Neptunium determination

ICP-MS (inductively coupled plasma mass spectrometry) is frequently used for determining ultratrace amounts of technetium [9]. In spite of the high cost of the equipment, this detection method is far superior to other radiometric methods as regards sensitivity. When a double focussing high-resolution system is used (HR-ICP-MS) and an ultrasonic nebulizer is introduced [10], the detection limit is in the order 0.002 mBq. The ICP-MS method has been successfully applied to the determination of environmental "Tc as well as to other long-lived radionuclides of neptunium and plutonium in the environment. 

Holm et al. [74] used a spectrometry for the determination of 237neptunium in seawater. The actinides are preconcentrated from a large seawater sample by hydroxide precipitation. The neptunium was isolated by ion exchange, fluoride precipitation, and extraction with TTA. 238Neptunium or 235neptunium was used to determine the radiochemical yield. 

Neptunium has been characterized from the +3 to +7 oxidation states in aqueous solution. The standard potentials for various Np ions have been determined from measured formal potentials of the various redox couples. These data have been thoroughly reviewed by Martinet [94] and Fahey [95]. Recently the standard potentials for the redox couples Np02 /Np02, Np +/Np +, and Np02 /Np" in acidic aqueous solution have been reevaluated with more detailed consideration of activity coefficients [49,50]. The standard potential accepted here for the Np02 /Np02 couple is 1.161 0.011 V as determined from... 

Barrero Moreno et al.49 determined neptunium and plutonium in the presence of high concentrations of uranium by ion chromatography coupled to ICP-MS. 

Uranium. Perricos and Belkas (25) have determined uranium in six coals by neutron activation followed by separation of the uranium daughter neptunium-239 by carrier-free extraction chromatography. The coals, from mines in northern Greece, had very high uranium concentrations (0.012-0.037%). However, uranium at the few parts per million level found in most coals could no doubt be determined by a modification of this method. 

A single oxo bridge may subtend an angle between 140° and 180°, this angle being determined by steric or electronic factors (Table 3).95 103 Almost all these examples refer to the solid state, but there are also several homo- and hetero-nuclear M—O—M and M—O—M—O—M species known in solution. Often these are intermediates in, or products of, electron transfer reactions with oxide-bridging inner-sphere mechanisms. Examples include V—O—V in V(aq)2+ reduction of VO(aq)2+, and Act—O—Cr in Cr(aq)2+ reduction of UOj+ or PuOj+ a useful and extensive list of such species has been compiled. Tlie most recent examples are another V—O—V unit, this time from VO(aq)2+ and VOJ,105 and an all-actinide species containing neptunium(VI) and uranium-(VI).106 An example of a trinuclear anion of this type, with the metal in two oxidation states, is provided by (31).107... 

Neptunium-237 undergoes an a, p, a, a, p, a, a, a, p, a, p sequence of radioactive decays. Determine the daughter nuclide after each decay and write a balanced nuclear equation for each step. 

The oxidation-reduction behaviors of neptunium, plutonium and americium in basic solution have been determined via polarographic and coulometric studies (6-9). These studies, which showed that the more soluble (V), (VI), and (VII) oxidation states of these actinides are stable in alkaline solution under certain redox conditions, helped identify possible actinide species and oxidation states in our experiments. Actual identification of radioelement oxidation states was not done in the present experiments. 

In this study, the effects of 12 Hanford waste solution components on the solubility of cobalt, strontium, neptunium, plutonium, and americium were determined. Also determined were the effects of the 12 components on the sorption of 5 radioelements on 3 representative Hanford sediments. A number of general observations were drawn from these studies. 

Foti, S. C. Freiling, E. C., "The Determination of the Oxidation States of Tracer Uranium, Neptunium, and Plutonium in Aqueous Media." Talanta 1964 11, 384-392. 

Table VI shows the concentrations of plutonium, neptunium, and uranium measured at the inlet and outlet of the unaltered and hydrothermally-altered basalt core fissures in the first five analog experiments (see Table I) Under conditions simulating a repository that was unaltered by groundwater interaction (Table I, Exp 1-3), both Np and Pu, in the concentrations developed in these analog experiments from the leaching of the waste form, were substantially retarded within the 14.6-cm basalt fissure In fact, as can be seen from Figure 4, almost all of Np activity was sorbed on the first one-third of the rock fissure The data in Figure 4 have an estimated error, based on counting statistics above, of approximately 2 counts per 1000 seconds Uranium retardation was determined to be not as complete ...

By filtering groundwater samples from the first and second vessel outlets through 0 1 14m filters, it was determined that the neptunium was in a soluble form, and that most of the plutonium was associated with filterable bentonite particles... 

Foti, S.C. and Freiling, E.C. (1964) The determination of the oxidation states of tracer uranium, neptunium and plutonium in aqueous media. Talanta, 11, 385-392. 

Inoue, U. and Tochiyama, O. (1977) Determination of the oxidation states of neptunium at tracer concentrations by adsorption on silica gel and barium sulphate./. Inorg. Nucl. Chem., 39, 1443-1447. 

Sill CW, Willis CP. 1966. Determination of radioisotopes of cerium, barium, lanthanum, and neptunium after separation by barium sulfate. Anal Chem 38 97-102. 

Of special interest in the mass spectrometric determination of transuranium elements is the characterization of microparticles stemming from different radioactivity release scenarios. Such microparticles bearing radionuchdes, in particular uranium, plutonium, neptunium and americium, can enter the environment and therefore the human food chain through different processes which can be related to the nuclear fuel cycle as well as to clandestine nuclear activities. In addition, nuclear safeguards programmes seek to determine the uranium isotope abundances of individual p,m sized particles. Anomalous amounts of or may indicate that artificial isotope enrichment... 

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