Transuranic nuclides

Kharkar DP, Thomson J, Turekian KK, Forster WO (1976) Uranium and thorium series nuclides in plankton from the Caribbean. Limnol Oceanogr 21 294-299 Krishnaswami S, Lai D, Somayajulu BLK, Weiss R, Craig H (1976) Large-volume in situ filtration of deep Pacific waters mineralogical and radioisotope studies. Earth Planet Sci Lett 32 420-429 Livingston HD, Cochran JK (1987) Determination of transuranic and thorium isotopes in ocean water in solution and in filterable particles. J Radioanal Nucl Chem 115 299-308 Masque P, Sanchez-Cabeza JA, Braach JM, Palacios E, Canals M (2002) Balance and residence times of °Pb and 4 o in surface waters of the northwestern Mediterranean Sea. Cont Shelf Res 22 2127-2146 Matsumoto E (1975) Th-234-U-238 radioactive disequilibrium in the surface layer of the oceans. Geochim Cosmochim Acta 39 205-212... 

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. 

The modes of formation and radioactive properties of some of the principal transuranic nuclides are presented in Table 1. 

An outstanding feature of inorganic mass spectrometry is its determination of precise and accurate isotopic abundances and isotope ratios. Isotopes of the same element (of the same number of protons or atomic number of element, Z) are, by definition, nuclides with different mass m and mass number A (A = Z + N) due to the different number of neutrons (N) in the nucleus. Isotope analyses are of special interest for characterizing the composition of samples with respect to stable and unstable isotopes in quite different concentration ranges - from the analysis of matrix elements down to the trace and ultratrace concentration level.1-9 Of 1700 isotopes, nearly 16 % (264 isotopes) are stable. The chemical elements Tc, Pm, Th, U and the transuranic elements do not possess stable isotopes. 

Different radionuclides have different chemistry, so it seems reasonable to include each nuclide in a specific matrix that is most stable for the desired nuclide. It is possible to find stable matrices for incorporation of numerous nuclides with similar chemical properties. The target elements for such incorporation are the long-lived radionuclides (transuranic elements), 90Sr, 137Cs, and Tc. Many extraction processes have been proposed for radionuclide removal from radioactive wastes. Typically, the goal of the processes is to extract one radionuclide or multiple radionuclides... 

Bennett, B.G. (1976) Transuranic element pathways to man. In Transuranic Nuclides in the Environment. Vienna IAEA, pp. 367-82. 

Edgington, D.N., Alberts, J.J., Wahlgren, MA., Martunnen, J.O. and Reeve, C.A. (1976) Plutonium and americium in Lake Michigan sediments. In Transuranic Nuclides in the Environments. IAEA, Vienna, pp. 493-516. 

The constant C was initially calculated for the nuclide zqzPu based on the first major resonance at 259 kJ/mol (2.68 eV) (12). For some nuclides, values of C were assumed based on the peak absorption cross section in the major resonance. Others were assumed based on proportionality to the resonance integral (which can be measured empirically without knowing the detailed energy-dependent spectrum). Then, these assumed values for C and also < 2200 were adJusted by trial and error procedures to produce reasonable agreement with experimentally determined tranmutation reactions. Table I shows values presently in use for the parameters 02200 and for both capture and fission for the transuranic nuclides considered in this program. 

Modifications to this process can be made to effect recovery of neptunium, americium, curium, californium, strontium, cesium, technetium, and other nuclides. The efficient production of specific transuranic products requires consideration of the irradiation cycle in the reactor and separation of intermediate products for further irradiation. 

Alpha-bearing wastes (also called transuranic, plutonium-contaminated material, or alpha wastes) include wastes that are contaminated with enough long-lived, alpha-emitting nuclides to make near-surface disposal unacceptable. They arise principally from spent fuel reprocessing and mixed-oxide fuel fabrication. The wastes may he disposed of in a similar manner to HLW. 

The majority of the longer-lived transuranic nuclides produced by neutron capture reactions decay primarily by a-emission. Most environmental samples contain radionuclides from the natural uranium and thorium series in concentrations often many times greater than transuranic concentrations. As a result, the chemical problems encountered in these measurements are derived from the requirement that separated trans-uranics should be free of a-emitting natural-series nuclides which would constitute a-spectrometric interferences. Table I lists those transuranic nuclides detected to date in marine environmental samples, together with some relevant nuclear properties. Their relative concentrations (on an activity basis) are indicated although the ratios may be altered by environmental fractionation processes which enrich and deplete the relative concentrations of the various transuranic elements. Alpha spectrometric measurements do not distinguish between 239p Pu, so these are... 

