Engineering topics

Krahn, Elizabeth O.

Publications and source records attributed to Krahn, Elizabeth O..

3 records

DOE OSTI2017

Design of a Fission 99 Mo Recovery Process and Implications toward Mo Adsorption Mechanism on Titania and Alumina Sorbents

Molybdenum-99 is a parent of the most widely used medical isotope technetium-99m. Proliferation concerns have prompted development of alternative Mo production methods utilizing low enriched uranium. Alumina and titania sorbents were evaluated for separation of Mo from concentrated uranyl nitrate solutions. System, mass transfer, and isotherm parameters were determined to enable design of Mo separation processes under a wide range of conditions. A model-based approach was utilized to design representative commercial-scale column processes. The designs and parameters were verified with bench-scale experiments. The results are essential for design of Mo separation processes from irradiated uranium solutions, selection of support material and process optimization. Mo uptake studies show that adsorption decreases with increasing concentration of uranyl nitrate; howeveL, examination of Mo adsorption as a function of nitrate ion concentration shows no dependency, indicating that uranium competes with Mo for adsorption sites. These results are consistent with reports indicating that Mo forms inner-sphere complexes with titania and alumina surface groups.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2012

Designs of Column Separation Processes for Recovery of Molybdenum from Dissolved High-Density LEU Target - Further Studies

The Global Threat Reduction Initiative (GTRI) Conversion Program develops technology necessary to convert civilian facilities that use high enriched uranium (HEU) to low enriched uranium (LEU) fuels and targets. The conversion of conventional HEU dispersion targets to LEU for the production of 99 Mo production requires approximately five times the uranium in a target to maintain the 99 Mo yield per target. Under GTRI, Argonne National Laboratory (Argonne) is developing two frontend options for the current processes to allow the use of LEU-foil targets. In both processes, the aim is to produce a product after the frontend that will be compatible with current purification operations and that will, with the same number of targets irradiated, provide the same or a higher yield of 99 Mo at the end of processing. The goal of the frontend process is to deliver a product solution that is of the same or higher Mo purity than the current solution and is of equal or better compatibility with current purification process. In the first frontend option, the LEU foil (contained in a thin [10–15 µm] Ni fission-recoil barrier) is removed from the annular target and dissolved in nitric acid. In the dissolution, the uranium, nickel, and all fission and activation products are dissolved; the solution will be ~7 mM Mo and ~450 g-U/L, and the nitricacid concentration after dissolution will be ~1 M. The resultant solution will then be run through a column to recover Mo from other target components; the Mo will be stripped from the column with a sodium hydroxide solution that will be compatible with the current purification processes used for dispersion targets. The volume of dissolved-foil solution is assumed to be 500 mL, and the pressure drop, ΔP, constraint of 0.8 atm is based on the use of vacuum/gravity fluid transfer system. Therefore pressure loss is limited to <1 atm; hence a value of 0.8 was chosen.

Stepinski, Dominique C.↗

DOE OSTI2010

Mechanical Stability Study

Argonne National Laboratory (Argonne), in collaboration with the BioSeparations Laboratory at Purdue University, is helping Babcock and Wilcox Technical Services Group develop the Medical Isotope Production System (MIPS), which will use an aqueous homogenous reactor (AHR) for the domestic production of 99 Mo. Roughly 200 L of low enriched uranium (LEU, 19.75% U-235) as a uranyl nitrate solution will be irradiated and passed through a column, which has been pre-equilibrated with nitric acid, for 2 hours. Column sizes have been predicted for the plant-scale production of 99 Mo by using Purdue University’s Versatile Reaction Separation (VERSE) simulator and experimental data provided by Argonne. In the plant, these columns will undergo multiple loading/washing/stripping cycles to purify 99 Mo from batches of irradiated LEU solutions. Since the previous report was distributed, the selection of sorbents to be used in the columns has been reduced to three titania-based sorbents. This report describes the results from mechanical stability studies that were performed to test the pressure drop and sorbent resistance to stress under relevant process conditions.

Krahn, Elizabeth O.↗