Purification and separation of <Superscript>239+240</Superscript>Pu and <Superscript>241</Superscript>Am in biological samples by anion-exchange and extraction chromatography for high resolution alpha-spectrometry analyses

Many biological samples (urines and faeces) have been analyzed by means of chromatographic extraction columns, utilizing two different resins (AG 1-X2 resin chloride and TRU), in order to detect the possible internal contamination of ^239+240Pu and ²⁴¹Am for some workers of a reprocessing nuclear plant in the decommissioning phase. The results obtained show on one hand the great suitability of the first resin for the determination of plutonium, and on the other, the great selectivity of the second one for the determination of americium.     

A practical method for monitoring <Superscript>129</Superscript>I concentration in airborne release

Summary To establish a practical method for monitoring ¹²⁹I concentration in airborne release from the Tokai reprocessing plant, the ¹²⁹I collecting performance of sampling media used was tested by in situ experiments. The results indicated that the combined use of an activated charcoal-impregnated filter paper and an activated charcoal cartridge gives a collection efficiency of more than 90% for a one-week sampling of real airborne effluent, at sampling flow rates of 40.6-75.0 l^. min^-1. The sampling and measurement conditions suitable for a routine-base monitoring are demonstrated.     

Determination of <Superscript>99</Superscript>Tc in environmental samples and depleted uranium penetrators using ICP-MS

A new method was developed for the determination of ⁹⁹technetium (Tc) by ICP-MS. We report, for the first time, an activity of ⁹⁹Tc for the reference material IAEA-315. For the IAEA-375, IAEA-373 and IAEA-381, our results confirmed the values already reported in the literature. The developed method was used for analysing sediments from the Yenisei river (collected downstream of a nuclear fuel reprocessing plant) and for characterizing corrosion products of depleted uranium penetrators that were fired during the Balkan conflict.     

Half-life measurement of <Superscript>126</Superscript>Sn isolated from Hanford nuclear defense waste

Summary Long-term risk assessment of residual and disposed nuclear fuel reprocessing waste requires good knowledge of component isotopes with long half-lives. For example, the accuracy of the accepted ¹²⁶Sn half-life of approximately 100,000 years is insufficient for desired risk assessments. From modeling and sampling, ¹²⁶Sn is known to exist in Hanford nuclear waste. Excess portions of waste characterization samples were used to isolate ¹²⁶Sn for measurement of its half-life. Isolation was performed with ion-exchange resins. The resulting ¹²⁶Sn was gamma-assayed with a hyperpure germanium spectrometer for decay photon identification and activity values. An inductively coupled plasma/mass spectrometer was used to measure the atom quantity of the isolated ¹²⁶Sn. The separation chemistry, observed gamma energies, and calculated half-life are presented. The half-life of ¹²⁶Sn estimated in this work is (2.33±0.10) ^. 10⁵ years.     

Effects of La<Superscript>3+</Superscript> on inward K<Superscript>+</Superscript> channels at plasma membrane in guard cells

The effects of La³⁺ on inward K⁺ channels at plasma membrane in vicia guard cells are investigated using the whole-cell patch-clamp recording mode. It is shown that La³⁺ on both sides of plasma membrane blocks inward K⁺ currents in a concentration-dependent manner, indicating that La³⁺ binding sites may exist on both sides of plasma membrane in guard cells in vicia. The dose response is fitted by the Michaelis-Menten relation characterized by an inhibitor constant K _i of 2.56±0.25 μmol · L⁻¹ (outside membrane) and (1.18±0.11)×10⁻¹⁵ mol · L⁻¹ (inside membrane). Intracellular La³⁺ has much stronger inhibitory effect on inward K⁺ currents than extracellular La³⁺ does, suggesting there may exist stronger binding sites inside membrane than outside membrane. Since ion channel activities of guard cells directly affect plant stomatal movement and water status, our results imply that rare earth elements might have potential practical values in regulating plant water status and strengthening plant drought endurance.     

