Nuclear power generation system

Abstract

The nuclear power generation system of the present invention comprises a reactor vessel. It further comprises a first crane gantry defining a fuel rod path along which nuclear fuel rods can be moved to/from the reactor vessel and a second crane gantry defining a component path along which reactor vessel components can be moved to/from the reactor vessel. The the first and second crane gantries both have a fixed radial orientation relative to the reactor vessel.

Claims

1. A nuclear power generation system comprising: a reactor vessel; a plurality of steam generators circumferentially spaced about the reactor vessel, the steam generators each having a vertically elongated vessel body portion; a first crane gantry defining a fuel rod path along which nuclear fuel rods can be moved to and from the reactor vessel; and a second crane gantry defining a component path along which reactor vessel components can be moved to and from the reactor vessel; wherein the first and second crane gantries both have a fixed radial orientation relative to the reactor vessel, the first crane gantry extends radially in a direction extending between a first and second of the plurality of steam generators, and the first crane gantry is vertically spaced below an upper extremity of the vertically elongated vessel body portion of each of the plurality of steam generators.

2. The system according to claim 1, wherein the second crane gantry extends radially in a direction extending between two of said plurality of steam generators other than between the first and second steam generators.

3. The system according to claim 2, wherein the second crane gantry is vertically spaced below the upper extremity of the plurality of steam generators.

4. The system according to claim 1, wherein the first and second gantries are at an oblique angle of between 110-140° relative to each other.

5. The system according to claim 1, further comprising a third crane gantry defining a further component path along which the reactor vessel components can be moved to and from the reactor vessel wherein the third crane gantry has a fixed radial orientation relative to the reactor vessel.

6. The system according to claim 5, wherein the third crane gantry path extends radially in a direction extending between two of said plurality of steam generators other than between the first and second steam generators and wherein the third crane gantry is non-parallel and non-coaxial with the first and second gantries.

7. The system according to claim 5, wherein the third crane gantry is vertically spaced below the upper extremity of the plurality of steam generators.

8. The system according to claim 5, wherein the first, second and third gantries are equally spaced around the circumference of the reactor vessel.

9. The system according to claim 5, wherein the second and third gantries are joined proximal the reactor vessel to form a combined component gantry so that the component path and the further component path together are a continuous combined component path.

10. The system according to claim 9, wherein the combined component gantry comprises an angular deflection proximal the reactor vessel.

11. The system according to claim 1, wherein the reactor vessel is circumferentially surrounded by a central support monolith.

12. The system according to claim 11, wherein the central support monolith further comprises one or more spoke portions extending radially from the central support monolith, the one or more spoke portions extending under a respective crane gantry portion.

13. A method of operating a nuclear power generation system, the method comprising: providing the system according to claim 1; moving the nuclear fuel rods along the fuel rod path in the fixed radial orientation relative to the reactor vessel; and/or moving the reactor vessel components along the component path in the fixed radial orientation relative to the reactor vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will now be described by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 shows a simplified schematic of a known nuclear power generation system;

(3) FIG. 2 shows a reactor vessel for use in an embodiment of the nuclear power generation system:

(4) FIG. 3 shows a side-view of a nuclear power generation system according to the embodiment of the nuclear power generation system; and

(5) FIG. 4 shows a plan-view of the nuclear power generation system shown in FIG. 3.

(6) FIG. 5 shows a schematic representation of the relative positions of components.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES

(7) FIG. 2 shows a pressurised reactor vessel 200 for use in a nuclear power generation system of the pressurised water reactor (PWR) type. The reactor vessel 200 has a removable reactor head 202 for closing an upper opening in the reactor vessel 200 in use, thereby establishing a pressure boundary. The interior 204 of the reactor vessel 200 contains a reactor core 206 for holding nuclear fuel rods 208, and reactor vessel internal components 210. In use, the reactor vessel is filled with pressurised water.

(8) A fluid outlet 212 is provided in a side-wall of the reactor vessel for transfer of hot pressurised water from the reactor vessel to a steam generator (not shown). A fluid inlet 214 is also provided in the side-wall of the reactor vessel for transfer of cool pressurised water back from the steam generator. As shown, the fluid outlet is positioned vertically above the fluid inlet. If more than one steam generator is used, then further inlets and outlets may be provided.

(9) Periodically, it is necessary to service the internal components 210, and to replace the fuel rods 208 once they become ‘spent’, e.g. once they have been irradiated to the extent that they are no longer usable for energy production.

(10) To service the internal components or replace spent fuel rods, the reactor head 202 first has to be removed, in order to reveal the interior of the reactor vessel. When the head has been removed, the internal components 210 and fuel rods 208 may be removed/replaced via the upper opening. For refuelling, some of the internal components 210 must also be removed, to enable access to the fuel rods 208 in the reactor core 206.

