DETERMINATION OF LONG-LIVED FISSION-PRODUCTS AND ACTINIDES IN SAVANNA-RIVER SITE HLW SLUDGE AND GLASS FOR WASTE ACCEPTANCE

Savannah River Site (SRS) is immobilizing the radioactive, high-level waste sludge in Tank 51 into a borosilicate glass for disposal in a ge ologic repository. A requirement for repository acceptance is that SRS report the concentrations cf certain fission product and actinide rad ionuclides in the glass. This paper presents measurements of many of t hese concentrations in both Tank 51 sludge and the final glass. The ra dionuclides were measured by inductively coupled plasma mass spectrome try and alpha, beta, and gamma counting methods. Examples of the radio nuclides are Sr-90, Cs-137, U-238 and, Pu-239. Concentrations in the g lass are 3.1 times lower due to dilution of the sludge with a nonradio -active glass forming frit in the vitrification process. Results also indicated that in both the sludge and glass the relative concentration s of the long lived fission products insoluble in caustic are in propo rtion to their yields from the fission of U-235 waste in the SRS react ors. This allowed the calculation of a fission yield scaling factor. T his factor in addition to the sludge dilution factor can be used to es timate concentrations of waste acceptance radionuclides that cannot be measured in the glass. Examples of these radionuclides are Se-79, Zr- 93, and Pd-107.