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ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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Latest News
First astatine-labeled compound shipped in the U.S.
The Department of Energy’s National Isotope Development Center (NIDC) on March 31 announced the successful long-distance shipment in the United States of a biologically active compound labeled with the medical radioisotope astatine-211 (At-211). Because previous shipments have included only the “bare” isotope, the NIDC has described the development as “unleashing medical innovation.”
F. J. Homan, T. B. Lindemer, E. L. Long, Jr., T. N. Tiegs, R. L. Beatty
Nuclear Technology | Volume 35 | Number 2 | September 1977 | Pages 428-441
Performance and Performance Modeling | Coated Particle Fuel / Fuel | doi.org/10.13182/NT35-428
Articles are hosted by Taylor and Francis Online.
Two fuel failure mechanisms were identified for coated particle fuels that are directly related to fuel kernel stoichiometry. These mechanisms are thermal migration of the kernel through the coating layers and chemical interaction between rare-earth fission products and the silicon carbide (SiC) layer (the primary barrier to diffusion of metal fission products out of the particle) leading to failure of the SiC layer. Thermal migration appears to be most severe for oxide fuels, while chemical interaction is most severe with carbide systems. Thermodynamic calculations indicated that oxide-carbide fuel kernels may permit a stoichiometry that reduces both problems to manageable levels for currently planned high-temperature gas-cooled reactors. Such stoichiometry adjustment is possible over the complete spectrum from UO2 to UO2 for the present recycle fuel, a weak acid resin (WAR)-derived fissile kernel. Thermodynamic calculations indicate that WAR kernels containing <15% UC2 (>85% UO2) will develop excessive CO overpressures within the particle during irradiation. In 100% UO2 particles, thermal migration and oxidation of the SiC layer were observed after irradiation. The calculations also indicate that WAR kernels containing >70% UC2 (<30% UC2) contain insufficient oxygen to oxidize the rare-earth fission products formed in fuel operated to the maximum burnup levels of 75% fissions per initial metal atom (75% FIMA). Instead, the rare earths are present in part or completely as dicarbides. As such, they were observed to segregate from the kernel and collect at the SiC interface on the cold side of the particle, react with the SiC, and eventually fail this coating. Five WAR kernel stoichiometries were irradiated. These are either UO2 kernels, UO2 plus 15, 50, or 75% UC2, or 100% UC2. Results of these tests are consistent with thermodynamic calculations. Additional tests are in progress to establish the optimum stoichiometry; preliminary indications suggest an optimum value of ∼35% conversion with a permissible range of ±20%.
