Transuranium

Planet pluto) Plutonium was the second transuranium element of the actinide series to be discovered. The isotope 238pu was produced in 1940 by Seaborg, McMillan, Kennedy, and Wahl by deuteron bombardment of uranium in the 60-inch cyclotron at Berkeley, California. Plutonium also exists in trace quantities in naturally occurring uranium ores. It is formed in much the same manner as neptunium, by irradiation of natural uranium with the neutrons which are present. 

Because of the high rate of emission of alpha particles and the element being specifically absorbed on bone the surface and collected in the liver, plutonium, as well as all of the other transuranium elements except neptunium, are radiological poisons and must be handled with very special equipment and precautions. Plutonium is a very dangerous radiological hazard. Precautions must also be taken to prevent the unintentional formulation of a critical mass. Plutonium in liquid solution is more likely to become critical than solid plutonium. The shape of the mass must also be considered where criticality is concerned. 

Dmitri Mendeleev) Mendelevium, the ninth transuranium element of the actinide series discovered, was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment of the isotope 253Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was 256Md, which has a half-life of 76 min. This first identification was notable in that 256Md was synthesized on a one-atom-at-a-time basis. 

Transportation Index Transport phenomena Transposons Transputer chips Transuranic waste Transuranium elements... 

Special techniques for experimentation with the actinide elements other than Th and U have been devised because of the potential health ha2ard to the experimenter and the small amounts available (15). In addition, iavestigations are frequently carried out with the substance present ia very low coaceatratioa as a radioactive tracer. Such procedures coatiaue to be used to some exteat with the heaviest actinide elements, where only a few score atoms may be available they were used ia the earHest work for all the transuranium elements. Tracer studies offer a method for obtaining knowledge of oxidation states, formation of complex ions, and the solubiHty of various compounds. These techniques are not appHcable to crystallography, metallurgy, and spectroscopic studies. 

Fig. 4. Futuristic periodic table showing predicted locations of a large number of transuranium elements (atomic numbers in parentheses).

Comphcated theoretical calculations, based on filled shell (magic number) and other nuclear stabiUty considerations, have led to extrapolations to the far transuranium region (2,26,27). These suggest the existence of closed nucleon shells at Z = 114 (proton number) and N = 184 (neutron number) that exhibit great resistance to decay by spontaneous fission, the main cause of instabiUty for the heaviest elements. Eadier considerations had suggested a closed shell at Z = 126, by analogy to the known shell at = 126, but this is not now considered to be important. 

The effects of a rather distinct deformed shell at = 152 were clearly seen as early as 1954 in the alpha-decay energies of isotopes of californium, einsteinium, and fermium. In fact, a number of authors have suggested that the entire transuranium region is stabilized by shell effects with an influence that increases markedly with atomic number. Thus the effects of shell substmcture lead to an increase in spontaneous fission half-Hves of up to about 15 orders of magnitude for the heavy transuranium elements, the heaviest of which would otherwise have half-Hves of the order of those for a compound nucleus (lO " s or less) and not of milliseconds or longer, as found experimentally. This gives hope for the synthesis and identification of several elements beyond the present heaviest (element 109) and suggest that the peninsula of nuclei with measurable half-Hves may extend up to the island of stabiHty at Z = 114 andA = 184. 

G. T. Seaborg,. J. Katz, and W. M. Manning eds.. The Transuranium Elements Research Papers, National Nuclear Energy Series, Div. IV, 14B, McGraw-Hill Book Co., Inc., New York, 1949. 

G. T. Seaborg, Man-Made Transuranium Elements, Prentice-HaH, Inc., Englewood CHffs, N.., 1963. 

In this process, uranium metal is electrodeposited at the cathode, while plutonium and other transuranium elements remain in the molten salt as trichlorides. Plutonium is reduced in a second step at a metallic cathode to produce Cd—Pu intermetallics. The refined plutonium and uranium metals can then be refabricated into metallic fuel (137). 

