Control drum drive mechanism

Abstract

A control drum drive mechanism 100 having a first section 10, a second section 20 and a third section 30. The first section is removably attached to the second section and includes a motor 12. The sec

Description

TITLE Control Drum Drive Mechanism CROSS-REFERENCE TO RELATED APPLICATIONS This represents the first application directed towards the subject-matter. FIELD This disclosure relates to nuclear power systems, and more specifically mechanisms for controlling the movement of control drums. BACKGROUND Control drums can be used to control the rate at which fission events occur within a reactor core of a nuclear fission reactor. To control the rotational position of the control drum, the control drum is usually attached via a driveshaft to a control drum drive mechanism (CDDM). The CDDM may include an electromagnetic clutch both to transfer torque, and as a failsafe mechanism, as, should the power supply to the CDDM fail, the electromagnetic clutch will disengage, and the control drum will return to a position in which it will reduce the rate at which fission events occur. Designing hardware to operate in the environment around the reactor core is challenging, owing in part to the extreme heat generated by the reactor core, which travels up the driveshaft of the control drum. CDDMs can be expensive to build and time consuming to replace. Improvements to CDDMs would therefore be desirable. SUMMARY The present disclosure provides a control drum drive mechanism as set out in claim 1, and a nuclear fission reactor as set out in claim 7. Optional features are included in the dependent claims. According to a first aspect there is provided a control drum drive mechanism comprising a first section, a second section, and a third section, wherein the first section is removably attached to the second section, and comprises a motor, the second section is removably attached to the third section, and comprises a first electromagnetic clutch component and a first cooling jacket, and the third section comprises a second electromagnetic clutch component and a second cooling jacket, the third section being removably attachable to a driveshaft. The third section of the control drum drive mechanism may further comprise opposing spring elements configured to return the driveshaft to a predetermined rotational position. The third section of the control drum drive mechanism may further comprise a Hall effect sensor to measure rotation of the driveshaft. The maximum diameter of the third section of the control drum drive mechanism may be the same or greater than the maximum diameter of the second section, and the maximum diameter of the second section may be the same or greater than the maximum diameter of the first section. The first cooling jacket of the control drum drive mechanism may be provided with water, liquid nitrogen, gaseous nitrogen, or a liquid metal comprising sodium-potassium alloy (NaK) or Galinstan®. The second cooling jacket of the control drum drive mechanism may be provided with water, liquid nitrogen, gaseous nitrogen, ora liquid metal comprising sodium-potassium alloy (NaK) or Galinstan®. According to a second aspect there is provided a nuclear fission reactor comprising the control drum drive mechanism of the first aspect. The nuclear fission reactor may comprise a pressure vessel, with the third section being removably attachable to the pressure vessel. The pressure vessel may be a secondary pressure vessel. The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive, any feature described herein may be applied to any aspect and / or combined with any other feature described herein. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments will now be described by way of example only with reference to the accompanying drawings, in which: FIG. 1 shows a schematic sectional view of components of an example control drum drive mechanism; FIG. 2 shows a further schematic sectional view of the example control drum drive mechanism of FIG. 1; FIG. 3 shows a schematic sectional side view of another example CDDM; FIG. 4 shows a schematic sectional side view of another example CDDM; and FIG. 5 shows a schematic sectional side view of a nuclear fission reactor. DETAILED DESCRIPTION FIG. 1 shows a schematic sectional view of components of an example control drum drive mechanism (CDDM) 100 arranged for attachment to one another, according to the present disclosure. Referring to FIG. 1, the CDDM includes three sections: a first section 10, which houses a motor 12; a second section 20 which houses a first electromagnetic clutch component 22 and a first cooling jacket 24; and a third section 30 which houses a second cooling jacket 32 and a second electromagnetic clutch component 36. The first cooling jacket is located in proximity to the first electromagnetic clutch component 22. The first electromagnetic clutch component 22 may include coil windings. During operation of the CDDM, current will be passed through the coil windings in order to generate a magnetic field and thereby activate the electromagnetic clutch. Passing current through the coil windings will cause the coil windings to heat up. Therefore the coil windings need to be cooled to prevent the breakdown of the insulation material separating the coil windings, and the wires within the coil windings, from one another. The primary purpose of the first cooling jacket 24 is to extract heat energy generated by the first electromagnetic clutch component 22. A first coolant inlet 40 and first coolant outlet 42 allow coolant to flow into and out of the first cooling jacket 24. Suitable coolants for the first cooling jacket 24 include water, liquid or gaseous nitrogen, and liquid metals such as