Migration processes of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr in compartments of a lake ecosystem

Summary The dispersion of radioactive substances in the environment following nuclear weapon tests in atmosphere since 1954 and accidents to nuclear plants, like that in Chernobyl in 1986, have allowed us to study the migration processes of some radionuclides in complex ecosystems such as lakes are. In the present paper the behavior of ¹³⁷Cs and ⁹⁰Sr in different compartments of the Monterosi Lake (central Italy) was assessed. The ¹³⁷Cs concentration was measured in lake water as well as sediment, stream water, aquatic plant and fish samples. ⁹⁰Sr concentration in water and sediments was also determined. A total inventory of 4206±76 Bq ^. m^-2 and 958±79 Bq ^. m^-2 (on 27/6/01) has been found for ¹³⁷Cs and ⁹⁰Sr, respectively. The experimental data presented here allow to calibrate theoretical models predicting the temporal trend of radionuclide concentration in similar ecosystems. Moreover, information on cesium and strontium migration processes can be extended to other pollutants having similar environmental behavior.     

Thermodynamic behavior of complexation of 18-crown-6 with Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Zn<Superscript>2+</Superscript> metal cations in methanol-water binary media

The equilibrium constants and thermodynamic parameters for complex formation of 18-Crown-6 (18C6) with Tl⁺, Pb²⁺, Hg²⁺, and Zn²⁺ metal cations have been determined by conductivity measurements in methanol (MeOH)-water (H₂O) binary solutions. 18-Crown-6 forms 1:1 complexes with Hg²⁺ and Zn²⁺ cations, but in the case of Tl⁺ and Pb²⁺ cations, in addition to 1:1 stoichiometry, 1:2 (ML₂) complexes are formed in some binary solvents. The thermodynamic parameters (ΔH _c⁰ and ΔS _c⁰), which were obtained from the temperature dependences of equilibrium constants, show that in most cases the complexes are enthalpy destabilized but entropy stabilized. Non-linear behavior is observed between the equilibrium constants (log K _f ) of complexes and the composition of the mixed solvent. The selectivity of the ligand for these metal cations is sensitive to the solvent composition, and, in some cases, the selectivity order is reversed in certain compositions of the mixed solvent. The results also show that the mechanism of complexation reactions and the stoichiometry of complexes of some metal cations change with the nature and even with the composition of the mixed solvent. The article was submitted by the authors in English.     

Temporal and spatial variations of <Superscript>137</Superscript>Cs in the waters off a nuclear fuel reprocessing facility in Rokkasho,Aomori, Japan

Five survey cruises were carried out from 2004 to 2007 to determine ¹³⁷Cs concentrations in the water columns off Rokkasho Village, Aomori Prefecture, Japan, where the spent nuclear fuel reprocessing plant of Japan Nuclear Fuel Ltd has been undergoing test operation since March 2006. Seawater samples were collected with a large volume in situ filtration and concentration system at different depths in the water column. ¹³⁷Cs in particulate form could not be detected in the survey area. Dissolved ¹³⁷Cs showed temporal variation, especially in the surface water. Based on the results, it was concluded that no observable ¹³⁷Cs contamination was present in the investigated area. The distribution of ¹³⁷Cs concentrations was influenced by the mixing between the Tsugaru and Oyashio Currents.     

Adsorption of <Superscript>85</Superscript>Kr radioactive inert gas into hardening mixtures

Changes in volumetric activity of ⁸⁵Kr radioactive inert gas take place in the atmosphere: it has increased by around 50% during the past 15 years. The main source of such gas is the operation of nuclear power plants and spent nuclear fuel reprocessing plants. ⁸⁵Kr as an inert gas spreads throughout the entire atmosphere and its ionizing radiation may result in changes of atmospheric electric phenomena. Therefore it is necessary to control ⁸⁵Kr emission into the atmosphere. However, there is no effective method for this as inert gases, under normal conditions, can hardly be adsorbed in different adsorbents and stored in special containers for a long period of time. This paper tries to show the possibility of keeping ⁸⁵Kr longer within the adsorbent by changing its aggregate state: gas is adsorbed into liquid adsorbent and desorption takes place from solid adsorbent. For this purpose, an epoxy resin is used which, after adding a special hardener at room temperature, turns into a solid material with density of around 1.2 × 10³ kg m⁻³. As a result of sample blending with substances which contribute to better solubility of ⁸⁵Kr, diffusion coefficient of this gas (i.e. desorption speed) changes within the adsorbent in the solid state.     

