Radionuclides in ground waters from observation holes in the Shelter local area

The volume activity of ³H, ⁹⁰Sr, ¹³⁷Cs, ²³⁴U, ²³⁵U, ²³⁸U, ²³⁸Pu, ^239+240Pu, and ²⁴¹Am in ground waters from observation holes 1-G-6-G in the north section of the Shelter local area of the Chernobyl Nuclear Power Plant (CNPP) was measured. The distribution of radionuclides in the suspension fractions of the ground waters was evaluated. The main contribution to the pollution of ground waters with uranium is due to natural uranium isotopes: ^234,235,238U. The activity ratios of ²³⁸Pu, ^239+240Pu, and ²⁴¹Am in ground waters are similar to those in the spent fuel of 4th CNPP block.     

Complexation and Disproportionation of Np(V) in K10P2W17O61 Solutions

Complexation of NpO₂ ⁺ and NpO₂ ^{2 +} with unsaturated K _n P₂W₁₇O₆₁ ^{n - 1 0} (L ^x-) heteropolyanion and disproportionation of Np(V) in the presence of L ^x- were studied spectrophotometrically. The logarithms (logK) of the formation constants of NpO₂ ^VL and NpO₂ ^{V I}L are 3 and 7, respectively. The K⁺ and Na⁺ cations bind the L ^x- anions, thus decreasing the yield of the complexes. Neptunium(V) disproportionation in K₁₀P₂W₁₇O₆₁ solutions containing 1 M (HClO₄ + NaClO₄) (pH from 0 to 4) and free from NaClO₄ (pH 2-6.5) was studied. The disproportionation rate is described by the equation -d[Np(V)]/dt = k[Np(V)][L ^x-]. The pH dependence of the rate constant passes through a maximum at pH 1. The rate constant decreases with increasing [Na⁺]. The reaction is inhibited by its product, Np(IV). The Np(V) complex is not involved in disproportionation; the reactive species is NpO₂ ⁺ aqua ion, which is probably converted into NpO^{3 +}L ^x-. Then NpO^{3 +}L ^x- rapidly reacts with NpO₂ ⁺, which occurs simultaneously with, or is preceded by release of the second oxygen atom.     

Spatial distribution of radionuclides produced in copper by photonuclear spallation reactions

The spatial distribution of radionuclides produced in a 15 cm thick copper target, which is commonly used as accelerator material, was measured by bombarding the bremsstrahlung radiation generated by 900 MeV electrons. The production of radionuclides of ⁶⁴Cu, ⁶¹Cu, ⁶⁰Cu, ⁵⁸Co, ⁵⁷Co, ⁵⁵Co, ⁵⁶Mn, ⁵²Mn, ⁴⁸Sc, ⁴⁷Sc,and ^44mSc was clearly identified up to about 10 cm in depth. The spatial distribution of bremsstrahlung radiation in copper was also calculated by the electromagnetic cascade Monte Carlo code, EGS-4. By comparing the experimental data and the calculated results, the effective cross sections and the effective energy ranges were derived for ⁶⁵Cu(γ,n)⁶⁴Cu, ⁶³Cu(γ,2n)⁶¹Cu, ⁶³Cu(γ,3n)⁶⁰Cu and other photonuclear spallation reactions.     

Ion probe technique for the study of gallium diffusion in silicon nitride films

The penetration of Ga in films of amorphous Si₃N₄ about 2000 Å thick on Si substrates has been studied. The films were produced by pyrolysis. Diffusion profiles were obtained by surface exposure to Ga vapor, and the implantation profiles by ion bombardment in an isotope separator. Evaluation of the profiles was effected by means of sputtering in a secondary ion microanalyzer. For depth calibration, ion yield profiles of ⁶⁹Ga⁺ of ⁷¹Ga⁺ were compared with the profiles of ³⁰Si⁺, ⁷⁰(Si₂N⁺, SiN⁺₃) and ⁷²Si₂O⁺. The integration of implantation peaks furnished a means of obtaining absolute values of Ga concentrations from the secondary ion intensities. Hence the surface concentration of vapor-deposited Ga at 1100°C was assessed to be of the order of 8 × 10²⁰ atoms cm^-3. The diffusion coefficient of Ga in Si₃N₄ at 1100°C was found to be about 5 × 10^-17 cm² s^-1. The method, which combines sputtering and mass spectrometry, appears to be applicable for measuring diffusion coefficients in this system down to about 3 × 10^-18 cm² s^-1.     

