Potential Hazard of Ferrocyanide Salts in High-Level Waste Tanks Within the Hanford Tank Farm

Abstract

ABSTRACTOver the past few years, there has been an increased awareness of the potential hazard of energetic chemical reactions in high-level radioactive waste tanks at the Hanford tank farm. In particular, a mixture of Na2NiFe(CN)6 with NaNO3 and NaNO2 in several high-level waste tanks has caused concern. The problem of the FeCN tanks is fundamentally one of a potentially unstable mixture of fuel (the CN- moiety) and oxidizer (NO3- or NO2-).At Los Alamos National Laboratory, we have performed an extensive reanalysis of the safety problems associated with the presence of Na2NiFe(CN)6 mixed with NaNO3/NO2 for a particular tank (104-BY) that contains by far the largest amount of the nickel ferrocyanide salt (∼2E5 mol). Our approach is to use conservative assumptions to bound both the energy density for a potential runaway reaction and the mass that could participate if we assume ignition as the result of bounding radionuclide concentrations. The subsequent progress of the accident is analyzed using an advanced hydrodynamics computer code called MESA to evaluate the loads on the structure and the generation of aerosols. The subsequent doses are shown to be low both on and off the site. The conservatism in the analysis is quite large, and the expected results using more realistic assumptions are discussed.