Reactor control system

Abstract

To provide a compact reactor unit.SOLUTION: A reactor control system (100) for a nuclear fission reactor system comprising a nuclear reactor unit (300) having a reactor core (302) with a central axis (320) extending along the length of the reactor core (302). The nuclear reactor unit (300) comprises a first region (310) provided in the reactor core (302) and a second region (312) provided on the outside of the reactor core (302). The control system (100) comprises a control duct (200) having a first portion (210) configured to extend through the first region (310) and a second portion (220) configured to extend through the second region (312). The duct (200) is filled with a series of control units (400), and each of the control units (400) is configured to travel along the control duct (200).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to nuclear reactor control systems.

[0002] In particular, the present disclosure relates to a reactor control system for a nuclear fission reactor system including a reactor unit. [Background technology]

[0003] An aspect of all graphite-moderated nuclear fission reactor units is that their core size is proportionally significantly larger compared to water-moderated reactors for a given power capacity due to the low moderation of graphite. Thus, unlike water-cooled reactors, the reactor unit and associated components generally dominate the overall sizing of the power generation package.

[0004] As an example, an example of a graphite-moderated nuclear fission reactor 1 (General Atomics GT-MHR) is shown in Figure 1. Common to many designs, this arrangement has conventional straight control rods 2 that must be placed above the reactor vessel 3. As is well known, the control rods must extend into and out of the reactor. Therefore, a space equal to the core height must be available to allow the control rods to be completely removed from the reactor.

[0005] The elimination of the control rod support structure 4 reduces the size and weight of the reactor unit 1. Additionally, reducing the size of the reactor unit reduces the overall volume of space required to house it, and consequently reduces the amount of material, and therefore weight, required to house the power unit. This is important because in some applications, space and weight are at a premium. For example, reducing the size of the reactor unit in a nuclear vessel (particularly a submersible vessel, e.g., a submarine) can create space for other equipment or contribute to the goal of making the vessel smaller and lighter.

[0006] Therefore, a configuration that allows for a more compact reactor unit design for the same power output and control level is highly desirable. Summary of the Invention

[0007] According to the present disclosure, there is provided an apparatus and system / method as set out in the accompanying claims. Other features of the invention will become apparent from the dependent claims and the following description.

[0008] Thus, a reactor control system (100) may be provided for a nuclear fission reactor system including a reactor unit (300) having a core (302) with a central axis (320) extending along the length of the core (302). The reactor unit (300) may include a first region (310) disposed within the core (302) and a second region (312) disposed outside the core (302). The control system (100) may include a control duct (200) having a first portion (210) configured to extend through the first region (310) and a second portion (220) configured to extend through the second region (312). The duct (200) may be filled with a series of control units (400), each configured to travel along the control duct (200).

[0009] The control duct (200) may be configured for translation of the control unit (400) in a first direction D1 and a second direction D2. The first direction D1 may be a direction of travel from the second portion (220) towards the first portion (210). The second direction D2 may be a direction of travel from the first portion (210) towards the second portion (220).

[0010] The control duct (200) may have a first arcuate portion (230) extending between the first portion (210) and the second portion (220), and the first portion (210), first arcuate portion (230), and second portion (220) of the control duct (200) together define a continuous path for the passage of the control unit (400).

[0011] The control duct (200) may include a second arcuate portion (240) extending between the first portion (210) and the second portion (220), the second arcuate portion (240) being provided at opposite ends of the first portion (210) and the second portion (220) relative to the first arcuate portion (230) such that the first arcuate portion (230) is spaced from the second arcuate portion (240) by the first portion (210) and the second portion (220). The first portion (210), first arcuate portion (230), second portion (220), and second arcuate portion (240) of the control duct (200) may together define a single continuous loop path for passage of the control unit (400).

