Steam generator for nuclear power plants
The steam generator support system using tension members and lateral restraints addresses thermal expansion and cooling pump failure issues, enhancing structural integrity and modularity in nuclear power plants.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ROLLS-ROYCE SMR LTD
- Filing Date
- 2023-10-23
- Publication Date
- 2026-04-13
AI Technical Summary
Conventional steam generators in nuclear power plants face issues with thermal expansion displacement and potential failure of cooling pumps, leading to stress on connecting piping and inadequate support structures, especially in smaller modular reactors.
The steam generator is supported by tension members extending from a lower proximal end to a higher distal end, with articulated connectors allowing for lateral movement and redundancy, and lateral restraints to maintain structural integrity, reducing stress on piping and accommodating thermal expansion.
This support system reduces stress-induced strain in piping, provides redundancy, and increases space for equipment, while also facilitating modular construction and reducing construction costs by integrating transport frames for easier assembly.
Smart Images
Figure 2026511291000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a steam generator for a nuclear power plant.
Background Art
[0002] A nuclear power plant converts thermal energy from the nuclear decay of fissile materials contained in the fuel assemblies in the reactor core into electrical energy. A pressurized water reactor (PWR) plant typically has a primary cooling circuit connecting the following pressurized components: a reactor pressure vessel (RPV) containing fuel assemblies, one or more steam generators, and a pressurizer. The cooling pumps in the primary circuit circulate pressurized water through the pipes between these components. The RPV houses the reactor core that heats the water in the primary circuit. The steam generator functions as a heat exchanger between the primary circuit and the secondary system.
[0003] FIG. 1 is a schematic view of a PWR20. The RPV22 containing fuel assemblies is disposed at the center of the reactor. Around the RPV, three steam generators 24 connected to the RPV by the pipes 26 of the pressurized water primary cooling circuit 32 are concentrated. The pressurizer 28 maintains the water pressure in the primary cooling circuit. The cooling pump 30 suspended below the steam generator circulates pressurized water in the primary cooling circuit, sending the heated water from the RPV to the steam generator and the cooled water from the steam generator to the RPV. In the steam generator, heat is transferred from the pressurized water to the feed water circulating in the pipes of the secondary cooling circuit 26, thereby generating steam, which is used to drive a turbine, which in turn drives a generator. The steam is then condensed and returned to the steam generator.
[0004] Conventionally, the construction and operation of large PWR plants having outputs significantly exceeding 1 GW e involve high capital costs. Due to these high capital costs and the desire to supply small power grids, the industry is shifting towards the development of smaller units. A small modular reactor (SMR) is about 700 MW eThese are reactors with an output of less than 10
[0005] Steam generators are traditionally supported by vertical supports subjected to compressive loads, such as legs or columns extending from the steam generator base to the floor of the nuclear power plant. However, these supports may not adequately accommodate the displacement of the system due to thermal expansion, which can lead to stress on the connecting piping. Furthermore, the supports of a given steam generator may be located adjacent to its cooling pump, raising concerns that a (less likely) catastrophic failure of the cooling pump that generates the high-energy missile could impair the ability of the supports to bear the weight of the steam generator. [Overview of the project] [Problems that the invention aims to solve]
[0006] This invention was conceived in light of the above considerations. [Means for solving the problem]
[0007] In a first embodiment, the Disclosure provides a steam generator for a nuclear power plant, the steam generator having an upright, elongated body, and having tension members extending from proximal ends, which are mounted at each mounting position on the elongated body, to distal ends, which are configured to be mounted at each load-bearing mounting position within the nuclear power plant, with each proximal end lower than its respective distal end, thereby, in use, the tension members are subjected to a tensile load by the steam generator and transmit substantially all of the weight of the steam generator to the load-bearing mounting positions within the nuclear power plant.
[0008] Multiple tension members provide redundancy in the event of failure of an individual tension member. This also increases the available space beneath the steam generator for other equipment, such as a cooling pump. Because the proximal end of a tension member is lower than its distal end, the tension member naturally extends upward and away from the steam generator body. This keeps the tension member away from any equipment located beneath the steam generator (e.g., a cooling pump), thus reducing the risk that the tension member's ability to support the steam generator may be compromised in the event of failure of such equipment. Conveniently, the mounting position of the tension member on the elongated body can be located on the side between the upper and lower ends of the body.
[0009] The tension members can be easily adapted to accommodate system displacement due to thermal expansion. For example, each tension member may have articulated connectors at its proximal and distal ends to attach the tension member to its respective mounting position on the elongated body and to its load-bearing mounting position within the nuclear power plant. The articulated connectors are configured to accommodate lateral movement or vibration of the steam generator relative to the nuclear power plant, allowing the steam generator to move relative to the load-bearing mounting position within the nuclear power plant. In this way, stress-induced strain in the connecting piping to the steam generator can be reduced. Conveniently, each of the articulated connectors can be a pin joint connector.
