Properties and Structure of Vitrified Iron Phosphate Nuclear Wasteforms

Abstract

The structure of vitreous iron phosphates containing up to 35 wt% of one or more common nuclear waste components such as Na2O, Cs2O, SrO, UO2 or Bi2O3 have been investigated using Fe-57 Mössbauer, X-ray absorption, X-ray photoelectron and Raman spectroscopies and high energy X-ray and neutron diffraction techniques. The glass samples investigated were prepared by melting appropriate chemicals in air at approximately 1200°C for 2 h in alumina crucibles. The chemical durability of the glasses was investigated by measuring their dissolution rates in distilled water at 90°C using the product consistency test (PCT) methodology. The chemical durability of these glasses is characterized by dissolution rates of 10−10-10−11 g/cm2/min. The Mössbauer spectra indicate the presence of both Fe(II) and Fe(III). However, the maximum Fe(II) fraction, Fe(II)/[Fe(II) + Fe(III)], was 0.34. X-ray absorption data show that, on average, both species of iron ions are coordinated with approximately 5 near neighbor oxygens and that the iron-oxygen coordination is only slightly (<10%) influenced by the type or the concentration of the waste elements. Iron ions are also coordinated with 4-6 phosphorous ions in the second shell. Only a minority of the oxygen ions, about 22%, take part in bridging -P-O-P- bonds. Raman spectra show that the phosphorous-oxygen network, which is dominated by (P2O7)4− dimer units, in different samples are similar.

Department(s)

Materials Science and Engineering

Sponsor(s)

United States. Department of Energy

Keywords and Phrases

P150; R110; S440; X120; X130

International Standard Serial Number (ISSN)

0022-3093; 1873-4812

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2000 Elsevier, All rights reserved.

Publication Date

01 Mar 2000

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