[0012] The control system may further comprise a first tank (700) for storing the control unit (400). The control duct (200) may be configured to receive the control unit (400) from the first tank (700) and / or supply the control unit (400) to the first tank (700). The control system may further comprise a second tank (720) for storing the control unit (400). The control duct (200) may be configured to receive the control unit (400) from the second tank (720) and / or supply the control unit (400) to the second tank (720). The first tank (700), the first portion (210), the first arcuate portion (230), the second portion (220), and the second tank (720) may be arranged consecutively to define a path for the passage of the control unit (400).

[0013] Some of the control units 400 may be absorber units 410. Some of the control units may be displacer units 420.

[0014] The absorber unit (410) may be less heavy than the displacer unit (420).

[0015] The control unit (400) may be spherical and have an outer diameter that is the same as or slightly smaller than the diameter of the control duct (200).

[0016] The control system may further comprise a drive mechanism (600) operable to drive the control unit (400) in a first direction D1 along the control duct (200) in a first operating mode, and operable to drive the control unit (400) in a second direction D2 along the control duct (200) in a second operating mode.

[0017] The drive mechanism (600) may include a screw (602) having a track (604) for engagement with the control unit (400) such that when the screw (602) is rotated, the control unit (400) is driven along the duct (200).

[0018] The screw (602) may be configured to move between a first position in which it is operable to drive the control unit (400) and a second position in which a gap is maintained between the screw (602) and the control unit (400).

[0019] The reactor control system (100) may further include a check mechanism (1100) provided within the control duct (200) configured to have a first operating mode in which the control unit (400) is movable relative to the control duct (200) and a second operating mode in which the control unit (400) is fixed in a predetermined position relative to the control duct (200).

[0020] The control duct (200) may have a substantially constant diameter along its length.

[0021] At least a portion of the second portion (220) of the control duct (200) may have a diameter greater than the diameter of the first portion (210) of the control duct (200). The second portion (220) may be in fluid communication with a pressure source (1000) such that the control unit (400) is forced in a first direction D1 by the pressure source when the screw (602) is in the second position.

[0022] The plurality of absorber units (410) may be disposed adjacent to one another in succession along the control duct (200) to form a row (416) of absorber units (410). A first plurality of displacer units (420) may be disposed adjacent to one another in succession along the control duct (200) to form a first row (422) of displacer units (420). A second plurality of displacer units (420) may be disposed adjacent to one another in succession along the control duct (200) to form a second row (424) of displacer units (420). The first row (422) of displacer units (420) may extend from a first end (412) of the row of absorber units (410). A second row (424) of displacer units (420) may extend from the second end (414) of the row of absorber units (410).

[0023] The piston (500) may be arranged between the first row (422) of displacer units (420) and the second row (424) of displacer units (420) such that in a first direction D1, the plurality of absorber units (410) are spaced apart from the piston (500) by the first row (422) of displacer units (420), and in a second direction D2, the plurality of absorber units (410) are spaced apart from the piston (500) by the second row (424) of displacer units (420).

[0024] The piston (500) may be configured and arranged within the duct (200) such that when the screw (602) is in the second position, the piston (500) acts on the control unit (400) below it to move the control unit (400) along the duct (200).

[0025] The first portion (210) of the control duct (200) may extend substantially parallel to the core central axis (320). The second portion (220) of the control duct (200) may extend substantially parallel to the core central axis (320).

[0026] A nuclear fission reactor system may be provided that includes a reactor unit (300) and a reactor control system (100) according to the present disclosure.

[0027] Thus, a control system for a nuclear fission reactor is provided that is more compact than conventional designs and significantly reduces the overall size of the reactor unit involved.

