Uranium-series ages of secondary uranium minerals with applications to the long-term evolution of spent nuclear fuel

Conference · Thu Aug 01 04:00:00 EDT 1996

OSTI ID:264486

Finch, R J ^[1]; Suksi, J ^[2]; Rasilainen, K ^[3]; Ewing, R C ^[4]

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1. Univ. of Manitoba, Winnipeg, Manitoba (Canada)
2. Univ. of Helsinki (Finland)
3. VTT Energy, Espoo (Finland)
4. Univ. of New Mexico, Albuquerque, NM (United States)

Uranium-series activity ratios for U(VI) minerals from the Shinkolobwe mine in southern Zaire indicate that these minerals have not experienced significant preferential loss of uranium since their formation more than 100,000 years ago. The minerals examined include rutherfordine, UO{sub 2}CO{sub 3}, schoepite, [(UO{sub 2}){sub 8}O{sub 2}(OH){sub 12}]{center_dot}12H{sub 2}O, becquerelite, Ca[(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}]{center_dot}8H{sub 2}O, and uranophane, Ca[(UO{sub 2}){sub 2}(SiO{sub 3}OH){sub 2}]{center_dot}5H{sub 2}O. No correlation between mineral species and mineral age was evident. The oxidative dissolution of primary uraninite (UO{sub 2+x}) has maintained ground waters supersaturated with respect to all of the secondary U(VI) minerals, providing an inexhaustible source of dissolved U{sup 6+} for mineral formation and growth. As long as uraninite persists in an oxidizing environment, the assemblage of secondary U(VI) phases is determined by local ground water chemistry (including transitory changes), but not necessarily a unidirectional reaction path towards equilibrium with U(VI) minerals of lower solubility. Thus the Shinkolobwe mine displays a complex assemblage of U(VI) minerals that reflects variations in the availability of dissolved elements besides U. Similarly, for a geologic repository exposed to oxidizing waters, the assemblage of corrosion products that will form during the corrosion of spent UO{sub 2} fuel is likely to be as complex as mineral assemblages found in natural uranium deposits under similar conditions.

• OSTI ID: 264486
• Report Number(s): CONF-951155--; ISBN 1-55899-315-0
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
GROUND WATER
ISOTOPE DATING
ISOTOPE RATIO
MINERALOGY
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE FACILITIES
RADIONUCLIDE MIGRATION
SIMULATION
SITE CHARACTERIZATION
SPENT FUELS
URANIUM DIOXIDE
URANIUM MINERALS
URANIUM MINES
WATER CHEMISTRY
ZAIRE REPUBLIC