US4683113A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Nuclear fuel assembly
Assignee: Hitachi Ltd
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Filing: 1985-05-16
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Granted: 1987-07-28
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Expires: 2005-05-16
Abstract
Abstract A nuclear fuel assembly has a plurality of fuel rods each containing a multiplicity of fuel pellets. The fuel rods include a plurality of first fuel rods and a plurality of second fuel rods. Each of the first fuel rods contains a burnable poison over substantially the entire axial length thereof. The first fuel rod also has a greater means enrichment in the upper axial region thereof than that in the lower axial region thereof. Each of the second fuel rods contains no burnable poison and has a uniform enrichment distribution over substantially the entire axial length thereof. In each cross-section of the fuel assembly perpendicular to the axis thereof, the outer peripheral portion has a greater mean enrichment than the central portion. The first fuel rods are disposed in the peripheral portion except the outermost peripheral portion of the cross-section of the fuel assembly.
Inventors
- 👤 Takaaki Mochida
- 👤 Junichi Yamashita
- 👤 Toshiro Yoshioka
- 👤 Michihiro Ozawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:32
CPC Classifications
G; G21; G21C; G21C3/00; G21C3/02; G21C3/04; G21C3/16; G21C3/18; G21C3/30; G21C3/32; G21C3/326; G21C3/328; Y; Y02; Y02E; Y02E30/00; Y02E30/30
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
83 words
A nuclear fuel assembly having a plurality of fuel rods each containing a multiplicity of fuel pellets, comprising: first fuel rods each containing a burnable poison over substantially the entire axial length thereof, said first fuel rod having upper and lower axial regions and a greater mean enrichment in the upper axial region thereof than that in the lower axial region thereof; and second fuel rods containing no burnable poison and having a uniform enrichment distribution over substantially the entire axial length thereof.
Claim 2
Dependent Claim
83 words
A nuclear fuel assembly having a plurality of fuel rods each containing a multiplicity of fuel pellets, comprising: first fuel rods each containing a burnable poison over substantially the entire axial length thereof, said first fuel rod having upper and lower axial regions and a greater mean enrichment in the upper axial region thereof than that in the lower axial region thereof; and second fuel rods containing no burnable poison and having a uniform enrichment distribution over substantially the entire axial length thereof.
Claim 3
Dependent Claim
52 words
A nuclear fuel assembly according to claim 1, wherein the boundary between the said upper axial region and said lower axial region of said first fuel rod is positioned within a range between 1/3 and 7/12 of the overall length of said first fuel rod as measured from the lower end thereof.
Claim 4
Dependent Claim
28 words
A nuclear fuel assembly according to claim 1, wherein said first fuel rods are disposed in the portion of said fuel assembly except the outermost peripheral portion thereof.
Claim 5
Dependent Claim
52 words
A nuclear fuel assembly according to claim 3, wherein the boundary between the said upper axial region and said lower axial region of said first fuel rod is positioned within a range between 1/3 and 7/12 of the overall length of said first fuel rod as measured from the lower end thereof.
Claim 6
Dependent Claim
30 words
A nuclear fuel assembly according to claim 1, wherein the infinite multiplication factor in the upper region of said fuel assembly is greater than that in the lower region thereof.
Claim 7
Dependent Claim
28 words
A nuclear fuel assembly according to claim 5, wherein said first fuel rods are disposed in the portion of said fuel assembly except the outermost peripheral portion thereof.
Claim 8
Dependent Claim
52 words
A nuclear fuel assembly according to claim 6, wherein the boundary between the said upper axial region and said lower axial region of said first fuel rod is positioned within a range between 1/3 and 7/12 of the overall length of said first fuel rod as measured from the lower end thereof.
Claim 9
Dependent Claim
116 words
A nuclear fuel assembly having a plurality of fuel rods each containing a multiplicity of fuel pellets, comprising: first fuel rods each containing a burnable poison over substantially the entire axial length thereof, said first fuel rod having upper and lower axial regions and a greater mean enrichment in the upper axial region thereof than that in the lower axial region thereof; and second fuel rods containing no burnable poison and having a uniform enrichment distribution over substantially the entire axial length thereof, wherein the mean enrichment in the outer peripheral portion of a cross-section of said fuel assembly perpendicular to the axis of said fuel assembly is greater than that in the central portion thereof.
