Nuclear reactor including a reactor cover and an attached inner cover

Abstract

The present invention relates to a nuclear reactor (1), in particular a liquid metal cooled nuclear reactor, comprising: a main vessel (2) comprising a hot pipe section (6) and a cold pipe section (7), the cold pipe section (7) surrounding the hot pipe section (6); a reactor core (4) immersed in the hot pipe section (6); at least one heat exchanger (20); at least one main fluid circulation pump (40) for pressurizing one of the hot pipe section (6) and the cold pipe section (7); a reactor cover (3); a gas plenum (10); and an inner cover (8) arranged below the reactor cover (3) to cover the hot pipe section (6) and the cold pipe section (7).

Description

Technical Field

[0001] The present invention relates to a nuclear reactor, in particular a liquid metal cooled nuclear reactor, comprising:

[0002] - a main container containing a main fluid, said main fluid being a liquid metal or an alloy;

[0003] a cylindrical separation structure extending vertically within the vessel and separating a hot pipe section (log) from a cold pipe section, the cold pipe section surrounding the hot pipe section, and providing at least one opening in the cylindrical separation structure to enable fluid to flow from the cold pipe section to the hot pipe section;

[0004] - A core immersed in a heat pipe section for heating the main fluid;

[0005] - at least one heat exchanger having an inlet from the hot pipe section and an outlet to the cold pipe section for transferring heat from the primary fluid to a secondary fluid of an external connection circuit;

[0006] - at least one primary fluid circulation pump for circulating the primary fluid in the primary container and pressurizing one of the pipe sections;

[0007] - a reactor cover covering the primary vessel; and

[0008] A gas plenum below the reactor head and above the hot and cold tube sections. Background Art

[0009] A liquid metal-cooled nuclear reactor (LMCR) is an advanced type of nuclear reactor in which the primary coolant is a liquid metal or alloy, such as lead, lead alloy, mercury, or sodium. In a pool-type design, the entire core and heat exchangers are immersed in a pool of liquid metal coolant. A cylindrical separator structure extends vertically within the reactor vessel, separating the hot section of the reactor core from the surrounding cold section. Due to the operation of the primary fluid circulation pump, a liquid level difference between the hot and cold sections of this reactor can reach several meters.

[0010] Due to the height of the reactor vessel, the heavy deadweight of the liquid metal, and the large free surface of the molten coolant, seismic loads and sloshing can become a significant problem.

[0011] Furthermore, the cost of building a nuclear reactor depends largely on the size of the main system.

[0012] Therefore, it is desirable to reduce the production cost of reactors.

[0013] It is also hoped to reduce vulnerability to earthquakes.

[0014] It is also desirable to extend the life of the main circulation pump. Summary of the Invention

[0015] We therefore propose the initially mentioned nuclear reactor, wherein an inner cover is provided below the reactor cover to cover a pressurized leg, while another leg is open towards the gas plenum and the reactor cover.

[0016] The inner cover allows the covered pipe section to be overpressurized relative to the other pipe sections. This reduces the difference in liquid level between the cold and hot pipe sections, potentially significantly reducing the required height of the reactor vessel, and thus its volume. For example, a 1-bar overpressure could reduce the height of a nuclear reactor vessel by 1 meter, which can result in significant cost savings. Lowering the height of the reactor vessel further reduces the height of the building in which it is housed. Furthermore, it reduces the required pump shaft length, which reduces vibration and can increase its lifespan. Because most of the pool is covered, sloshing is also reduced.

[0017] Other preferred aspects may be:

[0018] - When the pump is running, the covered pipe section is pressurized to an overpressure in the range of 0.5-10 bar compared to the other pipe section.

[0019] - The main fluid circulation pump comprises a pump discharge port connected to the covered pipe section.

[0020] The inner cover is provided with pressure relief means, preferably in the form of at least one pressure relief valve, to prevent overpressure exceeding a predetermined threshold.

[0021] - The distance between the inner cover and the reactor cover is 0.1-1 m, preferably 30-50 cm.

[0022] The pump is driven by a pump motor on top of the reactor cover, which is connected to the impeller via a pump shaft that passes through the reactor cover, the gas plenum, and the inner cover. Therefore, the seals and bearings on the reactor cover are protected from the effects of the liquid coolant.

