A heat exchanger unit, a heat exchanger assembly, a nuclear reactor, and a method of servicing a nuclear reactor

Abstract

According to a first aspect of the present disclosure, there is provided a heat exchanger unit (1200) for a nuclear reactor (1) The heat exchanger unit (1200) features an inner channel for accepting a working fluid flow as a separate flow from a source fluid flow contacting the heat exchanger unit (1200). The heat exchanger unit (1200) also features a connector block (1220) for providing a mechanical and flowing connection to a manifold (1100) of a heat exchanger assembly (1000). The connector block (1220) attaches the heat exchanger unit (1200) to the manifold (1100) through a vertically operated mechanical attachment interface. The connector block (1220) features a port (1222), which is coupled to a counterpart on the manifold (1100) through a single vertical motion for connecting the inner channel to a flowing connection with the manifold (1100).

Description

[0001] A HEAT EXCHANGER UNIT, A HEAT EXCHANGER ASSEMBLY, A NUCLEAR REACTOR, AND A METHOD OF SERVICING A NUCLEAR REACTOR

[0002] FIELD

[0003] The present disclosure relates to nuclear reactors.

[0004] BACKGROUND

[0005] Safety is a priority in designing, operating, and maintaining nuclear reactors. Regular maintenance operations require disassembling and inspection of parts of the reactor’s cooling system. This task becomes particularly challenging for small modular reactors featuring an integrated design, in which primary heat exchangers are installed inside the reactor vessel. With conventional attachment methods the available space becomes filled with pipes and joints. Designing the cooling system in such way that enables removing the heat exchanger units for maintenance while retaining the compact size of the reactor vessel becomes a formidable task. It is an objective of certain aspects of the present disclosure to meet that need.

[0006] SUMMARY

[0007] The invention is defined by the features of the independent claims.

[0008] According to a first aspect of the present disclosure, there is provided a heat exchanger unit for a nuclear reactor. The heat exchanger unit features an inner channel for accepting a working fluid flow as a separate flow from a source fluid flow contacting the heat exchanger unit. The heat exchanger unit also features a connector block for providing a mechanical and flowing connection to a manifold of a heat exchanger assembly. The connector block attaches the heat exchanger unit to the manifold through a vertically operated mechanical attachment interface. The connector block features a port, which is coupled to a counterpart on the manifold through a single vertical motion for connecting the inner channel to a flowing connection with the manifold.

[0009] According to a second aspect of the present disclosure, there is provided a heat exchanger assembly. The heat exchanger assembly includes at least one such heat exchanger unit as well as a manifold. The manifold features a housing, which defines a central volume for accepting the at least one heat exchanger unit. The manifold also features a working fluid flow channel, which is formed at least in part into the housing for communicating with a secondary circuit. The manifold further features a carrier block, which is formed adjacent to the central volume for attachment to a respective connector block of the at least one heat exchanger unit through the single vertical motion. The manifold has a port for connection to the respective port on the at least one heat exchanger unit through the single vertical motion for establishing a fluid connection between the inner channel and the working fluid flow channel.

[0010] According to a third aspect of the present disclosure, there is provided a nuclear reactor featuring a containment vessel, a reactor vessel contained within the containment vessel, and a primary circuit contained within the reactor vessel. The nuclear reactor also features a heat exchanger assembly according to the second aspect with the housing integrated to and between the containment vessel and the reactor vessel.

[0011] According to a fourth aspect of the present disclosure, there is provided a method of servicing a heat exchanger unit of the nuclear reactor according the third aspect. The method involves:

[0012] - removing a lid of the containment vessel;

[0013] - removing a lid of the reactor vessel;

[0014] - removing the at least one affixer from the connector block and carrier block from above;

[0015] - lifting the at least one heat exchanger unit off the carrier block;

[0016] - performing maintenance or inspection on the at least one heat exchanger unit;

[0017] - installing the inspected or serviced at least one heat exchanger unit or a replacement heat exchanger unit by lowering the heat exchanger unit onto the carrier block;

[0018] - securing the heat exchanger unit to the carrier block with at least one affixer from above;

[0019] - closing the lid of the reactor vessel, and

[0020] - closing the lid of the containment vessel.

[0021] According to a fifth aspect of the present disclosure, there is provided a manifold for a heat exchanger assembly of a nuclear reactor. The manifold features a peripheral housing, which defines, at least in part, a central volume for accepting at least one heat exchanger unit. The housing features at least one port, which communicates with the central volume. The manifold features a working fluid flow channel formed at least in part into the housing. The working fluid flow channel includes a collector channel section, which extends along the housing, and at least one inlet channel section, which connects a corresponding at least one port to the collector channel section. The manifold also features a passage for connecting the collector channel section to a secondary circuit. According to a sixth aspect of the present disclosure, there is provided a nuclear reactor comprising featuring a containment vessel, a reactor vessel contained within the containment vessel, a primary circuit contained within the pressure vessel, and the manifold according to the fifth aspect integrated to and between the containment vessel and the reactor vessel.

