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
• • 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
• • 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

• Nuclear fuel sintered body method for producing a nuclear fuel sintered body and fuel rod with a cladding tube
• the invention relates to a nuclear fuel sintered body, to a method for producing a nuclear fuel sintered body and to a fuel rod with a cladding tube.
• a nuclear fuel sintered body made of a chemical compound of oxygen and at least one of the substances uranium and plutonium is usually used in a nuclear reactor.
• the nuclear fuel sintered body first shrinks and then swells as the burnup progresses.
• nuclear fuel sintered bodies are stacked as cylindrical bodies in a column in the cladding tube, e.g. made of a zirconium alloy, a fuel rod of a nuclear reactor fuel element. Due to the high pressure of the coolant in the nuclear reactor on the outside of the cladding tube, the cladding tube initially creeps until it rests on the nuclear fuel sintered bodies. However, it is stretched back when the nuclear fuel sintered bodies start to swell.
• the cladding tube forms an essential barrier for, in particular gaseous fission products released by the nuclear fuel sintered bodies due to combustion. It is therefore important that the cladding tube is not stressed too much by the nuclear fuel sintered body during the service life of the fuel rod in the nuclear reactor.
• the invention is generally based on the object of designing such a nuclear fuel sintered body in such a way that the stress on the cladding tube of a fuel rod which contains such nuclear fuel sintered bodies is caused by these nuclear fuel Sintered material is low due to burn-up in a nuclear reactor.
• a method for producing a nuclear fuel sintered body is also to be specified.
• An appropriately equipped fuel rod must also be specified.
• the first-mentioned object is achieved by a first design of a nuclear fuel sintered body according to the invention, which corresponds to patent claim 1. It assumes that the swelling of the nuclear fuel sintered body in a nuclear reactor can be attributed to the volume requirement of predominantly gaseous fission products that arise during fission. A nuclear fuel sintered body with different local pore size distributions also has different local dimensional change behavior in the nuclear reactor. The dimensional change of the nuclear fuel sintered body as a whole due to erosion in a nuclear reactor can accordingly be adjusted by selection of the different local pore size distributions and preferably kept relatively small.
• the first-mentioned object is also achieved by a second inventive design of a nuclear fuel sintered body according to claim 2. It is based on the fact that different local dimensional change behavior of the nuclear fuel sintered body in the nuclear reactor is also caused by different local concentrations of fissile isotopes in the nuclear fuel sintered body which can be brought about in a nuclear reactor leads to locally different burns within the nuclear fuel sintered body.
• the first-mentioned object is also achieved by a third inventive design of a nuclear fuel sintered body according to claim 5. It is based on the fact that broodable isotopes only after a time delay in a nuclear reactor to form fissile isotopes in the nuclear fuel tere body and accordingly lead only with a time delay to locally varying degrees of burn in the nuclear fuel sintered body, which can be important for the fine adjustment of the dimensional change of the nuclear fuel sintered body in a nuclear reactor.
• the first concentration mentioned in claim 5 can also be zero.
• a development according to claim 8 is based on the fact that locally different concentrations of aluminum in the nuclear fuel sintered body cause a locally different shrinking speed of the nuclear fuel sintered body in a nuclear reactor. They therefore also open up a possibility for fine adjustment of the dimensional change of the nuclear fuel sintered body in the nuclear reactor.
• the first concentration mentioned in claim 8 can also be zero.
• a further development according to claim 9 makes use of the fact that lanthanides and tantalum are neutron poison and therefore can also cause locally varying degrees of burnup in locally different concentrations in the nuclear fuel sintered body and thus locally differently varying dimensions in a nuclear reactor. Also, it is useful for fine-tuning the dimensional change of the nuclear fuel sintered body in a nuclear reactor.
• the first concentration mentioned in claim 9 can also be zero.
• the second-mentioned object is alternatively achieved by the measures listed in patent claims 10, 11, 12, 13 and 14.
• a nuclear fuel sintered body according to claim 1 with the method according to claim 11, a nuclear fuel sintered body according to claim 2 and with the Method according to claim 12, a nuclear fuel sintered body can be produced according to claim 5.