[0010] Typically, tension members can be arranged in a circumferential row around an elongated body, spaced at equal angles. For example, a steam generator can be supported by four tension members spaced 90° apart.
[0011] Typically, a steam generator may have a reactor cooling pump suspended beneath an elongated body, and the weight of the reactor cooling pump is transmitted to the load-bearing mounting position within the nuclear power plant via the elongated body and tension members.
[0012] A steam generator may have lateral restraints configured to limit or prevent lateral movement of the steam generator. These lateral restraints can help maintain the structural integrity of the steam generator when subjected to external forces, for example, caused by seismic activity. The lateral restraints may be positioned above the tension members. They can be spaced equally at an angle in a circumferential row around the elongated body. For example, a steam generator may have four lateral restraints spaced 90° apart.
[0013] In a second embodiment, the Disclosure provides a combination of a transport frame and a steam generator of the previous embodiment mounted on the transport frame, the transport frame being configured to transport the steam generator to a nuclear power plant site, the distal end of a tension member being attached to each load-bearing mounting position within the transport frame, the tension member receiving a tensile load from the steam generator and transmitting the weight of the steam generator to the load-bearing mounting position (preferably transmitting substantially all of the weight of the steam generator). The transport frame provides structural support to the steam generator during transport, typically between the off-site factory environment and the nuclear power plant. Furthermore, mounting the steam generator to the transport frame via the tension member improves the ability to manufacture the steam generator in an off-site factory environment.
[0014] Typically, the transport frame can be made of steel.
[0015] In a third aspect, the Disclosure provides a nuclear power plant including a steam generator for a nuclear power plant according to a first aspect, wherein the distal end of a tension member is attached to each load-bearing mounting position within the nuclear power plant, thereby the tension member receives a tensile load from the steam generator and transmits substantially all of the weight of the steam generator to the load-bearing mounting positions within the nuclear power plant.
[0016] In a fourth aspect, the Disclosure provides a nuclear power plant including a combination of a transport frame and a steam generator in a second aspect, wherein the transport frame is a first transport frame, which is integrated with a further transport frame within the nuclear power plant on which other components of the nuclear power plant are mounted, and the first and further transport frames thereby form a permanent part of the nuclear power plant, the distal ends of tension members are attached to the respective load-bearing mounting positions of the first transport frame, thereby the tension members receive tensile loads from the steam generator and transmit substantially all of the weight of the steam generator to the load-bearing mounting positions of the first transport frame. This dual use of the transport frame for both transport and final installation reduces the construction cost of the nuclear power plant and improves the modularity of the plant.
[0017] In a fifth embodiment, the Disclosure provides a method for constructing a nuclear power plant, the method being: The steps include providing a combination of a transport frame and a steam generator according to a second embodiment, The steps include transporting the transport frame and steam generator combination to the nuclear power plant site, Steps for installing a transport frame and steam generator combination in a nuclear power plant, wherein the transport frame is a first transport frame, which is integrated with a further transport frame within the nuclear power plant on which other components of the nuclear power plant are mounted, so that the first and further transport frames form a permanent part of the nuclear power plant, and the distal ends of tension members are attached to the respective load-bearing mounting positions of the first transport frame, so that the tension members receive a tensile load from the steam generator and transmit substantially all of the weight of the steam generator to the load-bearing mounting positions of the first transport frame, and Includes.
[0018] The present invention includes such combinations of the described embodiments and preferred features, unless such combinations are clearly unacceptable or explicitly avoided.
[0019] Embodiments and experiments illustrating the principle of the present invention will be discussed below with reference to the accompanying drawings.
Brief Description of the Drawings
[0020] [Figure 1] It is a schematic diagram of a pressurized water reactor. [Figure 2] It is a side view of the bottom of a steam generator for a nuclear power plant and the side of a cooling pump suspended below the steam generator. [Figure 3] It is a perspective view schematically showing a steam generator mounted on a transport frame. [Figure 4] It is a perspective view schematically showing the arrangement of a transport frame on a containment structure base mat of a nuclear power plant.
Modes for Carrying Out the Invention
[0021] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in the text are incorporated herein by reference.
[0022] FIG. 2 shows a side view of the bottom of the upright elongated body of a steam generator 124 for a nuclear power plant. The steam generator receives pressurized and heated water from the plant's reactor vessel through an inlet pipe 132 of a primary cooling circuit. Inside the steam generator, heat is extracted from the water to generate steam used to drive a power generation turbine in a secondary cooling circuit (not shown). The water from the primary cooling circuit exits the steam generator through an outlet pipe 134. A cooling pump 130 suspended below the steam generator on the outlet pipe 134 circulates the water in the primary cooling circuit.
