Neptunium Holdup Analysis Using the In Situ Object Counting System Calibration
Software and the Line Activity Consistency Evaluator Tool

Measurements performed at the Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory were analyzed to determine the mass of 237Np holdup in equipment in support of the laboratory’s nuclear material control and accountability program. The Genie 2000 Gamma Acquisition and Analysis Software and the In Situ Object Counting System (ISOCS) calibration software were used for gamma spectroscopy and analysis of these measurements. The equipment measured at REDC included a rotary kiln, which is used in the process of converting neptunium nitrate solution to neptunium oxide, and an additional set of pipes previously used in the rotary kiln. These two pieces of equipment were measured in several different geometries and modeled using ISOCS. Because of the nature of holdup in the equipment, creating the models involved many unknowns and assumptions. To improve the accuracy of the analysis, the Line Activity Consistency Evaluator (LACE) tool in the Genie 2000 software was used to optimize and validate these unknown physical parameters. The average measured 237Np mass of the rotary kiln, with measurements taken 6 months apart, was found to be 49.45 and 40.53 g. The additional set of pipes had an average measured 237Np mass of 27.08 g. This work demonstrates the application and limitations of ISOCS and the LACE tool for measurement of holdup material.