Research and dEvelopements for the Production of innovAtive RadioElements – REPARE

For numerous cancers, alpha emitters are particularly promising since they lead to a high treatment efficiency while sparing the surrounding healthy tissues. The REPARE project aims at bringing together research laboratories strongly involved in the field to develop new technologies in order to optimize production methods of innovative radioelements for nuclear medicine and more specifically for targeted alpha therapy. We propose to study and develop high power target systems able to exploit the very high beam intensities soon delivered by the linear accelerator of SPIRAL2. This would be used to synthesize the astatine-211 alpha emitter (used as a case study), to design a continuous online extraction system in the case of a liquid target, and to envisage the design of a radon/astate prototype generator allowing an optimal use of the astatine produced in the beta decay of radon.

To achieve these objectives, it is planned to measure the production cross-sections of the harmful contaminants 210At and 209,210Po in the alpha and 6,7Li-induced reactions on bismuth targets as well as on lead-bismuth eutectic mixtures. These cross-section measurements will in part be essential in determining the suitability of high-power target designs. Two different types of design will be studied in detail: a rotating solid target system using convection and conduction cooling, and an ambitious liquid target system with an online extraction system of the produced 211At.

In the case of direct production of astatine, hydro- and thermo-dynamical calculations will be carried out by the experts of the field that are present in our partnership in order to propose a solution that will also include the design of the system extracting the astatine from the irradiated targets. A prototype will be manufactured and tested in-beam. Feasibility studies will first be performed to identify any potential difficulties associated with the design of the liquid target. This includes aspects of beam characteristics, choice of target material and container, as well as cooling constraints. As a result of this work, thermal calculations and prototype design will be carried out. A continuous and on-line extraction system of the 211At will be proposed. The constraints associated to safety and radiation protection, particularly in the GANIL basic nuclear facility, will be addressed.

The final aspect of this project concerns the indirect production of astatine-211, i.e. the study of 211At production by beta decay of 211Rn produced in lithium-induced reactions and having a half-life approximately twice as long as that of astatine, allowing a much more extended distribution range and a more appropriate use of 211At compared to the classical way. For this, studies of radon trapping in nano / microporous materials and optimization of experimental parameters will be performed. When possible, modeling of the collected data will also be done. The choice of material for the optimal elution of 211At from the point of view of its future use in clinical trials is critical and will be studied in detail. Lithium beam irradiation tests will be carried out with SPIRAL2.

For this project as a whole, the TGIR GANIL grants a beam day per month of operation of SPIRAL2. Experiments will also be proposed and realized at ARRONAX and GANIL. The partnership built for this innovative project is composed of internationally recognized experts in their field of expertise: nuclear physics, use of particle beam, design of high power targets, thermal calculations, radiochemistry.