[0023] The steam generator 124 is supported in a nuclear power plant by tension members 144 that extend outwardly and upwardly from a proximal end attached to respective attachment positions on the elongated body of the steam generator to a distal end attached to respective load support attachment positions within the nuclear power plant. The tension members receive a tension load from the steam generator and transmit substantially all of the weight of the steam generator and the suspended cooling pump 130 to the load support attachment positions.
[0024] Each tension member 144 is attached at both ends by an articulated pin joint connector. More specifically, the proximal end has an inner pin joint connector 142 and the distal end has an outer pin joint connector 140. These connectors have sufficient play to allow the steam generator 124 to move relative to the load support attachment locations within the nuclear power plant. Thus, it is possible to accommodate lateral movement of the steam generator relative to the nuclear power plant, thereby reducing or avoiding the generation of stress-induced strain in the junction piping of both the primary and secondary cooling circuits.
[0025] By supporting the steam generator via the tension members 144, more space is made available under the generator for the cooling pumps 130 compared to that which was available with conventional lower, compression load-bearing vertical supports. Also, increasing the distance between the tension members and the cooling pumps reduces the risk that a high energy missile resulting from a catastrophic failure of the cooling pumps could compromise the ability of the tension members supporting the steam generator. The plurality of tension members also provides redundancy in the event of failure of an individual tension member.
[0026] In this specific example of FIG. 2, the steam generator 124 has four tension members 144 spaced equidistantly at 90° in a circumferential row around its elongated body.
[0027] The steam generator 124 also has four lateral restraints 146. These restraints are spaced 90° apart and positioned above their respective tension members 144. The lateral restraints limit the overall lateral movement of the steam generator by physically preventing lateral movement. These stoppers include a combination of guides and snubbers positioned between the steam generator and each restraint position within the nuclear power plant. They allow lateral movement of the steam generator (up to limits defined by the adjustable stoppers) to account for the expansion / contraction of the primary cooling circuit piping during normal operation, and also help maintain the structural integrity of the steam generator when subjected to external forces, for example, caused by an earthquake.
[0028] The number and position of both the tension members 144 and the lateral restraint members 146 can be changed according to the requirements of a given nuclear power plant.
[0029] Figure 3 schematically shows a perspective view of a steam generator 124 mounted on a transport frame 154. More specifically, the steam generator is supported within the transport frame by four tension members 144. The transport frame is typically an open-type grid steel frame and provides structural support to the steam generator both during transport to the site and during operation as part of the nuclear power plant once the frame is incorporated into the plant. Thus, the distal ends of the tension members are attached to predetermined positions within the transport frame, and these positions become permanent load-bearing mounting positions for the tension members within the nuclear power plant. In use, as described above, the tension members transfer substantially all of the steam generator's weight to the load-bearing mounting positions. However, during transport, additional supports and / or packing can be provided to firmly hold the steam generator in place within the frame.
[0030] Figure 4 schematically shows a perspective view of the arrangement of transport frames on the base mat of the containment structure of a nuclear power plant. More specifically, three steam generator transport frames 154 rest on their respective cavities formed in the base mat 160. When in use, each steam generator is mounted on its transport frame, and the cooling pumps for the steam generators are placed in the cavities. An additional transport frame 158 for pressurizers is positioned adjacent to the steam generator transport frames. Further cavities are formed in the base mat for the central RPV, piping, and other nuclear power plant equipment. These transport frames 154 and 158 facilitate the integration of plant components with each other and form a permanent part of the plant. Thus, they improve the modularity of the plant components. As a result, the time and cost associated with plant construction can be reduced.
[0031] Features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, and expressed as appropriate in their specific form, or in terms of means for performing the disclosed functions, or methods or processes for obtaining the disclosed results, can be used individually or in any combination of such features to realize the present invention in its various forms.
[0032] While the present invention has been described in relation to the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art once this disclosure is given. Therefore, the exemplary embodiments of the present invention described above are illustrative and not limiting. Various modifications to the described embodiments can be made without departing from the spirit and scope of the invention.
[0033] To avoid any ambiguity, any theoretical explanations provided herein are provided solely for the purpose of improving the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.
[0034] The section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described herein.
[0035] Throughout this specification, including in the following claims, unless otherwise required by context, the words “comprise” and “include,” as well as variations such as “comprises,” “comprising,” and “including,” will be understood to mean that they include the described thing or step or thing or group of steps, but not any other thing or step or thing or group of steps.
