GB2177249A - Nuclear fuel bodies - Google Patents
Nuclear fuel bodies Download PDFInfo
- Publication number
- GB2177249A GB2177249A GB08517110A GB8517110A GB2177249A GB 2177249 A GB2177249 A GB 2177249A GB 08517110 A GB08517110 A GB 08517110A GB 8517110 A GB8517110 A GB 8517110A GB 2177249 A GB2177249 A GB 2177249A
- Authority
- GB
- United Kingdom
- Prior art keywords
- matrix
- seed
- fuel body
- particles
- seed particles
- 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
Links
- 239000003758 nuclear fuel Substances 0.000 title claims abstract description 10
- 239000002245 particle Substances 0.000 claims abstract description 28
- 239000011159 matrix material Substances 0.000 claims abstract description 26
- 239000013078 crystal Substances 0.000 claims abstract description 15
- 229910010293 ceramic material Inorganic materials 0.000 claims abstract description 11
- 239000000463 material Substances 0.000 claims abstract description 9
- FLDALJIYKQCYHH-UHFFFAOYSA-N plutonium(IV) oxide Inorganic materials [O-2].[O-2].[Pu+4] FLDALJIYKQCYHH-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000000843 powder Substances 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims abstract description 5
- 239000001257 hydrogen Substances 0.000 claims abstract description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims abstract description 3
- 239000000446 fuel Substances 0.000 claims description 26
- 238000005245 sintering Methods 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 8
- 239000000919 ceramic Substances 0.000 claims description 5
- 238000002360 preparation method Methods 0.000 claims 2
- 239000000470 constituent Substances 0.000 claims 1
- 239000008188 pellet Substances 0.000 abstract description 9
- 238000000137 annealing Methods 0.000 abstract description 2
- FCTBKIHDJGHPPO-UHFFFAOYSA-N uranium dioxide Inorganic materials O=[U]=O FCTBKIHDJGHPPO-UHFFFAOYSA-N 0.000 description 18
- 230000004992 fission Effects 0.000 description 9
- 239000007789 gas Substances 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 4
- UTDLAEPMVCFGRJ-UHFFFAOYSA-N plutonium dihydrate Chemical compound O.O.[Pu] UTDLAEPMVCFGRJ-UHFFFAOYSA-N 0.000 description 4
- 238000001953 recrystallisation Methods 0.000 description 4
- 230000002035 prolonged effect Effects 0.000 description 3
- 230000008961 swelling Effects 0.000 description 3
- 238000007792 addition Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000004308 accommodation Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- OOAWCECZEHPMBX-UHFFFAOYSA-N oxygen(2-);uranium(4+) Chemical compound [O-2].[O-2].[U+4] OOAWCECZEHPMBX-UHFFFAOYSA-N 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- -1 uranium hydride forms Chemical group 0.000 description 1
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
- G21C3/42—Selection of substances for use as reactor fuel
- G21C3/58—Solid reactor fuel Pellets made of fissile material
- G21C3/62—Ceramic fuel
- G21C3/623—Oxide fuels
-
- 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
Landscapes
- 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)
Abstract
Nuclear fuel pellets are made by incorporating seed particles, eg. UO2 seed crystals into a matrix of powdered ceramic material having nuclear characteristics, eg. UO2, and annealing. The UO2 seed crystals can be obtained by heating compacts of UO2 powder or presintered material in dry hydrogen above 1750 DEG C, holding at temperature, cooling and sifting to obtain predominantly single crystals which are used as the seed material. The seed material may also be PuO2, a mixture thereof with UO2, or enriched UO2, and the matrix material may be depleted UO2. A two layered pellet may be produced. <IMAGE>
Description
SPECIFICATION
Nuclear fuel bodies
This invention relates to nuclear fuel bodies and in particular to the production of nuclear fuel bodies with a large mean grain size and to novel fuel bodies produced thereby.
Hitherto, nuclear fuel bodies made from ceramic material, particularly uranium dioxide (us2), have tended to be made from powder particles of uniform small size, the accent having been on achieving densities close to maximum theoretical on subsequent sintering.
