Studies on the Surface Morphology and Chemical Durability of Borosilicate Glass with Uranium and Rare Earths

Abstract

Indian nuclear industries emphasize on metal fuel which shows significant advantages over ceramic fuels in fast reactor fuel cycles, where sodium is used as bonding material. The sodium discharged from rejected sodium bonded metal fuel pins is blended with uranium and plutonium metals labelled as contaminated sodium. This contaminated sodium is converted to borosilicate glass with the addition of suitable glass formers and modifiers. Pristine borosilicate glass of known composition and doped glasses were prepared with fixed Na/Si ratio by addition of (i) U₃O₈ (5 wt %) and (ii) oxides of U, Ce, Nd, and Gd (together 5 wt %) labelled as BSGU and BSGURE respectively. Thermo-physical properties of these glasses are favourable towards safe disposal however, it is essential to evaluate aqueous alteration named as chemical durability (at 363 K) before using contaminated sodium. Surface morphology and chemical durability of pristine BSG were evaluated and compared with doped BSGs. The normalized leach rate for seven days was found to be 1.8 × 10^–4, 5.5 × 10^–5, and 4.2 × 10^–5 g cm^–2 day^–1 for pristine BSG, BSGU, and BSGURE respectively. The enhancement of chemical durability on doped glasses is due to addition of dopants.