[0022] One or more embodiments of the first aspect may include one or several features from the following itemized list:

[0023] - the heat exchanger unit comprises a shell;

[0024] - the shell encloses the inner channel;

[0025] - the shell is configured to accept the source fluid flow through the shell for contacting the exterior of the inner channel;

[0026] - the connector block extends from the shell;

[0027] - the connector block is provided to the side of the shell;

[0028] - the connector block is provided to the top of the shell;

[0029] - the shell is elongated along the vertical dimension;

[0030] - the connector block extends from the shell in a non-vertical dimension;

[0031] - the inner channel extends between an inlet end and an outlet end;

[0032] - said port is an inlet port provided to the inlet end of the inner channel;

[0033] - the block comprises another such port as an outlet port;

[0034] - the outlet port is provided to the outlet end of the inner channel.

[0035] - the inner channel extends vertically from the port(s);

[0036] - the connector block is configured to accept at least one affixer there through for attaching the connector block to the manifold;

[0037] - the port comprises a coupler,

[0038] - the coupler is a male or female fitting,

[0039] - the fitting is configured to be inserted or received into a corresponding female or male fitting on the manifold, respectively, through the single linear motion;

[0040] - the heat exchanger assembly comprises at least one affixer securing the connector block of at least one heat exchanger unit to the carrier block in the vertical dimension;

[0041] - at least some of the servicing steps is / are performed with a remote-operated device

[0042] - the housing comprises an outer collar;

[0043] - the outer collar forms the outer perimeter of the manifold;

[0044] - the outer collar is configured to be formed as an integral part of a containment vessel of an integrated dual-vessel nuclear reactor; - the housing comprises an inner collar;

[0045] - the inner collar forms an inner perimeter defining the central volume of the manifold;

[0046] - the inner collar is configured to be formed as an integral part of a reactor vessel of an integrated dual-vessel nuclear reactor;

[0047] - the housing is annular;

[0048] - the housing comprises steam channels;

[0049] - the steam channels extend vertically;

[0050] - the steam channels are disposed along the housing;

[0051] - the steam channels are disposed between the inner collar and outer collar;

[0052] - the housing is made up by one or more than one peripheral housing element(s);

[0053] - the housing is configured to accept a plurality of such heat exchanger units ;

[0054] - the manifold comprises a carrier block;

[0055] - the carrier block is formed adjacent to the central volume;

[0056] - the carrier block comprises a support surface for supporting the at least one heat exchanger unit;

[0057] - the support surface comprises said at least one inlet port;

[0058] - the carrier block is configured to accept at least one affixer used to fasten the heat exchanger unit(s) to the manifold;

[0059] - the inlet channel sections extend at least in part in a vertical dimension;

[0060] - the collector channel section extends horizontally along the inner or outer perimeter of the housing;

[0061] - the working fluid flow channel comprises a connecting channel sections for each port;

[0062] - the connecting channel sections connects the respective inlet channel section to the collector channel section;

[0063] - said working fluid flow channel is a working fluid return flow channel and the manifold comprises a working fluid discharge flow channel, which is formed at least in part into the housing;

[0064] - a collector channel section of the working fluid discharge flow channel extends along the inner or outer perimeter of the housing and adjacent to the collector channel section of the working fluid return flow channel;

[0065] - at least one inlet channel section of the working fluid discharge flow channel connects a corresponding port, which communicates with the central volume, to the collector channel section; - the manifold comprises an inlet cover, which closes the collector channel section of the working fluid discharge flow channel and comprises an inlet connector for connecting the manifold to the secondary circuit;

[0066] - the working fluid flow channel comprises several circuits formed by respective several collector channel sections;

[0067] - the collector channel section is provided as an open indentation extending along an inner or outer perimeter of the housing; the manifold comprises a cover, which closes the collector channel section:

[0068] - the cover comprises a connector for forming said passage;

[0069] - the collective channel section is provided as an add-on channel formed by a separate conduit, which is attached to the housing;

[0070] - the manifold comprises a plurality of such ports for each heat exchanger unit;

[0071] - one port of the plurality of ports of the housing is configured as an inlet port for connecting one working fluid flow channel to supply the heat exchanger unit with working fluid;

[0072] - and another port of the plurality of ports of the housing is configured as outlet port for connecting another working fluid flow channel to receive working fluid from the heat exchanger unit;

[0073] - the ports of the plurality of heat exchanger units and the ports of the manifold are in alignment with each other

[0074] - the manifold is welded to the containment vessel and reactor vessel;

[0075] - the nuclear reactor is a district heating reactor.

[0076] Considerable benefits are gained with the aid of the novel proposition. As the mechanical and flowing connection between the heat exchanger unit and the secondary circuit may be established and broken with a single vertical motion, the heat exchangers can be removed for inspection and maintenance from above after the reactor vessel has been opened. This greatly simplifies assembly and disassembly of heat exchanger units, which is beneficial for both manned and remote-operated maintenance.

