WO2025117017A1

WO2025117017A1 - Modular shell and tube heat exchanger

Info

Publication number: WO2025117017A1
Application number: PCT/US2024/049314
Authority: WO
Inventors: Stephen Moore
Original assignee: TerraPower LLC
Current assignee: TerraPower LLC
Priority date: 2023-12-01
Filing date: 2024-09-30
Publication date: 2025-06-05
Anticipated expiration: 2026-06-01

Abstract

A heat exchanger is formed of a shell, a mounting plate, a plurality of tube modules disposed within the shell through holes formed in the mounting plate, and nozzles coupled to each of the tube modules. The nozzles may be selectively removed from the tube modules to allow inspection or repair of the tube modules. Similarly, the tube modules may be selectively removable from the shell through the mounting plate to allow inspection, repair, or replacement of individual tube modules.

Description

MODULAR SHELL AND TUBE HEAT EXCHANGER

GOVERNMENT LICENSE RIGHTS

[0001] This invention was made with government support under DOE Cooperative Agreement No. DE-NE0009054 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

FIELD OF THE DISCLOSURE

[0002] This disclosure is directed to an intermediate heat exchanger configured as a modular assembly to allow more efficient inspection and maintenance of the tubes.

BACKGROUND

[0003] Nuclear reactors typically have a fissioning core that generates heat. Primary coolant flows through the core and absorbs the heat from the reactor core which reduces the overall temperature of the core as the heated primary coolant leaves the core. After leaving the core, the heated primary coolant flows through a heat exchanger where the thermal energy of the primary coolant is transferred to a second working fluid passing through the heat exchanger. The second working fluid flows out of the nuclear reactor and delivers the thermal energy to other systems for other purposes, such as to a steam generator that uses the thermal energy to superheat water to generate steam and drive a steam turbine to make electricity. The heat exchanger located within the nuclear reactor is typically a large heat exchanger, and in many cases, is a primary driver of the overall size of the reactor vessel. When the heat exchanger requires service, maintenance, or repair, the reactor must be shut down and the heat exchanger is removed for repair or replacement. This requires advanced planning in order to schedule the shutdown of the reactor and a large time commitment to remove the heat exchanger from the reactor vessel.

[0004] Furthermore, leakage in the heat exchanger is typically a breach of the primary coolant boundary which also requires complete removal of the heat exchanger to perform maintenance. Finally, in a shell and tube configuration, there is little to no access to the tubes within the shell and tube heat exchanger for inspection or maintenance. [0005] It would be advantageous to provide a heat exchanger that can be serviced or repaired without having the remove the entire heat exchanger from the reactor vessel. These, and other advantages, will become readily apparent to those of skill in the art by reference to the following description and figures.

SUMMARY

[0006] According to some embodiments, a shell and tube heat exchanger is formed as a modular system in which individual tube modules are individually inserted into the shell. In this way, tube modules can be selectively removed for inspection, repair, or replacement without having the remove the entire heat exchanger from the reactor vessel.

[0007] In some cases, a modular shell and tube heat exchanger includes a shell having a mounting plate coupled to an upper end of the shell and one or more outlets, the mounting plate defining one or more tube module apertures; a nozzle having an inlet and an outlet; and a tube module having a first end coupled to the nozzle and extending through the one or more tube module apertures, the tube module having a central inlet tube in fluid communication with the inlet and a bundle of tubes surrounding the central inlet tube in fluid communication with the outlet; wherein the tube module is configured for selective removal from the shell. [0008] The modular shell and tube heat exchanger may further include one or more nozzle lifting lugs coupled to the nozzle and configured to allow the nozzle to be lifted from the tube module.

[0009] A seal between the tube module and the mounting plate may be provided to create a fluid tight seal between the tube module and the mounting plate. In some cases, one or more tube module lifting lugs are coupled to the tube module and configured to allow the tube module to be lifted from the mounting plate.

[0010] One or more tube baffles may be disposed within the tube module and configured to create a tortuous fluid flow path through the tube module. This slows the fluid flow and encourages turbulent flow to improve the thermal energy transfer.

[0011] In some examples, a tube module plenum is located at a second end (e.g., lower end) of the tube module, the tube module plenum in fluid communication with the central inlet tube and the bundle of tubes. The tube module plenum is an area where the inlet fluid changes direction from inlet to outlet flow. In some cases, the inlet is a vertically down inlet flow while the outlet flow is vertically upward through the tube bundle.

[0012] In some cases, the central inlet tube is coupled to the inlet of the nozzle, and the bundle of tubes is concentric around the central inlet tube.

[0013] In some embodiments, the shell and tube heat exchanger includes a plurality of tube modules coupled to the shell mounting plate. For instance, the mounting plate may have apertures to allow 3, 4, 5, 7, 9, 11, 12, or more tube modules to be installed into the shell and tube heat exchanger. Each of the tube modules may be accessed individually, such as by removing the nozzle associated with individual ones of the tube modules.