[0036] It should be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include the plural form unless explicitly stated otherwise in the context. In this specification, ranges may be expressed as "about" one particular value and / or "about" another particular value. When such a range is expressed, another embodiment includes that one particular value and / or other particular value. Similarly, when a value is expressed as an approximation by the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" with respect to numbers is optional and means, for example, ±10%. [Explanation of symbols]
[0037] 124 Steam Generator 130 Cooling pump 132 Inlet piping 134 Outlet piping 140 External pin joint connector 142 Internal pin joint connector 144 Tension Member 146 Lateral restraint section 154 Transport Frame 158 Further transport frames 160 Base Mat
Claims
1. A steam generator (124) for a nuclear power plant, wherein the steam generator has an upright, elongated body and a tension member (144) extending from a proximal end attached to each mounting position on the elongated body to a distal end configured to be attached to each load-supporting mounting position within the nuclear power plant, the proximal end being lower than the distal end, so that when in use, the tension member receives a tensile load from the steam generator and transmits substantially all of the weight of the steam generator to the load-supporting mounting position within the nuclear power plant.
2. Each tension member (144) has an articulated connector at its proximal and distal ends for attaching the member to its respective mounting position on the elongated body and its load-supporting mounting position within the nuclear power plant, wherein the articulated connector is configured to allow the steam generator to move relative to the load-supporting mounting position within the nuclear power plant, and to accommodate lateral movement of the steam generator relative to the nuclear power plant or vibration of the steam generator, as described in claim 1.
3. The steam generator (124) for a nuclear power plant according to claim 2, wherein each articulated connection part is a pin joint connection part (140, 142).
4. The steam generator (124) for a nuclear power plant according to any one of claims 1 to 3, wherein the tension members (144) are spaced equally apart in a circumferential row around the elongated body.
5. A steam generator (124) for a nuclear power plant according to claim 4, having four tension members (144) spaced at 90° intervals.
6. A steam generator (124) for a nuclear power plant according to any one of claims 1 to 5, further comprising a reactor cooling pump (130) suspended below the elongated body, wherein the weight of the reactor cooling pump is transmitted to the load-supporting mounting position in the nuclear power plant via the elongated body and the tension member (144).
7. A steam generator for a nuclear power plant (124) according to any one of claims 1 to 6, further comprising a lateral restraint (146) configured to restrict or prevent lateral movement of the steam generator.
8. The steam generator (124) for a nuclear power plant according to claim 7, wherein the lateral restraining portion (146) is positioned above the tension member (144).
9. The steam generator (124) for a nuclear power plant according to claim 7 or 8, wherein the lateral restraint portion (146) is spaced equally apart in a circumferential row around the elongated body.
10. A steam generator (124) for a nuclear power plant according to claim 9, having four lateral restraining portions (146) spaced apart at 90° intervals.
11. A combination of a transport frame (154) and a steam generator (124) mounted on the transport frame according to any one of claims 1 to 10, wherein the transport frame is configured to transport the steam generator to the site of a nuclear power plant, the distal end of the tension member is attached to each load-supporting mounting position within the transport frame, and the tension member receives a tensile load from the steam generator and transmits the weight of the steam generator to the load-supporting mounting position.
12. The combination according to claim 11, wherein the transport frame (154) is a steel frame.
13. A nuclear power plant comprising a steam generator (124) for a nuclear power plant according to any one of claims 1 to 10, wherein the distal end of the tension member (144) is attached to each load-supporting mounting position within the nuclear power plant, so that the tension member receives a tensile load from the steam generator and transmits substantially all of the weight of the steam generator to the load-supporting mounting position within the nuclear power plant.
14. A nuclear power plant comprising a combination of a transport frame (154) and a steam generator (124) according to claim 11 or 12, wherein the transport frame is a first transport frame and is integrated with a further transport frame within the nuclear power plant on which other components of the nuclear power plant are mounted, the first transport frame and the further transport frame thereby forming a permanent part of the nuclear power plant, the distal end of the tension member (144) is attached to the respective load-bearing mounting position of the first transport frame, thereby the tension member receives a tensile load from the steam generator and transmits substantially all of the weight of the steam generator to the load-bearing mounting position of the first transport frame.
15. A method for constructing a nuclear power plant, The step of providing a combination of a transport frame (154) and a steam generator (124) according to claim 11 or 12, The steps include transporting the combination of the transport frame and the steam generator to the site of the nuclear power plant, Steps of installing the combination of the transport frame and the steam generator in the nuclear power plant, wherein the transport frame is a first transport frame and is integrated with a further transport frame within the nuclear power plant on which other components of the nuclear power plant are mounted, so that the first transport frame and the further transport frame form a permanent part of the nuclear power plant, and the distal end of the tension member (144) is attached to the respective load-bearing mounting position of the first transport frame, so that the tension member receives a tensile load from the steam generator and transmits substantially all of the weight of the steam generator to the load-bearing mounting position of the first transport frame. Methods that include...