The Hanford Ferrocyanide Task Team is addressing issues involving ferrocyanide precipitates in the single-shell waste storage tanks (SSTs), in particular the risk of explosion, This Task Team, which is composed of researchers from Westinghouse Hanford Company (WHC), Pacific Northwest Laboratory (PNL), and outside consultants, was formed in response to the need for an updated analysis of safety questions on the Hanford SSTs. The Ferrocyanide Safety Project, discussed in this report, is being conducted by PNL as part of the Waste Tank Safety Program led by WHC. The overall purpose of the WHC program, which is sponsored. by the U.S. Department of Fnerg,c's Tank Safety Project Office, is to provide technical information on ferrocyanide chemistry, and its interaction and reactive behavior with other tank constituents. Ultimately, this information will be used ',o maintain the tanks in a safe condition, implement interim stabilization strategies, and identify optimal disposal options. While by itself ferrocyanide is a stable complex of ferrous ion and cyanide, it can be made to explode in the laboratory in the presence of oxidizing materials such as nitrates and/or nitrites at tempera. tures above 280"C or by sufficient electrical spark. The specific goal of the PNL project i,_to determine the conditions necessary for the ferrocyanide.bearing wastes in Hanford SSTs to represent a hazard, to determine the conditions where these same wastes are not a hazard, or to determine the conditions which are necessary to assure the wastes are safe prior to treatment for permanent disposal. This annual report gives the results of the work conducted by PNL in FW 1991. The activities mainly focused on preparing and characterizing synthetic wastes and alkali nickel ferrocyanides produced using &e In-Farm cesium scavenging flowsheet and Fare potential nickel ferrocyanides thai: could be produced by ali of the cesium scavenging flowsheets.

The goal of this program is to determine the feasibility of solventdissolved coordination complexes for the separation of gas mixtures under bench-scale conditions. In particular, mixtures such as low-Btu gas will be examined for CO and Hz separation. Two complexes, Pdz(dpm) 2 Br 2 and Ru(CO)z(PPh 3) 3 , were examined in a benchscale apparatus for the separation of binary (CO-Nz or Hz-N2) and quinary {Hz, CO, co 2 , CH 4 , and Nz) mixtures. The separation of CON 2 was enhanced by the i i i