Determination of <Superscript>237</Superscript>Np, <Superscript>93</Superscript>Zr and other long-lived radionuclides in medium and low level radioactive waste samples

The majority of long-lived radionuclides produced in the nuclear fuel cycle can be regarded as “difficult-to-measure” nuclides, hence chemical separation is needed before the nuclear measurement of them. A combined radiochemical procedure that enables the simultaneous determination of some “difficult-to-measure” nuclides in medium and low level radioactive wastes has been developed in our laboratory. Recently, this method has been extended for determination of ²³⁷Np and ⁹³Zr. ²³⁷Np and ⁹³Zr are pre-concentrated by co-precipitation on iron(II) hydroxide and zirconium oxide, separated by extraction chromatography using UTEVA, and measured by inductively coupled plasma mass spectrometry (ICP-MS). As even traces of polyatomic ions and isotopes at m/z 237 or 93 cause considerable interferences during ICP-MS detection, a purification step by extraction chromatography was needed. Analyzing real samples (evaporation concentrates of a nuclear power plant) 66–99% and 31–99% chemical yields were achieved for Np and Zr, respectively.     

Measuring <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K and decay products of <Superscript>226</Superscript>Ra and <Superscript>232</Superscript>Th in samples of different nature by a multidetector spectrometer

A coincidence method for measuring ¹³⁷Cs, ⁴⁰K, ²²⁶Ra and ²³²Th decay products activity in soil, vegetation and fish samples, was applied to the six-crystal gamma-coincidence spectrometer PRIPYAT-2M. In this way, some problems appeared in simultaneous measurement of ¹³⁷Cs, ²²⁶Ra and ²³²Th by NaI(Tl) detectors and the PRIPYAT-2M spectrometer were solved. The obtained results were agreeable with the HPGe spectrometer ones.     

Determination of <Superscript>3</Superscript>H, <Superscript>226</Superscript>Ra, <Superscript>222</Superscript>Rn and <Superscript>238</Superscript>U in Austrian ground- and drinking water

Screening measurements for ³H, ²²⁶Ra, ²²²Rn and ²³⁸U in ground water were performed within a ground- and drinking water project in Austria. The aim of this project is to get an overview of the distribution of natural radionuclide activity concentration levels in ground water bodies. In some cases this water is used for drinking water abstraction. In this paper methods and results of the screening measurements are presented. Regions with high activity concentrations were identified and in these regions further investigation for ²²⁸Ra, ²¹⁰Pb and ²¹⁰Po will be conducted.     

Determination of <Superscript>241</Superscript>Am/<Superscript>243</Superscript>Am ratios

Determination of ²⁴¹Am/²⁴³Am ratios is required for vanous purposes including assay of Am by isotope dilution techniques. Alpha-spectrometry on electrodeposited sources is a preferred technique for this determination. However, there is an inherent problem of tail contribution which necessitates the use of suitable algorithms to account for the same. Recently, in the frame of a Coordinated Research Program (CRP) of the International Atomic Energy Agency (IAEA), WinALPHA software has been developed which is a combination of an asymmetrical Gaussian for the main part of the peak and a low energy function. Therefore, it was of interest to compare the use of this algorithm with the routinely used method, in our laboratory, based on geometric progression (G. P.) decrease. Since, there are no reference materials available commercially for ²⁴¹Am/²⁴³Am ratios, synthetic mixtures covening a wide range (0.3 to 2.0) of ²⁴¹Am/²⁴³Am α-activity ratios were used and un-ignited electrodeposited sources were prepared for α-spectrometry. The α-spectra obtained using PIPS detector, were evaluated using the two algonthms The ²⁴¹Am/²⁴³Am α-activity ratios obtained were also compared with those determined by thermal ionization mass spectrometry (TIMS). An agreement of about 1% was obtained in the ²⁴¹Am/²⁴³Am ratios determined by the two methods and also by using the two algorithms for α-spectrum evaluation.     

<Superscript>1</Superscript>H and <Superscript>31</Superscript>P nuclear spin-lattice relaxation in C-phosphorylated oximes

The ¹H spin-lattice relaxation times of the proton-bearing groups and the ³¹P spin-lattice relaxation times in C-phosphorylated oximes R¹C(=NOH)P(=O)R²R³ (R¹ = Ph, R² = R³ = OMe; R¹ = Ph, R² = OMe, R³ = OCH²CH²Br; R¹ = PhCH², R² = R³ = OCHMe²) and dioxime R²P(=O)C(=NOH)(CH₂)₄C(=NOH)P(=O)R² (R = OMe) in DMSO-d₆ were measured. The characteristic reorientation times of the whole molecules were estimated using the measured values of the ¹H relaxation times and the results of semiempirical PM3 quantum chemical calculations of the molecular geometries. The reorientation times were used to identify the contributions of different relaxation mechanisms to the rate of ³¹P spin-lattice relaxation. The anisotropy of the chemical shielding of ³¹P nuclei was evaluated from the difference between the ³¹P relaxation rates measured at 101.27 and 161.92 MHz.     