sodium-potassium alloy (NaK), Galinstan®, or silver alloys with melting points below 0°C. The second cooling jacket 32 is located in proximity to where the driveshaft 50 can be received by the third section 30 of the CDDM. The driveshaft 50 can be supported by driveshaft bearings 64. The second cooling jacket 32 is provided primarily to remove heat energy transferred into the third section 30 of the CDDM 100 by the driveshaft 50, the driveshaft being heated as a result of both extending closer to the reactor core, and being in contact with the control drum which is heated due to its proximity to the reactor core. A second coolant inlet 52 and second coolant outlet 54 allow coolant to flow into and out of the second cooling jacket 32. Suitable coolants for the second cooling jacket 32 include water, liquid or gaseous nitrogen, and liquid metals such as sodium-potassium alloy (NaK), Galinstan®, or silver alloys with melting points below 0°C. By providing separate first 24 and second 32 cooling jackets, a greater amount of heat energy can be removed from the CDDM than by either cooling jacket in isolation. Furthermore, having two separate cooling jackets provides a degree of redundancy, in that in the event of one cooling jacket failing, the CDDM is still provided with a degree of fluid cooling, meaning it can be safely shut down I operated at a reduced power level until such a time as the section containing the failed cooling jacket can be replaced. Furthermore, by separating the cooling for the first electromagnetic component 22 from the cooling for the driveshaft 50, any repairs required to one of the first electromagnetic component or the cooling for the driveshaft can be done without needing to also replace the other, making maintenance of the CDDM quicker, simpler, and cheaper than CDDMs of the prior art. When the first electromagnetic clutch component 22 includes coil windings, the second electromagnetic clutch component 36 may include an armature. When current is passed through the coil windings of the first electromagnetic clutch component 22, an electromagnetic field will be generated which will attract the armature towards the coil windings, until contact between a motor shaft 16 extending from the motor 12 and the second electromagnetic clutch component is established, allowing the rotational motion of the motor 12 to be transmitted (in the example of FIG.1 and FIG. 2 via the motor shaft 16, supported on shaft bearings 44) to the driveshaft 50. The skilled person will appreciate the location of the coil windings and armature could be reversed, such that the first electromagnetic clutch component 22 may include an armature, and the second electromagnetic clutch component 36 may include coil windings. The second electromagnetic clutch component 36 may be supported by electromagnetic clutch component bearings 66. The first section 10 has a plurality of first through holes 14, which in the example of FIG.1 and FIG. 2 can be aligned with corresponding first blind holes 26 in the second section 20. Fixing elements 28 (see FIG. 2) can then be inserted through the first through holes 14 and into the corresponding first blind holes 26 in order to attach the first section 10 to the second section 20. The second section 20 has a plurality of second through holes 60 which can be aligned with corresponding second blind holes 34 in the third section 30, such that further fixing elements 38 (see FIG. 2) can be inserted through the second through holes 60 and into the second blind holes 34 in order to attach the second section 20 to the third section 30. The fixing elements and further fixing elements may take any suitable form which can fix the first 10, second 20, and third 30 sections together when needed and allow for them to be taken apart when necessary. That is to say, the first 10, second 20, and third 30 sections are designed to be removably attachable to one another, the attachment being made via appropriate fixing and further fixing elements. The fixing elements or further fixing elements may, for example, be screws or bolts. The third section 30 can have a plurality of third through holes 58, through which attachment means (not shown) can be inserted in order to attach the CDDM to an internal structure of a nuclear fission reactor, such as a pressure vessel or secondary pressure vessel (see internal structure 210 in FIG. 5, for example). Constructing the CDDM from three separate and separable sections provides advantages. For example, should a part of the CDDM fail, only the relevant section needs to be replaced, rather than the entire CDDM unit. For example, if the motor 12 fails, the first section 10 can be removed from the second section 20 and replaced, rather than replacing the entire CDDM, and without needing to remove the second 20 and third 30 sections. Equally, when installed as part of a nuclear fission reactor 200 (see FIG. 5), the first 10 and / or second 20 sections of the CDDM can be removed without needing to detach the third section 30 from an internal structure 210 of the nuclear fission reactor 200. This reduces the time taken to make a repair, which means less time in the vicinity of the reactor for the maintenance teams. In this way, the CDDM of the present disclosure is compliant with the ALARP principle, in that it reduces risk, and also saves time and money over CDDMs known in the prior art. Also, the cost of manufacturing the CDDM is reduced, as it is simpler and quicker to produce the CDDM in three smaller sections than it is to produce an entire CDDM as a single piece. FIG. 2 shows a schematic sectional view of the example control drum drive mechanism (CDDM) 100 of FIG. 1 with the first section 10 and second section 20 attached via fixing elements 