IRRADIATION OF METAL-FIBER-REINFORCED THORIA-URANIA. Final Report- Metallurgy Program 6.2.4

Technical Report · Fri Dec 01 04:00:00 EST 1961

DOI:https://doi.org/10.2172/4818296· OSTI ID:4818296

Neimark, L. A.; Kittel, J. H.; Hoenig, C. L.

Randomly oriented fibers of either molybdenum or niobium were incorporated into hot-pressed pellets of 10, 30, and 50 wt% UO/sub 2/ in ThO/sub 2/ to improve thermal conductivity and thermal shock resistance. Pellets, 9.5 mm in diameter and 9.5 mm in length, were irradiated in NaK capsules, both bare and jacketed with Zircaloy-2, with the annulus between pellet and jacket filled with lead or helium. They were irradiated to burnups ranging up to 34 500 Mwd/T (1 0 x 10/sup 21/ fiss/cc) at central temperatures of the order of 3000 deg C. Integral kd theta values ranged from 34 to 129 w/cm. Fracture and metallographic sections of the irradiated specimens confirmed out-of-pile measurements that the molybdenum fibers increased the effective thermal conductivlty of the mixed oxides. It was possible to give the fibered pellets higher heat ratings than unfibered pellets before comparable thermal effects occurred. The fibers tended to reduce central void formation, retard recrystallization, and maintain the integrlty of the pellet. In some helium- bonded specimens, the molybdenum fibers coalesced into a central sphere after melting during irradiation. The coalescence did not occur in lead-bonded specimens. The niobium fibers were found to react with the oxide. Fission gas release from unclad fibered pellets was a maximum of 15.3% of theoretical at a burnup of 3l,500 Mwd/T (8.3 x l0/0 fiss/cc) and an integral kd theta value of 57 w/cm. Gas release from similarly irradiated unfibered pellets was a maximum of 6.3% at 21,800 Mwd/T 16.6 x 10/0 fiss/cc) and an integral kd theta value of 92 w/ cm. The disparity in gas release is attributed to the breaking into pieces of the unfibered pellets early in the irradiation and their consequent operation at significantly lower temperatures than the fibered pellets. (auth)

• Research Organization: Argonne National Lab., Ill.
• DOE Contract Number: W-31109-ENG-38
• NSA Number: NSA-16-007924
• OSTI ID: 4818296
• Report Number(s): ANL-6397
• Country of Publication: United States
• Language: English

Related Subjects

BURNUP
CAPSULES
CHEMICAL REACTIONS
FIBERS
FISSION PRODUCTS
GASES
HELIUM
HIGH TEMPERATURE
HOT WORKING
IRRADIATION
JACKETS
LEAD
MATERIALS TESTING
MELTING
METALLOGRAPHY
METALS, CERAMICS, AND OTHER MATERIALS
MOLYBDENUM
NIOBIUM
PELLETS
POTASSIUM ALLOYS
RADIATION EFFECTS
SODIUM ALLOYS
THERMAL CONDUCTIVITY
THERMAL SHOCK
THERMAL STRESSES
THORIUM OXIDES
URANIUM DIOXIDE
ZIRCALOY