[0077] BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In the following certain exemplary embodiments are described in greater detail with reference to the accompanying drawings, in which:

[0079] FIGURE 1 illustrates a cross-sectional view of a nuclear reactor in accordance with at least some embodiments; FIGURE 2 illustrates a perspective view of a heat exchanger assembly in accordance with at least some embodiments featuring manifold and one heat exchanger unit detached from the manifold;

[0080] FIGURE 3 illustrates a perspective view of the manifold of FIGURE 2;

[0081] FIGURE 4 illustrates a partial perspective section view of the manifold and heat exchanger unit of FIGURE 2;

[0082] FIGURE 5 illustrates a partial top elevation view of the manifold and heat exchanger unit of FIGURE 2:

[0083] FIGURE 6 illustrates a section view of the manifold and heat exchanger unit of FIGURE 5 taken along line A-A;

[0084] FIGURE 7 illustrates another section view of the manifold and heat exchanger unit of FIGURE 5;

[0085] FIGURE S illustrates a partial perspective section view of the manifold and heat exchanger unit of FIGURE 2 with the manifold an heat exchanger unit attached to each other;

[0086] FIGURE 9 illustrates a perspective explosion view of the manifold and heat exchanger unit of FIGURE 7, and

[0087] FIGURE 10 illustrates a perspective detail view of the mating elements of the manifold and heat exchanger unit of FIGURE 2.

[0088] EMBODIMENTS

[0089] FIGURE 1 illustrates a nuclear reactor 1 in accordance with at least some embodiments. The nuclear reactor 1 comprises a reactor core 400 encased in a reactor vessel 200, which in turn comprises a lid 201 .

[0090] A fuel and control system is located inside the reactor vessel 200. The function of the fuel and control system is to provide the fuel for operating the reactor core 400 as well as a mechanism for controlling the nuclear reaction. The number of fuel units and the configuration of the control rod system varies between different reactor types. While in operation, the fuel units are located in the lower section of the reactor vessel 200, and gathered together to make up the reactor core 400. The control rod system may be installed either inside or outside the reactor vessel. The exemplary nuclear reactor 1 is a district heating reactor but the principles disclosed herein are applicable to other reactor types as well. The nuclear reactor 1 features a doublevessel configuration with the reactor vessel 200 contained within a containment vessel 300, which is closed by a lid 301. It is, however, to be noted, that the embodiments herein discloses may be applicable to other vessel configurations.

[0091] An annular inner wall is provided within the reactor vessel 200 to create a riser barrel 500. The riser barrel 500 may extend from a fuel unit housing towards the upper plenum 502. Alternatively, the riser barrel 500 may envelop the fuel unit housing and even the reactor core 400. The purpose of the riser barrel 500 is to define a fluid circulation path for the primary fluid or coolant contained in the reactor vessel 200. The riser barrel 500 forms a riser 501 on top of the reactor core 400. The riser 501 is the inner volume defined by the riser barrel 500. The space defined between the riser 501 , i.e. the top level of the riser barrel 500, and a split seam between the reactor vessel body and lid 201 , is an upper plenum.

[0092] An annular space is formed between the riser barrel 500 and the reactor vessel 200 as a downcomer 504. A heat exchanger assembly 1000 is provided between the upper plenum 502 and the downcomer 504. The downcomer 504 communicates with a lower plenum 505, which is formed between a bottom support plate of the reactor core 400 and the bottom of the reactor vessel 200.

[0093] FIGURE 1 sketches nuclear reactor 1 under normal operation, in which primary fluid flows along a natural or forced fluid circulation path. The natural fluid circulation path begins at the reactor core 400, at which the primary fluid is heated, raises up through the riser 501 , diverts down to the heat exchanger assembly 1000 at the upper plenum 502, continues down the downcomer 504, and back to the reactor core 400 through the lower plenum 505. While flowing through the heat exchanger assembly 1000 the primary fluid heats up a secondary fluid, which enters the heat exchanger assembly 1000 from outside the containment vessel 300.

