Application of the Pressurised Unsaturated Flow (PUF) Test for Accelerated Ageing of Waste Forms

The pressurised unsaturated flow (PUF) test method is an emerging technique for studying the long-term durability or weathering of waste forms and other geologic materials. We have used the technique to monitor the complex coupling between primary phase dissolution, secondary phase precipitation and unsaturated flow behaviour, including changes in the hydraulic properties of the materials. New experimental data with low-activity waste glasses has shown that the technique effectively accelerates the hydrolysis and ageing processes by as much as 50 times over conventional static tests run at the same temperature. Rapid, sustained increases in the corrosion rate of three low-activity waste glasses were detected with the PUF technique in only a few days that required months to observe in static experiments. The ability to quickly detect long-term performance problems with waste forms may make it possible to formulate second generation materials concurrently with meaningful long-term durability screening.