[0023] -The pump shaft of each pump is sealed by a labyrinth seal at the inner cover. The labyrinth seal may leak some liquid metal, but this is acceptable because it will only flow back to the open liquid metal surface (hot pipe section) at the inner cover.

[0024] The main fluid circulation pump comprises an impeller arranged on top of the heat exchanger, preferably no more than 0.5 m below the reactor head. Thus, the pump is in a relatively cool area of ​​the reactor, which reduces wear and corrosion.

[0025] - The inner cover covers the cold pipe sections, while the hot pipe sections are open-ended towards the reactor cover.

[0026] - At least one main fluid circulation pump is immersed in the cold pipe section;

[0027] - at least one heat exchanger is immersed in the cold pipe section;

[0028] - The main fluid circulation pump includes a pump discharge port connected to the cold pipe section. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A simplified schematic diagram of a liquid-cooled nuclear reactor is shown.

[0030] Figure 2 Shown is a simplified, enlarged view of a heat exchanger and pump assembly in a liquid-cooled nuclear reactor. DETAILED DESCRIPTION

[0031] Figure 1-2 A nuclear reactor 1 is shown, in particular a liquid metal cooled nuclear reactor, comprising

[0032] A cylindrical primary vessel 2 is covered by a reactor cover 3, and a core 4 is contained within the vessel 2. A cylindrical separator structure 5, or core barrel, extends vertically within the vessel and separates a central hot pipe section 6 from a cold pipe section 7 surrounding the hot pipe section 6. At least one opening 12 is provided in the cylindrical separator structure 5 to enable fluid to flow from the cold pipe section 7 to the hot pipe section 6. The core 4 is immersed in the hot pipe section 6 and heats a primary fluid F1, such as a liquid metal or alloy, such as lead, a lead alloy, mercury, or sodium, which circulates within the vessel 2 to transfer heat from the core 4 to a plurality of heat exchangers 20, thereby cooling the core 4. The heat exchangers 20 transfer heat from the primary fluid F1 to a secondary fluid F2, such as water, which is transferred via connecting pipes 52, 53 to an external circuit (not shown) as is known in the art.

[0033] An inner cover 8 is provided to cover the high-pressure-side pipe sections 6 and 7, in the illustrated example, the cold pipe section 7. The inner cover 8 extends horizontally between the upper end of the cylindrical separation structure 5 and the inner wall 9 of the main vessel 2. A gas plenum 10 is bounded upward by the reactor head 3, downward by the inner cover 8 and the liquid level 11 of the hot pipe section 6, and radially by the inner wall 9 of the vessel 2. The distance d between the inner cover 8 and the reactor head 3 can be, for example, in the range of 0.1-1 m, preferably 30-50 cm. A protective gas, such as argon, is supplied to the gas plenum 10. The inner cover 8 can be provided with a pressure relief device to manage pressure buildup in the cold pipe section 7 in the event of a tube rupture in one of the heat exchangers 20, i.e., in the event of overpressure exceeding a predetermined threshold. For example, this can be accomplished by providing the inner cover 8 with at least one pressure relief valve (not shown) to allow steam to enter the gas plenum 10. The reactor head 3 is gastight, but may also be equipped with one or more pressure relief valves. If desired, the reactor head 3 can be water-cooled.

[0034] A main fluid circulation pump 40 is mounted on top of each heat exchanger 20, each pump 40 being driven by a corresponding pump motor 50. The motor 50 drives the pump 40 via a pump shaft 43. Each pump shaft 43 is sealed with a gas-tight seal at the level of the reactor head 3, i.e., between the outside of the vessel 2 and the gas plenum 10.

[0035] The motor 50, pump 40, and heat exchanger 20 form an integral unit 20, 40 that is partially inserted into the reactor 1 through an opening in the reactor head 3 and a corresponding opening in the inner head 8, such that the pump 40 and heat exchanger 20 are immersed in the cold pipe section 7, while the motor 50 remains outside the main vessel 2. Each motor 50 is mounted on a corresponding reactor head closing plate 51, which closes the opening in the reactor head 3.

[0036] Connecting structure 49 connects reactor cover closure plate 51 to the upper portion of unit cell 20, 40. This connecting structure is inner cover closure plate 48, which closes a corresponding opening in inner cover 8. Closing plate 48 has a downwardly facing beveled edge, and the opening in inner cover 8 has an upwardly facing beveled edge of a complementary shape. Connecting structure 49 can be, for example, several rods or cylinders with an opening toward gas plenum 10.

