Continuous-flow leach testing method for various nuclear waste forms

Nuclear waste is planned to be buried in deep geological repositories. If these repositories were ever invaded by ground water, the waste form could be corroded and the nuclear waste released to the surrounding geologic medium. The rate at which this flowing ground water corrodes the waste form can be studied using the Lawrence Livermore National Laboratory's single-pass continuous-flow leaching test. This repository-relevant leaching test places the waste form of interest into a flowing stream of leachant. The flow rates can be set to approximate the low flow rates encountered in actual aquifers. The leachant contacts the waste only once and then exits the cell where it is collected and analyzed. Such a scheme avoids potential solution saturation problems encountered with static tests. The composition of leachants used with this test has ranged from saturated salt brine to distilled water. Temperature has been varied from 250C to 750C. These values cover the range of ambient temperatures expected at depths of 2 to 3 km. This test was designed to reproduce conditions of a flooded repository in the laboratory. The testing methodology is discussed as well as examples of data obtained from leaching a variety of waste forms under various conditions