The Australian Nuclear Science and Technology Organisation (ANSTO) has made significant strides in developing a more cost-effective method for producing the medical radioisotope molybdenum-99 (Mo-99). This innovative approach reduces the need for uranium-235 (U-235) enrichment and minimizes waste generation, addressing key challenges in the production of this critical medical material.
Mo-99 is essential in the medical field as it serves as the precursor to technetium-99m, a widely used radioisotope for nuclear diagnostic imaging. This imaging technique plays a vital role in diagnosing conditions such as cancer, heart disease, and various organ functions. ANSTO is a primary supplier of Mo-99 to the Australian medical community, underlining the importance of advancements in its production.
New Porous Targets Under Development
The research team at ANSTO is currently testing porous, cylindrical reusable targets in the OPAL multi-purpose reactor. These targets aim to optimize the production of Mo-99 while maximizing the consumption of U-235. Senior Principal Research Scientist Prof Gordon Thorogood emphasized the goal of enhancing Mo-99 production efficiency, stating, “The more effectively this is done, the larger the sustainability index.”
Recent efforts have concentrated on modeling neutron yields from these innovative targets. This research has produced four academic papers, three patents, and a PhD awarded to Robert Raposio, who conducted his studies under the supervision of Distinguished Professor Anatoly Rosenfeld at the University of Wollongong. The findings were published in the journal Frontiers in Nuclear Engineering, detailing the investigation into the shape of uranium targets and their impact on Mo-99 production.
Target Shape and Performance Analysis
In a series of computer simulations, the research team analyzed three target shapes: flat (rectangular), spherical, and cylindrical. Each target was created from the same material and density, allowing a fair comparison under typical operating conditions. The cylindrical target emerged as the most effective design, yielding the highest Mo-99 production while maintaining long-term usability and generating the least amount of undesirable by-products.
The simulations indicated that all target shapes maintained low heat levels, which reduces concerns about overheating during the production process. Following the successful modeling phase, proof-of-concept experiments were conducted using simulated targets to validate predicted yields and stability. These prototypes were irradiated in the OPAL reactor, confirming their effectiveness.
The newly developed spherical target design facilitates the ejection of Mo-99 from the matrix into the porous structure, allowing for easier extraction with a liquid that is compatible with ANSTO’s existing molybdenum extraction processes. “Once the uranium-235 is exhausted, it can be disposed of using ANSTO’s Synroc® waste encapsulation technology,” said Prof Thorogood.
This research not only advances production techniques for Mo-99 but also provides training opportunities in nuclear materials research, enhancing the skill set of those involved. Dr. Robert Raposio, now a Process Performance Manager at ANSTO, continues to seek improvements in the Mo-99 production process, contributing to ongoing efforts to enhance medical diagnostics.
Currently, two nuclear chemists, Dr Jessica Veliscek-Carolan and Dr Tim Ablott, are engaged in synthesizing and testing the new spherical targets. Additionally, the research team, along with a Master’s student from the University of Wollongong, Mr James Manning, is exploring whether Mo-99 can be produced using accelerator-based neutron systems. This development could pave the way for smaller-scale production methods compared to traditional reactor-based systems.
In summary, ANSTO’s innovative approach to Mo-99 production represents a significant advancement in medical technology, with potential benefits for healthcare systems both in Australia and globally. As research continues, the implications for improved diagnostic capabilities and reduced environmental impact may redefine the future of medical imaging.
