EP0148452A2
Expired / Lapsed
EP
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A coolant flow mixing grid for a nuclear reactor fuel assembly
Assignee: Westinghouse Electric Corp
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Filing: 1984-12-14
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Granted: —
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Expires: 2004-12-14
Abstract
Abstract The invention relates to a coolant-flow mixing grid for a nuclear-reactor fuel assembly. The mixing grid, which has essentially no fuelrod supporting function, is composed of straps (44) interleaved in egg-crate-like fashion to define cell openings (46, 60) for fuel rods, each of which cell openings has associated therewith at least one mixing vane (52) disposed on the downstream edge of one of the straps, and at least one impact-preventing protrusion (54) projecting from the side of the strap into the associated cell opening so as to protect the mixing vane associated therewith from impact when a fuel rod therein undergoes lateral motion. The mixing grid includes a peripheral strap (58) to which the interleaved straps (44) are connected and which lends added structural integrity. The inner straps (44) preferably are of substantially lower height than the peripheral strap (58) in order to minimize coolant pressure drop through the grid as well as the amount of structural material capable of parasitically absorbing neutrons.
Inventors
- 👤 Edmund Emory Demario
- 👤 Raymond Francis Boyle
- 👤 Peter Jacob Kuchirka
- 👤 David James Sperhac
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 19:59
CPC Classifications
G; G21; G21C; G21C3/00; G21C3/30; G21C3/32; G21C3/322; G21C3/34; G21C3/356; G21C3/3563; G21C3/3432; Y; Y02; Y02E; Y02E30/00; Y02E30/30
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
197 words
A coolant-flow mixing grid for promoting the mixing of coolant flow through a nuclear-reactor fuel assembly along and between fuel rods supported by transverse support grids mounted on control-rod guide thimbles of the fuel assembly, characterized in that said coolant-flow mixing grid (34) comprises a plurality of interleaved inner straps (44) arranged in an egg-crate-like configuration to define a plurality of inner cell openings (46) for receiving therethrough respective ones of the fuel rods; at least one mixing vane (52) for each of at least a number of said inner cell openings (46), said mixing vane being disposed on one of the inner straps and projecting therefrom in the downstream direction of said coolant flow, and inwards generally toward the longitudinal axis of the cell opening, in a manner such as to deflect coolant laterally from one fuel rod toward an adjacent fuel rod; and a rigid protrusion (54) associated with each mixing vane (52) which protrusion is disposed on said inner strap and projects therefrom into the associated inner cell opening (46) so as to protect the associated mixing vane (52) from damaging impact when a fuel rod disposed in the cell opening undergoes lateral motion.
Claim 2
Dependent Claim
197 words
A coolant-flow mixing grid for promoting the mixing of coolant flow through a nuclear-reactor fuel assembly along and between fuel rods supported by transverse support grids mounted on control-rod guide thimbles of the fuel assembly, characterized in that said coolant-flow mixing grid (34) comprises a plurality of interleaved inner straps (44) arranged in an egg-crate-like configuration to define a plurality of inner cell openings (46) for receiving therethrough respective ones of the fuel rods; at least one mixing vane (52) for each of at least a number of said inner cell openings (46), said mixing vane being disposed on one of the inner straps and projecting therefrom in the downstream direction of said coolant flow, and inwards generally toward the longitudinal axis of the cell opening, in a manner such as to deflect coolant laterally from one fuel rod toward an adjacent fuel rod; and a rigid protrusion (54) associated with each mixing vane (52) which protrusion is disposed on said inner strap and projects therefrom into the associated inner cell opening (46) so as to protect the associated mixing vane (52) from damaging impact when a fuel rod disposed in the cell opening undergoes lateral motion.
Claim 3
Dependent Claim
45 words
A coolant-flow mixing grid according to claim 1, characterized in that each inner cell opening (46) is defined by interconnecting segments of four of the inner straps (44), one of the interconnecting strap segments having said mixing vane (52) disposed on the downstream edge thereof.
Claim 4
Dependent Claim
34 words
3, A coolant-flow mixing grid according to claim 2, characterized in that said protrusion (54) is disposed on the inner lateral face of said one strap segment and upstream of the mixing vane (52).
Claim 5
Dependent Claim
36 words
A coolant-flow mixing grid according to claim 2 or 3, characterized in that each of the strap segments defining an inner cell opening (46) has one said protrusion (54) disposed on the inner lateral face thereof.
Claim 6
Dependent Claim
47 words
A coolant-flow mixing grid according to claim 4 or 5, characterized in that the protrusions (54) on opposite strap segments and projecting into the same cell opening (46) are spaced apart a distance exceeding the diameter of the fuel rod to be received in said cell opening.
Claim 7
Dependent Claim
56 words
A coolant-flow mixing grid according to claim 4 or 5, characterized in that two of the protrusions (54) associated with an inner cell opening (46) lie in one of two parallel spaced planes perpendicular to the longitudinal axis of the cell opening, and the other two of said protrusions lie in the other of said planes.
Claim 8
Dependent Claim
62 words
A coolant-flow mixing grid according to any one of the preceding claims, characterized in that the mixing grid (34) includes an outer peripheral strap (58) having the opposite terminal ends of each inner strap (44) connected thereto so as, together with the inner straps, to form an integral structure and to define border cell openings (60, 62) for receiving fuel rods therethrough.