[0014] The shell may further include a primary fluid inlet disposed within an upper half of the shell and one or more outlets disposed at a lower end of the shell. The primary fluid inlet may be formed as a plurality of holes through the shell to allow primary fluid to enter the shell through the plurality of holes. For instance, the plurality of holes may be a screen through which primary coolant circulating in the hot pool of the nuclear reactor may enter the heat exchanger.

[0015] In some cases, one or more shell baffles are provided within the shell and are formed with apertures therein to provide lateral support to corresponding tube modules inserted therein. In other words, the tube modules may pass through the apertures formed in the shell baffles and the shell baffles provide lateral support for the tube modules.

[0016] In some cases, the shell has a convex sidewall and an opposing concave sidewall, the convex and concave sidewalls each having a radius of curvature that shares a center of curvature. This configured provides a curved shell that may approximate the shape of a reactor vessel wall.

[0017] The tube module may be supported by the mounting plate. That is, the tube module may have a lip that engages with the mounting plate to determine the distance the tube module extends into the shell.

[0018] In some instances, a vent is formed in the shell to allow gas within the shell to escape through the vent. For example, when the heat exchanger is installed into a reactor vessel head, the vent may be located above a level of the primary coolant within the reactor vessel, such that any gas within the shell can escape through the vent to a location above the primary coolant pool.

[0019] In some examples, an expanding plug is configured to be inserted into one of the tubes of the bundle of tubes and expanded to isolate the tube from fluid flow. The expanding plug can be deployed near a bottom of the tube, such as near an end of the tube adjacent to the plenum. Similarly, a second expanding plug can be deployed near an upper end of the tube to isolate the tube from fluid flow. In this way, a leaky tube can be isolated and the remainder of the tube bundle can continue to function after eliminating the leak.

[0020] Some of the unique features described herein allow a module shell and tube heat exchanger to be inspected, repaired, or replaced very efficiently. For instance, a method for repairing the modular shell and tube heat exchanger includes decoupling a first nozzle from a first tube module; lifting the first nozzle off of the first tube module; inspecting the interior of a plurality of tubes within the first tube module; and plugging, with one or more plugs, at least one tube of the plurality of tubes.

[0021] The method may further include removing the first tube module from a shell by lifting the first tube module out of the shell through the mounting plate. In some cases, the method includes replacing the first tube module with a second tube module. Of course, a single tube may be replaced, or the entire tube bundle may be replaced, or the tube module may be replaced.

[0022] The method may further include lifting the nozzle off of the tube module by coupling one or more lifting lugs of the nozzle to an overhead crane. The crane can then be actuated to lift the nozzle.

[0023] Where one of the tubes is plugged, such as to isolate a leaking tube, the method may include inserting an expandable plug into a first tube; advancing the expandable plug to a lower end of the first tube; and expanding the expandable plug to occlude the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 illustrates various components of a nuclear reactor, according to some embodiments. [0025] Figure 2 illustrates an elevation view of a shell and tube heat exchanger, in accordance with some embodiments.

[0026] Figure 3 illustrates a plan view of a shell and tube heat exchanger, in accordance with some embodiments.

[0027] Figure 4A illustrates an elevation view of a shell and mounting plate of a shell and tube heat exchanger, in accordance with some embodiments.

[0028] Figure 4B illustrates a cross-sectional view of the shell of Figure 4A taken along line A-A, in accordance with some embodiments.

[0029] Figure 4C illustrates a cross-sectional view of the shell of Figure 4A taken along line B-B, in accordance with some embodiments.

[0030] Figure 4D illustrates a cross-sectional view of the shell of Figure 4A taken along line C-C, in accordance with some embodiments.

[0031] Figure 5 illustrates a cutaway elevation view of a modular shell and tube heat exchanger, in accordance with some embodiments.

[0032] Figure 6A illustrates a cutaway view of a tube module, in accordance with some embodiments.

[0033] Figure 6B illustrates a plan view of the tube module of Figure 6A, in accordance with some embodiments.

[0034] Figure 7A illustrates an elevation view of a nozzle configured to be coupled to a tube module, in accordance with some embodiments.

[0035] Figure 7B illustrates a plan view of the nozzle of Figure 7A, in accordance with some embodiments.

[0036] Figure 8A illustrates an elevation view of a nozzle and tube assembly, in accordance with some embodiments.

[0037] Figure 8B is a plan view of the nozzle and tube assembly of Figure 8A, in accordance with some embodiments.

