EP0871961A1 - Spacer for a fuel assembly and a fuel assembly - Google Patents
Spacer for a fuel assembly and a fuel assemblyInfo
- Publication number
- EP0871961A1 EP0871961A1 EP96917751A EP96917751A EP0871961A1 EP 0871961 A1 EP0871961 A1 EP 0871961A1 EP 96917751 A EP96917751 A EP 96917751A EP 96917751 A EP96917751 A EP 96917751A EP 0871961 A1 EP0871961 A1 EP 0871961A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- spacer
- latticework
- orthogonal
- upstream
- orthogonal latticework
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
Links
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/34—Spacer grids
- G21C3/352—Spacer grids formed of assembled intersecting strips
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Definitions
- the present invention relates to a spacer for a nuclear fuel assembly for a light-water nuclear reactor, more particularly a boiling water reactor, and a nuclear fuel assembly compri ⁇ sing spacers according to the present invention.
- the fuel assembly comprises a bundle of elongated fuel rods which are retained and fixed by a number of spacers arranged in spaced relationship to each other along the bundle.
- the spacers comprise a number of cells for mutually fixing the fuel rods.
- the bundle is surrounded by a fuel channel.
- the fuel assembly normally comprises a top tie plate and a bottom tie plate, to which the ends of the fuel rods are fixed.
- a coolant for example water, is adapted to flow from below and up through the normally vertically arranged fuel assembly and, during a nuclear reaction, to cool the fuel rods arranged in the assembly.
- the design of the spacers comprised by the fuel assembly is very important for the performance of the fuel assembly. Above all, it is important to minimize the resistance to the flow which flows from below and up through the fuel assembly and to achieve an even cooling of all the fuel rods arranged in the fuel assembly. In those cases where the cooling is not sufficient, so-called dryout may occur in a boiling water reactor. In serious cases, dryout gives rise to penetration of the fuel rods.
- the spacers influence the flow of the coolant and hence the cooling of the fuel. It is known that, in a region imme- diately below the spacer, where the coolant has not yet passed through the spacer, a deterioration of the coolant film occurs on the fuel rods, whereas in a region above the spacer, where the coolant has just passed through the spacer, a reinforce ⁇ ment of the water film instead occurs.
- the reinforcement of the coolant film is due to the turbulence which arises in the coolant when it passes through a spacer. The greatest risk of dryout exists in the upper part of the fuel just below the spacers.
- the object of the present invention is to achieve a spacer with additionally improved properties, primarily as regards cooling of the fuel rods.
- a further object of the invention is to achieve a spacer which has a low pressure drop and which is robust so as to withstand forces to which it may be subjected during handling, and to minimize the risk of obliquity of the spacer.
- the present invention relates to a spacer and a fuel assembly comprising such spacers, with properties which provide a low pressure drop, an improved margin with respect to dryout and a greater resistance to damage due to handling. These properties are achieved by means of a spacer according to the characterizing part of claim 1.
- the spacer comprises an orthogonal latticework which is surrounded by a sleeve-shaped outer structure which extends outside the orthogonal structure both upstream and downstream and has one structural part which creates turbulence and one structural part which facilitates the guiding, which structu ⁇ ral parts are separated in the axial direction.
- the corners, comprising the guiding structure are formed stiff to absorb the forces acting on the bundle during operation and during handling of the bundle.
- the turbulence-creating structural part extends downstream of the spacer and is arranged substantially at the sides of the spacer. The turbulence is created by means of vanes which direct the coolant towards the centre of the spacer.
- the guiding function consists of a part of the structure which extends upstream of the spacer and is arranged substantially at the corner portions of the spacer.
- the guiding is important when inserting a bundle of elongated elements retained by spacers into a fuel channel.
- the guiding is achieved by means of a structural part provided with so-called guiding studs which consist of a plate flap or the like, the plane of which is arranged parallel to the direction of flow of the coolant and one side edge of which extends slopingly from the lower edge of the structure in a direction downstream of the spacer towards the corners of the structure.
- Two such guiding studs are arranged perpendicular to each other in respective corners forming a claw-shaped guiding means.