[0094] FIGURE 2 shows a partial view of an exemplary heat exchanger assembly 1000 that can incorporated to a double-vessel design, such as that shown in FIGURE 1. The heat exchanger assembly 1000 features a manifold 1100 that is designed to couple at least one but ideally several heat exchanger units 1200 to the nuclear reactor 1. In the illustrated example the manifold 1100 is designed to accommodate 12 heat exchanger units 1200 in circular formation. More particularly the manifold 1100 positions the heat exchanger units 1200 into the annular space between the reactor vessel 200 and riser barrel 500 as well as between the upper plenum 502 and downcomer 504 to guide the flow of primary fluid through the heat exchanger units 1200. The manifold 1100 also accommodates the intake and discharge of a working fluid from outside the containment vessel 300. The manifold 1100 features a working fluid flow channel 1400. The flow channel 1400 may be accessed through an inlet connector 1131 , which is formed into an inlet cover 1130. This working fluid channel 1400 is intended to act as an inlet into the manifold 1100. In other words this channel 1400 is a working fluid return channel for leading the working fluid back into the nuclear reactor 1 from a secondary circuit outside the nuclear reactor 1. This relatively cool fluid is returning to the nuclear reactor 1 from the secondary circuit, where the previously relatively hot fluid had released heat to an exothermic process at the secondary circuit. The manifold 1100 also features another flow channel 1500. The flow channel 1500 may be accessed through an outlet connector 1121 , which is formed into an outlet cover 1120. This working fluid channel 1500 is intended to act as an outlet from the manifold 1100. In other words this channel 1500 is a working fluid discharge channel for leading the working fluid out of the nuclear reactor 1 into a secondary circuit outside the nuclear reactor 1 . The fluid is discharged from the nuclear reactor 1 in a relatively hot temperature having been heated during passage through the heat exchanger unit 1200. The secondary circuit may include a heat consumer, such as a turbine or another heat exchanger connecting the secondary circuit to the district heating network.

[0095] The overall design of the manifold 1100 is shown in detail in FIGURE 3, wherein the heat exchanger unit 1200, inlet cover 1120, and outlet cover 1130 have been omitted for the sake of clarity. The manifold 1100 is designed to be integrated into a double-vessel design of a nuclear reactor 1. The manifold 1100 has a housing 1110 that therefore complies to the generally cylindrical shape of the nuclear reactor 1 and therefore exhibits a generally annular design that defines a central volume 1300. To facilitate such integration, the manifold 1100 features an outer collar 1114 that extends axially from the housing 1110 at its outer periphery. The outer collar 1114 is intended to be incorporated to the containment vessel 300. More specifically, the outer collar 1114 is designed to form part of the structure of the containment vessel 300. This means that the material, dimensions, heat treatment, and / or surface treatment of the outer collar 1114 is generally matched with that of the containment vessel 300. The outer collar 1114 may be integrated to the containment vessel 300 by welding, for example.

[0096] Alternatively, the outer collar 1114 may feature a flange, to which a corresponding flange on the containment vessel is attached with affixers, such as bolts, welding, or any other foreseeable technique. Such a flange may extend in a non-vertical dimension, such as along the horizontal. Such integration may require adaptation of the host containment vessel 300 by omitting a corresponding section of the vessel for accommodating the housing 1110. As highlighted in FIGURE 6, the mating surfaces of the outer collar 1114 and the containment vessel 300 preferably feature reliefs, such as chamfers, for facilitating welding.

[0097] The illustrated embodiment features such collars 1113, 1114 extending to both vertical directions, i.e. upward and downward from the housing 1110. It could also be foreseen to provide a collar only to either side or to replace either collar with a non-vertical flange.

[0098] The same applies to the integration of the manifold 1100 to the reactor vessel 200 (FIGURE 3). To facilitate such integration, the manifold 1100 features an inner collar 1113 that extends axially from the housing 1110 at its inner peripheral region adjacent to the central volume 1300. The inner collar 1113 is intended to be incorporated to the reactor vessel 200. More specifically, the inner collar 1113 is designed to form part of the structure of the reactor vessel 200. This means that the material, dimensions, heat treatment, and surface treatment of the inner collar 1113 is generally matched with that of the reactor vessel 200. The inner collar 1113 may be integrated to the reactor vessel 200 by welding, for example. Alternatively, the inner collar 1113 may feature a flange, to which a corresponding flange on the containment vessel is attached with affixers, such as bolts, welding, or any other foreseeable technique. Such integration may require adaptation of the host reactor vessel 200 by omitting a corresponding section of the vessel for accommodating the housing 1110. The mating surfaces of the inner collar 1113 and the reactor vessel 200 preferably feature reliefs, such as chamfers, for facilitating welding.

[0099] The housing 1110 occupies the space between the containment vessel 300 and the reactor vessel 200. To connect the volumes above and below the manifold, to enable passage of steam in that space for example, the housing 1110 is provided with a plurality of steam channels 1600. The steam channels 1600 may take the form of axially extending passages provided around along the housing 1110 between the inner collar 1113 and outer collar 1114. In this context, the expression axial is intended to refer to dimension, in which the nuclear reactor 1 is elongated, typically vertically.