Nuclear Waste Reprocessing. Liquid waste remaining from processing of spent reactor fuel for military plutonium production is typically acidic and contains substantial transuranic residues. The cleanup of such waste in 1996 is a higher priority than military plutonium processing. Cleanup requires removal of long-Hved actinides from nitric or hydrochloric acid solutions. The transuranium extraction (Tmex) process has been developed for... 

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, The Transuranium Elements, Addison-Wesley Publishing Co., Reading, Mass., 1958. 

R. G. Haire and. K. Gibson, ia L. R. Morss and. Fuger, eds.. Transuranium Elements A Half Centuy, American Chemical Society, Washiagtoa,... 

C. KeUer, in The Chemisty of the Transuranium Elements, Vedag Chemie, Weinheim, Germany, 1971, Chapt. XIV. 

Production in Fission of Heavy Elements. Tritium is produced as a minor product of nuclear fission (47). The yield of tritium is one to two atoms in 10,000 fissions of natural uranium, enriched uranium, or a mixture of transuranium nucHdes (see Actinides and transactinides Uranium). 

ION EXCHANGE DETERMINATION OF TRANSURANIUM ELEMENTS CONTENT IN ENVIRONMENT OBJECTS... 

E. McMillan and P. Abdson synthesized the first transuranium elemeni sjNp. Others were synthesized by O. T. Seaborg and his colleagues during die next 15 y. 

A further group of elements, the transuranium elements, has been synthesized by artificial nuclear reactions in the period from 1940 onwards their relation to the periodic table is discussed fully in Chapter 31 and need not be repeated here. Perhaps even more striking today are the predictions, as yet unverified, for the properties of the currently non-existent superheavy elements.Elements up to lawrencium (Z = 103) are actinides (5f) and the 6d transition series starts with element 104. So far only elements 104-112 have been synthesized, ) and, because there is as yet no agreement on trivial names for some of these elements (see pp. 1280-1), they are here referred to by their atomic numbers. A systematic naming scheme was approved by lUPAC in 1977 but is not widely used by researchers in the field. It involves the use of three-letter symbols derived directly from the atomic number by using the... 

Prior to 1940 only the naturally occurring actinides (thorium, protactinium and uranium) were known the remainder have been produced artificially since then. The transactinides are still being synthesized and so far the nine elements with atomic numbers 104-112 have been reliably established. Indeed, the 20 manmade transuranium elements together with technetium and promethium now constitute one-fifth of all the known chemical elements. 

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. 

Since the radioactive half-lives of the known transuranium elements and their resistance to spontaneous fission decrease with increase in atomic number, the outlook for the synthesis of further elements might appear increasingly bleak. However, theoretical calculations of nuclear stabilities, based on the concept of closed nucleon shells (p. 13) suggest the existence of an island of stability around Z= 114 and N= 184. Attention has therefore been directed towards the synthesis of element 114 (a congenor of Pb in Group 14 and adjacent superheavy elements, by bombardment of heavy nuclides with a wide range of heavy ions, but so far without success. 

The transuranium elements must all be prepared artificially. In the case of plutonium about 1200 tonnes have so far been produced worldwide, about three-quarters of it in civilian reactors. 

Apart from g Pu, which is a nuclear fuel and explosive, the transuranium elements have in the past been produced mainly for research purposes. A number of specialized applications, however, have led to more widespread uses. I Pu (produced by neutron bombardment of I Np to form 93 Np which decays by jS-emission to 94Pu) is a compact heat source (0.56 Wg as it decays by a-emission) which, in conjunction with PbTe thermoelectric elements, for instance, provides a stable and totally reliable source of electricity with no moving parts. It has been... 

D. C. Hoffman, Proc. Robert A. Welch Foundation Conference XXXIV. Fifty Years with Transuranium Elements, October 1990, pp. 255-76. D. C. Hoffman, Chem. Eng. News, May 2, 24 - 34 (1994). 

E. M. McMillan and G. T. Seaborg (Berkeley) discoveries in the chemistry of the transuranium elements. 

Some of the reactions used to prepare transuranium elements are listed in Table 19.1. Neutron bombardment is effective for the lower members of the series (elements 93 through... 

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