[0038] Figure 9 illustrates a cutaway elevation view of a tube module and nozzle, in accordance with some embodiments. DETAILED DESCRIPTION

[0039] This disclosure generally relates to method and systems for manufacturing, installing, maintaining, and operating a modular intermediate heat exchanger (IHX) within a nuclear reactor. In some cases, a heat exchanger is formed of a shell, a mounting plate, tube modules disposed within the shell, and nozzles coupled to each of the tube modules. The nozzles may be selectively removed from the mounting plate, and the tube modules may additionally be removable from the shell through the mounting plate.

[0040] Referring to Figure 1, many of the components and sub-assemblies of a nuclear reactor 100 are illustrated. For example, a reactor head 102, reactor and guard vessel 104, but also illustrates many ancillary reactor components such as structural members, flanges, cover plates, piping, railing, framing, connecting rods, and supports. While the illustrated nuclear reactor 100 is a sodium fast reactor (SFR), it should be appreciated that the components and embodiments described herein could be applied to any suitable reactor configuration. For example, the modular shell and tube heat exchanger embodiments described herein could be utilized in any reactor that utilizes a heat exchanger that penetrates the reactor head.

[0041] The nuclear reactor 100 is designed to hold a number of nuclear fuel pins (not shown) in a reactor core 108 located at the bottom of the reactor and guard vessel 104. The reactor head 102 seals the radioactive materials within the reactor vessel 106 and guard vessel 104. In the embodiment shown, the reactor core 108 can only be accessed through the reactor head 102. For example, an in-vessel fuel handling machine 116 is provided. The fuel handling machine 116 allows fuel pins and other core components and instruments to be lifted from the core 108 and removed from the vessel 106 via a set of large and small rotating plugs 118 located in the reactor head 102. This design allows the reactor vessel 106 to be unitary and without any penetrations.

[0042] In some cases, sodium, which is a liquid at the nuclear reactor operating temperatures, is the primary coolant for removing heat from the reactor core 108. The reactor vessel 106 is filled to some level with sodium which is circulated through the reactor core 108 using pumps 110. In some embodiments, two or more sodium pumps 110 are provided, which may be electromagnetic pumps. In some cases, one or more pumps 110 may include an impeller which may extend through the reactor head 102 to a motor located above the reactor head 102.

[0043] In some embodiments, the pumps 110 are configured to circulate the sodium through one or more intermediate heat exchangers (IHX) 112 located within the reactor vessel 106. Sodium from the cold pool 122 near the bottom of the reactor vessel 106 is pumped up into the core 108 where it becomes heated from the nuclear fission reactions taking place therein. The heated sodium travels up out of the core and into the hot pool 124. The sodium flows upwardly by natural circulation as heated sodium has a lower density than cold sodium in the cold pool, and also by forced pressure from the one or more pumps 110. The heated sodium in the hot pool is drawn into the intermediate heat exchangers 112 which transfer heat from the primary sodium coolant to a secondary coolant. Fresh secondary coolant is piped through the reactor head 102 via one or more heat transport loop pipes 120 to the intermediate heat exchangers 112 where it is heated. Heated secondary coolant then flows out of the reactor head 102 through the heat transport loop piping 120. In some embodiments, the heated secondary coolant is used to generate steam which transferred to a power generation system. The secondary coolant may be a sodium coolant or a salt coolant such as a magnesium sodium coolant.

[0044] Figure 2 illustrates an elevation view of a shell and tube heat exchanger 112, in accordance with some embodiments. The heat exchanger 112 includes a shell 202 that is generally hollow and allows fluid to flow therein. An inlet screen 204 allows primary coolant to enter the shell and then exit through one or more primary outlet nozzles 205. The shell 202 may have a mounting plate 206 secure to an upper end of the shell. In some cases, the mounting plate is sealed to the shell and may be attached to the shell through any suitable method, but in some cases, the mounting plate 206 is welded to the shell 202.

[0045] The shell may have a plurality of apertures forming a cover gas vent 208 to allow gas within the shell to escape. For instance, the plurality of apertures may be in communication with a cover gas area within the reactor vessel and allows gas from within the shell to escape to the cover gas area. The plurality of apertures are typically located above the level of primary coolant in embodiments installed within a pool type reactor. A pool type reactor is one in which the primary coolant is a pool bounded by the reactor vessel and filled to a predetermined level within the reactor vessel and the reactor core is immersed in the pool of primary coolant. Generally, the level of the primary coolant within the reactor vessel will be above the inlet screen 204 and below the cover gas vent 208 to allow gas within the reactor vessel to escape to the cover gas area.

[0046] One or more nozzles 210 may be coupled to the mounting plate 206 and provide a flow path for a second working fluid to enter the heat exchanger 112, flow through tubes within the heat exchanger 112, and exit the heat exchanger after 122 taking thermal energy from the primary coolant within the shell. In some cases, the nozzles 210 may have an inlet 212 for the second working fluid to enter the heat exchanger 112 and an outlet 214 for the second working fluid to exit the heat exchanger 112. In some cases, the second working fluid may be sodium. Of course, other working fluids are possible, including, without limitation, liquid metals, molten salt, water, oil, among others.

