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Conference Spotlight
2025 ANS Winter Conference & Expo
November 8–12, 2025
Washington, DC|Washington Hilton
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Latest News
Japan gets new U for enrichment as global power and fuel plans grow
President Trump is in Japan today, with a visit with new Prime Minister Sanae Takaichi on the agenda. Takaichi, who took office just last week as Japan’s first female prime minister, has already spoken in favor of nuclear energy and of accelerating the restart of Japan’s long-shuttered power reactors, as Reuters and others have reported. Much of the uranium to power those reactors will be enriched at Japan’s lone enrichment facility—part of Japan Nuclear Fuel Ltd.’s Rokkasho fuel complex—which accepted its first delivery of fresh uranium hexafluoride (UF₆) in 11 years earlier this month.
Robert J. Tuttle
Nuclear Science and Engineering | Volume 21 | Number 4 | April 1965 | Pages 451-462
Technical Paper | doi.org/10.13182/NSE65-A18789
Articles are hosted by Taylor and Francis Online.
The variation of neutron importance with energy and position has been investigated in a multiregion critical assembly having a series of test regions typical of slightly epithermal to fast power reactors. Values of neutron importance at the center of the test regions were measured using neutron sources and a reactivity oscillator. The variation of neutron importance with position was determined using neutron sources in conjunction with a dynamic reactivity-measurement technique. Analysis of data from similar beryllium- and carbon-moderated test regions indicates the significance of the Be(n, 2n) reaction. The neutron sources used in this study were Po-Be, Po-B11, Po-CaF2, Po-Li7, Mock Fission and Sb-Be. Published source spectra were used in the analysis of the data; the Mock-Fission-source spectrum was determined by gamma-ray spectroscopy. Relative yields of these sources were determined by calibration in a manganese sulfate bath.
