Ferrocyanide safety program: Credibility of drying out ferrocyanide tank waste by hot spots

Abstract

The single-shell waste tanks at the Hanford Site that contain significant quantities of ferrocyanide have been considered a possible hazard, since under certain conditions the ferrocyanide in the waste tanks could undergo an exothermic chemical reaction with the nitrates and nitrites that are also present in the tanks. The purpose of this report is to assess the credibility of local dryout of ferrocyanide due to a hotspot. This report considers the following: What amount of decay heat generation within what volume would be necessary to raise the temperature of the liquid in the sludge to its boiling point? What mechanisms could produce a significant local concentration of heat sources? Is it credible that a waste tank heat concentration could be as large as that required to reach the dryout temperatures? This report also provides a recommendation as to whether infrared scanning of the ferrocyanide tanks is needed. From the analyses presented in this report it is evident that formation of dry, and thus chemically reactive, regions in the ferrocyanide sludge by local hotspots is not credible. This conclusion is subject to reevaluation if future analyses of tank core samples show much higher {sup 137}Cs or {sup 90}Sr concentrations than expected.more » Since hotspots of concern are not credible, infrared scanning to detect such hotspots is not required for safe storage of tank waste.« less