Claim 9
Dependent Claim
86 words
A coolant-flow mixing grid according to claim 7, characterized in that each of the border cell openings (60, 62) has associated therewith one said mixing vane (52) disposed on one of the inner strap segments associated with the respective border cell opening, each mixing vane (52) associated with a border cell opening having associated therewith one said protrusion (54) which extends into said border cell opening so as to protect the mixing vane from damaging impact by a fuel rod extending through the border cell opening.
Claim 10
Dependent Claim
52 words
A coolant-flow mixing grid according to claim 7 or 8, characterized in that said outer peripheral strap (58) has at least one dimple (64) disposed thereon at each border cell opening (60, 62), said dimple (64) projecting into the associated border cell opening from the inner face of the outer peripheral strap.
Claim 11
Dependent Claim
36 words
A coolant-flow mixing grid according to claim 9, characterized in that said dimple (64) is elongate, extends in the axial direction of the associated border cell opening, and is closed to coolant flow through the latter.
Claim 12
Dependent Claim
57 words
A coolant-flow mixing grid according to claim 7, 8, 9 or 10, characterized in that said outer peripheral strap (58) includes a plurality of coolant deflecting fins (66) extending, in spaced relationship with respect to each other, from the downstream edge of the peripheral strap and angled inwards generally toward the longitudinal axis of the mixing grid.
Claim 13
Dependent Claim
43 words
A coolant-flow mixing grid according to any one of claims 7 to 11, characterized in that the peripheral strap (58) includes a plurality of tabs (68) extending from the upstream edge thereof and curved inwards of the mixing grid as seen in extension.
Claim 14
Dependent Claim
47 words
A coolant-flow mixing grid according to any one of claims 7 to 12, characterized in that the outer peripheral strap (58) is formed of four partial straps connected together rectangularly so as to define four corners (70), the terminal ends of said partial straps being chamfered (72).
Claim 15
Dependent Claim
29 words
A coolant-flow mixing grid according to claim 13, characterized in that said terminal ends are chamfered approximately 52 degrees with respect to the longitudinal axis of the mixing grid.
Claim 16
Dependent Claim
48 words
A coolant-flow mixing grid according to any one of claims 7 to 14, characterized in that the inner straps (44) are substantially equal in height in the longitudinal direction of the grid, and said peripheral strap (58) is substantially higher in said longitudinal direction than said inner straps.
Claim 17
Dependent Claim
66 words
A coolant-flow mixing grid according to claim 15, characterized in that at least some of the inner straps (44) have reinforcing webs (74, 76) so formed on terminal end portions thereof as to reinforce the connection of the respective terminal end portions to the peripheral strap, and to prevent the latter from twisting and bowing due to thermal stresses introduced during operation in a fuel assembly.
Claim 18
Dependent Claim
61 words
A coolant-flow mixing grid according to claim 16, characterized in that each of the inner straps (44) with reinforcing webs (74, 76) thereon has one of said reinforcing webs formed integral therewith on the downstream edge of at least one terminal end portion thereof, said reinforcing web (74) sloping toward the peripheral strap (58) in the downstream direction of coolant flow.
Claim 19
Dependent Claim
63 words
A coolant-flow mixing grid according to claim 16 or 17, characterized in that each of the inner straps (44) with reinforcing webs (74, 76) thereon has one of said reinforcing webs formed integral therewith on the upstream edge of at least one terminal end portion thereof, said reinforcing web (76) sloping toward the peripheral strap (58) in the upstream direction of coolant flow.
Claim 20
Dependent Claim
55 words
A coolant-flow mixing grid according to claim 18, characterized in that said inner straps (44) alternately have a reinforcing web (74) on the downstream edge of one terminal end portion of the respective inner strap and a reinforcing web (76) on the upstream edge of the opposite end portion of the next following inner strap.
Claim 21
Dependent Claim
41 words
A coolant-flow mixing grid according to claim 18, characterized in that each of the inner straps (44) has a reinforcing web (74) on the downstream edge and a reinforcing web (76) on the upstream edge of each terminal end portion thereof.
Claim 22
Dependent Claim
33 words
A coolant-flow mixing grid according to any one of the preceding claims, characterized in that each protrusion (54) is so oriented as to present minimum resistance to coolant flow through the mixing grid.
Claim 23
Dependent Claim
53 words
A coolant-flow mixing grid according to any one of the preceding claims, characterized in that each protrusion (54) defines an arch extending transversely in a plane substantially perpendicular to the longitudinal axis of the respective cell opening (46), and which arch is open in the direction of coolant flow through the cell opening.
Claim 24
Dependent Claim
18 words
A coolant-flow mixing grid according to claim 22, characterized in that said arch is generally trapezoidal in shape.
Claim 25
Dependent Claim
61 words
A coolant-flow mixing grid according to any one of the preceding claims, characterized in that the interleaved inner straps (44) arranged in said egg-crate-like configuration define also thimble cell openings (48) for receiving therethrough respective ones of said control-rod guide thimbles (24), said thimble cell openings having associated therewith means (56) for mounting the mixing grid on said control-rod guide thimbles.
References Cited (Backward Citations)
No citation records indexed.
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