• the method according to claim 13 results in a nuclear fuel sintered body with a particularly high mechanical stability and the pressing body resulting from the method according to claim 14 is largely free of cracks and therefore also leads to a good surface quality of the sintered body obtained from it.
• the development of the method according to claim 16 leads to a nuclear fuel sintered body obtained from the compact, which not only has a high sintered density, but also a large grain size. Gaseous fission products can be retained in the large grain, so that a relatively large burn-up is achieved with the nuclear fuel sintered body in a nuclear reactor.
• the starting powder can consist of at least one of said powders uranium oxide powder, plutonium oxide powder and uranium-plutonium mixed oxide powder both for one type of granule and for both types of granule.
• a fuel rod with a hollow tube is favorable, in which there is at least one nuclear fuel sintered body according to one of the claims 1 to 9.
• FIG. 1 shows a greatly enlarged longitudinal section of a ceramic grinding of a cylindrical nuclear fuel sintered body according to the invention.
• Figure 2 illustrates the pore size distributions of the reed images of two sintered granules in Figure 1 and the sum of these pore size distributions.
• FIG 3 shows a partially sectioned side view of a fuel rod for a nuclear reactor fuel element.
• the abscissa is the pore diameter in ⁇ m and the ordinate is the differential volume of the pores based on the total volume of the nuclear fuel sintered body in percent.
• the dashed curve I is the differential volume of the pores of the micrograph 1 of a sintered granule 1 in FIG. 1 and the dashed curve II is the differential pore volume of the micrograph 2 of another sintered granule 2 in FIG. 1.
• the pore size distributions of the micrographs 1 and 2 are based on the area of the associated micrograph 1 or 2 and the associated differential pore volume proportional.
• the micrograph 1 in FIG. 1 and thus the associated sintered granule can also contain a first concentration of fissile isotopes U 235 and the micrograph 2 and thus the associated sintered granule a second concentration of fissile isotopes U 235. Both concentrations differ by at least 0.5% by weight absolute, advantageously by at least 0.7% by weight absolute or at least 0.9% by weight absolute.
• concentration of these fissionable isotopes can be determined by taking a sample from the sintered granule by mass spectrometry or gamma spectrometry on this sample.
• the micrograph 1 in FIG. 1 and thus the associated sintered granule can furthermore contain a first concentration of broodable thorium isotopes and the second micrograph 2 and thus the associated sintered granule a second concentration of broodable thorium isotopes.
• the second concentration of broodable thorium isotopes differs in absolute terms by at least 0.5% by weight from the first concentration of broodable thorium isotopes.
• the two concentrations can also advantageously differ by at least 0.7% by weight in absolute terms or by at least 0.9% by weight in absolute terms.
• the first concentration can also be 0.
• the associated sintered granule can also have a first concentration of aluminum and the micrograph 2 and thus the associated sintered granule can have a second concentration of aluminum.
• the second concentration differs from the first concentration by at least 30 ppm to 2000 ppm.
• the first concentration of aluminum can also be 0.
• the micrograph 1 in FIG. 1 and thus the associated sintered granule can also contain a first concentration of at least one of the substances from the group of lanthanides and tantalum and the micrograph 2 and thus the associated sintered granule a second concentration of at least one of the substances from said Have a group that differs from the first concentration by at least 0.5% by weight in absolute terms.
• the first concentration can also be 0.
• a compact is sintered from a mixture of a first type of granules and a second type of granules.
• the two types of granules can each be created by separately granulating the starting powder consisting of at least one of the powders uranium oxide powder (U0 2 ), plutonium oxide powder (Pu0 2 ) and uranium and plutonium oxide powder (U0 2 + Pu0 2 ).
• the two types of granules and their respective amounts in the compact are selected so that they have different pore size distributions in the sintered state in the nuclear fuel sintered body.
• the first type of granules is obtained, for example, by granulating uranium oxide powder, which was obtained from the intermediate uranyl fluoride (U0 2 F) by dry conversion of UF 6 in the presence of water vapor, hydrogen and nitrogen, while for the second type of granules len uranium oxide powder is granulated separately, which was prepared from an intermediate product obtained by wet conversion from UF 6.
• this intermediate is ammonium uranyl carbonate (AUC) and in the ADU process, ammonium diuranate (ADU) (cf.
• uranium oxide powder produced by calcining can be granulated.
