Analyses of high level radioactive glasses and sludges at the Savannah River Site

Reliable analyses of high level radioactive glass and sludge are necessary for successful operation of the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS). This facility will convert the radioactive waste sludges at SRS into durable borosilicate glasses for final disposal in a geologic repository. Analyses that are crucial to DWPF operation and repository acceptance of the glass are measurement of the radioactive and nonradioactive composition of the waste sludges and final glasses and measurement of the Fe(II)/Fe(III) ratio in a vitrified sample of melter feed. These measurements are based on the remote dissolutions of the glass and sludge followed by appropriate chemical analyses. Glasses are dissolved by a peroxide fusion method and a method using HF, HNO3, H3BO3, and HCl acids where the solutions are heated in a microwave oven. The resulting solutions are analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and atomic absorption spectroscopy (AAS) for nonradioactive elements and appropriate counting techniques for radioactive elements. Results of replicate samples of a standard simulated nuclear waste glass indicate a precision of 5% or better for the major components. The results agree well with the standard values indicating good accuracy. Results for two radioactive glasses containing actual radioactive waste are also presented. Sludges are dissolved by the Na2O2 fusion method and an aqua regia method. Analyses of replicate sludge samples indicate that the results have a precision of nominally 5% or better for the major components. Standard sludges are not available to test the accuracy of the methods; however, results of the standard glass analyzed concurrently indicate that the analyses are accurate. The two methods for the sludge are in excellent agreement indicating that they are reliable and accurate. 8 refs., 4 tabs