SWELLING IN ALPHA URANIUM DUE TO IRRADIATION

Journal Article · Sat Jul 01 04:00:00 EDT 1961 · J. Nuclear Materials

DOI:https://doi.org/10.1016/0022-3115(61)90126-X· OSTI ID:4837331

Pugh, S F

Phenomena thought to contribute to swelling in alpha uranium irradiated up to about 1/2% burn-up at 400 deg to 650 deg C are discussed in the light of recent experiments at AERE. Extensive metallographic examination indicated that in all specimens an array of small bubbles 0.1 microns in diameter and about 1/2 micron apart, presumably containing most of the fission product gases, is formed. In about 1 in 3 of the specimens, grain boundary cracks contributed about 1% to the volume increase, and were probably due to a combination of irradiation embrittlement and internal stressing caused by thermal cycling. In specimens irradiated at 425 deg C, ragged holes at the grain boundary were thought to be partly due to irradiation growth. In only three specimens holes up to 2 mm diameter were formed, accompanied by distortion of the specimen and large local volume increases. This was possibly due to severe overheating caused by film boiling in sodium. Acceleration of swelling leading to breakaway due to join up of the small gas bubbles is not expected below 11/2% burn-up in alpha uranium, provided the gas bubbles are always on the fine scale observed so far, but the possibility remains that breakaway swelling at 1/2% burn-up could be caused by internal cracks collecting sufficient fission product gas to blow up into round bubbles. The mechanism of nucleation and growth of fission gas bubbles in alpha uranium and the role of surface tension in controlling bubble size are discussed. The arguments for homogeneous nucleation on dislocation lines, for heterogeneous nucleation, for growth of fission product gas bubbles by vacancy diffusion and for growth by plastic deformation of the matrix, are presented. The possible effects of bombarding bubble nuclei and fission product gas bubbles by energetic fission fragments are also discussed. The results of experiments in which uranium irradiated at between room temperature and 350 deg C was subsequently heated in the range from 500 deg to 650 deg C, and the results of investigations on the diffusion and precipitation of xenon, krypton, and other inert gases in uranium and in other metals are reviewed in so far as they throw light on the problem of swelling in uranium. (auth) yield stress. The low number of defects per fission event obtained at higher dose rates at 60 deg C is thought to be due to a large number of unobservable defects. (P.C.H.)

• Research Organization: Atomic Energy Research Establishment, Harwell, Berks, Eng.
• NSA Number: NSA-15-031276
• OSTI ID: 4837331
• Report Number(s): AERE-R-3458
• Journal Information: J. Nuclear Materials, Journal Name: J. Nuclear Materials Vol. Vol: 4
• Country of Publication: United Kingdom
• Language: English

Related Subjects

ALLOTROPY
BEAMS
BOILING
BRITTLENESS
BUBBLES
BURNUP
CRACKS
DEFECTS
DEFORMATION
DIFFUSION
DISLOCATIONS
EXPANSION
FAILURES
FILMS
FISSION PRODUCTS
GASES
GRAIN BOUNDARIES
HEAT TREATMENTS
HEATING
INERT GASES
KRYPTON
LATTICES
METALLOGRAPHY
METALS
METALS, CERAMICS, AND OTHER MATERIALS
NUCLEATE BOILING
OSCILLATIONS
PRECIPITATION
RADIATION EFFECTS
SODIUM
STRESSES
SURFACE TENSION
TEMPERATURE
THERMAL CYCLING
URANIUM
URANIUM-ALPHA
VACANCIES
VOLUME
XENON