Extraction of microamounts of Eu and Am into nitrobenzene using a synergistic mixture of chlorinated hydrogen dicarbollylcobaltate and <Emphasis Type="Italic">N,N′</Emphasis>-diethyl-<Emphasis Type="Italic">N,N′</Emphasis>-diphenyl-2,6-dipicolinamide

Extraction of microamounts of Eu and Am with a nitrobenzene solution of chlorinated hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of N,N′-diethyl-N,N′-diphenyl-2,6-dipicolinamide (EtPhDPA, L) was studied. The equilibrium data were interpreted assuming that the complexes HL⁺, HL₂⁺, ML₂³⁺, ML₃³⁺, and ML^4/3+ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The extraction and stability constants of the species in water-saturated nitrobenzene were determined. The stability constants of the related complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2, 3, 4, in this medium are comparable.     

Leaching of radionuclides from products of underground nuclear explosions in granite: Experiments with radioactive samples of melted rock from explosion cavities on Semipalatinsk test site

Leaching of ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu from products of underground nuclear explosions in tunnels 504R, 148/5, and 190 of the Semipalatinsk test site was studied. Samples were taken from central zones of the explosions. Sample characteristics are presented. Leaching experiments were performed in the batch and dynamic modes. The degrees and rates of ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu leaching with granite aqueous extract were determined. The leach rates determined in batch experiments are in the following ranges: ⁹⁰Sr 2.3 × 10^?6?1.6 × 10^?4, ¹³⁷Cs 5.0 × 10^?6?2.5 × 10^?4, and ^239+240Pu 5.6 × 10^?7?2.1 × 10^?4 g cm^?2 day^?1, and those determined in dynamic experiments are in the following ranges: ⁹⁰Sr 9.2 × 10^?10?10^?8, ¹³⁷Cs 1.0 × 10^?9?1.6 × 10^?7, and ^239+240Pu 1.3 × 10^?11?2.5 × 10^?11 g cm^?2 day^?1. The values obtained are close to those reported in the literature for vitrified radioactive wastes.     

Effect of Site-Specific Parameters on the Transfer of 137Cs and 90Sr into Freshwater Fishes1,2

The content of ¹³⁷Cs in fallout, fish, and water was measured with the aim to study the role of site-specific parameters on the transfer of ¹³⁷Cs into fishes. The temporal changes of 137Cs and 90Sr in various types of fishes were studied at two sites of Lake Saimaa. The ¹³⁷Cs content in fishes in the Ukonvesi area, which is the north-western part of the lake, was clearly lower than that in the southern parts of the lake, in Ala-Saimaa, although the fallout of ¹³⁷Cs to the Ukonvesi area was somewhat higher than that to Ala-Saimaa. The fallout in 1986 was about 6 kBq m^{- 2} to the Ukonvesi area and about 3 kBq m^{- 2} to the southern parts of the lake. The ¹³⁷Cs content in fishes was the highest in 1988-1989 in Ala-Saimaa, approximately 700 Bq kg^{- 1}, while that in the Ukonvesi area was only about 300 Bq kg^{- 1}, where the values were the highest in 1987. In Ukonvesi the ¹³⁷Cs content in fishes decreased rapidly, being already in 1990 almost at the same level as in 2000. In the southern parts of the lake the decrease in the ¹³⁷Cs content in fishes was much slower. Also the ⁹⁰Sr content in fishes in Ukonvesi was lower than that in Ala-Saimaa. The ¹³⁷Cs content of the water in the Ukonvesi area decreased rapidly, being about 7 Bq m^{- 3} in 1998, while that in the lower areas of the lake was still 15 Bq m^{- 3} in 2000. The ⁹⁰Sr content in water was approximately the same at the both sampling sites (7-8 Bq m^{- 3}). The water chemical parameters, such as potassium, total phosphorus, total nitrogen, chlorophyll a, and electrical conductivity were significantly higher in Ukonvesi than in Ala-Saimaa.     