[0028] Examples of the present disclosure will now be described, by way of example only, with reference to the figures. [Brief explanation of the drawings]

[0029] [Figure 1] 1 illustrates a related art conventional moderated fission reactor; [Figure 2] 1 is a diagram of a reactor unit with a portion of its shell removed, having a reactor control system according to the present disclosure; [Figure 3] 3 is a cross-sectional view of the reactor unit and reactor control system shown in FIG. 2 in an operational configuration. [Figure 4] 3 is a cross-sectional view of the reactor unit and reactor control system shown in FIG. 2 in a shutdown configuration. [Figure 5] 1 is a cross-sectional view of an alternative example of a reactor unit and reactor control system according to the present disclosure in an operational configuration. [Figure 6] 6 is a cross-sectional view of the reactor unit and reactor control system shown in FIG. 5 in a shutdown configuration. [Figure 7]2 is an enlarged view of a portion of an example nuclear reactor control system according to the present disclosure in a shutdown configuration. [Figure 8] 1 is an expanded view of a portion of an example nuclear reactor control system according to the present disclosure. [Figure 9] 1 is an expanded view of a portion of an example nuclear reactor control system according to the present disclosure. [Figure 10] 2 is an enlarged view of a portion of a further example of a nuclear reactor control system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present disclosure relates to a reactor control system 100 for a nuclear fission reactor system. The present disclosure also relates to a nuclear fission reactor system comprising a reactor unit 300 and a reactor control system 100 according to the present disclosure.

[0031] For example, the reactor control system of the present disclosure may be used to control a high temperature gas cooled reactor (HTGR). The system may be a direct cycle design in which the reactor core directly heats a working fluid that drives a turbine to generate electricity. The coolant may be, for example, nitrogen. The features of such systems are well known in the art and therefore will not be described in detail herein.

[0032] Thus, the reactor control system 100 of the present disclosure may form part of a nuclear fission reactor system. As shown in Figures 2-6, the nuclear fission reactor system may include a reactor unit 300 having a core 302 including a central axis 320 extending along the length of the core 302 from a first end to a second end of the core 302. The figures of the present disclosure relate only to the reactor unit 300; other features of the nuclear fission reactor system (e.g., heat exchangers, turbines, etc.) are not shown.

[0033] As shown in Figures 2-6, the core 302 may be surrounded by a shield 184 (or "core barrel") and a casing shell 180 (defining a "reactor pressure vessel") that houses the core 302 and shield 184, the casing 180 being spaced from the shield 184 to define a cooling annulus 182, and the shell 180 defining an outer surface 186.

[0034] As shown in FIGS. 3 to 6 , the reactor unit 300 includes a first region 310 disposed within the core 302 and a second region 312 disposed outside the core 302. Thus, the second region 312 is located outside the periphery of the core 302. That is, the first region 310 is disposed within the core 302 inside the core shield 184, and the second region 312 is located outside the core shield 184. The second region 312 may be adjacent to the core shield 184. The second region 312 may be adjacent to the outer surface 186 of the shell 180. The second region 312 may be adjacent to the shell 180. The first region 310 is located between the central axis 320 and the second region 312, and the second region 312 is located outside the first region 310. The second region 312 may include the cooling annulus 182. For example, the first region 310 is the region defined by the shield 184 within (i.e., surrounded by) the dashed line labeled "310" in Figures 3-6, and the second region 312 surrounds (i.e., is outside) the first region 310 (i.e., outside the region defined by the dashed line labeled "310"). That is, the second region 312 defines a volume that is outside the volume defined by the shield 184 and defines a boundary for the first region 310.

[0035] The control system 100 includes a control duct 200. As shown in FIG. 2, the control system 100 may include a plurality of control ducts 200 spaced about a core central axis 320. The control duct or each control duct may be provided as a passageway, pipe, or tube and may be circular in cross section, for example, forming a cylindrical passageway. The control duct or each control duct 200 may include a first portion 210 configured to extend through a first region 310 and a second portion 220 configured to extend through a second region 312.

[0036] The second portion 220 of the control duct 200 may extend through the cooling annulus 182. The second portion 220 of the control duct 200 may be contained within the cooling annulus 182. That is, the second portion 220 of the control duct 200 may be located entirely within the cooling annulus 182.

[0037] The first portion 210 of the control duct 200 may extend substantially parallel to the core central axis 320. The second portion 220 of the control duct 200 may extend substantially parallel to the core central axis 320. Thus, the second portion 220 of the control duct 200 may extend substantially parallel to the first portion 210 of the control duct 200.

