Development of an Automatic Separation/Extraction Module for the Accelerator 99mTc Production from 100Mo-Enriched Molybdenum Metal Targets

The unexpected worldwide Technetium-99m (t1/2=6h, Eγ=140keV) shortening occurred on the radioisotope market in 2009-2010, due to the parent nuclide 99Mo production crisis, has prompted new ideas about alternative production routes of this important gamma emitter radionuclide used in 85% of diagnostic nuclear medicine procedures. At Legnaro laboratories of the Italian National Institute for Nuclear Physics (INFN) started in 2011 the APOTEMA project, funded by CSN5-INFN and focused on the possibility of replacing the current reactor-based method with the accelerator-based one by the 100Mo(p,2n)99mTc nuclear reaction. The purpose of this work was to develop a completely automatic extraction module for the 99mTc separation and purification process from enriched 100Mo metal targets. Several techniques (based upon both chemical and physics processes) are known to obtain separation of 9xTc from molybdenum; among them the most used ones are: the ABEC technique (Aqueous Biphasic Extraction Chromatography), the so-called Chattopadhyay’s method with ion exchanger cartridges (Dowex-1 x 8) and the solvent extraction method with MEK (Methyl Ethyl Ketone). Preliminary experimental studies pointed out that the solvent extraction technique is one of the most efficient methods, thanks to the selective affinity of the pertechnetate (9xTcO4-) for MEK and the affinity of the binegative molybdate (MoO42-) for the aqueous phase, providing high extraction yield of high quality 9xTc from molybdenum metal targets. Starting from this method and applying some corrections to the original procedure aimed at the optimization of operator’s radioprotection, a preliminary automatable extraction module was developed. In particular, the optimized procedure started with the dissolution of the metal target in H2O2 and NaOH; by vortex mixing of alkaline solution with MEK, it was possible to selectively extract the pertechnetate from the aqueous phase, that contained molybdate and other byproducts; by transferring the MEK phase with pertechnetate through a silica column in tandem with an alumina column, the final product has been easily purified from organic solvents and molybdate residuals; finally the 99mTc was eluted from alumina column with saline. In 35 minutes the semi-aitomatic module allowed to recover about 80% of the initial activity. Purity values of final pertechnetate saline solution were in agreement with values imposed by Pharmacopoeia for the generatorobtained product. The extraction was then completely automated with remote control, in order to ensure an optimal operator radioprotection and faithful reproducibility of the process