A Method for Determining the Isotope Composition of U, Pu, Am, and Cm in "Hot" Particles and Spent Nuclear Fuel

A method was proposed for determining the content of ^234-238U, ^238-242Pu, ^241-243Am, and ^242-244Cm in "hot" fuel particles and spent nuclear fuel. The method is based on high-precision measurement of the -activity in the sample and calculation of the relative contributions of individual nuclides or radionuclide groups to the total activity. Partitioning of U, Pu, Am, and Cm was carried out by ion-exchange chromatography. The contents of ²³⁴U, ²³⁶U, ²³⁸U, ²³⁸Pu, ^239+240Pu, ²⁴²Pu, ²⁴¹Am, ^242mAm, ²⁴³Am, ²⁴²Cm, and ²⁴⁴Cm in "hot" particles sampled in the Chernobyl area were reported. The applicability of the method proposed to determining the radionuclide composition of spent nuclear fuel was discussed.     

Cocrystallization of Radioiodine Compounds from the Gas Phase

The study of the behavior of ¹³⁷Cs¹³¹I in the presence of MCl (M = NH₄ ⁺, K⁺, Ag⁺, and Cu⁺) in the water vapor-gas phase showed that CsI aerosols are localized in the MCl matrix owing to both agglomeration cocrystallization [¹³⁷Cs¹³¹I-MCl systems (M = K⁺, Ag⁺, NH₄ ⁺)] and agglomeration capture [¹³⁷Cs¹³¹I-CuCl system]. The main advantage of the first process is formation of crystalline globules encapsulating radioiodine in their bulk, which prevents transformation of radioiodine into elemental iodine and methyl iodide.     

Speciation and behavior of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb in the riverine ecosystem of Cauvery,a major river of south India

The paper discusses the speciation and behavior of ²¹⁰Po and²¹⁰Pb in the soil and sediment samples in the Cauvery River environment. The samples were collected and the concentration of ²¹⁰Po and ²¹⁰Pb was measured using the standard radiochemical analytical method. The physicochemical parameters of the soil and sediment were studied to understand the dynamics of ²¹⁰Po and ²¹⁰Pb activity in the riverine environment. The dependence of the physicochemical parameters like clay and organic matter content on the speciation of ²¹⁰Po and ²¹⁰Pb in the riverine ecosystems were also studied. The mean activity of ²¹⁰Po and ²¹⁰Pb in soil was found to be 6.80 and 6.58 Bq kg^–1, respectively. The mean activity of ²¹⁰Po and ²¹⁰Pb in the sediment was found to be 3.30 and 6.34 Bq kg^–1, respectively. The activities of ²¹⁰Po and ²¹⁰Pb in both the soil and sediment are not in equilibrium. The activity concentrations of ²¹⁰Po and ²¹⁰Pb were correlated with the organic matter content in both the soil and sediment samples. Multivariate statistical analysis was used to confirm the interrelation between the physicochemical parameters and the activity of ²¹⁰Po and ²¹⁰Pb.     