[0038] In alternative examples not shown, the first portion 210 of the control duct 200 may extend at an angle relative to the core axis 320 and / or the second portion 220 of the control duct 200 may extend at an angle relative to the core axis 320. Thus, the second portion 220 of the control duct 200 may extend at an angle relative to and / or parallel to the first portion 210 of the control duct 200.

[0039] The duct 200 is filled with a series of control units 400 , each of which is configured to travel along the control duct 200 .

[0040] The control duct 200 is configured for translation of the control unit 400. That is, the control duct 200 is configured to allow the control unit 400 to travel along the control duct 200. The control duct 200 is configured for translation of the control unit 400 in a first direction D1 and a second direction D2. The first direction D1 is the direction of travel from the control duct second portion 220 towards the control duct first portion 210. The second direction D2 is the direction of travel from the control duct first portion 210 towards the control duct second portion 220.

[0041] The control duct 200 may include a first arcuate portion 230 extending between the first portion 210 of the control duct and the second portion 220 of the control duct such that the first portion 210, the first arcuate portion 230, and the second portion 220 of the control duct 200 define a continuous path for the passage of the control unit 400.

[0042] The first arcuate portion 230 of the control duct 200 may be semicircular, i.e., the first arcuate portion 230 may be configured to define a path for the control unit 400 to rotate 180 degrees from one of the control duct first portion 210 or the control duct second portion 220 (from which the first arcuate portion 230 extends) to the other of the control duct first portion 210 or the control duct second portion 220.

[0043] 2-4, the control duct 200 may include a second arcuate portion 240 extending between the first portion 210 and the second portion 220 of the control duct 200. In this example, the second arcuate portion 240 of the control duct 200 is provided at an opposite end of the first portion 210 and the second portion 220 relative to the first arcuate portion 230 such that the first arcuate portion 230 is spaced from the second arcuate portion 240 by the first portion 210 and the second portion 220.

[0044] The second arcuate portion 240 of the control duct 200 may be semicircular, i.e., the second arcuate portion 240 of the control duct 200 may be configured to define a path for the control unit 400 that rotates 180 degrees from one of the first portion 210 or the second portion 220 of the control duct 200 (from which the second arcuate portion 240 extends) to the other of the first portion 210 or the second portion 220.

[0045] Thus, as shown in the example of Figures 2 to 4, the first portion 210, the first arcuate portion 230, the second portion 220, and the second arcuate portion 240 of the control duct 200 define a single continuous loop path for passage of the control unit 400.

[0046] Thus, the first portion 210, the first arcuate portion 230, the second portion 220, and the second arcuate portion 240 of the control duct 200 may be arranged consecutively to define a single continuous loop path for passage of the control unit 400.

[0047] In an alternative example shown in Figures 5 and 6, instead of the second arcuate portion 240 of the example of Figures 2 to 4, a first tank 700 for storing the control unit 400 may be provided, where the control duct 200 is configured to receive the control unit 400 from the first tank 700 and / or supply the control unit 400 to the first tank 700, and a second tank 720 for storing the control unit 400, where the control duct 200 is configured to receive the control unit 400 from the second tank 720 and / or supply the control unit 400 to the second tank 720.

[0048] Thus, in the examples of Figures 5 and 6, the first tank 700, first portion 210, first arcuate portion 230, second portion 220, and second tank 720 of the control duct 200 are arranged consecutively to define a path for the passage of the control unit 400 between the first tank 700 and the second tank 720.

[0049] Core 302 and its central axis 320 may extend vertically (as shown). Thus, in the example of Figures 2-4, if reactor unit 300 were mounted on a horizontal substrate, such as the floor of a building, core 302 and its central axis 320 would extend such that second arcuate portion 240 would be vertically above first arcuate portion 230.

[0050] Alternatively, in the examples of Figures 5 and 6, if the reactor unit 300 is mounted on a horizontal substrate, such as the floor of a building, the core 302 and its central axis 320 extend such that the first tank 700 and the second tank 720 are vertically above the first arcuate portion 230.

