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GB2098787A - Production of pellets for nuclear fuel elements - Google Patents

Production of pellets for nuclear fuel elements Download PDF

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Publication number
GB2098787A
GB2098787A GB8214324A GB8214324A GB2098787A GB 2098787 A GB2098787 A GB 2098787A GB 8214324 A GB8214324 A GB 8214324A GB 8214324 A GB8214324 A GB 8214324A GB 2098787 A GB2098787 A GB 2098787A
Authority
GB
United Kingdom
Prior art keywords
pellets
portions
central portion
annular
nuclear fuel
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.)
Granted
Application number
GB8214324A
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GB2098787B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Nuclear Fuels Ltd
Original Assignee
British Nuclear Fuels Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by British Nuclear Fuels Ltd filed Critical British Nuclear Fuels Ltd
Priority to GB8214324A priority Critical patent/GB2098787B/en
Publication of GB2098787A publication Critical patent/GB2098787A/en
Application granted granted Critical
Publication of GB2098787B publication Critical patent/GB2098787B/en
Expired legal-status Critical Current

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Classifications

    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21CNUCLEAR REACTORS
    • G21C3/00Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/42Selection of substances for use as reactor fuel
    • G21C3/58Solid reactor fuel Pellets made of fissile material
    • G21C3/62Ceramic fuel
    • G21C3/623Oxide fuels
    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21CNUCLEAR REACTORS
    • G21C3/00Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/42Selection of substances for use as reactor fuel
    • G21C3/58Solid reactor fuel Pellets made of fissile material
    • G21C3/62Ceramic fuel
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00Energy generation of nuclear origin
    • Y02E30/30Nuclear fission reactors

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

A method for producing nuclear fuel pellets each made up of a central portion and an outer annular portion surrounding the central portion, the two portions differing in composition. Such pellets are termed annular-layered pellets. The method comprises the steps of pressing powdered refractory material which has been granulated to form separately a central portion and an outer annular portion, assembling the portions together, compacting the assembly and sintering the compact. The portions are bonded together during sintering. The difference in composition may include a difference in density or isotopic enrichment as well as a chemical difference.

