodiment, the flow skirt is connected to the tube support plate 63a and / or the annular lower support frame 66 via one or more tie rods 63b. Additionally, in one embodiment, the flow skirt is connected to the upper sealing support 76 or the lower support frame 66. The connection of the flow skirt to the tube support plate 63a is sufficient. The stabilization of additional tie rods 63b is for the purpose of holding the flow skirt in place to prevent the flow skirt from sliding downwards.

[0066] The flow skirt improves the flow circulation during the operation of the safety condenser.

[0067] The lower tube sheet 60 is connected to the annular support frame 66, in particular in a fluid-tight manner. The support frame 66 forms a casing. The lower tube sheet 60 is arranged at the lower end portion of the heat exchanger tubes 52. The diameter of the support frame 66 is larger than the diameter of the opening 40. The support frame is adapted to be supported by the bottom 34 of the housing 31. In one embodiment, a seal is provided between the bottom 34 and the annular support frame 66, in particular between the lining 32 and the support frame 66. For example, the seal may be a welded seal. The support frame 66 has a smaller diameter compared to the first opening 38, such that the heat exchanger 26 can be installed or replaced via the first opening 38.

[0068] Furthermore, below the lower end dome 56, a skirt support 68 is provided. Depending on the structure of the concrete housing 31, the skirt support 68 can serve as the main support or auxiliary support for the weight of the heat exchanger.

[0069] The lower end dome 56 is also provided with an outlet 70 specifically for condensate. For example, the outlet 70 is provided at the lower end of the lower end dome 56, in particular on the longitudinal axis X.

[0070] The upper end dome 54 is provided with a steam inlet 72 for steam from the steam generator 14. The steam inlet 72 extends in the radial direction with respect to the longitudinal axis X of the heat exchanger 26.

[0071] Hereinafter, a sealing device 74 between the upper end dome 54 and the housing 31 is described. The sealing device includes an annular sealing support 76. The inner opening of the sealing support 76 is larger than the diameter of the bundle of heat exchanger tubes 52 so as to allow the bundle of heat exchanger tubes 52 to move relative to the sealing support 76. The outer diameter of the sealing support 76 has a diameter larger than that of the first opening 38. Thus, the sealing support 76 is supported by the cover 36. In a cross-sectional view, the first opening 38 may have a stepped inner boundary. According to an embodiment, the sealing support 76 has a stepped outer boundary that at least partially complements the steps of the inner boundary of the first opening 38. In one embodiment, a seal 78 is arranged on one of the steps of the inner boundary of the first opening 38. In one example, the seal may be an elastomeric seal since the thermal load and mechanical load are low. In other embodiments, other materials such as metal or ceramic washers may be used. The sealing support 76 having in particular an axial compensator 80 is held in place relative to the first opening 38 in the concrete by a bolted joint. Due to its own weight and the weight of the pool water, the annular lower support frame 66 is pressed into its resting position in the concrete structure of the housing 31.

[0072] The axial compensator 80 (in particular having an annular shape) is fixed to the upper tube sheet 58 or the upper end dome 54 on its inner side and to the sealing support 76 on its outer side. The axial compensator 80 is capable of axially moving the upper end of the heat exchanger 26 relative to the sealing support 76 and / or the housing 31 along the longitudinal axis X while being fluid-tight or gas-tight.

[0073] Furthermore, a shielding baffle 82 is provided, which is fixed to the upper end dome 54 and / or the upper tube sheet 58. The shielding baffle 82 has an annular shape and surrounds the bundle of parallel heat exchanger tubes 52. The heat exchanger extends in the direction of the longitudinal axis X more than the axial compensator 80 extends in the direction of the longitudinal axis X. Thus, the heat exchanger tubes 52 are protected from the lateral forces exerted by the axial compensator 80. Additionally or alternatively, the shielding baffle 82 protects the axial compensator 80 from the thermal radiation from the heat exchanger tubes 52 and / or the upper tube sheet 58. The shielding baffle 82 is arranged spaced apart from the heat exchanger tubes 52 and / or the axial compensator 80.