[0051] 2-4, the reactor may be mounted horizontally. In such an example, when the reactor unit 300 is mounted on a horizontal substrate, such as the floor of a building, the core 302 and its central axis 320 extend horizontally such that the second arcuate portion 240 is at the same height as the first arcuate portion 230 above the substrate.

[0052] Some of the control units 400 are absorber units 410. At least some of the remainder of the control units 400 are displacer units 420.

[0053] The absorber unit 410 may be configured to absorb radiant energy. For example, the absorber unit 410 may be configured to absorb particles that contribute to carrying out a nuclear chain reaction. For example, the absorber unit 410 may be configured to absorb neutrons. The absorber unit 410 may comprise boron carbide particles. The displacer unit 420 is configured to have lower absorption characteristics than the absorber unit 410. The displacer unit 420 may comprise graphite.

[0054] In the illustrated example, the plurality of absorber units 410 are disposed adjacent to one another in succession (i.e., in line) along the control duct 200 to form a row 416 of absorber units 410. A first plurality of displacer units 420 are disposed adjacent to one another in succession (i.e., in line) along the control duct 200 to form a first row 422 of displacer units 420. A second plurality of displacer units 420 are disposed adjacent to one another in succession (i.e., in line) along the control duct 200 to form a second row 424 of displacer units 420. A first row 422 of displacer units 420 extends from a first end 412 of the row of absorber units 410 in a first direction D1 along the duct 200, and a second row 424 of displacer units 420 extends from a second end 414 of the row of absorber units 410 in a second direction D2 along the duct 200.

[0055] The absorber unit 410 may be less heavy than the displacer unit 420. The absorber unit 410 may be at least 2% lighter than the displacer unit 420, but not more than 80% lighter than the displacer unit. The absorber unit 410 may be at least 10% lighter than the displacer unit 420, but not more than 50% lighter than the displacer unit. The absorber unit 410 may be at least 20% lighter than the displacer unit 420, but not more than 30% lighter than the displacer unit.

[0056] The control unit 400 may be spherical. The control unit 400 may have an outer diameter that is the same as or slightly smaller than the diameter of the control duct 200.

[0057] The control unit 400 may have a diameter of at least 10 mm and not more than 300 mm. The control unit 400 may have a diameter of at least 50 mm and not more than 150 mm. The control unit 400 may have a diameter of at least 90 mm and not more than 110 mm. The control unit 400 may have a diameter of approximately 100 mm.

[0058] As shown in the examples of Figures 2 to 7, a drive mechanism 600 may further be provided which is operable to drive the control unit 400 in a first direction D1 along the control duct 200 in a first operating mode, and which is operable to drive the control unit 400 in a second direction D2 along the control duct 200 in a second operating mode.

[0059] As best shown in FIG. 7 , the drive mechanism 600 may include a screw 602 having a track 604 for engagement with the control unit 400 such that, when the screw 602 is rotated, the control unit 400 is driven along the duct 200. The track 604 may be provided as a screw thread to form an Archimedes screw type arrangement. The screw 602 may be rotatable about an axis 610 and drivable by a drive motor 606. A drive arm 608 may extend from the drive motor 606 to the screw 602. The drive motor 606 may thus be operable to rotate the screw 602 about the axis of rotation 610, thereby moving the control unit 400 along the duct 200.

[0060] 7, the screw 602 is configured to move between a first position (shown in FIG. 7) in which the screw 602 is operable to drive the control unit 400, and a second position (not shown) in which a gap is maintained between the screw 602 and the control unit 400. That is, in the second position, the screw 602 is spaced apart from the control unit 400. The screw 602 may be configured to move in a first displacement direction (indicated by arrow D3 in FIG. 7) between the first position (shown in FIG. 7) in which the screw 602 is operable to drive the control unit 400, and the second position in which a gap is maintained between the screw 602 and the control unit 400 such that the control unit 400 does not engage the screw 602 when it passes by it. The screw 602 may be configured to move in a second displacement direction (shown by arrow D4 in FIG. 7) between a second position in which the screw 602 is spaced apart from the control unit 400 and a first position (shown in FIG. 7) in which the screw 602 is operable to drive the control unit 400.

