Alpha-recoil effect on the dissolution of betafite: rapid natural annealing of radiation damage within a metamict phase

Conference · Tue Dec 31 23:00:00 EST 1985 · Mater. Res. Soc. Symp. Proc.; (United States)

OSTI ID:5474307

Eyal, Y; Lumpkin, G R; Ewing, R C

Betafite, a radioactive mineral, is the Ti-rich member of the pyrochlore group, A/sub 1-2/B/sub 2/X/sub 6/Y/sub 0-1/, (Fd3m, Z = 8), where A = Ca, Na, U, Th, REE (rare earth elements, Y, Ba, Sr, Bi, Pb; B = Nb, Ti, Ta, Zr, Sn, Fe: X = oxygen; Y = 0, OH and F. The pyrochlore structure (or structural derivatives, e.g. zirconolite in SYNROC) is a common constituent of polyphase, crystalline radioactive waste forms. Naturally occurring minerals with this structure often occur in the metamict state. Therefore, a principal concern is the effect of alpha-recoil damage on the structure and dissolution behavior of synthetic, analogue, waste-form phases which contain actinides. The authors describe the dissolution behavior of /sup 238/U, /sup 234/U, /sup 232/Th, /sup 230/Th and /sup 228/Th in betafite during leaching in a bicarbonate-carbonate solution. Results indicate enhanced leaching of recently produced alpha-recoil damage as evidenced by the more rapid dissolution rate of /sup 228/Th relative to /sup 232/Th and /sup 230/Th, and only slightly enhanced leaching of older damage as evidenced by a small increase in the dissolution rate of /sup 234/U relative to /sup 238/U. These experiments demonstrate that individual alpha-recoil tracks are preserved for some time as disordered regions of higher chemical reactivity in already fully-damaged, aperiodic structures. The authors estimate an annealing time for the alpha-recoil tracks of 2000 +/- 1300 yr in the metastable, aperiodic structure. Similar alpha-recoil tracks should be formed and annealed in other aperiodic nuclear waste forms, such as borosilicate glass.

• Research Organization: Israel Institute of Technology, Haifa
• DOE Contract Number: FG04-84ER45099
• OSTI ID: 5474307
• Report Number(s): CONF-850995-
• Journal Information: Mater. Res. Soc. Symp. Proc.; (United States), Journal Name: Mater. Res. Soc. Symp. Proc.; (United States) Vol. 50; ISSN MRSPD
• Country of Publication: United States
• Language: English

Related Subjects

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11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
36 MATERIALS SCIENCE
360605 -- Materials-- Radiation Effects
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
ANNEALING
DISSOLUTION
EVEN-EVEN NUCLEI
FISSION PRODUCT RELEASE
HEAT TREATMENTS
HEAVY NUCLEI
ISOTOPES
MATERIALS
METAMICT STATE
MINERALS
NUCLEI
PHYSICAL RADIATION EFFECTS
PYROCHLORE
RADIATION EFFECTS
RADIOISOTOPES
RECOILS
ROCKS
SYNTHETIC MATERIALS
SYNTHETIC ROCKS
THORIUM 228
THORIUM 230
THORIUM 232
THORIUM ISOTOPES
URANIUM 234
URANIUM 238
URANIUM ISOTOPES
YEARS LIVING RADIOISOTOPES