A demand has arisen for fuel bodies which allow higher burn-up to be achieved. Higher burn-up in turn calls for fuel bodies with enhanced fission gas retention properties. It has been recognised that fission gas retention can be enhanced if the fuel bodies, after sintering, contain uniform grains of largersize than conventional fuel bodies. Proposals have been made to achieve larger grain sizes involving, for example, prolonged treatment of the fuel bodies at elevated temperatures in excess of 2000"C which is expensive in terms of operating costs and installation of suitable furnace plant.
It is an object of the present invention to provide novel nuclear fuel bodies which exhibit the desirable property of enhanced fission gas retention at high burn-up and which can be produced without resorting to prolonged treatment at elevated temperatures.
According to the invention there is provided a ceramic fuel body formed by sintering a compacted matrix of powdered ceramic material having nuclear characteristics in which are dispersed seed particles which, during sintering, act preferentially as nuclei for growth of grains by consumption of matrix particles surrounding each seed particle.
The individual grain sizes produced by seedinduced growth may range up to 300 microns.
Large grain size fuel can be prepared by introducing seed crystals into a UO2 matrix and annealing. Such crystals will induce secondary recrystallisation and will grow epitaxially at an accelerated rate (inversely proportional to the matrix grain size) by consuming the smaller matrix grains and resulting eventually, if allowed to continue, in a fully recrystallised large grain structure. However, once the abnormally large grains impinge on one another, secondary recrystallisation is expected to largely cease, and the result will be a mixed grain size distribution structure consisting of the large seed-grown grains and the residual matrix grains.It is thus possible to produce a nuclear fuel body with a structure which includes recrystallised grains factors larger than the matrix grains without recourse to prolonged sintering times, additions of chemical additives, active atmospheres or elevated temperatures of of greater than 2000"C.
The seed crystals can be prepared by heating UO2 powder compacts or pre-sintered UO2 in dry hydrogen up to a temperature above 1750"C leading to the formation of hypostoichiometric UO2,. On cooling, uranium hydride forms on grain boundaries and the associated volume increase results in disintegration of the pellet into particles, a large proportion of which are essentially single crystals.Typical conditions were heating presintered UO2 pellets having initial mean grain size, after primary sintering, of approx. 10 microns to 2000"C at 200cumin in dry hydrogen, maintaining at 2000"C for 30 minutes, cooling to ambient at 40"C/min, sieving the fine powder so produced using a sonic sifter and obtaining fractions of and above, and less than, 53 microns. The undersized fraction was predominantly single crystal material with occasional bicrystals, and the oversize fraction was mostly polycrystalline agglomerates. The undersized fraction was employed as seed material, the mean size of the individual crystals being about 30 microns.Green pellets of UO2 powder with a median size less than 3 microns were produced by binderless technique with for example 5 wt/o seed crystals dispersed throughout the green pellets, and the pellets were sintered for 4 hours at about 1720"C (preferably not less than 1700 C) in moist hydrogen. The resulting product had a mean grain size of 44 microns and it was found that the recrystallised grains occupied in the region of 90% of the total volume, with the recrystailised grains approximately five times as large as the matrix grains. Seed additions can vary between 0.1 and 25wt/o, depending upon the choice of process parameters of temperature, sintering time and heating/cooling rates.
Pellets containing seeded grains exhibit lower densities than unseeded pellets depending upon the quantity of seed used. This is considered to be the result of porosity trapped within grains during the growth of the seeded grains. This porosity remains thermaliy stable and can therefore be employed for accommodation of fission product swelling in zones where diffusional creep of UO2 can occur.
Novel fuel structures which the seeding technique gives rise to are, firstly, a mixed enrichment UO2 with micro encapsulation. By nucleating a depleted UO2 matrix with enriched
UO2 seeds it is considered possible to obtain a fully or nearly fully recrystallised microstructure. The depleted UO2 shell surrounding each seed provides a long diffusion path between the source of fission products and the sink-the grain boundaries. In addition the shell would act as a reservoir for containing fission products and at the same time because of its much lower operating temperature help restrain the kernel, minimising fission gas swelling. This new form of dispersed fuel is expected to offer benefits from fission gas retention and swelling considerations.