[0061] The piston 500 is arranged between the first row 422 of the displacer units 420 and the second row 424 of the displacer units 420 such that in a first direction D1, the plurality of (i.e., a row of) absorber units 410 are spaced apart from the piston 500 by the first row 422 of the displacer units 420, and in a second direction D2, the plurality of (i.e., a row of) absorber units 410 are spaced apart from the piston 500 by the second row 424 of the displacer units 420.

[0062] The piston 500 is configured and arranged within the duct 200 such that when the screw 602 is in the second position (maintaining a clearance between the screw 602 and the control unit 400), the piston 500 acts on the control unit 400 below it, causing the control unit 400 to move along the duct 200. Thus, the piston 500 may have a mass that, by itself and / or when combined with the weight of at least some of the displacer units 420 in the first row 422 of displacer units 420 (e.g., when the reactor is mounted vertically as shown), causes the second row 424 of displacer units 420 to move along the duct 200 in the first direction D1 so that the absorber unit 410 is located (i.e., moved) in the first region 310 of the reactor core 302.

[0063] The screw 602 may be attached while being biased, for example by a spring, towards a second position in which the screw 602 is spaced away from the control unit 400. The screw 602 may be maintained in a first position in which the screw 602 is operable to drive the control unit 400 by pressure from an actuator and / or pressure source. In the event of a system failure, the actuator and / or pressure source releases the screw 602 so that the screw 602 assumes the second position, thereby allowing the control unit 400 to move along the duct 200.

[0064] As shown in Figures 8 and 9, the reactor control system 100 may further include a check mechanism 1100 provided within the control duct 200, configured to have a first operating mode in which the control unit 400 can move relative to the control duct 200, and a second operating mode in which the control unit 400 is fixed in a predetermined position relative to the control duct 200.

[0065] The check mechanism 1100 may be provided in the second portion 220. The check mechanism 1100 may be provided in the first portion 210.

[0066] As shown in Figures 8 and 9, the no-return mechanism 1100 may include a ratchet component 1102. In a first configuration (i.e., the operating configuration shown in Figures 3, 5, and 9), the control unit 400 can push / pass the ratchet component 1102 in a first direction D1 and / or a second direction D2. In a second configuration (i.e., the stopped configuration shown in Figures 4, 6, and 8), the ratchet component 1102 allows the control unit 400 to pass the ratchet component 1102 in the first direction D1, but does not allow the control unit 400 to pass the ratchet component 1102 in the second direction D2.

[0067] Thus, in normal operation (i.e., operating configuration), the check mechanism 1100 is in its first configuration. However, when shutdown is required, the check mechanism 1100 is transformed into its second configuration to allow the absorber unit 410 to move in a first direction D1 into the core (i.e., into or toward the first region 310) but prevent it from moving in a second direction D2 (i.e., into or toward the second region 312).

[0068] As shown in Figures 3-6, the control duct 200 may have a substantially constant diameter.

[0069] 10, at least a portion of the second portion 220 of the control duct 200 has a diameter larger than the diameter of the first portion 210 of the control duct 200. This region of enlarged diameter may be arranged such that the first portion 210, the region of enlarged diameter, and the drive mechanism 600 are provided successively in the second direction D2.

[0070] In this example, the second portion 220 is in fluid communication with the pressure source 1000 such that when the screw 602 is in the second position, the control unit 400 is forced in a first direction D1 by the pressure source.

[0071] Thus, in this example, the piston 500 and control duct 200 are enlarged so that there is an area difference between the diameter of the control unit 400 and the piston 500. The diameter of the enlarged area 250 may therefore be 5% to 10% larger than the diameter of the control unit 400. When the control unit 400 enters the enlarged area 250 of the control duct 200, it acts as a valve, thereby restricting the leakage of gas from the control duct 200 using the piston 500, which is vented in the drive mechanism. Then, when gas pressure is applied to the enlarged cross section 250, the pressure difference between the piston 500 and the control unit 400 ensures that the piston 500 is driven down the control duct 200 in the first direction D1, shutting down the core reaction.

