Structure and properties of iron phosphate glasses: A novel host matrix for the vitrification of high-level nuclear wastes

<p>"The atomic structure, glass forming and crystallization characteristics, and the chemical durability of vitreous binary iron phosphates of approximate batch composition 40Fe₂O₃-60P₂O₅ (mol%) and those containing up to 40 wt% of one or more common nuclear waste components such as Na₂O, CS₂O, SrO, UO₂, or Bi₂O₃ have been investigated. The analytical tools used are Fe-57 Mössbauer, x-ray absorption, x-ray photoelectron, and Raman spectroscopies, high energy x-ray and neutron diffraction techniques, differential thermal analysis (DTA), and the product consistancy test (ASTM C-1285-94). The excellent chemical durability of iron phosphate glasses containing nuclear waste components is indicated by dissolution rates (at 90 °C in distilled water) as low as 10^-10 to 10^-11 g/cm²/min. When melted in air at 1100 to 1200°C, these iron phosphate melts reach a redox equilibria corresponding to a Fe(II)/Fe(III) ratio less than 0.51. The Fe(II) content increases with increasing melting temperature and when melted in reducing atmospheres. However, the glass forming ability of the melts decreases when the Fe(II)/Fe(III) ratio exceeds ca. 0.67. Both species of iron ions are coordinated with 5 to 5.5 near neighbor oxygen ions. The phosphorous-oxygen network is dominated by (P₂O₇ )^4- dimer units. The iron-oxygen coordination and the phosphorous-oxygen network do not appreciably depend on the type or the concentration of the waste elements. The waste ions, which are situated outside the second shell coordination environment of iron and phosphorus ions, are not a major influence on the chemistry of the iron-oxygen-phosphorus host matrix. Therefore the addition of waste components does not cause major changes in properties such as the chemical durability of the iron phosphate host matrix. Vitreous iron phosphate host matrices appear to be a low cost and effective alternative to borosilicate glasses for vitrifying selected nuclear wastes"--Abstract, page iv.</p>

Name thesis:degree_name

Ph. D. in Physics

Grantor

University of Missouri--Rolla

Year dc:date.available

2016

Author dc:creator

• Karabulut, Mevlüt

• Physics

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/1335

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-2337