[0037] The pump 40 includes a pump housing 44 that houses an impeller 42 driven by a pump shaft 43. The pump shaft 43 of each pump 40 is sealed with a labyrinth seal between the gas plenum 10 and the cold pipe section 7. The pump housing 44 is arranged on top of the heat exchanger 20 and below the inner cover closure plate 48. The pump housing 44 has a vertically downward-facing pump suction inlet 45 that is connected to the heat exchanger outlet 24. The pump housing 44 has a pump discharge outlet 46 for radially discharging the primary fluid F1 to the cold pipe section 7. A third cylindrical perforated housing 47, which serves as a flow diffuser, surrounds the pump housing 44 so that the pump discharge outlet 46 faces the third perforated housing 47.

[0038] When pump 40 is not operating, each impeller 42 is positioned below the liquid level 11 of primary fluid F1. Preferably, each impeller 42 is no more than 0.5 m below inner cover 8. Pump 40 provides an operating overpressure of 0.5-10 bar to cold pipe section 7 relative to hot pipe section 6. Therefore, when pump 40 is operating, the liquid level 11 in hot pipe section 6 will be lower than that in cold pipe section 7.

[0039] Each heat exchanger 20 comprises a cylindrical housing 21 having a heat exchanger inlet 23 connected to the hot pipe segment 6 and a heat exchanger outlet 24 connected to a pump 40 for discharging the cooled primary fluid F1 to the cold pipe segment 7, and a tube bundle 22 housed in the housing 21, which carries the secondary fluid F2. The tube bundle 22 is connected to an inlet pipe 52 and an outlet pipe 53 for connection to an external circuit. Preferably, the number of heat exchangers 20 ranges from 5 to 20 and is evenly distributed in the cold pipe segment 7 around the hot pipe segment 6. In one example, there are 12 heat exchangers 20.

[0040] Each tube bundle 22 includes a plurality of flat spiral tube layers 25 that are arranged on top of each other to form a substantially annular tube bundle. The tube bundle 22 defines a substantially cylindrical inner region 27 extending in the vertical direction. The inner region 27 is fluidically connected to the heat exchanger inlet 23 for receiving the primary fluid F1 from the hot pipe section 6. Each tube layer 25 has a tube inlet in the inner region 27 that is connected to an inlet pipe 52 extending through the inner cover 8 and the reactor cover 3 for connection to an external circuit. The secondary fluid F2 is supplied to the tube bundle 22 via the inlet pipe 52. Each tube layer 25 has a tube outlet at the periphery of each layer 25 that is connected to an outlet pipe 53 that extends through the inner cover 8 and the reactor cover 3 for connection to an external circuit (not shown).

[0041] A first vertically extending cylindrical perforated shell 28 is arranged in the interior region 27, intersecting the tube bundle 22 in the radial direction. This allows the primary fluid F1 from the heat exchanger inlet 23 to exit the interior region 27 in the radial direction through the perforations and enter the tube bundle 22. A top plate 31 extends over the top of the tube bundle 22, vertically enclosing the tube bundle 22 and its interior region 27. Thus, the primary fluid F1 is prevented from exiting the tube bundle 22 and its interior region 27 in the vertical direction.

[0042] A second, vertically extending, cylindrical, perforated shell 29 is arranged around the tube bundle 22. The perforated shells 28 and 29 act as flow diffusers. The cylindrical shell 29 has a diameter that is smaller than the inner diameter of the shell 21, thereby forming an annular space 30 between the second perforated shell 29 and the shell 21. Thus, the primary fluid F1 can exit the tube bundle 22 in a radial direction via the perforations of the second perforated shell 29 to enter the annular volume 30. The annular volume 30 is fluidically connected to the heat exchanger outlet 24.

[0043] The materials of the pump impeller 42, the perforated housing 28, 29, 47 and the tubes in the tube bundle 22 are selected so as to reduce corrosion caused by interaction with the liquid metal. Such materials can be selected, for example, from: ferritic steel formed by aluminum oxide, austenitic steel formed by aluminum oxide, stainless steel formed by surface alloying or coating with a protective aluminum oxide forming austenitic or ferritic alloy.