The State of Disequilibrium between U and Th Series Isotopes in Marine Sediments from the Sudanese Red Sea Coast

The geochemical behavior of U, Th series nuclides in surface marine sediments collected fromthe Red Sea coastal environment of Sudan was examined using daughter/parent and nonisotopic activity ratios. Pronounced anomalous behavior of several series of nuclides has been observed, particularly at shallower depths. On the average, the ²³⁴U/²³⁸U ratio is fairly constant and close to 1.13, suggesting scavenging of ²³⁴U from the overlying water column. In shallow-water sediments collected from the biologically productive area of the fringing reef and from the tidal-flat of Sanganeb atoll, compared to harbor and deep-sea sediments, ²³⁸U was found in large excess relative to ²³²Th. The ²²⁸Th/²³²Th disequilibrium indicates rapid sedimentation at shallower sites, which agrees well with data reported in the literature for similar environments. Depletion was observed of precursor thorium isotopes (²³⁰Th, ²³²Th) with respect to their mobile daughter isotopes of radium (²²⁶Ra, ²²⁸Ra). On the other hand, there is surface enrichment of ²²⁸Th and ²¹⁰Po with respect to their progenitors ²²⁸Ra and ²²⁶Ra, as demonstrated by the ²²⁸Th : ²²⁸Ra and ²¹⁰Po : ²²⁶Ra activity ratio, which is greater than unity in all the sediments analyzed. The ²¹⁰Po/²²⁶Ra ratio is fairly constant (average 3.2).     

High-pressure investigations of positive ion-molecule reactions in a mixtureof H2S and CH4

The positive ion-molecule reactions in the mixtures of hydrogen sulfide and methane have been examined by means of quadrupole mass spectrometer with the high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. For each mixture major bimolecular ion-molecule reactions have been identified in the total pressure range from 0.7 to 33.3 Pa. The electron energy for all measurements was fixed at 300 eV and the repeller potential was maintained at 5 V. Relative intensities of ion currents for the observed ions C⁺, CH⁺, CH₂⁺, CH₃⁺, CH₄⁺, CH₅⁺, C₂H₃⁺, C₂H₄⁺, C₂H₅⁺, S⁺, HS⁺, H₂S⁺, H₃S⁺, H₃³⁴S⁺, CHS⁺, CH₃S⁺, S₂⁺, HS₂⁺ and H₂S₂⁺ were determined as a function of total gas pressure inside the ion source collision chamber, repeller potential and concentration of methane in the mixture.     

Orthorhombic electron spin resonance spectra of gadolinium ions in CdF2

The ESR spectra of Gd³⁺1bNa⁺ were measured in GdF₂ crystals, in which Na⁺ ions, compensating for the Gd³⁺ charge, occupy the nearest-neighbor Cd²⁺ sites. The b^m_n Hamiltonian constants were evaluated. The orthorhombic symmetry of neighborhood of the impurities was compared for the Na⁺-compensated Gd³⁺1bNa, and the O^2?-compensated Gd³⁺1bGd³⁺ impurities.     

Speciation of artificial radionuclides 60Co, 137Cs, 152Eu, and 241Am in bottom sediments of the Yenisei river

The speciation of artificial radionuclides ⁶⁰Co, ¹³⁷Cs, ¹⁵²Eu, and ²⁴¹Am in surface layers of bottom sediments of the Yenisei river, collected within the near zone of impact of the Mining and Chemical Combine (Rosatom), was studied. In these samples the radionuclides ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am are mainly associated with fractions of humic and fulvic acids. The fraction of ¹⁵²Eu associated with nonsilicate iron is approximately 92%. The migration capability of radionuclides collected near the Atamanovo settlement decreases in the order ¹⁵²Eu > ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. For samples collected near Bol’shoi Balchug settlement, this order is as follows: ¹⁵²Eu ≈ ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. The presence of radionuclide-bearing micro-particles in bottom sediments considerably complicates the distribution of radionuclides, in particular, of ²⁴¹Am and ¹³⁷Cs, among migration forms.     