Description

SPECIFICATION Production of pellets for nuclear fuel elements This invention relates to the production of pellets for nuclear fuel elements.
Nuclear fuel is manufactured at the present time as small right circular cylinders of ceramic nuclear material (for example uranium dioxide, thorium dioxide, plutonium dioxide or mixtures of these) commonly called pellets.
These pellets are normally produced by compacting a powdered ceramic compound in a die at room temperature and sintering the resulting compact at high temperature to produce a dense homogeneous ceramic body which is the pellet. However, to obtain increased benefit from nuclear fuel in the form of pellets it has been proposed that the pellets should be made up of a central portion and an outer annular portion surrounding the central portion, the two portions differing in composition. Such nuclear fuel pellets are hereinafter termed annular-layered pellets, The present invention seeks to provide a method for producing annular-layered pellets in which the central portion and annular portion in each pellet are bonded together during sintering.
According to the present invention the production of an annular-layered nuclear fuel pellet consisting essentially of a central portion and an outer annular portion surrounding the central portion comprises the steps of pressing powdered refractory material which has been granulated to form separately a central portion and an outer annular portion differing from each other in composition, assembling the portions together, compacting the assembly and sintering the compact.
Difference in composition is to be taken to include differences in density and isotopic enrichment as well as chemical differences.
There may be differences in more than one of these properties.
Both oxides and carbides are considered suitable refractory materials for use in nuclear fuel pellets and may be used in the present invention. However it is to be understood when selecting refractory material for use in the invention that normal precautions are to be undertaken by providing refractory powder of similar activity for the two portions, also that: a. the two portions are chemically compatible with each other and with the sintering atmosphere, b. the thermal expansion characteristics of the two portions are compatible, c. neither portion undergoes a phase change causing a change in volume in the temperature range experienced during sintering, d. the two portions are ceramically identical to the extent that they will shrink by the same amount and at approximately the same rate during sintering.
The preferred refractory material is uranium dioxide to which may be added other materials to aid sintering, enhance grain size/ growth or produce pores which control density, as well as additives providing nuclear characteristics, for example, plutonium dioxide.
Advantages of annular layered pellets in which the portions are bonded together in accordance with the invention are the clear division between, the portions, the fixed positions of the portions relative to one another and the full use of the space available for the fuel pellet.
In a preferred example of carrying the invention into effect two batches of uranium dioxide powders of 3.52% and 0.387% enrichment were taken. The 3.52% enriched powder was blended with sufficient ,fugitive pore former to lower the final sintered density of pellets made from this oxide by 5%--no addition was made to the 0.387% enriched oxide. The powders were separately precompacted at 0.75 te/cm2 and granulated through a sieve of size 1200 microns. 0.2% zinc stearate was added as a lubricant to both batches of granules which were then pressed in dies at 1.5 te/cm2 to form central and annular portions of pellets with a density of 4.9-5.2 g/cm3-the 3.52% enriched material was used for the outer annular portion and the 0.382% material for the centre.The outer annular portions were pressed in a die with a removable core rod which was withdrawn after pressing leaving a hole. A central portion was inserted in the hole in each outer portion and a plain top punch was then used to press the assembled portions to a final green density of 5.6-5.8 g/cm3 using a pressure of 4 te/cm2. The composite compacts were then sintered for approximately 5 hours at 1700"C. This yielded coherent pellets of overall density in the range 95.2-95.6% of theoretical 'he annulus and centre having approximate densities of 98.7 and 93.7% respectively.
Annular layered pellets with a central hole may be prepared similarly using a die with a fixed core rod for pressing the assembled central and outer annular portions.
1. A process for the production of an annular-layered nuclear fuel pellet consisting essentially of a central portion and an outer annular portion surrounding the central portion, the process comprising the steps of pressing powdered refractory material which has been granulated to form separately a central portion and an outer annular portion differing from each other in composition, assembling the portions together, compacting
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Production of pellets for nuclear fuel elements This invention relates to the production of pellets for nuclear fuel elements. Nuclear fuel is manufactured at the present time as small right circular cylinders of ceramic nuclear material (for example uranium dioxide, thorium dioxide, plutonium dioxide or mixtures of these) commonly called pellets. These pellets are normally produced by compacting a powdered ceramic compound in a die at room temperature and sintering the resulting compact at high temperature to produce a dense homogeneous ceramic body which is the pellet. However, to obtain increased benefit from nuclear fuel in the form of pellets it has been proposed that the pellets should be made up of a central portion and an outer annular portion surrounding the central portion, the two portions differing in composition. Such nuclear fuel pellets are hereinafter termed annular-layered pellets, The present invention seeks to provide a method for producing annular-layered pellets in which the central portion and annular portion in each pellet are bonded together during sintering. According to the present invention the production of an annular-layered nuclear fuel pellet consisting essentially of a central portion and an outer annular portion surrounding the central portion comprises the steps of pressing powdered refractory material which has been granulated to form separately a central portion and an outer annular portion differing from each other in composition, assembling the portions together, compacting the assembly and sintering the compact. Difference in composition is to be taken to include differences in density and isotopic enrichment as well as chemical differences. There may be differences in more than one of these properties. Both oxides and carbides are considered suitable refractory materials for use in nuclear fuel pellets and may be used in the present invention. However it is to be understood when selecting refractory material for use in the invention that normal precautions are to be undertaken by providing refractory powder of similar activity for the two portions, also that: a. the two portions are chemically compatible with each other and with the sintering atmosphere, b. the thermal expansion characteristics of the two portions are compatible, c. neither portion undergoes a phase change causing a change in volume in the temperature range experienced during sintering, d. the two portions are ceramically identical to the extent that they will shrink by the same amount and at approximately the same rate during sintering. The preferred refractory material is uranium dioxide to which may be added other materials to aid sintering, enhance grain size/ growth or produce pores which control density, as well as additives providing nuclear characteristics, for example, plutonium dioxide. Advantages of annular layered pellets in which the portions are bonded together in accordance with the invention are the clear division between, the portions, the fixed positions of the portions relative to one another and the full use of the space available for the fuel pellet. In a preferred example of carrying the invention into effect two batches of uranium dioxide powders of 3.52% and 0.387% enrichment were taken. The 3.52% enriched powder was blended with sufficient ,fugitive pore former to lower the final sintered density of pellets made from this oxide by 5%--no addition was made to the 0.387% enriched oxide. The powders were separately precompacted at 0.75 te/cm2 and granulated through a sieve of size 1200 microns. 0.2% zinc stearate was added as a lubricant to both batches of granules which were then pressed in dies at 1.5 te/cm2 to form central and annular portions of pellets with a density of 4.9-5.2 g/cm3-the 3.52% enriched material was used for the outer annular portion and the 0.382% material for the centre.The outer annular portions were pressed in a die with a removable core rod which was withdrawn after pressing leaving a hole. A central portion was inserted in the hole in each outer portion and a plain top punch was then used to press the assembled portions to a final green density of 5.6-5.8 g/cm3 using a pressure of 4 te/cm2. The composite compacts were then sintered for approximately 5 hours at 1700"C. This yielded coherent pellets of overall density in the range 95.2-95.6% of theoretical 'he annulus and centre having approximate densities of 98.7 and 93.7% respectively. Annular layered pellets with a central hole may be prepared similarly using a die with a fixed core rod for pressing the assembled central and outer annular portions. CLAIMS
1. A process for the production of an annular-layered nuclear fuel pellet consisting essentially of a central portion and an outer annular portion surrounding the central portion, the process comprising the steps of pressing powdered refractory material which has been granulated to form separately a central portion and an outer annular portion differing from each other in composition, assembling the portions together, compacting the assembly and sintering the compact.
2. A process as claimed in claim 1 wherein the central portion is annular.
3. A process as claimed in claim 1 or claim 2 wherein the central portion and the outer annular portion consist essentially of uranium dioxide and differ in isotopic enrichment.
4. A process as claimed in claim 1 or claim 2 wherein the central portion and the outer annular portion consist essentially of uranium dioxide and differ in density.
5. A process as claimed in any preceding claim wherein at least one of the portions contains plutonium dioxide.
6. A process for the production of an annular-layered nuclear fuel pellet substantially as herein before described with reference to the example.
7. An annular-layered nuclear fuel pellet produced by the process claimed in any preceding claim.
GB8214324A 1981-05-19 1982-05-17 Production of pellets for nuclear fuel elements Expired GB2098787B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8214324A GB2098787B (en) 1981-05-19 1982-05-17 Production of pellets for nuclear fuel elements

