Plutonium elements

As Z increases, the overall yield of the target element falls sharply, because many steps are required. Plutonium (element 94) has been produced in ton quantities by neutron bombardment of uranium-238. Up to curium (element 96), production in kilogram quantities is possible, but the yields fall by about one order of magnitude for each successive element beyond Z = 96. 

A few comments about uranium and plutonium elemental structures. 

G. T. Seaborg, Edwin McMillan, J. W. Kennedy, and A. C. Wahl prepare plutonium (element 94) in the cyclotron. 

Elements slightly heavier than uranium, produced by radioactive decay (see later), are found in tiny amounts in natural uranium ores. Plutonium (element 94) has also been found in nature, a product of the element-forming processes that happen in dying stars. So it is a tricky matter to put a precise number on the natural elements. 

There are several spaces in the Periodic Table between plutonium (element 94) and einsteinium (element 99). But by 1952 these had already been filled by scientists at Berkeley, using the cyclotron to bombard heavy nuclei with particles that, when captured, increased the nuclear mass. In 1944 Glenn Seaborg, Albert Ghiorso, and Ralph James made elements 95 and 96 this way. Kept secret until after the war, they were respectively called americium and curium. 

Scale Production - Separation - Recovery of Trans-plutonium Elements," ACS Symposium, 2nd Chem. Congr. 

Some elements are not foimd in nature but are produced artificially in particle accelerators like the one shown in Figure 3.10. These are known as synthetic elements. The synthetic elements, made by means of nuclear reactions, are marked on the periodic table. They include technetium, element 43, and all the elements after uranium, element 92. Although small amounts of neptunium and plutonium, elements 93 and 94, have been found in uranium ores, it is likely that they are the products of nuclear bombardment by radiation from uranium atoms. 

Normally, 30% to 4S% of the 85 fuel elements in the reactor will be 1.8 w/o plutonium in aluminum, the remainder swaged natural uranium oxide. Three loadings were given particular attention in the critical tests. A two-zone loading contained 36 plutonium elements in the periphery and 49 uranium elements in the center. A three-zone loading contained 30 plutonium elements in a ring... 

The fuel loading for a reactor operating on plutonium recycle will in general contain a mixture of standard enriched uranium oxide fuel elements and elements containing a mixture of plutonium and uranium oxides. When the fuel is recycled in the same reactor in which it was produced, the amount available would mean that some one third of the core would be composed of plutonium elements. On the other hand, it may be advantageous to load a whole core with plutonium elements only, since this would permit the lattice to be redesigned to take advantage of the nuclear characteristics of plutonium. The more important distinctions between uranium and plutonium fuel are summarized briefly below ... 

Since we believe that the trans-plutonium elements have localized 5f electrons, we are led to attempt to establish a relationship between their crystallographic properties and those of the rare earths. That is, we want to compare trivalent 6d transition... 

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