[0074] In addition, there may be a support frame 84 for an attenuator connected to the upper end dome 54, a measuring device, a fixed hanger 86, a fixed point for inspecting the gear, etc. The attenuator can reduce the lateral movement of components. The support frame 84 extends above the upper end dome 54 and is supported by the seal support 76 and / or the covering 36. For example, the fixed hanger 86 is connected between the top end of the upper end dome 54 and the support frame 84. In some embodiments combinable with other embodiments disclosed herein, the fixed hanger 86 can be used to install the entire tubular compact structure of the heat exchanger 26 in a partially suspended arrangement according to the conditions in the reactor building.

[0075] In some embodiments, the housing 31 may have a drain pipe 88 for draining water from the pool. The drain pipe 88 is positioned at the lowest point of the bottom 34 of the pool 30 in the housing 31.

[0076] Figure 3 The installation of the safety condenser 25 and the heat exchanger 26 is shown in more detail. The safety condenser 25 is preferably placed as high as possible above the steam generator 14 (or generally the steam generating component) in the reactor building to allow the return line 98 to be preferably connected to the steam source in the upper part of the steam generator at the height of its feed water manifold in the case of a PWR or at the height of the reactor core in the reactor pressure vessel 7' of the BWR shown later. Figure 5 to the steam source in the upper part of the steam generator.

[0077] The steam generator 14 has a steam dome 90 that collects the steam generated on the secondary side of the steam generator 14. The steam generator 14 has an outlet pipe 92 connected to the outlet 28 to direct the steam to a turbine (not shown) in the water-steam cycle or the secondary cooling circuit.

[0078] The safety condenser filling line 94 branches from the outlet pipe 92 via an optional valve 96 to supply steam to the heat exchanger tubes 52 of the safety condenser 25.

[0079] In addition, the return line 98 is connected between the outlet 70 of the heat exchanger 26 and the steam generator 14. The return line 98 from the safety condenser 25 is connected to the steam generator 14 at the height of the return line, particularly at the height of the feed water manifold, particularly allowing the condensate from the safety condenser to mix with the water circulating in the secondary circuit 16 in the steam generator 14, for example to avoid thermal loading on the components.

[0080] The return line 98 includes one or more return line valves 100, 101, particularly at least two return line valves 100, 101. For example, the return line includes at least one return line control valve 100 for adjusting the heat exchange capacity of the heat exchanger 26 and at least one return line shut-off valve 101 connected in parallel with the at least one return line control valve 100. Being connected in parallel means that the return line valves 100, 101 are arranged in parallel branches of the return line and can be operated independently of each other to control the flow in the return line 98. The at least one return line control valve 100 is operated to control the function of the power of the safety condenser 25, for example, by controlling the water level in the heat exchanger tubes 52. The water level in the heat exchanger tubes 52 can be controlled by throttling the condensate flow returning from the safety condenser 25 to the steam generator 14. The water level inside the safety condenser 25, particularly in the heat exchanger tubes 52 of the heat exchanger 26, is directly related to its heat removal capacity. According to one embodiment, the return line valves 100, 101 can be pneumatically actuated.

[0081] In one embodiment, the at least one return line shut-off valve 101 is opened by a passive pressure pulse transmitter (PPPT) 102. The at least one return line shut-off valve 101 is a normally closed valve.

[0082] From Figure 3 It can be seen that the steam generator 14 is optionally provided with a PPPT 102 ( Figure 4 ). The PPPT is adapted to trigger at least one return line shut-off valve 101 in at least one branch of the return line 98.

[0083] Figure 4 The PPPT 102 is schematically shown. The PPPT 102 is, for example, a small heat exchanger, particularly not larger than about 0.030 m 3 . The PPPT includes two compartments, namely a main chamber 106 and an auxiliary chamber 107. The main chamber 106 is connected to the vertical tube 118 via a first top nozzle 108 and a second bottom nozzle 110, see Figure 3 and Figure 5 , and the vertical tube 118 is in parallel with the steam generator 14 to which it is connected. The top nozzle 108 of the PPPT main chamber 106 is connected to the top of the steam generator 14 via the vertical tube 118, particularly to the secondary side of the steam generator 14, and the bottom nozzle 110 of the PPPT main chamber 106 is connected to the bottom of the secondary side of the steam generator 14 via the vertical tube 118. Both ends of the vertical tube 118 connected to the PPPT main chamber 106 are connected to the secondary side of the steam generator 14. The auxiliary chamber 107 of the PPPT 106 is isolated from the steam generator 14.