Most of the procedures for analysis of transuranic nuclides in seawater and marine sediments have been described in detail elsewhere both by our laboratory and those of other workers. A full discussion of these various procedures is found in a comprehensive state-of-the-art review of techniques proposed for the analyses of transuranic elements in the marine environment (4). Here we concentrate on the procedures used at the Woods Hole Oceanographic Institution, the problems encoim-tered, and what is being learned from the data. 

Table I. Transuranic Nuclides Measurable in Marine Environmental Samples...

The extraction of transuranic elements has been made by co-precipi-tation in several ways (5,6). We use either one of two methods, depending on what other nuclides are also sought in the sample. The first method is co-precipitation with 0.5-1.0 g iron as hydroxide at pH 9-10 using ammonium hydroxide while the second method is co-precipitation with calcium and strontium oxalate at pH 5-6 using oxalic acid. There are about 22 g calcium and 0.44 g strontium in 55 1. of open-ocean seawater. Because Sr is usually measured in the same seawater sample, we normally add 2 g strontium to that which is naturally present. 

Intra-transuranic element separation is made where resolution of the various nuclides being measured is not possible by a-spectrometry alone. 

Sr increase in deeper samples. This is consistent with our belief that the transuranic nuclides sink more rapidly than Sr and in association with sinking particles (12). 

Table VI shows the distribution of Pu, Tu, 239,24op j d within a sediment core collected several hundred miles northwest of the British Isles. Concentration profiles of plutonium and americium nuclides are rather similar in shape. The transuranic concentrations found in this sediment were surprisingly high. The high concentrations are believed to result from deposition of these nuclides from advected water carrying these nuclides from another area, rather than from the direct vertical transport of sinking particles.

One of the requirements of any nuclear facility is to monitor the effluent uxiste water to show compliance with existing standards. This paper describes a sequential procedure for the separation of the transuranic elements from water samples up to 60 1. The elements of interest are coprecipitated with calcium fluoride and then individually separated using a combination of ion exchange and solvent extraction, with a final sample preparation by electrodeposition. Alpha spectrometry of these samples allows the measurement of neptunium, plutonium, and transplutonium nuclides at sub-fCi/l, levels. 

The procedure involves the coprecipitation of the transuranic nuclides on calcium fluoride from acid solution after reduction of the plutonium and neptunium with bisulfite. The calcium fluoride precipitate is dissolved in aluminum nitrate-nitric acid solution and the plutonium and neptunium separated on an ion-exchange resin column. The column... 

The first transuranic element was produced in 1940. Neptunium (Z = 93) results from the capture of a neutron by U, followed by beta decay. Subsequent work by the American chemist Glenn Seaborg and others led to the production of plutonium (Z = 94) and heavier elements. In recent years, nuclides with Z as high as 116 have been made, but in tiny quantities. These nuclides have very short half-lives. 

Sanchez AL, Singleton DL. 1996. A radioanalytical scheme for determining transuranic nuclides and 90Sr in environmental samples. J Radioanal Nucl Chem 209(l) 41-50. 

The initiated radioactive inventory for spent reactor fuel consists of actinides, fission products and activation products. As noted previously, (Gi. 21) the shorter lived fission products, such as Sr and Cs, and transuranic elements, such as Pu, Pu, are the main contributors to the radioactivity. However, performance assessments strongly indicate that the waste form matrix and the near field engineered barriers (e.g. clay backfill, etc.), can successfully retain and prevent any migration to the far field viromnent for one thousand years and probably much longer (> lO years). After the first thousand years the long lived nuclides such as Cs, Sn, Tc and Se among the fission products and the actinides Np, Pu, Pu, and Am become the major concern. 

Bennett B. 1976b. Transuranic element pathways to man. IAEA-SM-199/40. In Transuranium nuclides in the environment. Vienna International Atomic Energy Agency, 367-383. 

Plutonium and other alpha-emitting and transuranic nuclides with half-lives greater than 1 year <0.5 millicuries... 

Waste after processing irradiated targets containing transuranic nuclides... 

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