Engineering study of the criticality issues associated with Hanford tank 241-Z-361

Tank 241-Z-361 vapor sampling and analysis plan

“…Both volume dischmge records and limited sludge sampling data strongly suggest the plutonium was distributed in relatively simple layers, with plutonium concentrations varying only within a factor of 2 from the mean of 0.4g/L (29 kg total inventory). A 1997 criticality study concluded that although the plutonium inventory is potentially sufficient to generate a criticality, its distribution within the sludge makes an inadvertent criticality extremely unlikely (Lipke et al 1997).…”

241-Z-361 Sludge Characterization Sampling and Analysis Plan

“…This same document suggests a probable inventory of 26.8 kg. An assessment of material unaccounted for estimated the tank contents as 3 1.2 kg plutonium (Lipke et al 1997). The same document presented a criticality evaluation based on the core and bottle samples taken.…”

“…Table 1-3 provides a summary of this core description; available information does not specify the exact riser used for sample collection. Lipke et al (1997) presents total plutonium concentrations in wet sludge from the five different locations and timeframes plotted in Figure 1-6. Summary statistics of these data are provided in Table 1-4. 1-15 HNF-4371 Rev.…”

“…If the minimum criticality concentration for plutonium is exceeded,' a criticality recovery plan will be prepared and implemented. For a tank inventory of 30 kg plutonium or less, the minimum critical concentration was estimated to be greater than or equal to 4.7 g L of plutonium (Lipke et al 1997).…”