- the advantage of the invention is that improved properties regarding cooling, and hence dryout, of a fuel assembly are achieved by means of a structure provided with deflection members according to the invention and by deflecting coolant towards the centre of the bundle while the coolant flows upwards along the wall of the fuel channel.
- improved cooling of the elongated elements is achieved, primarily immediately after the passage of the coolant through a spacer but also at some distance up in the bundle to the next spacer level.
- Another advantage of the invention is that a large damping surface between the structure and the wall of the fuel channel is obtained by the plane surfaces of the structure facing the fuel channel wall.
- Figure 1 shows a boiling water fuel assembly according to the prior art.
- Figure 2 shows a perspective view of a spacer with a surroun ⁇ ding structure according to the invention.
- Figure 1 shows a boiling water reactor fuel assembly 1 which comprises a long tubular container, of rectangular cross section, referred to as fuel channel 2.
- the fuel channel 2 is open at both ends so as to form a continuous flow passage through which the coolant of the reactor flows.
- the fuel assembly 1 comprises a large number of equally long tubular fuel rods 3, arranged in parallel in a bundle, in which pellets 4 of a nuclear fuel are arranged.
- the fuel rods 3 are retained at the top by a top tie plate 5 and at the bottom by a bottom tie plate 6.
- the fuel rods 3 are kept spaced from each other by means of spacers 7 and are prevented from bending or vibrating when the reactor is in operation.
- Figure 2 shows a spacer 7 with an orthogonal latticework com ⁇ posed of sleeves 9 where each sleeve 9 is intended to position a fuel rod 3 (not shown) extending through the sleeve.
- the orthogonal latticework is surrounded by a sleeve-shaped struc- ture 10.
- a spacer latticework composed of sleeves and being of the same type as that shown in Figures 1 and 2 is disclosed in Swedish patent application 9303583-0.
- the sleeve-shaped structure 10 is arranged extending both up- stream and downstream of the axial extent of the orthogonal latticework, that is, of the sleeves 9.
- the structural part extending upstream of the orthogonal latticework is arranged substantially at the corner portions of the orthogonal latticework and is designed for guiding the spacer into the fuel channel 2. Guiding is achieved by means of plate flaps 11 or the like, the plane of which is arranged parallel to the direction of flow of the coolant and one edge of which extends in an inclined manner from the lower part of the spacer in a direction downstream of the orthogonal latticework towards the corners of the orthogonal latticework.
- the side surface of the guiding stud is arranged parallel to the direction of flow, only the cross-section area of the guiding stud 11 perpendicular to the direction of flow will constitute an obstacle to the passage of the coolant through the bundle and thus will not give rise to any signi ⁇ ficant flow resistance.
- Two such guiding studs 11 are arranged perpendicular to each other in the respective corners of the structure 10 forming a claw-shaped guiding means. Upstream of the orthogonal latticework, the structure extends at least over a distance corresponding to half the axial extent of the orthogonal latticework.
- That part of the structure 10 which extends downstream of the orthogonal latticework is arranged substantially at the sides of the latticework and is designed for creating turbulence in the coolant flowing upwards along the fuel channel wall 22 and to direct the coolant towards the elongated elements 3 which are arranged at the centre of the orthogonal latticework. Turbulence is achieved by means of flaps 12 extending from the structure 10 and bent towards the central part of the structure 10 and centred between the elongated element 3 (not shown) extending through the orthogonal latticework.
- the flaps 12 are shaped such that turbulence is achieved which reinfor ⁇ ces the water film adhering to the fuel rods 3 so that its cooling effect reaches to a downstream spacer 7, located adjacent thereto, thus preventing dryout. Downstream of the orthogonal latticework, the structure extends over at least a distance corresponding to half the axial extent of the orthogonal latticework.
- Figure 2 shows an advantageous embodiment where only the corner portions of the orthogonal latticework are surrounded by the structure 10 to minimize the pressure drop.
- the structure 10 at the respective corner portions of the orthogonal latticework is provided with at least one first slit 13 for scraping off coolant flowing upwards through the fuel channel 2 and guiding this coolant towards the elongated elements.
- a second slit 14 is arranged at the res ⁇ pective corners of the structure between the orthogonal latticework and the structure extending upwards for guiding coolant at the elongated elements which are arranged in the corner portions of the latticework.