Claim 10
Dependent Claim
116 words
A nuclear fuel assembly having a plurality of fuel rods each containing a multiplicity of fuel pellets, comprising: first fuel rods each containing a burnable poison over substantially the entire axial length thereof, said first fuel rod having upper and lower axial regions and a greater mean enrichment in the upper axial region thereof than that in the lower axial region thereof; and second fuel rods containing no burnable poison and having a uniform enrichment distribution over substantially the entire axial length thereof, wherein the mean enrichment in the outer peripheral portion of a cross-section of said fuel assembly perpendicular to the axis of said fuel assembly is greater than that in the central portion thereof.
Claim 11
Dependent Claim
52 words
A nuclear fuel assembly according to claim 8, wherein the boundary between the said upper axial region and said lower axial region of said first fuel rod is positioned within a range between 1/3 and 7/12 of the overall length of said first fuel rod as measured from the lower end thereof.
Claim 12
Dependent Claim
28 words
A nuclear fuel assembly according to claim 8, wherein said first fuel rods are disposed in the portion of said fuel assembly except the outermost peripheral portion thereof.
Claim 13
Dependent Claim
52 words
A nuclear fuel assembly according to claim 10, wherein the boundary between the said upper axial region and said lower axial region of said first fuel rod is positioned within a range between 1/3 and 7/12 of the overall length of said first fuel rod as measured from the lower end thereof.
Claim 14
Dependent Claim
30 words
A nuclear fuel assembly according to claim 8, wherein the infinite multiplication factor in the upper region of said fuel assembly is greater than that in the lower region thereof.
Claim 15
Dependent Claim
28 words
A nuclear fuel assembly according to claim 12, wherein said first fuel rods are disposed in the portion of said fuel assembly except the outermost peripheral portion thereof.
Claim 16
Dependent Claim
52 words
A nuclear fuel assembly according to claim 13, wherein the boundary between the said upper axial region and said lower axial region of said first fuel rod is positioned within a range between 1/3 and 7/12 of the overall length of said first fuel rod as measured from the lower end thereof.
Claim 17
Dependent Claim
75 words
A nuclear fuel assembly according to claim 2, further comprising third fuel rods, said third fuel rods containing an enriched nuclear fuel material substantially over the entire axial length thereof, said third fuel rods having upper and lower axial regions with a boundary therebetween corresponding to the boundary of said first fuel rods, said third fuel rods containing a burnable poison in said upper axial region and no burnable poison in said lower axial region.
Claim 18
Dependent Claim
27 words
A nuclear fuel assembly according to claim 15, wherein each of said first, second and third fuel rods have at least one end region containg natural uranium.
Claim 19
Dependent Claim
22 words
A nuclear fuel assembly according to claim 16, wherein each of said second fuel rods have opposite end regions containing natural uranium.
Claim 20
Dependent Claim
57 words
A nuclear fuel assembly according to claim 15, further comprising a center portion and an outer peripheral portion surrounding said center portion in a cross-section of said fuel assembly perpendicular to the axis of said fuel assembly, said fuel assembly having a means enrichment which is greater in said outer peripheral portion than in said center portion.
Claim 21
Dependent Claim
28 words
A nuclear fuel assembly according to claim 18, wherein said first fuel rods are disposed in the portion of said fuel assembly except the outermost peripheral portion thereof.
Claim 22
Dependent Claim
27 words
A nuclear fuel assembly according to claim 19, wherein each of said first, second and third fuel rods have at least one end region containing natural uranium.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-07-27 | 1991-01-26 | 1991-07-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-07-27 | 1995-01-26 | 1995-07-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-07-27 | 1999-01-26 | 1999-07-28 | $7700.00 | Window Closed / Lapsed |