(11) FIGS. 3 and 4 show a PWR nuclear power generation system 300, which includes a first gantry 301 defining a fuel rod path extending from vertically above a fuel pond 306 to proximal the reactor vessel 200. The first gantry comprises a single, linear rail for supporting a fuel rod hoist (not shown) which is moveable along the first gantry 301. The first gantry 301 extends between a first steam generator 320′ and a second steam generator 320″.

(12) The system 300 further comprises a second gantry 302 which includes two linear, parallel rails 308 defining a component path extending from proximal and vertically above a reactor head storage position 310 to proximal the reactor vessel 200. The second gantry 302 supports a component hoist (not shown) which is movable along the second gantry 302.

(13) The second gantry 302 extends between the first steam generator 320′ and a third steam generator 320′″.

(14) The system 300 further comprises a third gantry 303 which includes two linear, parallel rails 309 defining a further component path extending from proximal and vertically above a reactor internals storage position 312 to proximal the reactor vessel 200. The third gantry 303 supports a further component hoist (not shown) which is movable along the third gantry 303. The third gantry 303 extends between the second steam generator 320″ and the third steam generator 320′″.

(15) As is clearly shown in FIG. 4, the first gantry 301, second gantry 302, and third gantry 303 each extend at different radial orientations relative to the reactor vessel 200. The angular separation between adjacent gantries is approximately 120°. The gantries 301, 302, 303 have a fixed radial orientation to the reactor vessel 200.

(16) Because the gantries 301, 302, 303 do not move (are fixed in position), there are three ‘safe’ zones/segments S around the reactor vessel, through which the hoists do not move. Components of the nuclear power generation system can therefore be placed in these zones, without the risk of becoming damaged by impact with the hoists.

(17) The three steam generators 320′, 320″, 320′″ and a pressuriser 322 are placed in these ‘safe’ zones S. Moreover, they are placed very close to the reactor vessel 200 (because there is no risk of collision with a hoist in a space extending circumferentially around the reactor vessel 200), thus keeping the total foot print of the occupied by the nuclear power generation system to a minimum.

(18) Because the steam generators 320 and pressuriser 322 are positioned in the safe zones S, the gantries 301, 302, 303 can be can be mounted at a vertical height between the top of the reactor vessel 200, and the top of the steam generators 320′, 320″, 320′″. This reduces the total height of the nuclear power generation system by approximately 10 m.

(19) Central support monolith 328 surrounds the reactor vessel 200, to provide structural support. Because of the proximity of the steam generators 320 to the central support monolith 328, it is possible to mount the steam generators 320 directly to the central monolith 328. This improves the structural stability of the nuclear power generation system. As shown, the radially innermost ends of the gantries 301, 302, 303 are also mounted directly to the central monolith 328.

(20) The central support monolith also comprises a first spoke portion 323 which comprises a pair of first spokes, one of which supports the first crane gantry 301. The first spoke portion 323 surrounds the fuel pond 306.

(21) The central support monolith also comprises a third spoke portion 324 which comprises a pair of third spokes that support the third crane gantry rails 309 and surrounds the reactor internals storage position 312.

(22) To perform a maintenance or refuelling operation, the reactor vessel 200 is first depressurised.

(23) Once depressurised, the component hoist is moved along the second gantry rails 308, until it is positioned above the reactor vessel 200. Once in this position, a reactor head tool attachment of the component hoist is lowered until it makes contact with the reactor vessel head 202, at which point it is attached to the reactor vessel head. Once attachment is complete, the component hoist is raised, thereby raising the reactor vessel head 202 away from the reactor vessel 200 to reveal the opening at the top of the reactor vessel. The component hoist is then moved along the rails 308 towards the reactor head storage position 310, where it is stored for the duration of the maintenance/refuelling operation.

(24) Once the reactor head 202 has been removed, the upper reactor vessel internal components can be removed. This is done by moving the further component hoist along the third gantry rails 309, until it is positioned over the reactor vessel 200. Once in this position, a reactor internals tool attachment of the further component hoist is lowered into the reactor vessel 200 until it makes contact with a reactor vessel internal component, at which point it is attached to the reactor vessel internal component. Once attachment is complete, the further component hoist is raised, thereby raising the reactor vessel internal component out of the reactor vessel 200. The further component hoist is then moved along the second component gantry rails 309 until it reaches the reactor internals storage position 312, where the reactor vessel internal component may be stored e.g. for maintenance.

(25) Once the above steps are complete, the reactor vessel 200 can be re-fuelled.

(26) The fuel rod tool hoist is moved along the first gantry 301 to a position above the reactor core 206 of the reactor vessel 200. From here, the hoist is lowered towards the reactor core 206 within the reactor vessel 200, until it makes contact with a (spent) fuel rod 208 at which point it is attached to the fuel rod 208. The fuel rod is then raised back out of the reactor vessel 200, and moved to a position above the fuel pond 306. From here, the spent fuel rod is lowered into the fuel pond.

(27) By reversing the above steps (using a fresh fuel rod from the fuel pond), the reactor vessel can thereby be refuelled, repaired, and re-sealed ready for operation.

(28) It will be understood that the invention 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.