[0100] The housing 1110 extends around the central volume 1300 and features a carrier block 1111 for facilitating at least one but preferably several heat exchanger units 1200. The carrier block 1111 has two purposes. Firstly, the carrier block 1111 serves as a mechanical attachment and support point for the heat exchanger units 1200. Secondly, the carrier block 1111 connects the heat exchanger units 1200 into a flowing connection with the secondary circuit. These two connections, namely mechanical and flowing, are established with a simple and effective connective motion in the vertical dimension. The carrier block 1111 extends towards the central volume 1300. The carrier block 1111 has a mating surface for providing said double-function. In the illustrated example the mating surface is horizontal for providing the vertical connective motion. The mating surface could, however, be angled as long as the surface extends in a skewed dimension that has a considerable horizontal component. The mating surface 1111 features a number of ports 1116, 1118 for fluid communication with the heat exchanger units 1200. The port 1116 shown on the right of each position is for feeding fluid into the heat exchanger unit 1200, whereas the port 1118 shown on the left of each position is for receiving fluid from the heat exchanger unit 1200. The carrier block 1111 also features a number of recesses 1112 for accepting the heat exchanger units 1200, which in the illustrated example are generally cylindrical, in a partly embedded fashion so as to minimize the space taken up by the heat exchanger assembly inside the nuclear reactor 1. The recesses 1112 may be radially extending cavities formed to an otherwise cylindrical surface, which faces the central volume 1300.

[0101] The manifold 1100 contains several channels for managing the flow of fluid within the nuclear reactor 1 and between the nuclear reactor 1 and the secondary circuit outside the containment vessel 300. As mentioned above, the steam channels 1600 manage steam flow between sections of the intermediate space between containment vessel 300 and reactor vessel 200 above and below the housing 1110. Steam flow between these sections of the intermediate space serves the purpose of facilitating passive removal of decay heat from the nuclear reactor by conduction through the vessels. Such passive decay heat removal process is known, per se, from WO 2022106756 A1 . The primary fluid flows inside the reactor vessel 200 along the flow path described above and flushes through the heat exchanger units 1200 in a manner, which will become apparent here after. The secondary fluid flows through the manifold 1100 and to an inner channel of each heat exchanger unit 1200, where it is kept separate from the primary fluid. The flow path of the secondary fluid is now discussed in greater detail with reference to FIGURES 2 to 7.

[0102] As far as the heat exchanger unit 1200 is concerned, the secondary fluid of the nuclear reactor 1 is the working fluid, which transmits heat from the nuclear reactor 1 to the secondary circuit. Analogously, the primary fluid of the nuclear reactor 1 is the source fluid. A working fluid originating from a secondary circuit flows into a working fluid return flow channel 1400 of the manifold 1100 through an inlet connector 1131. The working fluid return channel 1400 has three sections. The first one is a collector channel section 1403 that is collective for several heat exchanger units 1200. The collector channel section 1403 is accessed through an inlet connector 1131 formed into an inlet cover 1130, which closes the collector channel section 1403. According to the illustrated example the collector channel section 1403 is formed as an open indentation to the outer surface of the housing 1110. The collector channel section 1403 may extend around essentially the entire circumference of the housing 1110 or it may occupy only a certain portion of the periphery. According to the exemplary illustrated embodiment, the manifold 1100 features two working fluid return channels 1400 forming two distinct flow circuits and, respectively, two such collector channel sections 1403 extending approximately half of the peripheral length of the housing 1110. The collector channel section 1403 is shown in an open configuration in FIGURE 3 and in a closed configuration in FIGURE 2, wherein it is closed by the inlet cover 1130. Naturally, as there are two such working fluid return channels 1400, the manifold 1100 has two respective inlet covers 1130 for closing the channels.

[0103] The working fluid return flow channel 1400 also has an individual internal channel section 1401 for communicating with each heat exchanger unit 1200. This channel section 1401 feeds relatively cool working fluid from the secondary circuit to the heat exchanger unit 1200. The internal channel section 1401 is placed on the inner region of the housing 1110 and extends, at least in part, vertically. The internal channel section 1401 terminates to the port 1116 on the carrier block 1111 (see FIGURE 3). Connecting each internal channel section 1401 to the collective collector channel section 1403 is a connecting channel section 1402. The illustrated embodiment shows the internal channel section 1401 as a fully vertical and the connective channel section 1402 as fully horizontal sections as the preferred option from a manufacturing point of view as these channel sections may be produced by drilling from above and from the side, respectively. The inlet connector 1131 encloses an external channel section 1404 of the working fluid return flow channel 1400, which is the part of the channel closest to an external system, which is the secondary circuit of the nuclear power plant.

[0104] Similar flow channels are provided also for the outbound flow of the secondary fluid. A working fluid discharge flow channel 1500 is provided to act in parallel with the working fluid return flow channel 1400. As shown in FIGURE 7, the working fluid discharge flow channel 1500 has a collective collector channel section 1503 similar to the collective collector channel section 1403 of the working fluid return flow channel 1400. FIGURE 3 shows how the collector channel sections 1403, 1503 are provided on top of each other but separated by a peripherally extending part of the housing 1110. The working fluid discharge flow channel 1500 also has a number of individual internal channel sections 1501 and respective connecting channel sections 1502 similar to the internal channel sections 1401 and connecting channel sections 1402 of the working fluid return flow channel 1400.