[0084] The auxiliary chamber 107 is separated from the main chamber 106 by a wall or plate 111. The wall or plate 111 is arranged substantially vertically.

[0085] The PPPT further includes one or more blind tubes 112 extending from the wall 111 into the main chamber 106. For example, the blind tubes 112 extend horizontally. In some embodiments, the main chamber 106 may include fill tubes 113 (especially parallel and / or above the blind tubes 112) in order to reduce the volume of the main chamber. The blind tubes 112 open towards the auxiliary chamber 107. In other words, the blind tubes 112 are in fluid connection with the auxiliary chamber 107.

[0086] During normal operation of the nuclear power plant, the main chamber 106 is filled with water. In addition, the auxiliary chamber 107 is filled with water, at least above the level of the blind tubes 112.

[0087] The auxiliary chamber also has a top nozzle 114 and a bottom nozzle 116. The top nozzle 114 is provided for venting and / or filling. During normal operation, the top nozzle 114 is closed, especially in order to build up pressure. The bottom nozzle 116 is connected to at least one return line stop valve 101 in order to enable (open) the return line stop valve 101.

[0088] For example, in the case of a nuclear power plant shutdown or total feedwater loss, the filling level on the secondary side of the steam generator 14 drops, and the level in the vertical tube 118 drops as well. At the installation height of the PPPT 102, the main chamber 106 of the PPPT starts to be filled with steam, thus starting to heat the auxiliary chamber 107 via heat exchange across the blind tubes 112.

[0089] The water in the auxiliary chamber 107 of the PPPT 102 gets heated and evaporates, and a hydraulic pulse is generated from the bottom nozzle 116, which can in particular be used to trigger the valve guide of the return line stop valve 101. In one embodiment, by using a pneumatic additional load, the valve guide initiates the full opening of the return line stop valve 101, which activates the safety condenser 25. Thus, if the liquid level in a steam generating component (such as Figure 1 the steam generator 14 therein) drops below a predetermined level corresponding in particular to the installation level of the PPPT 102, the PPPT is adapted to emit a hydraulic pulse to at least one return line valve 101, especially at least one return line stop valve 101.

[0090] In an alternative embodiment, a solenoid-actuated guide reacting to power loss can be used to initiate the opening of the return line stop valve 101 in the return line 98.

[0091] Typically, the function of the safety condenser 25 is as follows. The safety condenser 25 provides another closed loop with an integrated heat exchanger, which integrated heat exchanger includes water as a heat sink. The safety condenser 25 effects the condensation of steam that is still generated, for example, by decay heat (due to the heat still being transported in the primary cooling loop 10) in a steam generating component (such as the steam generator 14 of a pressurized water reactor ( Figure 1 ). In all cases, the heat is thus transferred to the water in the pool 30. The condensed water is then again supplied to the steam generator 14 via the return line 98. Thus, the safety condenser 25 increases the safety of the nuclear power plant 1. The vertically arranged heat exchanger tubes 52 enable the power of the safety condenser 25 to be controlled or limited. The limitation or control of the safety condenser 25 is useful because the safety condenser 25 can also be used during accident situations and transients requiring controlled cooling of the facility (for example, steam generator tube rupture).

[0092] The function of the control of the safety condenser 25 is as follows. The safety condenser 26 is controlled since the condensate flow rate is regulated towards the steam generator 14 by the return line control valve 100 in the return line 98. The condensate filling level in the heat exchanger tubes 52 rises to a specific level. The portion of the heat exchanger tubes 52 filled with water (i.e., the condensed steam) does not transfer a large amount of heat to the water in the pool 30. Thus, the surface available for heat transfer towards the water in the pool 30 in the heat exchanger 26 is reduced. In other words, the water level in the heat exchanger tubes 52 determines the limit of the heat exchange capacity of the safety condenser 26. Thus, the vertically arranged heat exchanger tubes 52 simplify the control of the safety condenser 26 since only the geometry of the vertically arranged heat exchanger tubes 52 has to be considered.

