Oxide-cermet fuel rods: production, properties, and irradiation behavior

Technical Report · Wed Aug 01 04:00:00 EDT 1973

OSTI ID:4932657

Weimar, P; Zimmermann, H

Oxide--cermet fuel pins with idealized fuel structure and metallurgically bonded cladding have some properties which cannot be obtained by pins with oxide pellets. The continuous metal network in the fuel provides a considerably larger thermal conductivity and a lower central temperature during irradiation. The lower central temperature and the metallic envelopment of the fissionable oxide particles decrease or prevent the release of fission gases and volatile fission products. Therefore, the absence of a gas plenum is characteristic of cermet pins. For use in fast reactors only Cr and V are potential matrix metals because of their low cross sections for fast neutrons. The cermets with idealized structure were produced by metallizing UO/sub 2/ spheres with Cr, V, or Mo by a vapor-deposition process. The spheres are vibrated into the cladding tubes, for instance in Inconel 625 or Hastelloy X tubes in the case of UO/sub 2/-- Cr cermets. After electron beam welding of the tubes the pins are isostatically hot-pressed in He atmosphere. The metal content of the cermets was 20 and 30%, respectively. Some properties of the UO/sub 2/-- Cr, UO/sub 2/-V, and UO/sub 2/--Mo cermets are described. Seven irradiation capsules, one with UO/sub 2/--Mo, four with UO/sub 2/--Cr, and two with UO/sub 2/- -V samples, were irradiated in the FR 2 reactor at mean rod powers of 470 to 700 W/cm and mean cladding temperatures of about 600 deg C to 10 to 95 MWd/kg U burnup. Each of the capsules contained eight or four fuel rod samples. UO/sub 2/ -- 30 vol.% Cr cermets with Inconel 625 cladding were irradiated to 60 and 95 MWd/ kg U burnup without showing any failure. At these burnups the Hastelloy X claddings were probably damaged by microcracks. However, the temperatures of the Hastelloy X claddings were nearly 100 deg C higher than those of the Inconel 625 claddings. The high burnup UO/sub 2/--Cr samples with Inconel 625 or Hastelloy X cladding did not show dimensional changes in any case. The samples with 20% Cr showed a depletion of Cr in the fuel central region. Cr had been evaporated and condensed in the outer regions of the fuel. No such depletion was found in the cermet fuel with 30% Cr. The vanadium claddings of the UO/sub 2/--V cermets were damaged by many cracks in consequence of oxygen embrittlement during irradiation. It is suggested that UO/sub 2/--30% Cr fuel pins can be operated with linear rod powers of about 800 W'/cm and cladding temperatures of 650 deg C to bumups of 60 MWd/kg U and probably more. A further increase of the rod power can be achieved only with a matrik metal heaving a lower vapor pressure. (auth)

• Research Organization: Kernforschungszentrum Karlsruhe (F.R. Germany). Inst. fuer Material- und Festkoerperforschung
• Sponsoring Organization: Sponsor not identified
• NSA Number: NSA-29-000918
• OSTI ID: 4932657
• Report Number(s): KFK--1839
• Country of Publication: Germany
• Language: German

Related Subjects

BURNUP
CERMETS
CHROMIUM ALLOYS
DEPOSITION
EVAPORATION
FUEL CANS
HASTELLOY X
INCONEL 625
MOLYBDENUM ALLOYS
N50140* --Metals
Ceramics
& Other Materials--Ceramics & Cermets--Radiation Effects
N79300 --Reactors--Reactor Fuels
PHYSICAL PROPERTIES
PRODUCTION
SOLIDIFICATION VANADIUM ALLOYS
URANIUM DIOXIDE