[0105] Let us then turn to an exemplary construction of a cooperating heat exchanger unit 1200. As is shown in FIGURE 4, the heat exchanger unit 1200 has a generally cylindrical shell 1210 for exchanging heat between the source flow, which is the primary fluid flow inside the reactor vessel 200, and working fluid flow, which is the secondary fluid flow between the nuclear reactor 1 and an external secondary circuit. The cylindrical shell is preferred in pressurized flow applications, where pressure resistance may be achieved with minimum wall thickness. However, other shapes, such as annular sector shapes could be foreseen to optimize use of space with the expense of wall thickness.

[0106] The shell 1210 encloses a plurality of tubes extending along an inside the elongated shell 1210. The tubes may be formed of relatively thin-walled profiles, which are bound together by an upper tube sheet, a lower tube sheet or both an upper and lower tube sheet. The tubes are open to the central volume 1300 for accepting the flow of the source fluid there through. Extending inside the shell 1210 is an inner cavity for conveying the working fluid in thermal contact with the tubes but separated by the tubes from the source fluid flowing through the tubes. Such an exemplary design resembles a shell and tube heat exchanger type, which is known per se along with other suitable designs.

[0107] Extending from the shell 1210 is a connector block 1220, which is the heat exchanger’s 1200 counterpart to the carrier block 1111 of the manifold 1100. The purpose of the connector block 1220 is to provide for a mechanical and flowing connection to the carrier block 1111. As is perhaps best shown in FIGURES 4, 9, and 10, the connector block 1220 has a mating surface, which matches the mating surface on the carrier block 1111. In the illustrated example that mating surface is horizontal but also a skewed surface would do as long as the mating surface extends in a dimension that has a horizontal component. To provide for a mechanical connection, the connector block 1220 has through-holes for accepting affixers 1700, such as screws, there through to attach the connector block 1220 to the carrier block 1111 , which has corresponding receptive holes for a threaded connection.

[0108] FIGURES 9 and 10 also reveal how a flowing connection is also established by a single vertical movement. As described above, the flow channel of the working fluid is accessed by the port 1116 on the mating surface of the carrier block 1111 . A cooperating port 1222 is provided on the mating surface of the connector block 1220. The cooperating ports 1222, 1116 align with one another, once the mating surfaces on the connector block 1220 and carrier block 1111 engage. If, as illustrated, the mating surfaces are planar, the ports 1222, 1116 may be sealed with an intermediate gasket 1117, such as a compressive O-ring.

[0109] Such a construction is particularly advantageous in that the mechanical connection between the heat exchanger unit 1200 and the housing 1110 can be established by a simple threaded connection from direction, namely from above. This means that the heat exchanger unit 1200 may be installed or removed by accessing the containment vessel 300 from above. Such a simple construction facilitates convenient, optimally robotized maintenance of a nuclear reactor.

[0110] FIGURE 8 shows the heat exchanger unit 1200 attached to the carrier block 1111. The exemplary horizontal mating surfaces of the connector block 1220 and carrier block 1111 are engaged and secured to each other with the affixers extending vertically through the connector block 1220 and into the carrier block 1111. Alternatively, the carrier block could feature vertically protruding threaded studs that would extend through the connector block 1220 and secured with nuts tightened down from above. FIGURE 8 also shows the optional diverter plate 1211 , which is provided at the upper region of the shell 1210 as a flange for filling the space between adjacent heat exchangers 1200 for the purposes of diverting all fluid flow to inside the shell 1210.

[0111] FIGURES 6 and 7 show the interaction between the inner channel of the heat exchanger 1200 and the flow channel 1400, 1500 of the manifold 1100. The inner channel of the heat exchanger 1200 terminates at the port 1222 on the mating surface of the connector block 1220. The inner channel extends from the port 1222, at least initially, essentially vertically so as to match the orientation of the internal channel section 1401 , 1501. In the illustrated embodiment the inner channel is constructed as a tube extending between the inlet port 1222 and outlet port provided adjacent to each other on the connector block 1220. While the inner channel is not shown separately in FIGURES 6 and 7, FIGURE 7 shows the basic construction of the heat exchanger 1200 illustrating the outlet port of the heat exchanger 1200 on the left and the inlet port at the center of the shell 1210 with the tube extending vertically in the center region of the shell 1210.

[0112] The heat exchanger assembly 1000 is fully assembled, when the manifold 1100 is built into the double-vessel construction of the nuclear reactor 1 , the secondary circuit is connected to the housing 1110 via the inlet connector 1131 and outlet connector 1121 , and the heat exchanger units 1200 are attached into a mechanical and flowing connection with the housing 1110. Heat may then be exchanged between the source fluid flowing inside reactor vessel 200 and the working fluid flowing between the manifold 1100 and the secondary circuit. The source fluid flows along the path shown in FIGURE 1 thus heating the contact surfaces of the heat exchanger units 1200 placed between the upper plenum 502 and the downcomer 504. The hot contact surfaces, which in the illustrated embodiment are tubes, heat the working fluid flowing adjacent to the contact surfaces. In the illustrated example the working fluid is flowing in the inner channel of the heat exchanger unit 1200 formed between the shell 1210 and the tubes. The heated working fluid flows to the housing 1110 through one pair of aligned ports 1222, 1116 on the connector block 1220 and carrier block 1111. The hot working fluid escapes the manifold along the working fluid discharge flow channel 1500 and out through the outlet connector 1121 to the secondary circuit, where the working fluid releases heat to an exothermic load. The cooled working fluid is returned to the system through the inlet connector 1131. The cool working fluid flows along the working fluid return flow channel 1400 back into the heat exchanger unit 1200 another pair of aligned ports 1222, 1116 on the connector block 1220 and carrier block 1111.

