Production of Fluorine-18 by Small Research Reactor

Abstract

High purity 18F was prepared by irradiating 1g of lithium hydroxide or otherwise 0.14g of enriched lithium carbonate containing 50% 6Li in the pneumatic tube of a TRIGA-II research reactor at a thermal neutron flux of 1.2×10¹² n/cm2•sec.
After cooling for 20min, the irradiated lithium hydroxide was dissolved in distilled water. The resulting 18F was separated from the irradiated target by passing the lithium hydroxide solution successively through ion exchange columns of H-, OH- and H-forms. Use was also made of the Co-form ion exchange column in place of the H-form for the elimination of impurities. In the case of 6Li enriched lithium carbonate, the irradiated lithium carbonate was dissolved in hydrochloric acid, and ion exchange columns of Ag-, OH- and H-forms were used for purifying the ¹⁶F. The product ¹⁸F was obtained in the form of water containing ¹⁸F. The chemical yield for the purification of ¹⁸F was about 80% and the final radioactive impurities were less than 1ppm.
A neutron activation method for determining the isotopic abundance of ⁶Li was developed using the nuclear reactions ⁶Li(n, α)³H and ¹⁶O(t, n)¹⁸F. Aqueous solutions containing lithium were irradiated in pneumatic tube for 1hr. ¹⁸F was separated by steam distillation from the irradiated solutions and precipitated as magnesium fluoride. The chemical yield for the separation of ¹⁸F was about 80%. The sensitivity limit was estimated to be 4μg of natural lithium.