[0072] During normal operation of the nuclear fission reactor system (i.e., in the operating configuration), the control unit 400 is moved along the control duct 200 in a first direction D1 and a second direction D2 as needed to slow down the reaction within the reactor core 302 as needed by use of the drive mechanism 600.

[0073] The drive mechanism 600 can move the control unit 400 between an operating configuration shown in Figures 3 and 5, which illustrates an arrangement in which the control unit 400 in the first region 310 of the core 302 is mostly the displacer unit 420, and a shutdown configuration shown in Figures 4, 6, and 7, which illustrates an arrangement in which the control unit 400 in the first region 310 of the core 302 is mostly the absorber unit 410. The drive mechanism 600 is operable to position the control unit 400 between the positions shown in Figures 3 and 5 and the positions shown in Figures 4, 6, and 7.

[0074] However, as explained above, the reactor control system 100 is configured such that during a shutdown scenario, the drive mechanism is operable to enable the control unit to adopt the arrangements shown in Figures 4, 6 and 7.

[0075] Thus, a control system for a nuclear fission reactor is provided that is more compact than conventional designs and significantly reduces the overall size of the reactor unit involved compared to related art examples.

[0076] Because the reactor control and / or shutdown components of the present disclosure extend radially outward from the core rather than longitudinally from the end of the core, this enables substantial potential for improvement to the overall control system package design.

[0077] In some examples, the arrangements of the present disclosure allow the entire control system to be located within the reactor housing (eg, casing 180), thus not increasing the overall volume of the reactor.

[0078] The use of spherical control units instead of control rods has an additional important safety advantage, as control rods are prone to warping due to temperature differences and neutron irradiation. This has, in the past, led to jamming of the stop rods, preventing automatic shutdown in a fault condition. In contrast, spherical control units are not susceptible to such jamming due to the fundamental segmented nature of the design and the only point and line contacts within the control duct 200.

[0079] The use of an Archimedes screw or the like to move the control unit allows for precise drive control of the control unit, allowing for inherent speed variation from the drive motor, reducing the need for a control drive motor gearbox.

[0080] The control system 100 may also allow for horizontally mounted reactors. Horizontal mounting may have advantages in space-constrained environments, including within the hull of a submarine. However, when a horizontal arrangement is considered, gravity-induced shutdown may no longer be practical, and hydraulic or pneumatic insertion of shutdown elements may be required (e.g., as described with respect to FIG. 10 ).

[0081] Attention is directed to all articles and documents related to this application, filed contemporaneously herewith or prior to this application, and open to public inspection herewith, and the contents of all such articles and documents are incorporated herein by reference.

[0082] All of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive.

[0083] Each feature disclosed in this specification (including any accompanying claims, abstract, and drawings), unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

[0084] The invention is not limited to the details of the above embodiments, and extends to any novel one or any novel combination of features disclosed in this specification (including any accompanying claims, abstract and drawings), or any novel one or any novel combination of steps of any method or process so disclosed.

Claims

1. 1. A reactor control system for a nuclear fission reactor system including a reactor unit having a reactor core with a central axis extending along a length of the core, comprising: the reactor unit includes a first region provided within the reactor core and a second region provided outside the reactor core; The reactor control system includes a control duct, the control duct comprising: a first portion configured to extend through the first region; a second portion configured to extend through the second region; and and A nuclear reactor control system, wherein the control duct is filled with a series of control units, each of the control units being configured to travel along the control duct.

2. the control duct is configured for translation of the control unit in a first direction (D1) and a second direction (D2); the first direction (D1) is a traveling direction from the second portion toward the first portion, 2. The nuclear reactor control system of claim 1, wherein the second direction (D2) is a direction of travel from the first portion toward the second portion.

