Y-12 Legacy Measurement Techniques for Enriched Uranium Solution Tanks

The Y-12 Plant EUO Chemical Recovery Area has a series of horizontal holding tanks and a series of extraction columns. Prior to the plant safety stand-down in 1994, enriched uranium process solutions were transferred to these measurement points, blended, and sampled. Solution measurements involved the transfer of solution from the normal location to a calibrated tank, cleaning and verification of the original tank, and transfer of the measured solution back to the origination tank. After the period of stand-down, the restart of the Chemical Recovery processes was done in phases, which prevented several systems from being able to function long-term. Another consequence of the phased restart was that some systems were never restarted after stand-down. This made it impossible to move solution to calibrated tanks for accountability measurement. The task of accounting for material that could not be transferred to calibrated tanks was addressed by the implementation of an in-situ NDA solution measurement technique developed by Los Alamos National Laboratory (LANL). This method has been vetted and proven to be a valid technique for accountability measurement of solution in tanks. Because there are components in the Chemical Recovery area that will never be restarted, and the transfer of solution to calibrated tanks for measurement remains an impossibility, the in-situ NDA solution measurement methodology developed by LANL has been the primary method for accounting for enriched uranium in solution at Y-12.