[0113] The proposed construction is very advantageous for remote-controlled maintenance and inspection. The heat exchanger assembly 1000 may be disassembled for maintenance and inspection with a remote-controlled device. With the lids 301 , 201 of the containment vessel 300 and reactor vessel 200 removed, the heat exchanger units 1200 are accessible from above. The affixers 1700 are removed from above, whereby the mechanical and flowing connection between the heat exchanger units 1200 and the manifold 1100 can broken by simply lifting the heat exchanger units 1200 off the carrier block 1111. With the heat exchanger units 1200 inspected and potentially cleaned or replaced, they may be installed back in by lowering the heat exchanger units 1200 back into the central volume 1300 by mating the cooperating surfaces of the connector block 1220 and carrier block 1111. With the heat exchanger units 1200 in place, the mechanical connection is secured by reintroducing the affixers 1700 from above. The lids 301 , 201 may then be closed to resume operation of the nuclear reactor 1 .

[0114] There are several different ways to provide a housing 1110 for such a manifold 1100.

[0115] According to the illustrated embodiment, the housing 1110 is machined of a massive preform ring, which, in turn, may be cast or forged into an annular shape. The channels shown in the FIGURES are specifically designed to be manufactured by drilling. The collective channel sections 1403, 1504 may be manufactured by milling. The collars 1131 , 1114 may also be produced by machining a groove there between, e.g. by lathing.

[0116] According to an alternative embodiment, the housing may be produced exclusively by welding or assembling otherwise produced items by welding. The housing may for example be established by welding together two collars forming the inner and outer collars 1113, 1114 shown in the FIGURES and intermediate reinforcement plates forming the steam channels 1600. The carrier block may be provided by welding a massive component or a hollow enclosure to the inner surface of the inner collar. The covers may be welded on similarly to the massive ring embodiment of FIGURES 2 to 10. Alternatively, the housing may be produced by welding two forged collars together via connecting tubes and support structures.

[0117] According to an alternative embodiment, the housing may be produced with an additive manufacturing technique, more specifically a layering manufacturing technique.

[0118] According to the illustrated embodiment, the housing 1110 is constructed as a single piece, which comprises two inlet flow circuits (working fluid return flow channel 1400) and two outlet flow circuits (working fluid discharge flow channel 1500) that are independent from each other. This embodiment may be varied by producing the housing from several components, such as one component including a first inlet flow circuit and a first outlet flow circuit and another component including a second inlet flow circuit and a second outlet flow circuit. Such components would therefore extend over half of the full circular coverage of the annular housing. The housing could alternatively be formed of more than one such sector. Alternatively, the flow channels could be provided as singular circuits extending along the entire periphery of the housing or only across a part of the periphery.

[0119] According to the illustrated embodiment the collective channel sections are provided on the outer periphery of the housing. According to an alternative embodiment, the either collective channel section or both collective channel sections can be provided on the inner periphery of the housing that is adjacent to the central volume. In such case, the connecting channel section connects the collective channel section to the outer periphery of the housing, which includes a connector to the secondary circuit.

[0120] According to an alternative embodiment, the collective channel section is not provided as an open channel but a void inside the housing not closed by a separate cover as in the illustrated embodiment. Such a void may be provided by producing the housing with an additive manufacturing technique.

[0121] According to an alternative embodiment, the collective channel section is provided as an add-on channel formed by a separate conduit, which is attached to the housing. According to a foreseeable variant, a tube covering part of the entirety of the periphery of the housing may act as a collector communicating with a respective external channel section and connective channel sections via additional conduit.

[0122] According to the illustrated embodiment, the contact interface of the connector block of the heat exchanger unit and carrier block of the housing is planar. According to a further embodiment, the contact interface between the connector block and carrier block may feature a penetrative coupler. More particularly, the coupler may feature a male or female fitting at the port 1222 of the connector block. This fitting may be configured to be inserted or received into a corresponding female or male fitting at the port 1116 on the housing 1110. The fitting may take the form a cylindrical shoulder extending from the connector block 1220, which may be inserted into the port 1116 of the carrier block during the single linear motion in the vertical dimension that is used to bring the connector block 1220 and the carrier block 1111 into to contact. Naturally, the fitting may be reversed by providing such a sealing collar to extend from the mating surface of the carrier block 1111.

