Structural features and properties of lead–iron–phosphate nuclear wasteforms

The structure and properties of vitreous and crystalline lead–iron–phosphate glasses containing up to 21 wt% of a simulated high level waste have been investigated using Fe-57 Mössbauer, X-ray diffraction and Raman spectroscopies. The Mössbauer spectra indicated that both Fe(II) and Fe(III) ions were present in all the samples. The Raman spectra for the glasses contained two dominant bands, which were characteristic of pyrophosphate groups, (P–O) stretching mode of P–O nonbridging oxygen at 1074 cm−1 and sym stretching mode of bridging oxygen at 760 cm−1, respectively. The chemical durability of glassy and crystallized samples was investigated by measuring their weight loss in distilled water at 90 °C for up to 32 days. The weight loss of the lead–iron–pyrophosphate wasteforms was up to 100 times less than that for window glass. X-ray diffraction patterns showed that FeSiO3 and SiP2O7 phases are present in samples containing more than 14 wt% of the simulated nuclear waste.