Evaluation of lead-iron-phosphate glass as a high-level waste form

Abstract

SUMMARYThe lead-iron-phosphate (Pb-Fe-P) glass developed at Oak Ridge National Laboratory was evaluated for its potential as an improvement over the current reference nuclear waste form, borosilicate (B-Si) glass. The evaluation was conducted as part of the Second Generation HLW Technology Subtask of the Nuclear Waste Treatment Program at Pacific Northwest Laboratory. The purpose of this work was to investigate possible alternatives to B-Si glass as secondgeneration waste forms. While vitreous Pb-Fe-P glass appears to have substantially better chemical durability than B-Si glass, severe crystallization or devitrification leading to deteriorated chemical durability would result if this glass were poured into large canisters as is the procedure with B-Si glass. Cesium leach rates from this crystallized material are orders of magnitude greater than those from B-Si glass. Therefore, to realize the potential performance advantages of the Pb-Fe-P material in a nuclear waste form, the processing method would have to cool the material rapidly to retain its vitreous structure.; i i CONTENTS

Studies of lead–iron phosphate glasses by Raman, Mössbauer and impedance spectroscopy

“…They found that the corrosion rate of these glasses was 1000 times lower than that of borosilicate glasses, the only glass currently approved in the US. However, because of low waste loading and low corrosion resistance of its crystallized counterparts, they are not used in the current vitrification program [4].…”

Local environment of iron and uranium ions in vitrified iron phosphate glasses studied by Fe K and U LIII-edge x-ray absorption fine structure spectroscopy

“…2 Because of their low melting temperature, excellent chemical durability, and low melt viscosity at the glass processing temperature, lead-iron phosphate glasses were considered as potential hosts for long-term storage of certain high-level nuclear wastes (HLW) in the 1980s, and their properties and structure were investigated in detail. 6 Properties of a potential nuclear waste glass are usually compared to borosilicate nuclear waste glass as a relative measure because borosilicate glass is approved by the DOE as a long-term storage medium for some HLW. 6 Properties of a potential nuclear waste glass are usually compared to borosilicate nuclear waste glass as a relative measure because borosilicate glass is approved by the DOE as a long-term storage medium for some HLW.…”

Proposed research and development plan for mixed low-level waste forms

“…Phosphate glasses have been used to immobilize radioactive wastes in the former Soviet Union &LNL 1996). The iron-phosphate glass (Day 1995) and the lead-iron phosphate glasses (Chick 1986) were only demonstrated at a very limited laboratory-scale.…”

“…Refractory corrosion is a more serious concern associated with phosphate glasses (Chick 1986), and no significant data are available on the refractory corrosion of phosphate glasses in treating wastes at a scale beyond laboratory crucible melting. The cold wall melter is being adopted more widely for waste glass melting where the refractory corrosion can be minimized (Wilson 1996).…”