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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.
Michel Mélice
Nuclear Science and Engineering | Volume 37 | Number 3 | September 1969 | Pages 451-477
Technical Paper | doi.org/10.13182/NSE69-A19119
Articles are hosted by Taylor and Francis Online.
This paper presents a new attempt towards the development of a systematic method for solving the fuel cycling management optimization problem in modern PWR cores. When the infinite multiplication factor k is used as a single variable to describe the fuel distribution over the core at any stage of its life, the analysis of any reloading pattern can be performed on the basis of its corresponding k-map in the X-Y plane, or more simply, on the basis of its equivalent “k-profile” in cylindrical geometry. Conversely, it is shown how the reloading pattern can be synthesized from the k-profile, which becomes, therefore, the main tool of the method. The search for the best k-profile rests on the analysis of the necessary relations existing, for any particular reloading mode (batch, multiregion, salt-and-pepper, etc.) between the k-profiles and cycle times, and on the use of a cycle “internal optimality condition” aiming to maximize the reactivity of the reloading k-profile, and consequently, the cycle life time, with a constraint on the power-peak factor. As a result, the general many-variable cycling problem can be contracted into a single control-variable problem which, in turn, can be separated into the following two simpler tasks: a cycle internal optimization problem consisting of finding the reloading mode and the single control variable which minimize the stationary cycle cost and a cycle external optimization problem aiming to minimize the cost penalty associated with any deviation of the cycling sequence from the optimal stationary cycle. Using the particular class of optimal k-profiles complying with the maximum power (minimum peak factor) condition, the method is applied to the analysis of the stationary and transient cycles of the SENA reactor, with the three-region mixed reload mode. The methods for calculating the optimal profile classes corresponding to an arbitrary peak factor are also indicated.