Method for Enriching Reprocessed Uranium in a Cascade of Gas Centrifuges with Simultaneous Decrease in the 232,234,236 U
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od for Enriching Reprocessed Uranium in a Cascade of Gas Centrifuges with Simultaneous Decrease in the 232,234,236U Content A. Yu. Smirnova,*, G. A. Sulaberidzea, A. A. Dudnikovb, and V. A. Nevinitsab aNational b
Research Nuclear University MEPhI, Moscow, 115409 Russia National Research Center Kurchatov Institute, Moscow, 123182 Russia *e-mail: [email protected] Received June 9, 2016
Abstract—It is shown that reprocessed uranium can be enriched with simultaneous dilution of 232,234,236U isotopes in a cascade of gas centrifuges that has three feed flows (depleted uranium, low-enriched uranium, reprocessed uranium). Computational experiments are carried out for different 235U content of the lowenriched uranium. It is demonstrated that the chosen combination of diluents can simultaneously reduce the cost of the separation procedure and the consumption of natural uranium, which in turn ensures cost reduction relative to not only the earlier used multiflow cascades but also the standard cascade for enrichment of natural uranium. Keywords: reprocessed uranium, isotope separation, separation cascade DOI: 10.1134/S1063778818080173
INTRODUCTION According to experts, despite anticipated development and commissioning of fast-neutron reactors, imbalance between the evaluated resources of natural uranium and its consumption for fueling the currently operating thermal-neutron reactors is almost inevitable in the foreseeable future [1]. Thus, to provide these reactors with fuel, it becomes necessary to use fissionable materials separated from spent fuel. One of these materials is reprocessed uranium, which will allow the need for natural uranium to be reduced and the amount of buried radioactive waste to be noticeably decreased as compared to the open fuel cycle [2]. Reprocessed uranium can be used for producing low-enriched uranium (LEU) in cascades of gas centrifuges [2–7]. However, its enrichment is made difficult by its constituent 232U and 236U isotopes [2]. The content of these isotopes in LEU is strictly regulated by the necessity of meeting the radiation safety requirements in fabrication of fuel elements and maintaining the neutron characteristics of nuclear fuel. A number of methods have been proposed for enriching reprocessed uranium in separation cascades of gas centrifuges. Many of them employ the simplest cascade with one feed flow, product, and waste (depleted uranium). This cascade can be used, for example, for [8]: —Enriching reprocessed uranium diluted beforehand with natural uranium;
—Producing enriched uranium from reprocessed uranium with subsequent dilution with natural uranium or other diluent; —Enriching natural uranium to a slightly higher 235U content than required for a nuclear fuel and mixing the resulting product with reprocessed uranium. The main drawback of these reprocessed uranium enrichment methods is separative work loss during the mixing of uranium with different 235U content. In addition to those mentioned above, there are other reprocessed uranium enrichment methods based on multiflow
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