• a first and a second type of granules also result from separate granulation of two batches of uranium oxide powder, which are obtained by calcining one of the above-mentioned intermediates uranyl fluoride, AUC and ADU to form U0 2 .
• At least one of the calcination parameters for the first batch differs from the corresponding calcination parameter for the second batch.
• suitable calcination parameters are: calcination temperature, calcination time and the amount and ratio of the calcination gases hydrogen and water vapor.
• the first and second types of granules can also be obtained by granulating uranium oxide powder differently.
• Different granulation means separate granulation of two powder batches, at least one of the granulation parameters for one powder batch being different from the same granulation parameter for the other powder batch.
• Granulation parameters are, for example: grinding time, fineness of the grinding, pressing pressure when pressing the uranium oxide powder before granulation, and thus the density of the granules obtained, size of the granules produced during granulation and the amount and type of additives added to the uranium oxide powder before granulation.
• additives are lubricants such as zinc stearate and aluminum di-stearate, plastic Fizierer such as polyvinyl alcohol, pore formers such as U 3 0 8 and azodicarboxylic acid dia id as well as ammonium carbonate and oxalic acid dia- id.
• Another additive can also be grinding abrasion that occurs when grinding nuclear fuel sintered bodies made of U0 2 .
• tests can always be used to determine how two types of granules are produced from at least one of the powders U0 2 -, Pu0 2 - and (U, Pu) 0 2 powder (ie uranium oxide powder, plutonium oxide powder and uranium-plutonium mixed oxide powder) can be so that the sintered after the sintering of a compact made from them in the nuclear fuel sintered body have different pore size distributions.
• uranyl fluoride is produced from UF 6 by dry conversion at a conversion temperature of 550 ° C and calcined at a calcination temperature of 650 ° C.
• U 3 0 8 powder and zinc stearate are added to this U0 2 powder so that it contains 30% by weight of U 3 O ⁇ powder and 0.3% by weight of zinc stearate.
• This first batch is granulated so that the first type of granules obtained have a density of 5 g / cm 3 . These granules have an average diameter of 0.65 mm.
• a second batch of U0 2 powder is obtained by dry conversion of UF 6 to uranyl fluoride at a conversion temperature of 650 ° C and subsequent calcination of this uranyl fluoride at a calcination temperature of 700 ° C.
• This U0 2 powder contains no U 3 0 8 and no zinc stearate, but 200 ppm aluminum.
• a second type of granule with a density of 3.8 g / cm 3 is obtained by granulating this U0 2 powder. These granules have an average diameter of 0.85 mm.
• the granules of the first and second type produced from the two batches of U0 2 powder are mixed in equal parts and the mixture is pressed into a compact with a density of 6 g / cm 3 .
• This compact is finally sintered into a nuclear fuel sintered body.
• the sintering temperature is 1680 ° C at an oxygen partial pressure in the sintering atmosphere of hydrogen during the sintering of 10 ⁇ 12 atm and when cooling to room temperature of 10 " 2C atm.
• the nuclear fuel sintered body obtained in this way has a density of 10.51 g / cm 3 and an average grain size of 12 ⁇ m. After a burn-up of 40,000 MWd / tU, the volume of this nuclear fuel sintered body has increased by 2.8%.
• a nuclear fuel sintered body which is obtained from a compact with a density of 6 g / cm 3 by sintering under the same sintering conditions given above and for which only granules of the first type are used, has an average grain size of only 7.8 ⁇ m. After a burn-up of 40,000 MWd / tU, the volume of this nuclear fuel sintered body has increased by 3.8%.
• the fuel rod 4 shown in FIG. 3 is intended for a nuclear reactor fuel element and has a cladding tube 5 made of a zirconium alloy.
• this cladding tube 5 there are cylindrical nuclear fuel sintered bodies 7, which are designed according to the invention and are arranged in a column so that their cylinder axes fall into the longitudinal axis of the cladding tube 5.
• This cladding tube 5 is closed at both tube ends with a plug 6, which is also made of a zirconium alloy and is welded to the cladding tube 5 in a gas-tight manner.

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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)
• Inorganic Compounds Of Heavy Metals (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
• Powder Metallurgy (AREA)

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• 1997
  • 1997-08-11 TW TW086111448A patent/TW359837B/zh active
  • 1997-09-05 EP EP97943838A patent/EP0931316A2/de not_active Withdrawn
  • 1997-09-05 KR KR1019997002305A patent/KR20010029512A/ko not_active Application Discontinuation
  • 1997-09-05 JP JP10514233A patent/JP2001500619A/ja not_active Ceased
  • 1997-09-05 WO PCT/EP1997/004838 patent/WO1998012708A2/de not_active Application Discontinuation

Non-Patent Citations (1)

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