Ferrocyanide tank safety program: Cesium uptake capacity of simulated ferrocyanide tank waste. Final report

Abstract

DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document.The objective of this project is to determine the capacity for 137Cs uptake by mixed metal ferrocyanides present in Hanford Site waste tanks, and to assess the potential for aggregation of these '37Cs-exchanged materials to form "hot-spots'' in the tanks. This research, performed at Pacific Northwest Laboratory (PNL) for Westinghouse H a r d Company, stems from concerns regarding possible localized radiolytic heating within the tanks. After ferrocyanide was added to 18 high-level waste tanks in the 1950s, some of the ferrocyanide tanks received considerable quantities of saltcake waste that was rich in '37Cs. If radioactive cesium was exchanged and concentrated by the nickel ferrocyanide present in the tanks, the associated heating could cause tank temperatures to rise above the safety limits specified for the ferrocyanide-containing tanks, especially if the supernate in the tanks is pumped out and the waste becomes drier.For this study, two simulants, In-Farm-2 and U-Plant-2, were chosen to represent the waste generated by the cesium scavenging process. These simulants were formulated using protocols from the original cesium scavenging campaign. The effects from later additions of cesium-rich waste from various processes were also considered. The simulants were prepared and centrifuged to obtain a moist ferrocyanide sludge. This moist sludge was then used in three different sets of experiments: 1) batch equilibrium testing, 2) layering tests, and 3) intercalation of excess dissolved cesium into the settled sludge.The batch equilibrium testing was performed at room temperature to examine the effects of cesium and the cesium-to-nickel ferrocyanide ratio on the distribution coefficients 0. The maximum capacities of U-Plant-2 and In-Farm-2 simulants were also determined from these experiments. The maximum capacity of U-Plant-2 simulant was 0.50 mole of cesium per mole of nickel ferrocyanide and the maximum capacity of In-Farm-2 simulant was 0.80 mole of cesium per mole of nickel ferrocyanide. An evaluation of the effects of the sodium concentration and the sodium-to-cesium ratio indicated a slight but noticeable decrease in the distribution coefficients as the concentration of sodium was increased.Potential concentration mechanisms were also evaluated. A concentrated region of '"Cs nickel ferrocyanide could form in several ways, depending upon the settling and intercalation characteristics of the materials: 1) after exchange of cesium from solution, the cesium form of the nickel ferrocyanide could settle at a different rate than the sodium form of nickel ferrocyanide; 2) after exchange of cesium from solution, the cesium nickel ferrocyanide could settle at a different rate than the remaining solids present in the bulk of the waste (sodium salts). This concentration mechanism assumes a large portion of the nickel ferrocyanide exists as cesium nickel ferrocyanide. A concentr...

Ferrocyanide safety project ferrocyanide aging studies. Final report

“…Solid sodium nickel ferrocyanide materials are also ~O W R to be excellent ion exchange materials for cesium (Loewenschuss 1982;Loos-Neskovic et al 1976Burgeson et al 1994). Selectivity for cesium over sodium is very high (Campbell et al 1990;Loos-Neskovic et al 1976).…”