NUCLEAR REFUELLING DEVICE

Abstract

The present disclosure provides a refuelling device for lifting a fuel rod assembly from a reactor core of a nuclear power generation system in a deployment location and transporting it to a storage location. The refuelling device comprises a device body having an open base and defining a chamber for housing a coolant. A sealing plate is movable between an open position in which the chamber is open and a closed position in which the chamber is sealed. The device further comprises a shielding element formed of radioactive shielding material and moveably mounted within the chamber. It has a storage cavity having an open lower end, the shielding element being movable between a retracted position in which it is fully contained within the chamber and an extended position in which it extends from the chamber through the open base of the device body. The device further comprises a rod lifting system having a rod connector for releasable connection to the fuel rod assembly and configured to raise the fuel rod assembly to within the storage cavity when the device is in the deployment location, the sealing plate is in the open position and the shielding element is in its extended position.

Claims

1. A refuelling device for lifting a fuel rod assembly from a reactor core of a nuclear power generation system in a deployment location and transporting it to a storage location, the refuelling device comprising: a device body having an open base and defining a chamber for housing a coolant; a sealing plate movable between an open position in which the chamber is open and a closed position in which the chamber is sealed; a shielding element formed of radioactive shielding material, the shielding element being moveably mounted within the chamber and defining a storage cavity having an open lower end, wherein the shielding element is movable between a retracted position in which it is fully contained within the chamber and an extended position in which it extends from the chamber through the open base of the device body; and a rod lifting system having a rod connector for releasable connection to a fuel rod assembly and configured to raise the fuel rod assembly to within the storage cavity when the device is in the deployment location, the sealing plate is in the open position and the shielding element is in its extended position.

2. The refuelling device according to claim 1 wherein the device body is formed of steel and the shielding element is formed of lead.

3. The refuelling device according to claim 1 further including a shielding element lifting system for extending and retracting the shielding element.

4. The refuelling device according to claim 3 wherein the shielding element lifting system comprises a pinion mounted on or embedded in the device body and a rack mounted on/embedded in the shielding element.

5. The refuelling device according to claim 1, wherein the rod lifting system comprises one or more winches/hoists mounted on an outer surface of the device body.

6. The refuelling device according to claim 1 further comprising a coolant circuit comprising a coolant inlet, a coolant outlet and a heat exchanger mounted externally on the device.

7. The refuelling device according to claim 1 comprising a wheeled frame for guiding movement of the refuelling device between the deployment location and the storage location.

8. The refuelling device according to claim 7 comprising two parallel spaced rails having frame wheels with two perpendicular cross struts extending therebetween, the device body being movably mounted on the cross struts.

9. A nuclear power generation system comprising a refuelling device according to claim 1 and a reactor vessel having: a reactor vessel body defining a cavity housing a reactor core containing a control rod assembly and upper internals for guiding the control rod assembly; and a closure head configured to seal against the reactor vessel body to close an opening to the reactor vessel body cavity.

10. The nuclear power generation system according to claim 9 comprising an integrated head package comprising the closure head, and a control rod drive mechanism housed within a shroud, the control rod drive mechanism comprising at least one drive rod extending through the closure head, the or each drive rod having a coupling element for releasably coupling to a control rod assembly within the reactor core, the at least one drive rod being movable to a maintenance/refuelling position in which the at least one drive rod is uncoupled from the control rod assembly and at least partially retracted into the integrated head package, the integrated head package further comprising at least one locking element for locking the at least one drive rod in the maintenance/refuelling position.

11. The nuclear power generation system according to claim 10 comprising a containment structure where the working floor of the containment structure surrounds and is substantially vertically aligned with the opening to the cavity.

12. The nuclear power generation system according to claim 11 wherein the working floor comprises at least one pathway extending from adjacent the reactor vessel to the storage location, the at least one pathway comprising tracks/rails substantially vertically aligned with the opening to the cavity in the reactor vessel body.

