Description: In the Plutonium Reclamation Facility a critically-safe geometry of the processing vessels, combined with economical utilization of building space, has resulted in manifolded, vertical tanks for blending, receiving, holding, etc. The pumps attached to the bottom-outlet manifolds of the tanks are of a canned motor type. The extremely short life of these pumps (considerably below that expected even in severe abrasive and corrosive service) prompted a series of studies using glass tanks containing process solutions which, except for the associated radioactivity, duplicate plant process streams. Circulation, blending, and reaction characteristics of simulated process streams in glass duplicates of the 234-5 Bank Tanks TK-17, TK-27, and TK-37 revealed circulation patterns that result in intermittent cavitation within the canned motor transfer pumps. This cavitation, combined with the unavoidable corrosion and abrasion, rapidly destroys the pumps. The circulation patterns, under varying liquid levels as encountered in plant operation, cause single and dual phase transfer of the organic aqueous solutions to process colunans at different times, which results in flooding and erratic extraction efficencies. Reduction of cavitation and elimination of mixed phase transfer has been demonstrated by means of parallel controllable orifices in the external circulation lines. Elimination of cavitation and uniformity of mixing in the four separate vessels comprising the bank-tank assembly have also been demonstrated by means of changes in the inlet and outlet manifolds. The reduction of cavitation can be accomplished by changes in the system components remotely located from the tanks proper, i.e., in piping located in hoods. Complete elimination of cavitation and uniformity requires alteration of the tank headers and, while more desirable, also entails appreciable cost. (auth)
Date: April 30, 1974
Creator: Dunn, J.
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