28, and the second section 20 and third section 30 attached via further fixing elements 38. To aid with the attachment and detachment of the first, second, and third sections 10, 20, 30 to one another, and with attachment of the CDDM to a nuclear fission reactor, in the example CDDM of FIG. 1 and FIG. 2 the maximum diameter of the third section is greater than the maximum diameter of the second section, and the maximum diameter of the second section is greater than the maximum diameter of the first section. In this way, attachment points located proximal to the points of maximum diameter can be more readily accessed for the insertion and removal of, for example, screws or bolts. FIG. 3 shows a schematic sectional side view of another example CDDM. In the example CDDM of FIG. 3, the third section has a plurality of third through holes 58 which align with the plurality of second through holes 60 of the second section. This variation allows further fixing elements 38 to pass through the second 20 and third 30 sections to reach (for example) an internal structure 210 of a nuclear fission reactor 200, and in doing so removably attach the second 20 and third 30 sections to one another. The third section 30 of a CDDM can contain a first spring element 52 and second spring element 54. The first and second spring elements 52, 54 are connected to the driveshaft 50 and to the third section 30, and are arranged such that the forces they exert upon the driveshaft are in opposition - which is to say that if the driveshaft is rotated one way, one of the first and second spring elements 52, 54 will be placed under tension, and the other will be placed under compression, and vice-versa should the driveshaft 50 be rotated in the opposite direction. The first and second spring elements 52, 54 are arranged such that the driveshaft (and consequently the control drum the driveshaft is attached to) is at a predetermined rotational position when the forces exerted by both of the first and second spring elements 52, 54 are balanced, such that the driveshaft will remain stationary unless an external force acts upon it. For example, the first and second spring elements 52, 54 may both be at their lowest potential energy state, i.e. neither under compression nor tension, when the driveshaft 50 is at the predetermined rotational position. The predetermined rotational position of the driveshaft 50 may be a safety shut-down position, i.e. a rotational position where neutron-absorbing material contained within the control drum 110 (see FIG. 5) is brought as close as possible to the nuclear fission reactor core 250, so as to reduce the rate at which fission events occur. In this way, should the supply of electricity to the first or second electromagnetic clutch components 22, 36 fail, or a scram procedure for the nuclear fission reactor be initiated, the driveshaft 50 will be released from the rotational force of the motor 12, and will rotate, under the combined force of the first and second spring elements 52, 54, back to the safety shut-down position, so as to reduce the rate at which heat energy is being produced by the reactor core 250 in the event of a SCRAM or electrical power loss to the nuclear fission reactor 200. The third section 30 further includes a Hall effect sensor 56. The Hall effect sensor 56 can be used to measure the rotation of the driveshaft 50, and therefore the rotation of the control drum 110. This is important in enabling the CDDM to accurately position the control drum, and therefore to accurately adjust the rate at which fission events occur within the reactor core 250. FIG. 4 shows a schematic sectional side view of another example CDDM, with other features common to the example CDDMs of FIG 1 and FIG. 3 omitted for clarity. In the example CDDM of FIG. 4, the first 10, second 20, and third 30 sections have aligned through holes 14, 58, 60. This variation allows fixing elements 28 to pass through the first 10, second 20, and third 30 sections to reach (for example) an internal structure 210 of a nuclear fission reactor 200, and in doing so removably attach the first 10, second 20, and third 30 sections to one another. FIG. 5 shows a schematic sectional side view of a nuclear fission reactor 200 having a CDDM as described above. The CDDM can be attached to an internal structure 210 of the nuclear fission reactor 200 containing the reactor core 250. The internal structure may, for example, be a reactor vessel or pressure boundary, such as a pressure vessel or secondary pressure vessel, within which the control drums can 110 reside. The third section of the CDDM can be removably attached to the internal structure 210 by means of an appropriate fixing means (for example, be screws or bolts, not shown) inserted through one or more third through holes 58. Various examples have been described, each of which comprise one or more combinations of features. It will be appreciated by those skilled in the art that, except where 5 clearly mutually exclusive, any of the features may be employed separately or in combination with any other features and the invention extends to and includes all combinations and sub-combinations of one or more features described herein. For example, whilst the example CDDMs have been described with a plurality of through holes 14, 58, 60, for receiving fixing elements 28, 38, the skilled person will appreciate the first 10, second io 20, and third 30 sections may only have a single through hole each, providing the sections incorporate other alignment features such as tongue and groove feature sets that will keep the sections in a fixed positional relationship with one another when brought together by virtue of a 28 fixing element or further fixing element 38.

