Experiment close out of lysimeter testing of low-level radioactive waste forms

Abstract

The program is obtaining information on the performance of radioactive waste forms (WFs). These experiments were recently shut down and the contents of the lysimeters have been examined in accordance with a detailed waste form and soil sampling plan. Ion-exchange resins from a commercial nuclear power station were solidified into waste forms using portland cement and vinyl ester-styrene. These waste forms were tested to (a) obtain information on performance of waste forms in typical disposal environments, (b) compare field results with bench leach studies, (c) develop a low-level waste data base for use in performance assessment source term calculations, and (d) apply the DUST computer code to compare predicted cumulative release to actual field data. The program includes observed radionuclide releases from waste forms in field lysimeters at two test sites over 10 years of successful operation. The purpose of this paper is to present the results of the examination of waste forms and soils of the two lysimeter arrays after shut down. During this examination, the waste forms were characterized after removal from the lysimeters and the results compared to the findings of the original characterizations. Vertical soil cores were taken from the soil columns and analyzed with radiochemistry to define movement of radionuclides in the soils after release from the waste forms. A comparison is made of the DUST code predictions of releases using recently developed partition coefficients to actual radionuclide movement through the soil columns as determined from these core analyses. This paper discusses soil and waste form sampling in which vertical cores were removed from the lysimeter soil columns for laboratory characterization. Those samples will be analyzed for radionuclide movement from the waste forms and through the soil columns.