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8115360 1981-05-19
GB8214324A GB2098787B (en) 1981-05-19 1982-05-17 Production of pellets for nuclear fuel elements

Publications (2)

Publication Number Publication Date
GB2098787A true GB2098787A (en) 1982-11-24
GB2098787B GB2098787B (en) 1985-09-18

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0416778A3 (en) * 1989-09-06 1991-11-21 British Nuclear Fuels Plc Nuclear fuel bodies and the production thereof
EP0556027A3 (en) * 1992-02-13 1993-11-03 British Nuclear Fuels PLC The production of nuclear fuel
WO1996018999A1 (en) * 1994-12-16 1996-06-20 British Nuclear Fuels Plc Manufacturing ceramic articles
EP0840330A1 (en) * 1996-11-01 1998-05-06 General Electric Company Segmented pellet and production thereof
WO2000021095A1 (en) * 1998-10-06 2000-04-13 Siemens Aktiengesellschaft Fuel tablet comprising a layered structure
EP2399951A1 (en) 2010-06-25 2011-12-28 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Pellets and method for their manufacture
CN103366835A (en) * 2013-04-01 2013-10-23 中科华核电技术研究院有限公司 Nuclear fuel pellet and manufacturing method thereof, and nuclear reactor
CN103366836A (en) * 2013-04-01 2013-10-23 中科华核电技术研究院有限公司 Nuclear fuel pellet and manufacturing method thereof, and nuclear reactor
US9997267B2 (en) * 2013-02-13 2018-06-12 Battelle Memorial Institute Nuclear reactor target assemblies, nuclear reactor configurations, and methods for producing isotopes, modifying materials within target material, and/or characterizing material within a target material
CN113012832A (en) * 2019-12-20 2021-06-22 中核北方核燃料元件有限公司 UO2Composite UN-UO2Method for producing fuel pellets

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0416778A3 (en) * 1989-09-06 1991-11-21 British Nuclear Fuels Plc Nuclear fuel bodies and the production thereof
EP0556027A3 (en) * 1992-02-13 1993-11-03 British Nuclear Fuels PLC The production of nuclear fuel
WO1996018999A1 (en) * 1994-12-16 1996-06-20 British Nuclear Fuels Plc Manufacturing ceramic articles
US5916497A (en) * 1994-12-16 1999-06-29 British Nuclear Fuels Plc Manufacturing of ceramic articles
EP0840330A1 (en) * 1996-11-01 1998-05-06 General Electric Company Segmented pellet and production thereof
WO2000021095A1 (en) * 1998-10-06 2000-04-13 Siemens Aktiengesellschaft Fuel tablet comprising a layered structure
EP2399951A1 (en) 2010-06-25 2011-12-28 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Pellets and method for their manufacture
DE102010030547A1 (en) 2010-06-25 2011-12-29 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Pellets and process for their preparation
US9997267B2 (en) * 2013-02-13 2018-06-12 Battelle Memorial Institute Nuclear reactor target assemblies, nuclear reactor configurations, and methods for producing isotopes, modifying materials within target material, and/or characterizing material within a target material
CN103366835A (en) * 2013-04-01 2013-10-23 中科华核电技术研究院有限公司 Nuclear fuel pellet and manufacturing method thereof, and nuclear reactor
CN103366836A (en) * 2013-04-01 2013-10-23 中科华核电技术研究院有限公司 Nuclear fuel pellet and manufacturing method thereof, and nuclear reactor
CN103366836B (en) * 2013-04-01 2016-01-06 中科华核电技术研究院有限公司 Fuel ball, method for making and nuclear reactor
CN103366835B (en) * 2013-04-01 2016-01-06 中科华核电技术研究院有限公司 Fuel ball, method for making and nuclear reactor
CN113012832A (en) * 2019-12-20 2021-06-22 中核北方核燃料元件有限公司 UO2Composite UN-UO2Method for producing fuel pellets

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Publication number Publication date
GB2098787B (en) 1985-09-18

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19970517