[0093] Due to the vertical arrangement of the heat exchanger tubes 52, the heat exchange capacity of the heat exchanger 26 is proportional to the height of the space in the heat exchanger tubes 52 not occupied by condensate. Thus, the heat exchange capacity of the heat exchanger 26 can be easily controlled by the above-described means. The vertical arrangement of the heat exchanger 26 simplifies the installation of the heat exchanger 26 as well as the access to the upper end dome 54 and the lower end dome 56, which may contain openings for maintenance. In addition, the upper end dome 54 and the lower end dome 56 may contain access to measuring devices. For example, the heat exchanger 26 can be fully transferred and simply installed in the housing with all necessary connections. Only some welding within the pool 30 is required. In addition, due to the weight of the heat exchanger 26, many seals are sealed. According to an embodiment, the number of welds subject to thermal and physical stresses is minimized. Thus, the connections between the components of the heat exchanger 26 are subject to physical or thermal stresses.

[0094] In addition, due to the arrangement of the upper end dome 54 and the lower end dome 56 of the heat exchanger 26 outside the housing 31, they do not come into contact with the water in the pool 30, such that the equipment connected to the lower end dome 54 and the upper end dome 56 has less requirements for the composition of the water.

[0095] Figure 5 A simplified schematic overview of a nuclear power plant 1' with a boiling water reactor (BWR) 120 is provided. Identical features are denoted by the same reference numerals as in Figure 1 The boiling water reactor includes a reactor pressure vessel 7'. In a boiling water reactor, steam is directly generated in the reactor pressure vessel 7', such that the reactor pressure vessel 7' itself serves as a steam generating component - whose function is similar to that of the steam generator 14 in the pressurized water reactor 3. Inside the reactor pressure vessel 7', one or more recirculation pumps 122 are arranged.

[0096] The reactor pressure vessel is connected to a water-steam circulation line 124 via at least one outlet 126 of the reactor pressure vessel 7'.

[0097] The steam generated in the reactor pressure vessel 7' of the boiling water reactor is guided to one or more turbines 18 via at least one first outlet 126 arranged at the upper end of the reactor pressure vessel 7' and a water-steam circulation line 124 that respectively drives the generator 20 to generate electricity. The steam is further guided from the turbines 18 to a condenser 22, where the steam is cooled and condensed. Then it is pumped back to the reactor pressure vessel 7' by a condensate pump 24.

[0098] The reactor pressure vessel 7' has a steam dome 90, which collects the steam generated in the core 5 of the reactor pressure vessel 7'.

[0099] Similarly for the boiling water reactor 120, the safety condenser provides an additional radiator for the reactor coolant (here the water in the primary circuit).

[0100] The reactor pressure vessel 7' includes a second outlet or outlet nozzle 128, which is connected to a safety condenser filling line 94. The second outlet 128 can also alternatively be connected to the first outlet 126. In other words, also in this embodiment, the safety condenser filling line 94 is connected to the steam generating component 7', which is in particular in the form of a reactor pressure vessel. The second end of the heat exchanger 26 is in particular connected to the reactor pressure vessel 7' via a return line 98, in particular above the reactor core 5.

[0101] Therefore, the safety condenser 25 described above is connected to the steam generating component in a water-cooled nuclear reactor, and in the case of a boiling water reactor, it is connected to the reactor pressure vessel 7'.

[0102] In principle, the safety condenser 25 and related components (such as the passive pressure pulse transmitter PPPT102) as described above can also be installed at the steam generating components of a light water cooled nuclear reactor using the steam cycle as the drive medium for the turbine or as a radiator for removing decay power.

[0103] For example, in the case of a boiling water reactor, the reactor pressure vessel 7' directly generates steam, and the steam generating component is the reactor pressure vessel 7'. Therefore, for application in a boiling water reactor, the safety condenser 25 and the passive pressure pulse transmitter 102 together with its vertical pipe 118 are directly connected to the reactor pressure vessel 7'. The technical functions and devices for controlling and limiting the heat removal capacity of the safety condenser 25 remain the same as those in the application in the pressurized water reactor 3.