Claims

1. A control drum drive mechanism comprising:a first section, a second section, and a third section; wherein:the first section is removably attached to the second section, and comprises a motor;the second section is removably attached to the third section, and comprises a first electromagnetic clutch component and a first cooling jacket; andthe third section comprises a second electromagnetic clutch component and a second cooling jacket, the third section being removably attachable to a driveshaft.

2. The control drum drive mechanism of claim 1, wherein the third section further comprises opposing spring elements configured to return the driveshaft to a predetermined rotational position.

3. The control drum drive mechanism of claim 1 or claim 2, wherein the third section further comprises a Hall effect sensor to measure rotation of the driveshaft.

4. The control drum drive mechanism of any preceding claim, wherein the maximum diameter of the third section is the same or greater than the maximum diameter of the second section, and the maximum diameter of the second section is the same or greater than the maximum diameter of the first section.

5. The control drum drive mechanism of any preceding claim, wherein the first cooling jacket is provided with water, liquid nitrogen, gaseous nitrogen, or a liquid metal comprising sodium-potassium alloy (NaK) or Galinstan®.

6. The control drum drive mechanism of any preceding claim, wherein the second cooling jacket is provided with water, liquid nitrogen, gaseous nitrogen, or a liquid metal comprising sodium-potassium alloy (NaK) or Galinstan®.

7. A nuclear fission reactor comprising the control drum drive mechanism of any preceding claim.

8. The nuclear fission reactor of claim 7, wherein the nuclear reactor comprises a pressure vessel, and the third section is removably attachable to the pressure vessel.

9. The nuclear fission reactor of claim 8, wherein the pressure vessel is a secondary pressure vessel.Intellectual Property OfficeApplication GB2505235.8Search report under Section 17 of the Patents Act 1977Date search completed: 07 August 2025Claims searched: 1-9International classificationSubclass and subgroup Valid from G21C7 / 14 01 / 01 / 2006Field of searchWorldwide search of patent documents classified in the following areas of the IPC:F16D, G21CDatabases used in the preparation of this search report:SEARCH-NPL; SEARCH-PATENTDocuments considered to be relevantPatent literatureCategory Relevant claims Document of relevance A — US 2022 / 0059246 A1 (CRAWFORD), See figures 3-5 and paragraphs [0039], [0050], [0051] and [0057]-[0059].Intellectual Property Office is an operating name of the Patent Officewww.gov.uk / ipoA -- CN 117253632 A (SHANGHAI NUCLEAR ENG RES &DESIGN INST CO LTD), See figures 1-4 and the description thereof. A -- WO 2025 / 007093 A1 (WESTINGHOUSE ELECTRIC CO LLC), See figures 3 and 4 and paragraphs [0047]-[0053].Categories Letter or symbol Description X Document indicating lack of novelty or inventive step. Y Document indicating lack of inventive step, if combined with another document of the same category. & Member of the same patent family. A Document indicating technological background. P Document published on or after the priority date but before the fling date of the present application. E Earlier application published on or after the filing date of the present application.

Images