Behavior of Trace Amounts of Cd and Zn in Sorption and Coprecipitation in Tetrahydrofuran Solutions

Sorption of trace amounts of ¹⁰⁹Cd and ⁶⁵Zn on zeolites NaX and NaA in the presence of divalent lanthanides Ln²⁺ (Ln = Tm, Dy, Nd) from tetrahydrofuran (THF) solutions is studied. In contrast to ¹³⁷Cs⁺ and similar to ⁸⁵Sr²⁺, trace amounts of ¹⁰⁹Cd and ⁶⁵Zn are not practically sorbed on zeolites (about 99% of these radionuclides remains in the solution). The distribution coefficients K _d of ¹⁰⁹Cd and ⁶⁵Zn are ∼0.3 and ∼0.4 ml g⁻¹, respectively. In THF solutions, Tm²⁺ is oxidized to Tm³⁺, and TmI₃ ⋅ 3THF is precipitated. Study of cocrystallization of trace amounts of ¹⁰⁹Cd and ⁶⁵Zn and also of ⁸⁵Sr with this precipitate from THF solutions containing Tm²⁺ revealed that, in contrast to ⁸⁵Sr²⁺, ¹⁰⁹Cd and ⁶⁵Zn traces cocrystallize with the solid solvate phase. The cocrystallization coefficients D of ¹⁰⁹Cd and ⁶⁵Zn increase with increasing Tm³⁺/Tm²⁺ ratio in the solution. The mechanism suggested is that, in the presence of Tm²⁺, ¹⁰⁹Cd²⁺ and ⁶⁵Zn²⁺ are reduced to single-charged cations M⁺, which then rapidly react with the double-charged cations M²⁺ with the formation of dimers M ₂ ³⁺ (M = Cd, Zn).__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 261–264.Original Russian Text Copyright © 2005 by Veleshko, Kulyukhin.     

Redox ratio and optical absorption of polyvalent ions in industrial glasses

The changes in glass structure and redox ratio, R (reduced ion to oxidized ion) of Mn²⁺-Mn³⁺, Cu⁺-Cu²⁺, Cr³⁺-Cr⁶⁺, Ni²⁺-Ni³⁺ and Co²⁺-Co³⁺ couples and optical absorption due to Mn³⁺, Cu²⁺, Cr³⁺, Ni²⁺ and Co²⁺ ions in industrial soda-lime-silica glass were investigated as a function of Na₂O concentration in the range 11–19 mol%. With increasing Na₂O concentration in the experimental glasses, the basicity, expressed as calculated basicity, Λ_cal, increased. ²⁹Si NMR and X-ray diffraction were used to investigate the structural change in glasses. The NMR spectra showed high non-bridging oxygens (NBOs) when the basicity of glass was increased. The results were interpreted to be due to the tetrahedral networks; Q ⁴ species were depolymerized by replacing the bridging oxygens (BOs) with NBOs to Q ³ species. These results confirmed the shift of broadening peaks of XRD patterns. The redox reactions of the Mn²⁺-Mn³⁺, Cu⁺-Cu²⁺ and Cr³⁺-Cr⁶⁺ couples shifted more toward their oxidized ions due to the oxygen partial pressure, p(O₂), during melting and the oxide ion activity, a _O2−, increased with increasing glass basicity. These changes caused the redox ratio of these ion couples to decrease. The Ni²⁺-Ni³⁺ and Co²⁺-Co³⁺ couples were assumed to be present only in the Ni²⁺ and Co²⁺ ions in these glasses, respectively. The optical absorption bands due to Mn³⁺, Cu²⁺, Cr³⁺, Ni²⁺ and Co²⁺ ions were also investigated. Their spectra occurred at constant wavelengths with different optical densities or intensities as a function of glass basicity. The increase in the intensities of the absorption bands of these absorbing ions, except for Cr³⁺ ion, at the maximum wavelength, depends not only on the ion concentration but also on the increase of polarizability of oxide (−II) species, α _oxide(−II), surrounding the ions. This value affected directly the extinction coefficients of the ions, ɛ _ion. The increase of ɛ _ion caused the colour of glasses appearing in high intensity. In the case of Cr³⁺ ion, the results were reversed such that the lower the concentration, the higher the intensities of colour.     

