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Yucca Mountain project [electronic resource] : FY 2006 annual report for waste form testingactivities

Published
Argonne, Ill. : Argonne National Laboratory, 2006.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators
Argonne National Laboratory and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
This report describes the experimental work performed at Argonne National Laboratory (Argonne) during fiscal year (FY 2006) under the Bechtel SAIC Company, LLC (BSC) Memorandum Purchase Order (MPO) contract number B004210CM3X. Because this experimental work is focused on the dissolution and precipitation behavior of neptunium, the report also includes, or incorporates by reference, earlier results that are relevant to presenting a more complete understanding of the likely behavior of neptunium under experimental conditions relevant to the Yucca Mountain repository. Important results relevant to the technical bases, validations, and conservatisms in current source term models are summarized. The CSNF samples were observed to corrode following the general contour of the surface rather than via (for instance) grain boundary attack. This supports the current approach of estimating the effective surface area of corroding CSNF based on the geometric surface area of fuel pellet fragments. It was observed that the neptunium and plutonium concentrations in corroded CSNF samples were somewhat higher at and near the corrosion front (i.e., at the interface between the alteration product ''rind'' layer and the underlying fuel) than in the bulk fuel. The neptunium and plutonium at the corrosion front and in the uranyl alteration layer were found to be in the quadravalent (4+) oxidation state. The uranyl phases that constitute most of the alteration rind were depleted in neptunium relative to the bulk fuel: neptunium concentrations in the uranyl alteration rind were less than 20% of that in the parent fuel. Homogeneous precipitation tests have shown that solids precipitate from a 1 x 10⁻⁴ M Np(V) solution over the temperature range of 200-280 C, but no evidence was found that any solids precipitated from the same solution at 150 C through 289 days. The solids formed in the homogeneous precipitation tests were predominantly a Np(IV)-bearing phase, probably NpO₂. The presence of UO₂ resulted in the rapid precipitation at room temperature of similar amounts of Np(IV)- and Np(V)-bearing phases, probably NpO₂ and Np₂O₅. Although the UO₂ is presumed to act as a reducing agent for Np(V) that leads to the precipitation of a Np(IV)-bearing phase, the observed formation of a Np(V)-bearing phase suggests that the UO₂ also catalyzes Np₂O5 precipitation under these test conditions.
Report Numbers
E 1.99:anl-06/49
E 1.99:anl0649
anl0649
anl-06/49
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Note
Published through SciTech Connect.
11/01/2006.
"anl-06/49"
"anl0649"
Fortner, J. A.; Ebert, W. L.; Cunnane, J. C.; Guelis, A. V.
Funding Information
DE-AC02-06CH11357
View MARC record | catkey: 14409165