Aqueous corrosion of aluminum-based nuclear fuel.

Kaminski, M.

Argonne National Laboratory

关键词: Corrosion;    Light Scattering;    Electron Microscopy;    Uranium;    Spent Fuels;   

DOI  :  10.2172/810463
RP-ID  :  ANL-CMT-03/1
RP-ID  :  W-31-109-ENG-38
RP-ID  :  810463

美国|英语

来源: UNT Digital Library

【 摘 要 】

As part of the U.S. National Spent Nuclear Fuel Program, aluminide fuels (UAl{sub x}) are being tested under conditions that might exist in the proposed repository at Yucca Mountain, Nevada. Intermittent drip tests at 90 C were completed for up to 183 days on partially declad, unirradiated, low-enriched UAl{sub x} samples. Through 183 days of exposure to modified water from the J-13 well at 90 C, the fuel coupon remained in good mechanical condition. Only a tarnishing of the surface was observed and no spalled products were found in the fuel holder. The mechanism for alteration is consistent with that observed from dry oxidation experiments on UAl{sub x} (for the initial corrosion) and humid UO{sub 2} oxidation (for the subsequent paragenesis). Specifically, solid-state conversion of UAl{sub x} into UO{sub 2} and oxidized Al is followed by further oxidation, dissolution of the uranium, and reprecipitation as uranyl oxyhydroxides. The release rate of uranium varied from 0.23 to 2.9 mg/m{sup 2}/day (avg. = 0.97 mg U/m{sup 2}/day) depending on the specimen and test interval, but was similar in magnitude to that observed in earlier flow-through and drip tests with irradiated UAl{sub x} and UO{sub 2}. Most (mean=87%) of the released uranium sorbed to the vessel walls. Colloids were detected in the leachate samples, and dynamic light scattering of aliquots from most sampling periods favored a polydisperse distribution typical of environmental samples. In addition, the light scattering intensities measured in these tests were much higher than any measured from UO{sub 2} fuel tests in our laboratory. Electron microscopy of the colloids indicated that the colloids were individual and agglomerated silicates and aluminosilicates. No distinct uranium-rich colloids were found, although dissolved uranium would be expected to sorb to aluminosilicate colloids. In conclusion, the UAl{sub x} corroded slowly, releasing uranium at a rate comparable to UO{sub 2} fuels. Colloid production, however, was quite high with light scattering intensities that were much higher than any measured in previous tests with spent fuels in our laboratory.