Speaker
Description
Production of metastable Technetium-99 (Tc-99m), a decay product of Molybdenum-99 (Mo-99) is vital to the medical imaging community. One method of producing Mo-99 using accelerators is through the irradiation of Mo-100 targets using an electron beam. Los Alamos National Laboratory (LANL) provides support to NorthStar medical Radioisotopes (NMR) on their efforts to produce Mo-99. The NMR target consists of an Inconel window that allows the electron beam to penetrate and irradiate a stack of approximately 70, 24 mm, 0.74 mm thick Mo-100 discs. The discs are separated by 0.25 mm thin cooling channels through which pressurized helium flows and cools the discs during irradiation which generates large amounts of heat. We have found during cold testing of the target system that the Mo-100 discs undergo significant mass loss and disc breakage due to flow induced vibrations. The mass loss is not only undesirable due to monetary loss reduced final quantities of Mo-99, but also due to the hazards associated with radioactive material trapped in the cooling lines and particle filters. This work describes the experimental characterization of the flow induced vibrations and disc mass loss in a reduced scale set-up containing 10 Mo-100 discs. We use high speed imaging, displacement measurements and microphone measurements combined with signal processing to estimate the vibration frequency of each disc. The effect of disc thickness, target fit and duration of testing on the mass loss is described. It is found that for a looser fit, disc rotation leads to more mass loss than disc vibration. For tighter fits, it is found that with longer run times, the overall target fit loosens, leading to both rotation and vibration motion, leading to mass loss. Recommendations for target improvement are also presented.
| Themes for the contribution | 1 R&D to support concepts |
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