13. The nuclear power generation system according to claim 10 further comprising a control system for sending control signals for actuation of the sealing plate and/or the rod lifting system and/or the shielding element lifting system and/or for driving the frame wheels/device body wheels.

14. The nuclear power generation system according to claim 10 wherein the system is a pressurised water reactor system.

15. A method of removing a fuel rod assembly from an exposed reactor core within a nuclear power generation system according to claim 9 using the refuelling device according claim 1, the method comprising: removing the closure head and upper internals from the reactor vessel body, after removal of the closure head and upper internals from the reactor vessel body, moving the refuelling device to the deployment location vertically above the coolant-flooded reactor vessel body with the sealing plate in its closed position; lowering the device so that the sealing plate is below the surface of the coolant; moving the sealing plate to its open position; lowering the shielding element and the rod connector and connecting the rod connector to the fuel rod assembly; raising the fuel rod assembly vertically to within the storage cavity using the rod lifting system; raising the shielding element and fuel rod assembly to within the chamber; sealing the chamber by moving the sealing plate to its closed position; and moving the device to the storage location.

16. The method according to claim 15 further comprising circulating a coolant e.g. water or air through the device.

17. The method according to claim 15 comprising moving the refuelling device between the deployment and storage locations along a working floor of the containment structure that is substantially vertically aligned with the opening to the cavity.

18. The method according to claim 15 comprising moving the refuelling device to and from a storage location provided externally to the containment structure.

19. The method according to claim 15 comprising driving the frame wheels of the device along tracks or rails extending between the deployment location and the storage location and adjusting the deployment location by driving the device body wheels along the cross struts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Embodiments will now be described by way of example only with reference to the accompanying drawings in which:

[0098] FIG. 1 shows a schematic cross-sectional view through the refuelling device with the shielding element in its retracted position;

[0099] FIG. 2 shows a schematic cross-sectional view through the refuelling device with the shielding element in its extended position; and

[0100] FIGS. 3a and 3b show a schematic top view and side view respectively of the refuelling device on its wheeled frame.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES

[0101] FIGS. 1 and 2 show a refuelling device 1 comprising a device body 2 having an open base, a horizontal upper wall 3 and vertical side walls 4. The walls are formed of 150 mm thick steel. The walls 3, 4 define a cuboid chamber 5.

[0102] The device further comprises a sealing plate 6 which is pivotally moveable between an open position (shown in FIG. 2) in which the chamber 5 is open (through the open base of the device body 2) and a closed position (shown in FIG. 1) in which the chamber 5 is sealed (in a liquid tight manner) with the sealing plate 6 covering the open base and sealed against the device body 2.

[0103] The sealing plate 6 is also formed of 150 mm thick steel and is associated with an actuator (not shown) for driving it between its open and closed positons. The actuator is operably connected to a control system located remotely from the device.

[0104] The device further comprises a shielding element 7 formed of lead and having an upper wall 8 and four vertical walls 9 with an open lower end. The shielding element 7 defines a storage cavity 10. The storage cavity may comprise a lining tube (not shown) formed of steel.

[0105] The shielding element 7 is telescopically mounted within the device body 2. The device 1 comprises a shielding element lifting system (not shown) for moving the shielding element 7 between a retracted position (shown in FIG. 1) and an extended position (shown in FIG. 2). The shielding element lifting system comprises four rack gears, one mounted on each of the vertical walls 9 of the shielding element 7. These rack gears cooperate with pinion gears mounted on the inner surface of the vertical walls 4 of the device body 2 adjacent each rack gear. In this way, the racks and pinions can move relative to each other to extend and retract the shielding element 7. The shielding element lifting system is operably connected to the remote control system.

