Uranium fuel elements

Subsequently, solvent extraction was applied to recover the fission product technetium from the residue remaining after the fluorination of irradiated uranium fuel elements . The residue was leached with concentrated aluminum nitrate solution, which was extracted by 0.3 M trilaurylamine in a hydrocarbon diluent. After separation of uranium, neptunium, and aluminum nitrate, technetium was back extracted into a 4 N sodium hydroxide solution. 

Irradiated uranium fuel elements contain fission product isotopes, activation products produced by atoms exposed to the intense neutron, ot, (3, and y radiation in the reactor core, and actinides, produced by neutron capture of the nuclei of atoms with atomic... 

The heart of an atomic reactor or atomic pile can be a group of uranium fuel elements. These are made from natural uranium, which contains two kinds of atoms, uranium-235 which will undergo fission and uranium-238 which will not. 

Neptunium was discovered by the U.S. physicists Edwin M. McMillan and Phihp Abelson, in 1940, via the bombardment of with neutrons. The name of the element is related to the planet Neptune. Neptunium-237 occurs as a product of fission, and appears in uranium fuel elements. 

The first transuranium elements, neptunium and plutonium, were obtained in tracer amounts from bombardments of uranium by McMillan and Abelson and by Seaborg, McMillan, Kennedy, and Wahl, respectively, in 1940. Both elements are obtained in substantial quantities from the uranium fuel elements of nuclear reactors. Only plutonium is normally recovered and is used as a nuclear fuel since, like 235U, it undergoes fission its nuclear properties apparently preclude its use in hydrogen bombs. Certain isotopes of the heavier elements are made by successive neutron capture in 239Pu in high-flux nuclear reactors (> 1015 neutrons cm-2 sec- ). Others are made by the action of accelerated heavy ions of B, C, N, O or Ne on Pu, Am or Cm. 

The following examples are for the separation of plutonium from uranium similar procedures involving the same basic principles have been devised to separate Np and Am. The initial starting material in plutonium extraction is a solution of the uranium fuel element (plus its aluminum or other protec-... 

Because of such effects, spent uranium fuel elements from PWR, BWR, HWR, GCR and FBR differ in composition both from each other and between fuel batches from the same reactor. Furthermore, the composition differs betwe pins in the same fuel elemrat and for each pin also along its Iragth, especially when initial burnable poison concentration and enrichm t is graded along pins. The differraice is not so large that very different fuel... 

Magnox A group of magnesium alloys used to enclose uranium fuel elements in nuclear reactors. They usually contain some aluminium as well as other elements, such as beryllium. 

Since 1995 a progressive loading with slightly enriched uranium (0.85% wt) began, so that at present the core contains not only natural uranium fuel elements but also slightly enriched ones. 

Various types of fins (longitudinal, transversal, spiral, or herringbone) are used on natural uranium fuel elements to increase the effective heat-transfer surface (2). 

The diameter of the assembly was increased from 27 to60 in. The height was 48 In. The 848 natural uranium fuel elements were clad with 0.060-in. aluminum and aligned in a square array to give a moderator to fuel ratio of 6.46 1. The entire assembly was at a temperature of 180 1 2 F. 

The excess reactivity of three supercritical cores was determined using the period method and control rod calibrations. The initial core of Fig. 1 had an excess reactivity of 22.9 cents. Adding four fuel elements to positions H-4, H-14, J-4, and J-14 increased the core excess reactivity to 112.4 cents. Replacing two 12-wt% uranium fuel elements with two 8.S-wt% uranium fuel elements (positions 1-8 and 1-9) reduced the core reactivity back to a just critical condition, i.e., this change was worth 112.4 cents. Hence removing the four fuel elements in positions H-4, H-14, J-4, and J-14 from... 

Fabrication of uranium fuel elements Fabrication of mixed oxide fuel elements Interim storage of spent fuel elements... 

The reactor will be fueled with metallic uranium fuel elements coextruded in a zircaloy-2 Jacket. The fuel geometry selected Is that of two concentric fuel tubes. Figure 3-10 shows the fuel and process tube assembly. 

The use In NFR of metallic uranium fuel elements In high temperature water coolant represents a departure from past practice. Freedom from all fuel problems la not anticipated. However, It Is not anticipated that fuel performance will limit reactor power below the design level. 

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