Transuranic element

Energetic particles, either from naturally radioactive materials or from particle accelerators, can be used to bring about atomic transmutations and so form new isotopes. In this way, the number of known elements has been extended above uranium, the heaviest naturally occurring element, with atomic number 92. All these artificial heavy elements are radioactive, and many have very short Ufetimes. 

They form part of a series in which the 5f electron orbitals become occupied in the ground state of the elements. In this sense they can be considered to be analogous to the lanthanides, in which the 4f orbitals are occupied in the ground state of the elements, and have been named the actinides. The actinides are listed in Table 16.1. They appear in the periodic table after element 88, radium, Ra, and end with element 103, lawrencium, Lr. 

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The rapid fission of a mass of or another heavy nucleus is the principle of the atomic bomb, the energy liberated being the destructive power. For useful energy the reaction has to be moderated this is done in a reactor where moderators such as water, heavy water, graphite, beryllium, etc., reduce the number of neutrons and slow those present to the most useful energies. The heat produced in a reactor is removed by normal heat-exchange methods. The neutrons in a reactor may be used for the formation of new isotopes, e.g. the transuranic elements, further fissile materials ( °Pu from or of the... 

Albert Einstein) Einsteinium, the seventh transuranic element of the actinide series to be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 in debris from the first large thermonuclear explosion, which took place in the Pacific in November, 1952. The 20-day 253Es isotope was produced. 

Spent nuclear fuel has fission products, uranium, and transuranic elements. Plans call for permanent disposal in underground repositories. Geological studies are in progress at the Yucca Mountain site in Nevada. Until a repository is completed, spent fuel must be stored in water pools or in dry storage casks at nuclear plant sites. 

In 1934 Fermi decided to bombard uranium with neutrons in an attempt to produce transuranic elements, that is, elements beyond uranium, which is number 92 in the periodic table. He thought for a while that he had succeeded, since unstable atoms were produced that did not seem to correspond to any known radioactive isotope. I le was wrong in this conjecture, but the research itself would eventually turn out to be of momentous importance both for physics and for world history, and worthy of the 1938 Nobel Pri2e in Physics. 

In 1938 Niels Bohr had brought the astounding news from Europe that the radiochemists Otto Hahn and Fritz Strassmann in Berlin had conclusively demonstrated that one of the products of the bom-bardmeiit of uranium by neutrons was barium, with atomic number 56, in the middle of the periodic table of elements. He also announced that in Stockholm Lise Meitner and her nephew Otto Frisch had proposed a theory to explain what they called nuclear fission, the splitting of a uranium nucleus under neutron bombardment into two pieces, each with a mass roughly equal to half the mass of the uranium nucleus. The products of Fermi s neutron bombardment of uranium back in Rome had therefore not been transuranic elements, but radioactive isotopes of known elements from the middle of the periodic table. 

A third source of aquatic plutonium is liquid effluent discharged from laboratory operations into ponds and streams. An example of this is a former waste pond at Oak Ridge National Laboratory, Pond 3513, that received liquid wastes with low concentrations of transuranic elements before it was retired. This impoundment has water quality similar to high pH natural ponds. 

Air monitoring will be required, e.g., when volatiles are handled in quantity, where use of radioactive isotopes has led to unacceptable workplace contamination, when processing plutonium or other transuranic elements, when handling unsealed sources in hospitals in therapeutic amounts, and in the use of hot cells/reactors and critical facilities. Routine monitoring of skin, notably the hands, may be required. 

The Federal Research in Progress database lists ongoing studies about environmental effects of americium (FEDRIP 2000). These are shown in Table 6-7. The International Science and Technology Center (ISTC), headquartered in Moscow, which began operations on March 3, 1994, also is active in research concerning transuranic elements. 

BennettBG. 1976. Transuranic element pathways to man. U.S. Energy Research and Development Administration. IAEA-SM-199/40. 

Cataldo DA, Garland TR, Wildung RE, et al. 1980. Foliar absorption of transuranic elements Influence of physicochemical form and environmental factors. J Environ Qual 9(3) 364-369. 

EPA. 1984. U.S. Mussel watch program Transuranic element data from Woods Hole Oceanographic Institution 1976-1983. Narragansett, RE Environmental Research Laboratory, U.S. Environmental Protection Agency. WHOI-84-28. CRC-84-5. 

Fisher NS, Bjerregaard P, Fowler SW. 1983. Interactions of marine plankton with transuranic elements 3. Biokinetics of americium in euphausiids. Mar Biol 75 261-268. 

Livens FR, Hursthouse AS. 1993. Soil and sediment chemistry of the transuranic elements. Anal Proc 30 196-198. 

McClellan RO, Casey HW, Bustad LK. 1962. Transfer of some transuranic elements to milk. Health Phys 8 689-694. 

Ovcharenko EP. 1972. An experimental evaluation of the effects of transuranic elements on reproductive ability. Health Phys 22 641. 

Markus, R. Hyperfine Structur Measurements on Some Transuranic Elements. 

Kim, J.I., Stumpe, R., and Klenze, R. Laser-induced Photoacoustic Spectroscopy for the Speciation of Transuranic Elements in Natural Aquatic Systems. 157, 129-180 (1990). 

Durbin, P. W. (1962). Distribution of the transuranic elements in mammals, Health Phys. 8, 665. 

Data from Morse, J.W. and G.R. Choppin. 1991. The chemistry of transuranic elements in natural waters. Rev. Aquat. Sci. 4 1-22. 

Hanson, W.C. 1976. Studies of transuranic elements in Arctic ecosystems. Pages 28-39 in C.E. Cushing (ed.). Radioecology and Energy Resources. Proceedings of the Fourth National Symposium on Radioecology. 12-14 May 1975, Oregon State Univ., Corvallis, OR. Ecol. Soc. Amer., Spec. Publ. No. 1. 

Hetherington, J.A., D.F. Jefferies, N.T. Mitchell, RJ. Pentreath, and D.S. Woodhead. 1976. Environmental and public health consequences of the controlled disposal of transuranic elements to the marine environment. Pages 139-154 in Transuranium Nuclides in the Environment. IAEA-SM-199/11, Inter. Atom. Ener. Agen., Vienna. 

Transuranic elements Elements of atomic number >92. All are radioactive and produced artificially all are members of the actinide group. 

Tramex [Transuranic metal (or amine) extraction] A process for separating transuranic elements from fission products by solvent extraction from chloride solutions into a tertiary amine solution. Developed at Oak Ridge National Laboratory, TN, for processing irradiated plutonium. 

Truex [Transuranium extraction] A process for removing transuranic elements during the processing of nuclear fuel by solvent extraction. Developed by E. P. Howitz at the Argonne National Laboratory, Chicago, IL. See also SREX. 

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