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ORNL Collaboration Results in 3D Printed Stainless Steel Target for Medical Isotope-2018 China(Guangzhou)Int’l Meta
l &Metallurgy Exhibition-metal exhibition
5/17/2018 金屬展-冶金展-鋼鐵展-steel expo-metal &metallurgy expo |
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3D printing is increasingly finding use in the manufacture all sorts of end-use products, but it can also lend a hand to researchers on the way to reaching a final goal. A good example of this is a recent project that Oak Ridge National Laboratory in Tennessee, run by the Department of Energy (DOE) and already responsible for numerous 3D printing innovations, helped out with by providing research and development efforts.
The last time that the radioactive isotope molybdenum-99 (Mo-99), the parent of short-lived decay product technetium?99m (Tc-99m), was made in the US was during the late 1980s…until now. Tc-99m, best known for imaging blood flow in cardiac nuclear stress tests, is the most used radioisotope in medical diagnostic imaging.
This winter, the FDA approved the first Mo-99 that’s produced domestically without using highly enriched uranium (HEU). For nearly ten years, the US Department of Energy’s National Nuclear Security Administration (NNSA) has been supporting efforts to make Mo-99 without using HEU.
Mr Chris Bryan, who leads Mo-99 research at ORNL said that “We wanted to help prepare for the commercial production of molybdenum-99 here in the United States at full-cost-recovery pricing. We were excited to assist domestic efforts that don’t use highly enriched uranium.”
According to the NNSA, Mo-99 is used in over 40,000 medical procedures daily in the US, but is 100% supplied by foreign vendors, most of whom use HEU. To reduce how much the US relies on other countries for this, it provides funding for non-proprietary national technical support at several DOE laboratories, including Argonne National Laboratory, ORNL, Los Alamos National Laboratory, and the Savannah River National Laboratory.
Tc-99m loses potency in just 6 hours, while Mo-99 holds on a little longer at 66 hours. This kind of rapid decay is great for patients who don’t wish to be exposed to radiation for too long, but manufacturers who can’t stockpile Tc-99m are forced to deliver it before it grows too weak to produce high-contrast images. In this case, radiopharmacists use a device that runs a solution through a resin that’s been loaded with Mo-99; then, it releases Tc-99m, which is rushed straight to clinics and hospitals.
Wisconsin-based NorthStar Medical Radioisotopes and SHINE Medical Technologies both have cooperative agreements with the NNSA to increase domestic production of the isotope, and researchers from ORNL have also helped with several R&D projects aimed at making Mo-99 without HEU.
NorthStar is producing Mo-99 through a neutron-capture process that uses stable molybdenum target material. It’s similar to SHINE’s project in that it uses an accelerator, but differs because no uranium is involved. Instead, an electron accelerator bombards a target enriched in Mo-100 for six days, which creates intense gamma rays that knock a neutron right out of the mixture, resulting in Mo-99. Helium gas flows through the system to remove heat, so the material used to make the targets needs to be tough enough to hold up under stresses, but still lightweight so it can dissolve quickly, in order for the isotope to be recovered.
The only problem is that enriched Mo-100 is not cheap. ORNL made the initial target, a disc only the size of a half dollar that still cost a few thousand dollars in raw material. In addition, impinging electrons in the accelerator convert less than 10% of the Mo-100, which means that NorthStar has to recover and recycle the rest.
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