16O contamination in 4He analysis beams

The ⁴He⁺ beam from a Van de Graaff accelerator is often accompanied by an ¹⁶O⁺ beam of the same energy. If, after acceleration and before magnetic analysis, one electron is stripped from the oxygen ion to form ¹⁶O²⁺, these ions will not be separated from ⁴He⁺ during magnetic analysis. The ¹⁶O²⁺ fraction in the ⁴He⁺ beam was measured by analyzing back-scattering spectra for a thin Au film and the O to He ion charge ratio of 2:1 was confirmed by electrostatic deflection. Ion source conditions and the pressure in the beam lines strongly affect the ¹⁶O²⁺ fraction and the dependence of the O²⁺/O⁺ ratio on pressure is found to be in approximate agreement with predicted values. A formula for estimating the ¹⁶O²⁺ beam intensity, based on charge exchange data and measurement of the primary ¹⁶O⁺ beam intensity, is N[O²⁺] = 13 P(torr) l(cm) N[O⁺], where P is the total gas pressure, l the length of the beam line between the accelerator and switching magnet and N[O²⁺] and N[O⁺] are the beam intensities of the respective species. The ¹⁶O²⁺ contamination of ⁴He⁺ beams is easily removed by electrostatic separation.     

The luminescence of bismuth and manganese in LaMgB5O10

The luminescences of Bi³⁺ and Mn²⁺ in LaMgB₅O₁₀ are reported. The emission of the Bi₃₊ ion shows a small Stokes shift and is situated in the ultraviolet. From the decay times the ³P₀ and ³P₁ levels appear to be mixed. At 4.2 K no energy transfer between Bi³⁺ ions occurs, but at room temperature the critical distance for this energy transfer amounts to some 25 Å. This knowledge is used to explain energy transfer between Bi³⁺ and Tb³⁺ in LaMgB₅O₁₀, which is compared with that between Ce³⁺ and Tb³⁺ in the same lattice. The Mn²⁺ ion shows a red emission in LaMgB₅O₁₀. The Bi₃₊ ion acts as a sensitizer for this emission, whereas the Ce³⁺ ion does not.     

Geochemistry of the upper Han River basin, China: 2: Seasonal variations in major ion compositions and contribution of precipitation chemistry to the dissolved load

A total of 252 water samples were collected from 42 sites across the upper Han River basin during the time period from 2005–2006. Major ions (Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, Na⁺, K⁺, Ca²⁺ and Mg²⁺), Si, water temperature, pH, EC and TDS were determined and consequently correlation matrix, analysis of variance, factor analysis and principal component analysis were performed in order to identify their seasonal variations and atmospheric inputs into river solutes. The results reveal that pH, EC, TDS, Cl⁻, SO₄²⁻, HCO₃⁻, Ca²⁺ and Mg²⁺, K⁺ and Si generally tend to show the minimum compositions in months belong to the rainy season, while the dry season for NO₃⁻ and Na⁺. NO₃⁻, Mg²⁺ and Si have the maximum concentrations in months belong to the rainy season. By comparing the major ions relating to hydrological regime, NO₃⁻, contrary to other elements, has higher concentration in the rainy season. The overall water quality is non-polluted, while there are indications of enrichment of inorganic anions including NO₃⁻ causing water entrophication in the near future. The atmospheric inputs contribute to river solutes is limited with a mean inputs of approximate 1% in the basin. The understanding of the major ion dynamics would help water quality conservation in the basin for China's interbasin water transfer project.     

Energy transfer phenomena in GdMgB5O10

The luminescence of Mn²⁺, Bi³⁺, Ce³⁺ and Tb³⁺ in GdMgB₅O₁₀ and some codoped materials is reported. Energy transfer rates are derived from the experiments. The Bi³⁺ → Gd³⁺ and Gd³⁺ → Bi³⁺ transfer rates are about equal at room temperature. The excitation energy is able to migrate among the Gd³⁺ sublattice. The Ce³⁺ ion is a good sensitizer for this sublattice. By diluting the Gd³⁺ sublattice with La³⁺ ions, the energy migration in Gd³⁺ zig-zag chains was blocked and interchain energy transfer occurred. Very efficient phosphors can be obtained by using Ce³⁺ as a sensitizer, the Gd³⁺ sublattice as an intermediary and Tb³⁺ as an activator.