Transuranium elements production

G. T. Seaborg, "Transuranium Elements, Products of Modem Alchemy," Benchmark Papers in Physical Chemisty and Chemical Physics, Vol. 1, Dowden, Hutchison Ross, Stroudsburg, Pa., 1978. 

G. T. Seaborg (ed.), Transuranium Elements Products of Modem Alchemy, Dowden, Hutchinson Ross, Stroudsburg, 1978. This reproduces, in their original form, 122 key papers in the story of man-made elements. 

Seaborg, G. T. "The Transuranium Elements Products of Modern Alchemy," Dowden, Hutchinson and Ross, Inc., Stroudsburg, Pennsylvania, 1978, 488 pp. 

Tanthanide chemistry is approaching its 200th Anniversary, but except for data on thorium and uranium the chemistry of the actinides is a comparative youngster of some 30 years. However, the two chemistries are intimately associated because their elements are of the f transition type and thus formally comparable with each other and different from other elements. Indeed, these parallels made it possible to unravel actinide behavior in the early days of transuranium element production. In addition to their chemical similarities, the two series also share the properties of magnetism and radiant energy absorption and emission characteristic of /-electron species. However, important differences exist also, particularly in oxidation states, in bonding, and in complex-ion formation. 

FIG. 16.3. The major paths in transuranium element production in a thermal nuclear reactor fission and n-capture compete for available nuclei (From Seaborg). 

Seaborg GT (ed) (1978) Transuranium elements products of modem alchemy. Dow-den, Hutchinson Ross distrib Academic, San Di o... 

In addition to stable elements, radioactive elements are also produced in stars. The unstable but relatively long-lived isotopes °K, Th, and make up the internal heat source that drives volcanic activity and processes related to internal convection in the terrestrial planets. The short-lived transuranium elements such as Rn and Ra that are found on the Earth are all products of U and Th decay. 

The complexity of the reactions involved in the bombardment of plutonium and the production of higher transuranium elements can be seen from the following scheme which indicates the method of synthesis of einsteinium and fermium ... 

The third principal component of environmental radioactivity is that due to the activities of humans, the anthropogenic radionuclides. This group of nuclides includes the previously discussed cases of 3H and 14C along with the fission products and the transuranium elements. The primary sources of these nuclides are nuclear weapons tests and nuclear power plant accidents. These events and the gross nuclide releases associated with them are shown in Table 3.1. Except for 14C and... 

The synthesis reactions used to discover the transuranium elements are given in Table 15.2. All these reactions are complete fusion reactions in which the reacting nuclei fuse, equilibrate, and deexcite in a manner independent of their mode of formation. Other production reactions involving a partial capture of the projectile nucleus are also possible. 

The first scientific attempts to prepare the elements beyond uranium were performed by Enrico Fermi, Emilio Segre, and co-workers in Rome in 1934, shortly after the existence of the neutron was discovered. This group of investigators irradiated uranium with slow neutrons and found several radioactive products, which were thought to be due to new elements. However, detailed chemical studies by Otto Hahn and Fritz Strassman in Berlin showed these species were isotopes of the known elements created by the fission of uranium into two approximately equal parts (see Chap. 11). This discovery of nuclear fission in December of 1938 was thus a by-product of man s quest for the transuranium elements. 

Prior to 1939, elements of atomic number greater than 92 were unknown, and there was considerable doubt as to whether such elements could exist. In 1939, however, Edwin McMillan and Philip Abel-son reported the production of the first of the transuranium elements. By bombarding uranium with neutrons, they produced an element of atomic number 93, which was later named neptunium (Np). 

These developments led directly to the discovery of four additional transuranium elements. It should be emphasized that these are products of the laboratory and that none of the transuranium elements exists in nature in any appreciable concentration. Different isotopes of these elements may be formed by several types of nuclear transformations those given here are simply illustrative. 

The discovery of fission was a complete surprise and also a great shock, because it shattered fundamental ideas of nuclear behavior that had guided the investigation. The surprise was evident in the events of December 1938. On December 10, Enrico Fermi was awarded the Nobel Prize in physics. He and his group in Rome had been the first to irradiate uranium with neutrons and to propose that transuranium elements had been formed in the process. In his Nobel lecture, Fermi was so confident of the first two, elements 93 and 94, that he referred to them by name ausonium and hesperium. But at that very moment, the Berlin team of Otto Hahn, Lise Meitner, and Fritz Strafimann was on the verge of identifying barium among the uranium products. By the end of the year, they understood that uranium had split, explained the fission process, and concluded that the transuranium elements were false. When Fermi published his Nobel lecture, he added a footnote to that effect, but by then ausonium and hesperium were themselves footnotes (if that) in the history of science. [1]... 

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