[0104] If the safety condenser 25 and the PPPT 102 are directly connected to the reactor pressure vessel 7' of a boiling water reactor or other water cooled nuclear reactor (such as a small modular reactor), the filling level in the PPPT 102 and the related vertical pipe 118 reflects the water level in the RPV 7', see Figure 5 .. Both ends of the vertical pipe 118 are connected to the RPV 7'. If the water level in the reactor pressure vessel 7' drops below a certain level - this level must be selected to always ensure sufficient water coverage of the core - the passive pressure pulse transmitter 102 enables the safety condenser 25 as described above by opening the return line shut-off valve 101. Then, the safety condenser 25 serves as the final radiator for the steam source connected to the inlet and outlet of the safety condenser.

[0105] The steam source can generally also be the reactor pressure vessel of a light water cooled nuclear reactor. The function of limiting the heat removal capacity of the safety condenser 25 as described above can also be used to limit the inflow of cold water into the reactor pressure vessel 7', or for controlled cooling and depressurization if required.

[0106] It is expected that the elements of one embodiment can be advantageously used in other embodiments without further elaboration.

[0107] In some examples of embodiments, any feature of any embodiment described herein can be used in combination with any feature of any other embodiment described herein.

[0108] List of reference numerals:

[0109] 1 Nuclear power plant

[0110] 3 Pressurized water reactor

[0111] 5 Reactor core

[0112] 7, 7' Reactor pressure vessel

[0113] 10 Primary cooling circuit

[0114] 12 Reactor coolant pump

[0115] 14 Steam generator

[0116] 16 Secondary cooling circuit

[0117] 18 Turbine

[0118] 20 Generator

[0119] 22 Condenser

[0120] 24 Condensate pump

[0121] 25 Safety condenser

[0122] 26. Heat exchanger

[0123] 28 Outlet

[0124] 29 Lower duct section

[0125] 30 Pool

[0126] 31 Shell

[0127] 32 Lining

[0128] 34 Bottom

[0129] 36 Cover

[0130] 38 Opening

[0131] 40 Opening

[0132] 42 Side wall

[0133] 44 Opening

[0134] 46 Nominal water level

[0135] 48 Area

[0136] 50 Grating plate

[0137] 52 Pipe

[0138] 54 Upper end dome

[0139] 56 Lower end dome

[0140] 58 Upper tube sheet

[0141] 60 Lower tube sheet

[0142] 62 Support frame

[0143] 63a Pipe support plate

[0144] 63b Tie rod

[0145] 64 Flow skirt

[0146] 66 Support frame

[0147] 68 Skirt support

[0148] 70 Outlet

[0149] 72 Inlet

[0150] 74 Sealing device

[0151] 76 Sealing support

[0152] 78 Seal

[0153] 80 Axial compensator

[0154] 82 Shield baffle

[0155] 84 Support frame

[0156] 86 Fixed hanger

[0157] 88 Drain pipe

[0158] 90 Steam dome

[0159] 92 Outlet pipe

[0160] 94 Safety condenser filling line

[0161] 96 Valve

[0162] 98 Return line

[0163] 100 Return line control valve

[0164] 101 Return line stop valve

[0165] 102 Passive pressure pulse transmitter

[0166] 106 PPPT main chamber

[0167] 107 PPPT auxiliary chamber

[0168] 108 First top nozzle to vertical pipe

[0169] 110 Second bottom nozzle to vertical pipe

[0170] 111 Wall

[0171] 112 Blind pipe for heating auxiliary chamber

[0172] 113 Filling pipe

[0173] Connector for refilling of the 114 PPT auxiliary chamber

[0174] Displacer body of the 116 PPT auxiliary chamber

[0175] 118 Vertical pipe

[0176] 120 Boiling water reactor

[0177] 122 Recirculation pump

[0178] 124 Water-steam circulation pipeline

[0179] 126 Outlet

[0180] 128 Outlet, outlet nozzle

Claims

1. A safety condenser (25) intended to be connected to a steam generating component (14, 7') in a water-cooled nuclear reactor (3, 120), the safety condenser comprising: A heat exchanger (26) partly arranged in a pool (30) containing a cooling fluid, the heat exchanger (26) comprising a bundle of parallel heat exchanger tubes (52) extending vertically between a lower tube sheet (60) and an upper tube sheet (58), each heat exchanger tube (52) being intended to receive a downward steam flow from the steam generating component (14, 7'), the heat exchanger comprising an inlet (72) and an outlet (70), the inlet (72) being intended to receive steam generated in the steam generating component (7', 14), the heat exchanger (26) being configured to cool the steam to produce condensate by heat exchange with the cooling fluid contained in the pool (30), and the outlet (70) being configured to return the condensate to the steam generating component; and A cooling capacity regulator (100) configured to control the cooling capacity of the safety condenser (26) by adjusting the height of the condensate in the heat exchanger tubes, Characterized in that the heat exchanger (26) further comprises a lower end dome (56) and an upper end dome (54), the lower end dome (56) being connected to the lower tube sheet (60) and comprising the outlet (70) intended to be connected to the steam generating component (7', 14), the upper end dome (54) being connected to the upper tube sheet (58) and comprising the inlet (72) intended to be connected to an outlet pipe (92) of the steam generating component (7', 14), and the lower end dome (56) and the upper end dome (54) being located outside the pool (30).

