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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.”
G. J. Fischer, D. A. Meneley, R. N. Hwang, E. F. Groh, C. E. Till
Nuclear Science and Engineering | Volume 25 | Number 1 | May 1966 | Pages 37-46
Technical Paper | doi.org/10.13182/NSE66-A17499
Articles are hosted by Taylor and Francis Online.
Doppler effect measurements have been made in two plutonium-fueled fast reactor assemblies at the ZPR-3 reactor. One assembly, Assembly 45A, mocked up a large plutonium-uranium monocarbide fast power breeder reactor having a 239Pu-to-238U ratio of 1:7. The second assembly, Assembly 45, had a considerably softer spectrum, produced by replacing 40% of the canned sodium of the previous assembly by graphite. Zone-loading techniques were used to achieve these mockups. Doppler measurements were made with samples containing highly enriched 239Pu, 239Pu, and 238U mixed in a ratio of 1:7, as in a large breeder reactor, and 238U in two rod diameters. Various check experiments were performed to test the validity of the measurements. The experimental results showed a strong negative Doppler response for 238U, in good agreement with theoretical estimates. The 239Pu in the mixed isotope fuel composition gave only a small positive Doppler contribution. A separate measurement for 235U in the power breeder spectrum was positive and in reasonable agreement with theory. The 239Pu results were the most interesting. Three degrees of increasing “hardness” of neutron energy spectrum incident upon the 239Pu Doppler element were generated by Assembly 45, Assembly 45A, and Assembly 45A with natural B4C surrounding the Doppler element, respectively. The experimental positive 239Pu Doppler effect reactivity change was much smaller than calculated for the softest spectrum. The agreement between theory and experiment improved significantly, however, as the neutron energy spectrum hardened.