[0123] In the illustrated example channels 1400, 1500 provide an inlet and outlet for fluid entering and exiting the manifold 1100. However, the function of these channels and / or their position and / or orientation on the housing 1110 could be reversed.

[0124] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0125] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0126] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0127] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well- known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0128] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below. The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

[0129] REFERENCE SIGNS LIST

Claims

CLAIMS:1 . A heat exchanger unit (1200) for a nuclear reactor (1 ), comprising:- an inner channel for accepting a working fluid flow through the inner channel and separated from a source fluid flow contacting with the heat exchanger unit (1200) and- a connector block (1220) for providing a mechanical and flowing connection to a manifold (1100) of a heat exchanger assembly (1000), wherein the connector block (1220): o is configured to attach the heat exchanger unit (1200) to the manifold (1100) through a mechanical attachment interface operative vertically, and o comprises a port (1222), which is configured to be coupled to a counterpart on the manifold (1100) through a single vertical motion for connecting the inner channel to a flowing connection with the manifold (1100).

2. The heat exchanger unit (1200) according to claim 1 , wherein the heat exchanger unit (1200) comprises a shell (1210), which encloses the inner channel and which is configured to accept the source fluid flow through the shell (1210) for contacting the exterior of the inner channel, wherein the connector block (1220) extends from the shell (1210).

3. The heat exchanger unit (1200) according to claim 2, wherein the connector block (1220) is provided to the side of the shell (1210).

4. The heat exchanger unit (1200) according to claim 2 or 3, wherein the connector block (1220) is provided to the top of the shell (1210).

5. The heat exchanger unit (1200) according to any one of the preceding claims, wherein the shell (1210) is elongated along the vertical dimension, and the connector block (1220) extends from the shell (1210) in a non-vertical dimension.

6. The heat exchanger unit (1200) according to any one of the preceding claims, wherein the inner channel extends between an inlet end and an outlet end, wherein said port (1222) is an inlet port provided to the inlet end of the inner channel, wherein the connector block (1120) comprises another such port as an outlet port provided to the outlet end of the inner channel.

7. The heat exchanger unit (1200) according to any one of the preceding claims, wherein the inner channel extends vertically from the port(s).

8. The heat exchanger unit (1200) according to any one of the preceding claims, wherein the connector block (1120) is configured to accept at least one affixer (1700) there through for attaching the connector block (1220) to the manifold (1110).

9. The heat exchanger unit (1200) according to any one of the preceding claims, wherein the port (1222) comprises a coupler, which is a male orfemale fitting, which is configured to be inserted or received into a corresponding female or male fitting on the manifold (1100), respectively, through the single linear motion.

10. A heat exchanger assembly (1000) comprising:- at least one heat exchanger unit (1200) according to any one of the preceding claims, and- a manifold (1100), which comprises: o a housing (1110), which defines a central volume (1300) for accepting the at least one heat exchanger unit (1200), o a working fluid flow channel (1400) formed at least in part into the housing (1100) for communicating with a secondary circuit, and o a carrier block (1111 ), which:■ is formed adjacent to the central volume (1300),■ is configured to attach to a respective connector block (1220) of the at least one heat exchanger unit (1200) through the single vertical motion, and which■ comprises a port (1116), which is configured to be connected to the respective port (1222) on the at least one heat exchanger unit (1200) through the single vertical motion for establishing a fluid connection between the inner channel and the working fluid flow channel (1400).

11. The heat exchanger assembly (1000) according to claim 10, wherein the heat exchanger assembly (1000) comprises at least one affixer (1700) securing the connector block (1220) of at least one heat exchanger unit (1200) to the carrier block (1111 ) in the vertical dimension.

12. A nuclear reactor (1 ) comprising:- a containment vessel (300),- a reactor vessel (200) contained within the containment vessel (300),- a primary circuit contained within the reactor vessel (200), and- the heat exchanger assembly (1000) according to any one of the preceding claims 10 to 11 , wherein the housing (1110) is integrated to and between the containment vessel (300) and the reactor vessel (200).

13. A method of servicing a heat exchanger unit (1200) of the nuclear reactor (1 ) according to claim 12, the method comprising:(a) removing a lid (301 ) of the containment vessel (300);(b) removing a lid (201) of the reactor vessel (200);(c) removing the at least one affixer (1700) from the connector block (1220) and carrier block (1111 ) from above;(d) lifting the at least one heat exchanger unit (1200) off the carrier block (1111 );(e) performing maintenance or inspection on the at least one heat exchanger unit (1200);(f) installing the inspected or serviced at least one heat exchanger unit (1200) or a replacement heat exchanger unit (1200) by lowering the heat exchanger unit (1200) onto the carrier block (1111 );(g) securing the heat exchanger unit (1200) to the carrier block (1111) with at least one affixer (1700) from above;(h) closing the lid (201) of the reactor vessel (200), and(i) closing the lid (301 ) of the containment vessel (300).

14. The method of claim 13, comprising performing steps (c), (d), (f), and (g) with a remote-operated device.

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