[0047] Figure 3 illustrates a plan view of a shell and tube heat exchanger, in accordance with some embodiments. More specifically, Figure 3 illustrates the mounting plate 206 and a plurality of nozzles 210 coupled to the mounting plate 206. The mounting plate 206 may be formed as a planar piece of steel that may rest on the reactor head, and in some cases, may rest within a pocket formed in the reactor head. The mounting plate 206 may be welded to the reactor head, or coupled to the reactor head with other methods of fastening, such as bolts. The nozzles 210 may be coupled to the mounting plate through any suitable coupling mechanism, which may include bolts, welding, adhesives, threads, keyways, or some other form of permanent or non-permanent attachment. The nozzles 210 may be in fluid communication with a plenum 301, which may be provided on a supply side of the nozzles 210. In other words, a single supply line may be in fluid communication with each of the nozzles 210 and provide an incoming cold working fluid into the nozzles 210. Similarly, in some cases, the nozzle outlets may also be fluidically coupled to a return line by a plenum that takes the hot working fluid away from the intermediate heat exchanger.

[0048] The nozzles 210 may be formed to have nozzle lifting lugs 302 that are coupled to the nozzles 210. The nozzle lifting lugs 302 are formed integrally with the nozzles, or may be attached during manufacture, such as by welding or some other attachment mechanism. The nozzle lifting lugs 302 may provide an interference with the mounting plate 206 to prevent the nozzle from entering into the heat exchanger. Further, the nozzle lifting lugs 302 provide an attachment location in order to lift the nozzles 210 from their mounted position. For example, an overhead crane may attach to the nozzle lifting lugs 302 in order to lift the nozzles 210 off the mounting plate 206.

[0049] Similarly, the tube modules may have tube lifting lugs 304 attached to each of the tube modules. The tube lifting lugs 304 may interfere with the mounting plate 206 which may provide a positive stop when the tube modules are inserted through the mounting plate 206, and thus, the tube lifting lugs 304 may determine the depth at which the tube modules are inserted through the mounting plate 206. In some cases, the tube modules include a flange near their upper end. The flange may be concentric about the tube module and interfere with the mounting plate to cause the tube modules to be inserted to a predetermined depth within the shell. The tube lifting lugs 304 may be used to lift each of the tube modules out of the heat exchanger. The tube modules may be circular in cross-section ad fit within a circular hole formed in the mounting plate, as will be shown in later detail.

[0050] The mounting plate 206 may be formed with IHX lifting lugs 306 that may allow the intermediate heat exchanger to be lifted from the reactor vessel. For instance, an overhead crane may be coupled to the IHX lifting lugs 306 to allow the crane to lift the intermediate heat exchanger out of the reactor vessel, such as for maintenance, or replacement.

[0051] Figure 4A illustrates an elevation view of a shell and mounting plate of a shell and tube heat exchanger, in accordance with some embodiments. The shell 202 is generally hollow and allows fluid to flow therein. The primary coolant is able to enter the shell 202 through the inlet screen 204 and then exit through one or more outlet nozzles 205. The shell 202 has a mounting plate 206 secured to an upper end of the shell. The mounting plate 206 may be sealed to the shell and further sealed to a reactor vessel head to seal the shell 202 within the reactor vessel.

[0052] The shell 202 has a plurality of apertures forming a cover gas vent 208 that allows gas within the shell 202 to escape to a cover gas area which is typically confined within the reactor vessel. As such, the mounting plate 206 is sealed to the vessel head to prevent the cover gas from escaping the reactor vessel. The shell is positioned within the reactor vessel such that the level of the primary coolant within the reactor vessel is above the inlet screen 204 and below the cover gas vent 208 to allow gas within the reactor vessel to escape to the cover gas area.

[0053] One or more IHX lifting lugs 306 may be coupled to the mounting plate 206 and configured to allow the mounting plate 206 or the entire shell 202 to be lifted from the reactor vessel. This IHX lifting lugs 306 may be coupled to the mounting plate 206, such as by bolts, welding, or otherwise. The shell 202 may be formed from any suitable material, and in some cases is formed of steel.

[0054] The shell 202 may include one or more baffles 402 disposed with shell 202 and help with flow direction and/or obstruction. The baffles 402 may be formed as vanes or panels and may loosely capture the tubes, as will be described hereinafter.

[0055] Figure 4B illustrates a cross-sectional view of the shell of Figure 4A taken along line A-A, in accordance with some embodiments. The shell 202 may have an arcuate cross section. In some cases, the shell 202 is formed with a concave wall 404 and a convex wall 406. The concave wall 404 has a first radius of curvature and the convex wall 406 may have a second radius of curvature different from the first radius of curvature. In some embodiments, the first radius of curvature and the second radius of curvature may share a center of curvature. In these cases, the shell 202 may have a constant distance between the concave wall 404 and the convex wall 406. The convex wall 406 may be shaped to approximate a shape of the reactor vessel.