[0106] A rod lifting system 11 is mounted outside the chamber 5 on the outer surface of the upper wall 3 of the device body 2. The rod lifting system 11 comprises a winch/hoist (outside the chamber 5) and a winch cable (not shown) which extends through the upper wall 3 of the device body 2 and through the upper wall 8 of the shielding element 7 into the storage cavity 10. At the end of the winch cable is a rod connector (not shown) for connection to a fuel assembly. The rod lifting system 11 is operably connected to the remote control system.

[0107] The device 1 further comprises a water coolant circulation system comprising a coolant inlet 13 and a coolant outlet 14 with a heat exchanger (radiator) 15 mounted on the outside surface of a vertical wall 4 of the device body 2 for releasing heat within the coolant into the atmosphere. When in use, the device body 2 is filled with coolant.

[0108] As shown in FIG. 3, the device body 2 is mounted on a wheeled frame 16 which comprises two parallel spaced rails 17a, 17b with two perpendicular cross struts 18a, 18b extending therebetween. The rails 17a, 17b are mounted on frame wheels 19a, 19b. The device body 2 comprises device body wheels 20 which are mounted on the cross struts 18a, 18b so that the device body 2 can move along the cross struts 18a, 18b perpendicular to the rails 17a, 17b. The refuelling device 1 further comprises motors (not shown) for independently driving the frame wheels 19a, 19b and the device body wheels 20 to effect two-dimensional movement of the device body. The motors are operatively coupled to the control system.

[0109] The refuelling device 1 is provided to facilitate the removal from (and subsequent replacement) of a fuel rod assembly within the reactor core of a pressurised water reactor power generation system. Such a system comprises a reactor vessel having a reactor vessel body (not shown) defining a cavity housing the reactor core. The reactor vessel also comprises an integrated head package (IHP) comprising a closure head configured to seal against the reactor vessel body to seal the reactor core. The reactor core contains the fuel rod assemblies and upper internals configured to maintain horizontal spacing of the fuel rod assemblies and associated control rods (which control the nuclear reactions within the reactor core).

[0110] In order to expose the reactor core (to allow replacement of the fuel rod assemblies), the IHP and upper internals must first be removed from the reactor vessel body. The reactor vessel body is flooded with coolant (e.g. water).

[0111] Subsequently, the refuelling device 1 is moved from a storage location (e.g. in a shielded annex outside the containment structure) to a deployment location vertically over the reactor vessel body. The refuelling device 1 is moved to the deployment location by driving the frame wheels 17a, 17b along rails/tracks extending along a linear pathway on the containment working floor. The working floor and rails/tracks are substantially vertically aligned with the opening to the cavity in the reactor vessel body.

[0112] Once in the deployment location, the horizontal position of the device body 2 over the reactor core is adjusted by driving the device body wheels 20 along the cross struts 18a, 18b until the device body 2 is directly above the fuel assembly for extraction.

[0113] Once correctly positioned, the device body 2 is lowered so that the sealing plate 6 is below the surface of the coolant within the reactor vessel body so that the coolant circulating within the device body 2 remains within the chamber 5 when the sealing plate 6 is moved to its open position (shown in FIG. 2) where the chamber 5 is open through the open base of the device body 2. The rod lifting system 11 lowers the rod connector into the reactor core through the open base (between the cross struts 18a, 18b). Similarly, the shielding element lifting system lowers the shielding element 7 into the reactor core until both the rod connector and shielding element are proximal the fuel rod assembly (as shown in FIG. 2). The rod connector connects to the fuel rod assembly and then the rod lifting system 11 retracts the fuel rod assembly and rod connector into the storage cavity 10 within the shielding element 7. Next the shielding element 7 and the fuel rod assembly contained within the storage cavity 10 are retracted within the device body 2 using the rod lifting system 11 and the shielding element lifting system. Once fully retracted, the sealing plate 6 is moved back to its closed position to seal the fuel rod assembly within the device body 2.

[0114] The refuelling device 1 can then be moved (horizontally) away from the deployment location by driving the frame wheels 19a, 19b along the rails/tracks.

[0115] It will be understood that the disclosure is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.