A second type of novel micro encapsulated mixed oxide fuel body can be envisaged employing plutonium dioxide (PuO2) seeds, manufactured by a disintegration process or by mechanical attrition, dispersed in a depleted UO2 matrix and then sintered.
It is expected that an interface would form between the two materials. The subsequent growth of the seeded grains would proceed by movement of UO2 grain boundaries through the UO2 matrix and away from the UO2/PuO2 interface. The resulting microstructure would comprise large recrystallised grains centred on
Pu02 kernels. Full recrystallisation would not be necessary as fission would be confined to the PuO2 nuclei. Each recrystallised grain then offers a lengthened diffusion path and a possibly beneficial diffusivity gradient. However full recrystallisation gives a more uniform grain size distribution and is therefore desirable.
A further type of novel fuel body can be envisaged in which the seed crystals employed for growth are formed from mixtures of UO2 and Pu02 in mutually soluble proportions.
In a further application of the invention, the fuel bodies may have a duplex structure comprising an inner portion (which may be cylindrical or annular) and an outer portion (which may be annular). Both portions may, in the green state, comprise a matrix of powdered ceramic material, such as UO2, possibly with different degrees of enrichment, and at least one portion may be seeded in the manner described hereinbefore to produce a large grained structure. If both portions are seeded, the mean seed particle sizes or concentrations may differ.
Claims (17)
1. A ceramic fuel body formed by sintering a compacted matrix of powdered ceramic material having nuclear characteristics in which are dispersed seed particles which, during sintering, act preferentially as nuclei for growth of grains by consumption of matrix particles surrounding each seed particle.
2. A fuel body as claimed in Claim 1 in which said grains produced by seed-induced growth range in size up to about 300 microns.
3. A fuel body as claimed in Claim 1 or 2 in which said seed particles are composed of the same ceramic material as the matrix.
4. A fuel body as claimed in Claim 1 or 2 in which said seed particles are composed of a different ceramic material, also having nuclear characteristics.
5. A fuel body as claimed in Claim 4 in which said seed particles are composed of
Pu02 and said matrix is composed of UO2 powder.
6. A fuel body as claimed in Claim 3 in which said ceramic material comprises UO2.
7. A fuel body as claimed in Claim 6 in which the matrix is composed of depleted UO2 and said seed particles comprise enriched uO2.
8. A fuel body as claimed in Claim 1 or 2 in which said matrix comprises UO2 and said seed particles are formed from a mixture of
UO2 and PuO2 in mutuall soluble proportions.
9. A fuel body as claimed in any one of
Claims 1-8 in which the body comprises an inner portion surrounded by an outer portion both having a matrix composed of ceramic material or materials having nuclear characteristics and in which at least one of said portion contains said seed particles.
10. A fuel body as claimed in Claim 9 in which said inner portion contains said seed particles.
11. A fuel body as claimed in any one of
Claims 1-10 in which said seed particles are constituted essentially by single crystals.
12. A fuel body as claimed in any one of
Claims 1-11 in which essentailly all of said seed particles have a size exceeding the mean particle size of the matrix powder particles.
13. A process for the preparation of ceramic nuclear fuel bodies with a large mean grain size including the introduction of seed particles into a matrix of powdered ceramic material having nuclear characteristics and heat treating the matrix, said seed particles acting preferentially as nuclei for growth of grains by consumption of the matrix particles surrounding each seed particle.
14. A process as claimed in Claim 13 in which the seed material constituent within the matrix lies in the range of 0. 1 to 25 wt/o.
15. A process as claimed in Claim 13 or 14 in which the seed particles essentially comprise single crystals of UO2 derived by heating a compact of UO2 powder or pre-sintered UO2 powder in dry hydrogen to a temperature above 17500C, cooling the same so that the material disintegrates into particles, a large proportion of which are essentially single crystals and sifting the particles to isolate the essentially single crystal fraction.