[0056] The baffles 402 may be formed with apertures 408 that coarsely seal with the tube modules. In other words, the apertures 408 are sized to be approximately the size of the tube modules that extend therethrough. The baffles 402 may be formed in different configurations, such as an inner baffle and an outer baffle. For example, an inner baffle may be on in which the central area of the baffle obstructs fluid flow, but allows fluid to flow around the baffle toward the periphery of the shell. Similarly, an outer baffle is one that may seal against the wall of the shell, but allow fluid to pass along an inner region of the shell. By altering the arrangement of inner baffles and outer baffles, the fluid flowing through the shell must follow a tortuous pathway. [0057] Figure 4C illustrates a cross-sectional view of the shell of Figure 4A taken along line B-B of Fig. 4B, in accordance with some embodiments. Notably, a series of alternating outer baffles 410 and inner baffles 412 may be provided within the shell. As shown, the fluid within the shell must flow in a tortuous path as it enters the inlet screen 204 and flows downwardly through the shell through the outer baffles 410 and the inner baffles 412. The outer baffles 410 and inner baffles 412 may have apertures therethrough configured to allow the tube modules to pass therethrough. As the primary fluid flows downwardly through the baffles, its thermal energy is transferred to the tubes and the secondary working fluid flowing within the tubes. This cools the primary fluid as it flows downwardly toward the outlets.

[0058] Figure 4D illustrates a cross-sectional view of the shell of Figure 4A taken along line C-C, in accordance with some embodiments. In some cases, the internal baffle 402 is formed as a plate with apertures formed therethrough to accommodate one or more tube modules to pass therethrough. The apertures 408 may coarsely seal against the tube modules, and may be sized with a diameter that is relative to the tube module diameter. In some cases, the apertures may have a diameter that is 102% of the diameter of the tube modules, or 105%, or 110%, or 115%, or larger.

[0059] Figure 5 illustrates a cutaway elevation view of a modular shell and tube heat exchanger showing the tube modules, in accordance with some embodiments. The intermediate supply inlet 212 allows an intermediate fluid to enter a first set of tubes within a tube module disposed within the shell 202. The intermediate fluid flows down an inlet tube to a tube plenum 502 within a tube module. From the tube plenum 502, the intermediate fluid then flows upwardly through a second set of tubes in the tube module to the intermediate fluid outlet 214.

[0060] The primary fluid, which in some cases may be sodium, enters the shell through the inlet screen 204 and flows downwardly past the internal baffles 402 until exiting the shell at the primary fluid outlet 205 and back into the cold pool within the reactor vessel. The reactor vessel may be filled with a primary coolant, which may typically be filled to a level above the inlet screen 204, such as to the operating level 504 which is above the inlet screen 204 and below the cover gas vent 208. [0061] Figures 6A and 6B illustrates a cutaway elevational view of a tube module 602 and a plan view of the tube module, respectively. A tube module 602 includes a plurality of vertically oriented tubes having one end in communication with the nozzle and a second end in communication with the tube module plenum 502. The tube module has an overall height h, and the tubes within the tube module 602 may have a height on the order of 90% of the tube module height, or in some cases, may have a height that is 85%, or 80%, or 75%, or 70% or less of the overall height h of the tube module. In certain embodiments, the tubes within the module may have different heights (e.g., tube lengths). For example, some tubes may be formed to be shorter than other tubes within the tube module. The tubes may have any suitable cross-sectional shape, but in some cases, the tubes are formed to have a circular cross section, or a polygonal cross section. In some cases, the tubes have a hexagonal cross section, which may allow for efficient packing of the tubes within the tube module.

[0062] With additional reference to Figure 6B, the tube module 602 may include a central inlet tube 604 surrounded by concentric annular outlet tubes 606. The central inlet tube 604 may be in fluid communication with the inlet 212 of the nozzle 210. One or more tube baffles 608 may be disposed in either the central inlet tube or the annular outlet tubes or both. The tube baffles 608 may obstruct a free-flowing fluid and increase turbulence to promote heat exchange between the primary fluid and the secondary fluid flowing through the heat exchanger. The tube modules may be circular in cross section and sized to fit within an aperture formed in the mounting plate and shell baffles. The shell baffles thus may provide lateral support to the tube modules inserted therein.

[0063] In some cases, some of the tubes within the tube module may have different diameters. For example, the tubes nearer the periphery of the tube module 602 may have a larger diameter than tubes nearer the center of the tube module 602, which may cause the secondary to flow at a faster rate near the periphery of the tube module compared with fluid flowing through tubes nearer the center of the tube module that may have a larger diameter. In some cases, tubes nearer the periphery have a larger diameter than one or more tubes located nearer the center of the tube module 602.