2. The safety condenser according to claim 1, wherein the lower end dome (56) and the upper end dome (54) have a hemispherical shape.

3. The safety condenser according to claim 1 or 2, wherein the pool (30) is arranged in a housing (31) having a first opening (38) in a cover (36) and a second opening (40) in the bottom (34), the first opening (38) and the second opening (40) being vertically aligned with each other, and wherein the heat exchanger extends through the first opening (38) and the second opening (40).

4. The safety condenser according to claim 2, wherein the lower end dome (56) and the upper end dome (54) are located outside the housing (31).

5. The safety condenser according to claim 3 or 4, wherein the lower tube sheet (60) is connected to a support frame (62), the outer diameter of the support frame (62) being greater than the diameter of the second opening (40), and in particular, the outer diameter of the support frame (62) being less than the diameter of the first opening (38).

6. The safety condenser according to any one of claims 3 to 5, further comprising a sealing device between the upper end dome (54) and the housing (31), wherein the sealing device (74) includes an axial compensator (80) that enables the upper end of the heat exchanger (26) to move axially relative to the housing (31) along the longitudinal axis (X) of the heat exchanger (26).

7. The safety condenser according to claim 6, wherein a shielding baffle (82) is arranged spaced apart from the heat exchanger tubes (52) and / or the axial compensator (80).

8. The safety condenser according to claim 6 or 7, further comprising a sealing support (76), wherein the outer diameter of the sealing support (76) has a diameter larger than that of the first opening (38), and the axial compensator (80) is fixed to the sealing support (76).

9. The safety condenser according to claim 8, wherein the first opening (38) has a stepped inner boundary, and the sealing support (76) has a stepped outer boundary that at least partially complements the step of the inner boundary of the first opening.

10. The safety condenser according to any one of the preceding claims, wherein the cooling capacity regulator (100, 101) includes at least one valve (100, 101), in particular a plurality of valves connected in parallel, and the at least one valve is arranged in a return line (98) between the outlet (70) and the steam generating component (7', 14).

11. The safety condenser according to any one of the preceding claims, wherein the bundle of heat exchanger tubes (52) is at least partially surrounded by a flow skirt (64), and in particular, the flow skirt covers at least 50% of the length of the bundle of heat exchanger tubes (52).

12. The safety condenser according to any one of the preceding claims, wherein the heat exchanger tubes (52) are straight tubes.

13. A water-cooled nuclear reactor comprising the safety condenser according to any one of the preceding claims.

14. A water-cooled nuclear reactor, wherein the steam generating component is a steam generator (14) of a pressurized water reactor or a reactor pressure vessel (7') of a boiling water reactor.

15. The water-cooled nuclear reactor according to claim 13 or 14, further comprising a steam generating component (14, 90), wherein the inlet (72) of the heat exchanger is connected to the outlet pipe (92) of the steam generating component (7', 14), and the outlet (70) of the heat exchanger (26) is connected to the steam generating component (7', 14).

16. The water-cooled nuclear reactor according to any one of claims 13 to 15, further comprising a passive pressure pulse emitter (102) adapted to emit a hydraulic pulse to at least one of the return line valves (100) in the return line when the water level in the steam generating component (7', 14) drops below a predetermined level.

17. The water-cooled nuclear reactor according to any one of claims 13 to 16, wherein the nuclear reactor uses light water as the primary cooling medium.

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