Year
1995
Abstract
Nondestructive assay of holdup in solution tanks at Rocky Flats has been performed to address criticality safety concerns since 1974. Destructive analysis techniques were used for quantification of the fissile material content of the tanks. With termination of operations in 1989, including sparging and sampling of tanks, a need arose for nondestructive assay of solutions in tanks to confirm previous inventory values. Gamma ray measurement methodologies were investigated and several techniques, including Poor Man' s Densitometry were implemented. These techniques have been applied to several different types of tanks including: annular, raschig ring filled, and pencil tanks. For the annular tanks \"Poor Man's Densitometry\" is used, with the densities of the measured solutions normalized to the value of one \"accepted\" concentration tank. Measurement uncertainties for this technique has been better than was anticipated. Measurements are also performed at several levels to attempt to detect variations in density. For the current tank draining program, solution in tanks is assayed by the NDA gamma-ray technique before draining. Measurement results were obtained for plutonium, uranium, and mixtures of U/Pu solutions for concentrations ranging from less than 0.5 g/1 to 150 g/1. Tanks with expected concentrations were used to establish a relationship between concentration and count rate. \"Bootstrapping\" calibration techniques were used in some cases to obtain quantitative results.