3. 3. The nuclear reactor control system of claim 1, wherein the control duct includes a first arcuate portion extending between the first and second portions, and the first, first arcuate, and second portions of the control duct together define a continuous path for passage of a control unit.

4. The control duct is a second arcuate portion extending between the first portion and the second portion; Equipped with the second arcuate portion is disposed at an opposite end of the first and second portions relative to the first arcuate portion such that the first arcuate portion is spaced from the second arcuate portion by the first and second portions; 4. The nuclear reactor control system of claim 3, wherein the first section, the first arcuate section, the second section, and the second arcuate section of the control duct together define a single continuous loop path for passage of a control unit.

5. a first tank for storing a control unit, wherein the control duct is configured to receive a control unit from the first tank and / or to supply a control unit to the first tank; a second tank for storing a control unit, wherein the control duct is configured to receive a control unit from the second tank and / or to supply a control unit to the second tank. Furthermore, 4. The nuclear reactor control system of claim 1, wherein the first tank, the first portion, the first arcuate portion, the second portion, and the second tank are arranged consecutively to define a path for passage of a control unit.

6. some of the control units are absorber units; some of the control units are displacer units; A reactor control system according to any one of claims 1 to 5.

7. 7. The nuclear reactor control system of claim 6, wherein the absorber unit is less heavy than the displacer unit.

8. 8. A reactor control system according to any one of claims 1 to 7, wherein the control unit is spherical and has an outer diameter that is the same as or slightly smaller than the diameter of the control duct.

9. 9. A reactor control system as claimed in any one of claims 1 to 8, further comprising a drive mechanism operable to drive the control unit in a first direction (D1) along the control duct in a first operating mode and operable to drive the control unit in a second direction (D2) along the control duct in a second operating mode.

10. 10. The nuclear reactor control system of claim 9, wherein the drive mechanism comprises a screw having a track for engagement with the control unit such that when the screw is rotated, the control unit is driven along the control duct.

11. 11. The nuclear reactor control system of claim 10, wherein the screw is configured to move between a first position operable to drive the control unit and a second position in which a gap is maintained between the screw and the control unit.

12. 12. A reactor control system according to any one of claims 9 to 11, further comprising a check mechanism provided in the control duct configured to have a first mode of operation in which the control unit is movable relative to the control duct and a second mode of operation in which the control unit is fixed in a predetermined position relative to the control duct.

13. 13. A nuclear reactor control system according to any one of claims 1 to 12, wherein the control duct has a substantially constant diameter.

14. At least a portion of the second portion of the control duct has a diameter greater than a diameter of the first portion of the control duct; 13. The nuclear reactor control system of claim 1, wherein the second portion is in fluid communication with a pressure source such that the control unit is forced in a first direction (D1) when the screw is in the second position.

15. a plurality of absorber units are provided adjacent to one another in succession along the control duct to form a row of absorber units; a first plurality of displacer units disposed adjacent one another in succession along said control duct to form a first row of displacer units; a second plurality of displacer units disposed adjacent one another in series along the control duct to form a second row of displacer units; 15. The nuclear reactor control system of claim 1, wherein the first row of displacer units extends from a first end of the row of absorber units and the second row of displacer units extends from a second end of the row of absorber units.

16. 16. A reactor control system according to any one of claims 1 to 15, wherein the piston is provided between the first row of displacer units and the second row of displacer units such that in a first direction (D1), a plurality of absorber units are spaced from the piston by the first row of displacer units, and in a second direction (D2), a plurality of absorber units are spaced from the piston by the second row of displacer units.

17. 17. The nuclear reactor control system of claim 16 when dependent on claim 11, wherein the piston is constructed and arranged within the control duct such that when the screw is in the second position, the piston acts on the control unit below it to move the control unit along the control duct.

18. the first portion of the control duct extends substantially parallel to a core central axis; 18. A nuclear reactor control system according to any one of claims 1 to 17, wherein the second portion of the control duct extends substantially parallel to the core axis.

19. a reactor unit; 19. A nuclear fission reactor system comprising: a reactor control system according to any one of claims 1 to 18.

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