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2025 ANS Winter Conference & Expo
November 8–12, 2025
Washington, DC|Washington Hilton
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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.
P. Wälti
Nuclear Science and Engineering | Volume 36 | Number 2 | May 1969 | Pages 133-142
Technical Paper | doi.org/10.13182/NSE69-A19713
Articles are hosted by Taylor and Francis Online.
The mathematical model of age-dependent branching processes is used to describe neutron slowing down and multiplication in an infinite medium. To construct the probability measure of the neutron branching process, it is necessary to determine the probability density for a neutron of age θ(=time elapsed since birth of the fission neutron) to have energy E. This problem, which is equivalent to the time-dependent slowing down problem, is solved for a scattering law of the form v(E)Σs(E → E′)dE′ = aEµh(E′/E) (dE′/E) and an absorption cross section satisfying the relation v(E) Σa(E) = bEµ + c. In this case, it is proved that there always exist particular “invariant” probability densities suffering only contraction during ageing, i.e., having the form . For the time-dependent slowing down problem with a Greuling-Goertzel kernel, the results are compared with those of Koppel. Particular attention is paid to stationary energy spectra.