16. A ceramic fuel body substantially as hereinbefore described.
17. A process for the preparation of ceramic nuclear fuel bodies with large mean grain size, substantially as hereinbefore described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08517110A GB2177249B (en) | 1985-07-05 | 1985-07-05 | Nuclear fuel bodies |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08517110A GB2177249B (en) | 1985-07-05 | 1985-07-05 | Nuclear fuel bodies |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8517110D0 GB8517110D0 (en) | 1985-08-14 |
| GB2177249A true GB2177249A (en) | 1987-01-14 |
| GB2177249B GB2177249B (en) | 1988-12-14 |
Family
ID=10581875
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08517110A Expired GB2177249B (en) | 1985-07-05 | 1985-07-05 | Nuclear fuel bodies |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2177249B (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4965024A (en) * | 1987-10-20 | 1990-10-23 | British Nuclear Fuels Plc | Production of ceramic nuclear fuel pellets |
| EP0416778A2 (en) * | 1989-09-06 | 1991-03-13 | British Nuclear Fuels PLC | Nuclear fuel bodies and the production thereof |
| GB2255085A (en) * | 1991-04-17 | 1992-10-28 | British Nuclear Fuels Plc | Manufacture of sintered uranium dioxide |
| US5916497A (en) * | 1994-12-16 | 1999-06-29 | British Nuclear Fuels Plc | Manufacturing of ceramic articles |
| US5991354A (en) * | 1996-01-30 | 1999-11-23 | Siemens Power Corporation | Nuclear fuel pellet |
| US6002735A (en) * | 1996-01-30 | 1999-12-14 | Siemens Power Corporation | Nuclear fuel pellet |
| US10361008B2 (en) | 2014-09-08 | 2019-07-23 | Westinghouse Electric Sweden Ab | Method of making a nuclear fuel pellet for a nuclear power reactor |
-
1985
- 1985-07-05 GB GB08517110A patent/GB2177249B/en not_active Expired
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4965024A (en) * | 1987-10-20 | 1990-10-23 | British Nuclear Fuels Plc | Production of ceramic nuclear fuel pellets |
| EP0416778A2 (en) * | 1989-09-06 | 1991-03-13 | British Nuclear Fuels PLC | Nuclear fuel bodies and the production thereof |
| GB2235816A (en) * | 1989-09-06 | 1991-03-13 | British Nuclear Fuels Plc | Nuclear fuel bodies and the production thereof. |
| US5061434A (en) * | 1989-09-06 | 1991-10-29 | British Nuclear Fuels Inc. | Nuclear fuel bodies and the production thereof |
| EP0416778A3 (en) * | 1989-09-06 | 1991-11-21 | British Nuclear Fuels Plc | Nuclear fuel bodies and the production thereof |
| GB2235816B (en) * | 1989-09-06 | 1994-04-06 | British Nuclear Fuels Plc | Nuclear fuel bodies and the production thereof |
| US5211905A (en) * | 1991-04-17 | 1993-05-18 | British Nuclear Fuels Plc | Manufacture of sintered uranium dioxide |
| GB2255085A (en) * | 1991-04-17 | 1992-10-28 | British Nuclear Fuels Plc | Manufacture of sintered uranium dioxide |
| GB2255085B (en) * | 1991-04-17 | 1994-11-16 | British Nuclear Fuels Plc | Manufacture of sintered uranium dioxide |
| US5916497A (en) * | 1994-12-16 | 1999-06-29 | British Nuclear Fuels Plc | Manufacturing of ceramic articles |
| US5991354A (en) * | 1996-01-30 | 1999-11-23 | Siemens Power Corporation | Nuclear fuel pellet |
| US6002735A (en) * | 1996-01-30 | 1999-12-14 | Siemens Power Corporation | Nuclear fuel pellet |
| US10361008B2 (en) | 2014-09-08 | 2019-07-23 | Westinghouse Electric Sweden Ab | Method of making a nuclear fuel pellet for a nuclear power reactor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2177249B (en) | 1988-12-14 |
| GB8517110D0 (en) | 1985-08-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000705 |