[0044] In the example shown, the cold leg is pressurized. In another embodiment, the hot leg is pressurized. In this embodiment, the main fluid circulation pump is configured to pressurize the hot leg. This can be achieved, for example, by removing the main circulation pump 40 from the top of the heat exchanger 20 and positioning them so that the suction port 45 is in the cold leg 7 and the pump discharge port 46 is connected to the opening 12 leading to the hot leg 6. In this embodiment, the hot leg is provided with an inner cover.

[0045]

[0046]

[0047]

Claims

1. A nuclear reactor (1), comprising: - a main container (2) containing a main fluid (F1), said main fluid being a liquid metal or alloy; - a cylindrical separation structure (5) extending vertically within the main container (2) and separating the hot pipe section (6) from the cold pipe section (7), the cold pipe section (7) surrounding the hot pipe section (6), and at least one opening (12) provided in the cylindrical separation structure (5) to enable fluid to flow from the cold pipe section (7) to the hot pipe section (6); - a core (4) immersed in a heat pipe section (6) for heating the primary fluid (F1); - at least one heat exchanger (20) having an inlet from the hot pipe section (6) and an outlet to the cold pipe section (7) for transferring heat from the primary fluid (F1) to a secondary fluid (F2) of an external connection circuit; - at least one primary fluid circulation pump (40) for circulating the primary fluid (F1) in the primary container (2) and pressurizing one of the hot pipe section (6) and the cold pipe section (7); and - a reactor cover (3) covering the main container (2); - a gas plenum (10) below the reactor cover (3) and above the hot pipe section (6) and the cold pipe section (7); The invention is characterized in that an inner cover (8) is arranged below the reactor cover (3) to cover one of the pressurized hot pipe section (6) and the cold pipe section (7), while the other of the hot pipe section (6) and the cold pipe section (7) is open-ended toward the gas boost chamber (10) and the reactor cover (3).

2. The nuclear reactor according to claim 1, wherein: The nuclear reactor is a liquid metal cooled nuclear reactor.

3. The nuclear reactor according to claim 1, wherein: When the at least one primary fluid circulation pump (40) is in operation, one of the covered hot pipe section (6) and the covered cold pipe section (7) is pressurized to an overpressure in the range of 0.5-10 bar compared to the other of the hot pipe section (6) and the covered cold pipe section (7).

4. The nuclear reactor (1) according to claim 1, wherein: The at least one primary fluid circulation pump (40) includes a pump discharge port (46) connected to one of the covered hot pipe section (6) and the covered cold pipe section (7).

5. The nuclear reactor according to claim 1, characterized in that The inner cover (8) is provided with a pressure relief device to prevent overpressure from exceeding a predetermined threshold.

6. The nuclear reactor according to claim 5, characterized in that The pressure relief device is in the form of at least one pressure relief valve.

7. The nuclear reactor according to claim 1, wherein: The distance (d) between the inner cover (8) and the reactor cover (3) is in the range of 0.1-1 m.

8. The nuclear reactor according to claim 7, wherein: The distance (d) between the inner cover (8) and the reactor cover (3) is 30-50 cm.

9. A nuclear reactor (1) according to any one of claims 1 to 8, wherein: The corresponding main fluid circulation pump (40) is driven by a pump motor (50) on top of the reactor cover (3), which is connected to the impeller (42) via a pump shaft (43) passing through the gas boost chamber (10).

10. The nuclear reactor according to claim 9, wherein: The pump shaft (43) of the corresponding main fluid circulation pump (40) is sealed with a labyrinth seal between the gas plenum (10) and one of the covered hot pipe section (6) and cold pipe section (7).

11. A nuclear reactor (1) according to any one of claims 1 to 8, wherein: The main fluid circulation pump (40) includes an impeller (42) arranged on top of the heat exchanger (20).

12. The nuclear reactor (1) according to claim 11, wherein The impeller (42) is no more than 0.5 m below the cover (8).

13. A nuclear reactor (1) according to any one of claims 1 to 8, wherein: The inner cover (8) covers the cold pipe section (7), while the hot pipe section is open-ended toward the reactor cover (3).

14. The nuclear reactor (1) according to any one of claims 1 to 8, satisfying at least one of the following conditions: - at least one main fluid circulation pump (40) immersed in the cold pipe section (7); - at least one heat exchanger (20) is immersed in the cold pipe section (7); - At least one primary fluid circulation pump (40) comprising a pump discharge outlet (46) connected to the cold pipe section (7).

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