[0064] One or more tube module lifting lugs 304 may be coupled to the tube module to allow the tube module to be inserted and removed from the shell of the shell and tube heat exchanger, such as by a crane. In some cases, two tube module lifting lugs 304 are provided on opposite sides of the top of the tube module, of course, other configurations and locations of tube lifting lugs may be provided.

[0065] The tubes 606 may be formed in concentric annular rings about the tube module and surrounding the inlet tube 604. In some embodiments, the tubes 606 are in physical contact with one another along their walls. This may aid in flattening out the temperature gradient across the radius of the tube module.

[0066] Figure 7A illustrates an elevation view of a nozzle 210 configured to be coupled to a tube module, in accordance with some embodiments. The nozzle 210 has an inlet 212 that allows a secondary working fluid to enter the tube module within the heat exchanger. The nozzle 210 may further have an outlet 214 that allows fluid to flow out of the tube module to transport thermal energy away from the nuclear reactor core. The inlet 212 may be in fluid communication with the central inlet tube 604 within the tube modules and the outlet 214 may be in fluid communication with the tubes within the tube modules 602.

[0067] With additional reference to Figure 7B, which illustrates a plan view of the nozzle of Figure 7A, the nozzle 210 may be configured with a lip 702 that may be used to couple the nozzle 210 to the tube module 602 and/or the mounting plate of the heat exchanger. The nozzle may have one or more nozzle lifting lugs 704 that can be used to lift the nozzle 210 from a tube module 602. In some examples, the nozzle lifting lugs 704 are configured to be coupled to, such as by a crane, to lift an entire tube module out of the shell of the heat exchanger. The nozzle 210 may be coupled to a tube module 602 by any suitable mechanism, such as welding, fasteners, adhesives, or a combination. In certain embodiments, the nozzle 210 is removably coupled to a tube module 602 to allow disassembly of the tube module for inspection or repair.

[0068] Figures 8A and 8B illustrate a nozzle and tube assembly in an elevation view and plan view, respectively. As illustrated, the nozzle 210 can be mounted to an upper end of the tube module 602 with a fluid tight seal. In some examples, the nozzle is bolted to the tube module and a gasket or other type of seal may be disposed between the nozzle and tube module to create the fluid tight seal. Similarly, a seal may be disposed between the tube module and the mounting plate of the shell to provide a fluid tight seal between the tube module and the mounting plate. The seal between the tube module and the mounting plate may be a piston seal or other type of seal may be provided to create a fluid tight seal between the tube module and the mounting plate.

[0069] The cutaway view of Figure 8 A shows the individual tubes in tube bundles 802 disposed within the tube module 602 along with their respective tube baffles 608. One or more tube module lifting lugs 304 may be coupled to the tube module to allow the tube module to be lifted into and out of the shell ff the heat exchanger. Similarly, one or more nozzle lifting lugs 704 may be coupled to the nozzle to allow the nozzle to be lifted off of its corresponding tube module or may be used to lift the entire nozzle and tube assembly out of the shell of the heat exchanger.

[0070] Figure 9 illustrates a cutaway elevation view of a nozzle and tube assembly 900 comprising a nozzle 210 coupled to a tube module 602 and illustrates the secondary fluid flow. The cold secondary fluid supply 902, enters the nozzle inlet 212 and flows through the central inlet tube 604 as shown by arrows. The central inlet tube 604 is in fluid communication with the tube plenum 502 and the secondary fluid enters the plenum and is then caused to flow upwardly through the tube bundle 802. As the secondary fluid flows up the tube bundle 802 it receives thermal energy from the primary fluid flowing through the shell and surrounding the tube module. As described herein, the shell may contain one or more baffles to cause turbulent flow and mixing of the primary fluid. Similarly, the tube bundles 802 may likewise include baffles to cause turbulent flow and mixing of the secondary fluid. This mixing action increases the efficiency of the heat exchanger. The secondary fluid exits the tube bundle 802 at the nozzle 210 and exits the nozzle through the nozzle outlet 214 where the heated secondary fluid return 904 flow is directed away from the nuclear reactor core. In some cases, the heated secondary fluid return 904 is directed to another heat exchanger that may be associated with a steam generator and used to generate steam.

[0071] In some cases, the secondary fluid, which may be sodium in some examples, is pressurized to cause flow, as desired. Moreover, the pressurized secondary fluid may be at a higher pressure than the primary coolant. In this way, if a leak develops, the secondary fluid will flow into the primary fluid and inhibit the primary fluid, which may be activated, from exiting the pressure boundary of the nuclear reactor vessel.

