Actinides, determination

Actinide determinations in urine matrix using column separation automated in ion chromatographic instrument ICP-MS 60... 

Discussion of Actinide Ionization Potentials. The ionization potentials of actinides determined by laser techniques are given in Table IV together with values determined by surface ionization, appearance potential and semi-emperical methods. For uranium, all values are low compared with the values determined by laser techniques with the exception of the surface ionization value by Smith and Hertel.(z ) The spectroscopic values by Sugar jL were obtained from the 5f 7s - 5f 7s8s intervals interpolated from intervals known for the higher actinides. Except for Sugar s value, all the neptunium ionization potential values are low relative to the more accurate values determined by laser methods. The Rydberg series values are the preferred ionization potentials. 

DETERMINATION OE ACTINIDES DETERMINATION OE LOW-CONCENTRATION URINE URANIUM 235/238 ISOTOPE RATIOS... 

Liezers, M.,Tye, C. T., Mennie, D., and Koller, D. (1995). Ultra-low level (pg/L) actinide determinations and superior isotope ratio precisions by quadrupole ICP-MS. ASTM Spec.Tech. Pub.,p. 61. 

The reduction potentials for the actinide elements ate shown in Figure 5 (12—14,17,20). These ate formal potentials, defined as the measured potentials corrected to unit concentration of the substances entering into the reactions they ate based on the hydrogen-ion-hydrogen couple taken as zero volts no corrections ate made for activity coefficients. The measured potentials were estabhshed by cell, equihbrium, and heat of reaction determinations. The potentials for acid solution were generally measured in 1 Af perchloric acid and for alkaline solution in 1 Af sodium hydroxide. Estimated values ate given in parentheses. 

The throwaway fuel cycle does not recover the energy values present ia the irradiated fuel. Instead, all of the long-Hved actinides are routed to the final waste repository along with the fission products. Whether or not this is a desirable alternative is determined largely by the scope of the evaluation study. For instance, when only the value of the recovered yellow cake and SWU equivalents are considered, the world market values for these commodities do not fully cover the cost of reprocessing (2). However, when costs attributable to the disposal of large quantities of actinides are considered, the classical fuel cycle has been the choice of virtually all countries except the United States. 

Electron Probe X-Ray Microanalysis (EPMA) is a spatially resolved, quantitative elemental analysis technique based on the generation of characteristic X rays by a focused beam of energetic electrons. EPMA is used to measure the concentrations of elements (beryllium to the actinides) at levels as low as 100 parts per million (ppm) and to determine lateral distributions by mapping. The modern EPMA instrument consists of several key components ... 

Relatively few thermodynamic studies have been performed on compounds involving Th, U and Pu with noble metals. Most of the previous work has involved electrochemical cell determinations of free energies of formation, hence little has been published concerning the sublimation behavior of actinide intermetallics. 

Equilibrium vapor pressures were measured in this study by means of a mass spectrometer/target collection apparatus. Analysis of the temperature dependence of the pressure of each intermetallic yielded heats and entropies of sublimation. Combination of these measured values with corresponding parameters for sublimation of elemental Pu enabled calculation of thermodynamic properties of formation of each condensed phase. Previ ly reported results on the subornation of the PuRu phase and the Pu-Pt and Pu-Ru systems are correlated with current research on the PuOs and Pulr compounds. Thermodynamic properties determined for these Pu-intermetallics are compared to analogous parameters of other actinide compounds in order to establish bonding trends and to test theoretical predictions. 

The techniques used in the work have generally been spectroscopic visible-uv for quantitative determinations of species concentrations and infrared-Raman for structural aspects of the polymer. Although the former has often been used in the study of plutonium systems, there has been considerably less usage made of the latter in the actinide hydrolysis mechanisms. 

Since the pond is easily accessible and shallow, scientists at ORNL performed several manipulative experiments with caissons to determine the effects of aerobic and anaerobic environments upon the speciation of actinide elements(9). 

A ferrite waste treatment process is being investigated to determine if it can more effectively remove actinides from waste solution with less solid waste generation than the flocculant precipitation method presently used (18). 

Alvarez A, Navarro N. 1996. Methods for actinides and Sr-90 determination in urine samples. Appl Radiat Isot 47 869-873. 

The overall distribution of lanthanides in bone may be influenced by the reactions between trivalent cations and bone surfaces. Bone surfaces accumulate many poorly utilized or excreted cations present in the circulation. The mechanisms of accumulation in bone may include reactions with bone mineral such as adsorption, ion exchange, and ionic bond formation (Neuman and Neuman, 1958) as well as the formation of complexes with proteins or other organic bone constituents (Taylor, 1972). The uptake of lanthanides and actinides by bone mineral appears to be independent of the ionic radius. Taylor et al. (1971) have shown that the in vitro uptakes on powdered bone ash of 241Am(III) (ionic radius 0.98 A) and of 239Pu(IV) (ionic radius 0.90 A) were 0.97 0.016 and 0.98 0.007, respectively. In vitro experiments by Foreman (1962) suggested that Pu(IV) accumulated on powdered bone or bone ash by adsorption, a relatively nonspecific reaction. On the other hand, reactions with organic bone constituents appear to depend on ionic radius. The complexes of the smaller Pu(IV) ion and any of the organic bone constituents tested thus far were more stable (as determined by gel filtration) than the complexes with Am(III) or Cm(III) (Taylor, 1972). 

Livingston and Cochran [50] collected large seawater samples by using a cable-supported electrical pumping system for subsequent determination of thorium, americium, and plutonium isotopes. Particles were removed by filtration and actinides were collected by absorption on manganese dioxide-coated filters. The samples were then analysed by standard radiochemical and a spec-trometric techniques. 

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. 

ICP-MS may be applied to the determination of elements across the whole of the periodic table from lithium to the actinides. With certain exceptions, limits of detection are of the same order or better than those for graphite fumace-AA or ICP-AES. Table 8.4 makes a comprehensive comparison. 

The third category is the high coordination number lanthanides and actinides. The trivalent lanthanides show a decrease in with the progressive filling of the 4f orbitals, called the lanthanide contraction. Since the 4f orbitals are shielded by the filled 5s and 5p orbitals, the electronic configuration has no remarkable effect and therefore the variation in rM and an eventual change in coordination number and geometry determine the lability of the 1st coordination shell. 

Technician Velma Montoya, of the Actinide Analytical Chemistry Group at Los Alamos, works in a silica-free glove box to determine silicon content in plutonium samples using visible (near infrared) spectrophotometry. 

Lisa Townsend, a technician in the Radiochemistry section of the Actinide Analytical Chemistry Group, analyzes bulk components and impurities in plutonium-238 materials used to fabricate heat sources used in space exploration. She utilizes a combination of ion exchange and solvent extraction techniques and determines component concentrations using alpha and gamma radio-counting instrumentation. 

---