Chemical tuning and design optimization for the purification of Ac-225 in milliflow reactors

Introduction

In the context of producing Actinium-225 from the Radium-226 photonuclear reaction, the aim of this Master's thesis is to introduce the candidate to radiochemistry and solvent extraction in milliflow reactors. The system can be studied and optimised through extraction tests using analogue elements (lanthanum and barium) in batch and flow formats, with the introduction of radiotracers (actinium and radium) once the procedure has been validated. The objective is to optimise the chemical and physical variables to maximise the separation of actinium and radium. Ultimately, outside the scope of this work, the purified actinium solutions will be used to develop radiopharmaceuticals for target alpha therapy, an internal radiotherapy treatment that shows high potential for fighting hypoxic and chemo-resistant tumours while minimising side effects.

Objectives

The objective of this Master's thesis is to investigate the chemical variables to optimise the design and performance of the milliflow reactor. To achieve this, the student will first conduct a literature study and receive laboratory training. They will then perform batch extractions representative of the system using TODGA in dodecane as the organic phase and a nitric acid-based aqueous phase. These batch extractions will be used to calculate the performance of the separation at equilibrium. This chemical study can then be translated into the milliflow reactor itself at non-equilibrium regimens of extraction, with the two phases being pumped and separated thanks to a setup that has already been tested. Milliflow tests will produce samples that will be tested according to their contents using either ICP-MS or gamma spectrometry. The student will then make design suggestions, backed by the findings, to optimise the milliflow reactor setup. These suggestions may relate to the chemical composition of the phases or hardware variables, such as pumps, reactor lengths and flow rates. The Master's thesis body will be reviewed and its structure supported by experimental design and data elaboration.