[0072] The nozzle and tube assembly may be configured to be selectively inserted and removed from the shell potion of the shell and tube heat exchanger. In some example embodiments, the shell includes installation spaces for 5 tube modules. Of course, a shell may be configured to house a greater number, or a fewer number, of tube modules. In practice, a nozzle 210 may be removed from the heat exchanger. Removing the nozzle from the heat exchanger may include steps of coupling the nozzle, at the nozzle lifting lugs, to a crane, and actuating the crane to lift the nozzle from the heat exchanger. The nozzle 210 may first be decoupled from the tube module 602, or the nozzle may remain coupled to the tube module and the entire nozzle and tube assembly may be removed as one piece from the shell of the heat exchanger. Removing of just the nozzle from a tube assembly allows access to the internals of the tube module for inspection and repair. Furthermore, if there is a suspected leak, a tube module can be measured for differential pressure in relation to a prior measurement (or in relation to other tube modules) to detect indications of leakage and/or plugging.

[0073] Once a nozzle and tube assembly is removed from the shell of the heat exchanger, a new nozzle and tube assembly may be inserted into the location previously occupied by the removed assembly. The nozzle and tube assembly may be inspected, repaired, or replaced, as desired. Moreover, an individual nozzle may be removed to gain access to the tube module associate therewith. Consequently, the tubes within a tube module may be inspected without removing the tube module from the shell of the heat exchanger. In some cases, one or more of the tubes may be plugged, such as to aid inspection or to isolate a leaking tube. In some cases, a plug 906 may be inserted into one or more tubes and advanced to a location near the bottom of the one or more tubes. In some cases, the plug is expandable, and the plug may be expanded once it reaches a location near the bottom end of the tube. Similarly, a second plug 908 may be inserted into the tube to a location near the top of the one or more tubes. The second plug 908 near the top of the one or more tubes may likewise be an expandable plug which can be expanded to seal the tube near the top of the one or more tubes. By inserting plugs at both the lower end and upper end of the tubes, one or more tubes may be isolated from the heat exchanger and a leak within the isolated tubes may thereby be avoided. The plugs may be any suitable plug, and in some cases, are expandable plugs. Such expandable plugs may be any one or more of expansion pipe plugs, socket welded plugs, high pressure stoppers, bag plugs, expandable foaming material, or other suitable plug. [0074] The overall result is a modular shell and tube heat exchanger in which individual tube modules may be inspected, removed and/or replaced, as desired. In prior shell and tube heat exchanger, it was very difficult to inspect, repair or replace individual components of the heat exchanger, and most typically, the entire heat exchanger would need to be removed from the nuclear reactor core. This is no longer the case as the described embodiments allow a single module to be replaced without requiring removal of the entire heat exchanger. Moreover, because the tube modules penetrate the mounting plate of the shell, there are no additional changes that need to be made to the vessel head in order to implement the described shell and tube heat exchanger.

[0075] The foregoing description of specific embodiments will so fully reveal the general nature of embodiments of the disclosure that others can, by applying knowledge of those of ordinary skill in the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of embodiments of the disclosure. Therefore, such adaptation and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. The phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the specification is to be interpreted by persons of ordinary skill in the relevant art in light of the teachings and guidance presented herein.

[0076] The breadth and scope of embodiments of the disclosure should not be limited by any of the above-described example embodiments but should be defined only in accordance with the following claims and their equivalents.

[0077] Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language generally is not intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation.

[0078] Throughout the instant specification, the term “substantially” in reference to a given parameter, property, or condition may mean and include to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least approximately 90% met, at least approximately 95% met, or even at least approximately 99% met.

[0079] As used herein, the terms “about” and “approximately” may, in some examples, indicate a variability of up to ±5% of an associated numerical value, e.g., a variability of up to ±2%, or up to ±1%.

[0080] A person of ordinary skill in the art will recognize that any process or method disclosed herein can be modified in many ways. The process parameters and sequence of the steps described and/or illustrated herein are given by way of example only and can be varied as desired. For example, while the steps illustrated and/or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed.

[0081] The various exemplary methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or comprise additional steps in addition to those disclosed. Further, a step of any method as disclosed herein can be combined with any one or more steps of any other method as disclosed herein.

[0082] The various exemplary methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or comprise additional steps in addition to those disclosed. Further, a step of any method as disclosed herein can be combined with any one or more steps of any other method as disclosed herein. [0083] It is, of course, not possible to describe every conceivable combination of elements and/or methods for purposes of describing the various features of the disclosure, but those of ordinary skill in the art recognize that many further combinations and permutations of the disclosed features are possible. Accordingly, various modifications may be made to the disclosure without departing from the scope or spirit thereof. Further, other embodiments of the disclosure may be apparent from consideration of the specification and annexed drawings, and practice of disclosed embodiments as presented herein. Examples put forward in the specification and annexed drawings should be considered, in all respects, as illustrative and not restrictive. Although specific terms are employed herein, they are used in a generic and descriptive sense only, and not used for purposes of limitation.