- the structure 10 is provided with means in the form of flaps 15 extending from the upstream edge thereof and in an upstream direction.
- the flaps 15 are arranged for attachment to the orthogonal latticework by means of, for example, spot welding.
- the flaps 15 are made long and narrow in the axial direction so as to have a minimum influence on the upstream and guiding edge of the structure 10. It is also advantageous to arrange the flaps 15 so as to lie in the same vertical plane as the structure 10 from which they extend. By making the flaps 15 long and narrow and/or in the same vertical plane as the structure 10, a minimum influence on the pressure drop across the spacer 7 is obtained.
- the upstream edge surfaces 16 of the structure, both along the side surfa ⁇ ces of the structure 10 and along the oblique edges of the flaps 11, are bevelled.
- the bevel is preferably about 45° and adapted to guide the water flowing upwards along the fuel channel wall into the central part of the fuel channel wall.
- the bevel permits a reduced pressure drop compared with non- bevelled transverse edges.
- orthogonal lattice ⁇ work and the surrounding structure 10 in zircaloy. It is also possible to construct the orthogonal latticework in inconel whereas the surrounding structure 10 is made in zircaloy.
- the orthogonal latticework is shown in the figure as composed of sleeves.
- the latticework can also consist of cells or of crossed strip elements standing on end.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
- Containers And Packaging Bodies Having A Special Means To Remove Contents (AREA)
- Structure Of Emergency Protection For Nuclear Reactors (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9502120A SE504486C2 (en) | 1995-06-12 | 1995-06-12 | Sprinkler at a fuel cartridge and a fuel cartridge |
SE9502120 | 1995-06-12 | ||
PCT/SE1996/000550 WO1996042086A1 (en) | 1995-06-12 | 1996-04-26 | Spacer for a fuel assembly and a fuel assembly |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0871961A1 true EP0871961A1 (en) | 1998-10-21 |
Family
ID=20398577
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96917751A Ceased EP0871961A1 (en) | 1995-06-12 | 1996-04-26 | Spacer for a fuel assembly and a fuel assembly |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0871961A1 (en) |
JP (1) | JPH11507438A (en) |
SE (1) | SE504486C2 (en) |
WO (1) | WO1996042086A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
RU2331119C1 (en) * | 2006-12-22 | 2008-08-10 | Открытое акционерное общество "ТВЭЛ" | Fuel rod array and insert spacer component |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3330850A1 (en) * | 1983-08-26 | 1985-03-14 | Kraftwerk Union AG, 4330 Mülheim | CORE REACTOR FUEL ELEMENT |
JP3038266B2 (en) * | 1991-12-09 | 2000-05-08 | 株式会社東芝 | Fuel spacer |
SE505285C2 (en) * | 1993-06-30 | 1997-07-28 | Asea Atom Ab | Fuel cartridge for boiler water reactor, including seven spreader |
-
1995
- 1995-06-12 SE SE9502120A patent/SE504486C2/en not_active IP Right Cessation
-
1996
- 1996-04-26 WO PCT/SE1996/000550 patent/WO1996042086A1/en not_active Application Discontinuation
- 1996-04-26 JP JP9502370A patent/JPH11507438A/en active Pending
- 1996-04-26 EP EP96917751A patent/EP0871961A1/en not_active Ceased
Non-Patent Citations (1)
Title |
---|
See references of WO9642086A1 * |
Also Published As
Publication number | Publication date |
---|---|
JPH11507438A (en) | 1999-06-29 |
SE9502120D0 (en) | 1995-06-12 |
SE504486C2 (en) | 1997-02-17 |
WO1996042086A1 (en) | 1996-12-27 |
SE9502120L (en) | 1996-12-13 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19971209 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): CH DE ES FI LI |
|
17Q | First examination report despatched |
Effective date: 19990512 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
RTI1 | Title (correction) |
Free format text: SPACER FOR A FUEL ASSEMBLY AND FUEL ASSEMBLY HAVING SUCH A SPACER |
|
RTI1 | Title (correction) |
Free format text: SPACER FOR A FUEL ASSEMBLY AND FUEL ASSEMBLY HAVING SUCH A SPACER |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED |
|
18R | Application refused |
Effective date: 20000414 |