RESULTS OF SUPPLEMENTAL MST STUDIES

Peters, T ; David Hobbs, D ; Samuel Fink, S

Savannah River Site (S.C.)

关键词: Removal;    Materials Recovery;    Actinides;    Radioactive Waste Processing;    Recycling;   

DOI  :  10.2172/891660
RP-ID  :  WSRC-STI-2006-00012
RP-ID  :  DE-AC09-96SR18500
RP-ID  :  891660

美国|英语

来源: UNT Digital Library

【 摘 要 】

The current design of the Salt Waste Processing Facility (SWPF) includes an auxiliary facility, the Actinide Finishing Facility, which provides a second contact of monosodium titanate (MST) to remove soluble actinides and strontium from waste if needed. This treatment will occur after cesium removal by Caustic-Side Solvent Extraction (CSSX). Although the process changes and safety basis implications have not yet been analyzed, provisions also exist to recover the MST from this operation and return to the initial actinide removal step in the SWPF for an additional (third) contact with fresh waste. A U.S. Department of Energy (DOE) request identified the need to study the following issues involving this application of MST: Determine the effect of organics from the solvent extraction (CSSX) process on radionuclide sorption by MST; Determine the efficiency of re-using MST for multiple contacts; and Examine fissile loading on MST under conditions using a waste containing significantly elevated concentrations of plutonium, uranium, neptunium, and strontium. This report describes the results of three experimental studies conducted to address these needs: (1) Addition of high concentrations of entrained CSSX solvent had no noticeable effect, over a two week period, on the sorption of the actinides and strontium by MST in a direct comparison experiment. (2) Test results show that MST still retains appreciable capacity after being used once. For instance, reused MST--in the presence of entrained solvent--continued to sorb actinides and strontium. (3) A single batch of MST was used to sequentially contact five volumes of a simulant solution containing elevated concentrations of the radionuclides of interest. After the five contacts, we measured the following solution actinide loadings on the MST: plutonium: 0.884 {+-} 0.00539 wt % or (1.02 {+-} 0.0112) E+04 {micro}g/g MST, uranium: 12.1 {+-} 0.786 wt % or (1.40 {+-} 0.104) E+05 {micro}g/g MST, and neptunium: 0.426 {+-} 0.00406 wt % or (4.92 {+-} 0.0923) E+03 {micro}g/g MST. (4) Over the duration of an experiment with the sequential strikes, the ability of MST to sorb actinides improved with additional strikes. This trend is counter-intuitive, but is confirmed by replicate experiments for plutonium, uranium, and neptunium. Conversely, over the duration of the experiment, the ability of MST to sorb strontium decreased the more it was used. This trend is confirmed by replicate experiment.