[0084] Unless otherwise noted, the terms “a” or “an,” as used in the specification, are to be construed as meaning “at least one of.” Finally, for ease of use, the terms “including” and “having” (and their derivatives), as used in the specification, are interchangeable with and have the same meaning as the word “comprising.”

[0085] From the foregoing, and the accompanying drawings, it will be appreciated that, although specific implementations have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the appended claims and the elements recited therein. In addition, while certain aspects are presented below in certain claim forms, the inventors contemplate the various aspects in any available claim form. For example, while only some aspects may currently be recited as being embodied in a particular configuration, other aspects may likewise be so embodied. Various modifications and changes may be made as would be obvious to a person skilled in the art having the benefit of this disclosure. It is intended to embrace all such modifications and changes and, accordingly, the above description is to be regarded in an illustrative rather than a restrictive sense.

Claims

CLAIMS What is claimed is:

1. A modular shell and tube heat exchanger, comprising: a shell having a mounting plate coupled to an upper end of the shell and one or more outlets, the mounting plate defining one or more tube module apertures; a nozzle having an inlet and an outlet; and a tube module having a first end coupled to the nozzle and extending through the one or more tube module apertures, the tube module having a central inlet tube in fluid communication with the inlet and a bundle of tubes surrounding the central inlet tube in fluid communication with the outlet; and wherein the tube module is configured for selective removal from the shell.

2. The modular shell and tube heat exchanger as in claim 1, further comprising one or more nozzle lifting lugs coupled to the nozzle and configured to allow the nozzle to be lifted from the tube module.

3. The modular shell and tube heat exchanger as in claim 1, further comprising a seal between the tube module and the mounting plate to create a fluid tight seal between the tube module and the mounting plate.

4. The modular shell and tube heat exchanger as in claim 1, further comprising one or more tube module lifting lugs coupled to the tube module and configured to allow the tube module to be lifted from the mounting plate.

5. The modular shell and tube heat exchanger as in claim 1, further comprising one or more tube baffles disposed within the tube module and configured to create a tortuous fluid flow path through the tube module.

6. The modular shell and tube heat exchanger as in claim 1, further comprising a tube module plenum at a second end of the tube module, the tube module plenum in fluid communication with the central inlet tube and the bundle of tubes.

7. The modular shell and tube heat exchanger as in claim 1, wherein the central inlet tube is coupled to the inlet of the nozzle, and wherein the bundle of tubes is concentric around the central inlet tube.

8. The modular shell and tube heat exchanger as in claim 1, further comprising a plurality of tube modules coupled to the shell mounting plate.

9. The modular shell and tube heat exchanger as in claim 1, wherein the shell further comprises a primary fluid inlet disposed within an upper half of the shell and one or more outlets disposed at a lower end of the shell.

10. The modular shell and tube heat exchanger as in claim 9, wherein the primary fluid inlet is formed as a plurality of holes through the shell to allow primary fluid to enter the shell through the plurality of holes.

11. The modular shell and tube heat exchanger as in claim 1, further comprising one or more shell baffles, the one or more shell baffles disposed within the shell and having apertures therein to provide lateral support to corresponding tube modules inserted therein.

12. The modular shell and tube heat exchanger as in claim 1, wherein the shell has a convex sidewall and an opposing concave sidewall, the convex and concave sidewalls each having a radius of curvature that shares a center of curvature.

13. The modular shell and tube heat exchanger as in claim 1, wherein the tube module is supported by the mounting plate.

14. The modular shell and tube heat exchanger as in claim 1, further comprising a vent formed in the shell to allow gas within the shell to escape through the vent.

15. The modular shell and tube heat exchanger as in claim 1, further comprising an expanding plug configured to be inserted into one of the tubes of the bundle of tubes and expanded to isolate the tube from fluid flow.

16. A method for repairing the modular shell and tube heat exchanger of claim 1, comprising: decoupling a first nozzle from a first tube module; lifting the first nozzle off of the first tube module; inspecting an interior of a plurality of tubes within the first tube module; and plugging, with one or more plugs, at least one tube of the plurality of tubes.

17. The method as in claim 16, further comprising removing the first tube module from a shell by lifting the first tube module out of the shell through the mounting plate.

18. The method as in claim 17, further comprising replacing the first tube module with a second tube module.

19. The method as in claim 16, wherein lifting the nozzle off of the tube module comprises coupling one or more lifting lugs of the nozzle to an overhead crane.

20. The method of claim 16, wherein plugging, with one or more plugs, at least one tube of the plurality of tubes comprises: inserting an expandable plug into a first tube; advancing the expandable plug to a lower end of the first tube; and expanding the expandable plug to occlude the tube.