<Superscript>234</Superscript>U/<Superscript>235</Superscript>U activity ratios as a probe for the <Superscript>238</Superscript>U/<Superscript>235</Superscript>U half-life ratio

High-resolution alpha-particle spectrometry was performed on three uranium materials enriched in ²³⁵U. Besides the ²³⁵U peaks, separate peaks belonging to impurity traces of ²³⁴U could be quantified. Relying on the isotopic composition of the uranium, as determined by mass spectrometry, the ratio of the half-lives of ²³⁸U and ²³⁵U was determined via the activity ratio of ²³⁴U and ²³⁵U in the materials. As an intermediate link, the ²³⁴U/²³⁸U half-life ratio was taken from published mass spectrometric analyses of ‘secular equilibrium’ uranium material. The resulting half-life ratio T _1/2(²³⁸U)/T _1/2(²³⁵U) = 6.351±0.031 is in agreement with the commonly adopted half-life values determined by Jaffey et al.     

Modeling β-γ coincidence spectra of <Superscript>131m</Superscript>Xe, <Superscript>133</Superscript>Xe, <Superscript>133m</Superscript>Xe,and <Superscript>135</Superscript>Xe

In support of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), improvements have been made to the model of the Automated Radioxenon Sampler/Analyzer (ARSA) β-γ coincidence detector for radioxenon monitoring. MCNPX is used to simulate the detector response for all the electrons and photons emitted from ^131mXe, ¹³³Xe, ^133mXe, ¹³⁵Xe, and ¹³⁷Cs signals. A MatLab code was written to incorporate the MCNPX results in the calculation of β-γ coincidence spectra. These will aid in the development of the Spectral Deconvolution Analysis Tool (SDAT)¹ and to calibrate β-γ coincidence systems. The models developed for this work include improvements over previous models in their ability to address Compton scattering in the β-cell, and the β-distribution offset in the 31 keV γ-ray region for ¹³³Xe.     

Determination of <Superscript>93</Superscript>Zr in nuclear power plant wastes

A radioanalytical method (based on separation using UTEVA columns and ICP-MS measurement) has been used for determination of ⁹³Zr in 37 nuclear power plant samples. As ⁹³Nb might affect the detection of ⁹³Zr, Monte Carlo activation model was used to calculate the expected ⁹³Zr/^natZr mass ratio, which was compared to measured ones. It was found, that a decontamination factor of 10³ is sufficient to get a measurement uncertainty of less than 10%.     

Production and chemical separation of <Superscript>48</Superscript>V

Summary Vanadium-48 was produced with an activity of 222 MBq (6 mCi) by the ^natTi(d,xn)⁴⁸V nuclear reactions in the U-120 cyclotron. The energy of the irradiating beam was 13 MeV, its intensity 5 μA, and the metallic Ti target dimension 11’11 mm² (0.1 mm thickness). For target cooling, circulated water in target backside was used. After 3 cooling days, only ⁴⁸V and some ⁴⁶Sc (T_1/2 = 83.8 d), produced by the side nuclear reaction ⁴⁸Ti(d,α)⁴⁶Sc were found in the target. For production of the radiotracer of ⁴⁸V and for the preparation of source for standardization of ⁴⁸V by 4πβ-γ coincidence, the Ti target was dissolved either in HF or in H₂SO₄. For both dissolving methods an ion-exchange separation procedure was developed.     

Atmospheric deposition fluxes of <Superscript>7</Superscript>Be, <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po at Xiamen,China

The atmospheric deposition fluxes of ⁷Be, ²¹⁰Pb and ²¹⁰Po at Xiamen were measured. The samples were collected from March 2004 to April 2005 and the sampling period was one month. The ⁷Be and ²¹⁰Pb activity were measured using HPGe γ-spectrometer after concentration using Fe(OH)₃ co-precipitation method. The ²¹⁰Po was counted with an α-spectrometer after the sample was digested and spontaneous plated onto a silver planchet. At Xiamen, the atmospheric deposition fluxes of ⁷Be varied between 0.11 and 2.93 Bq·m⁻²·d⁻¹ and the average was 1.64 Bq·m⁻²·d⁻¹; ²¹⁰Pb fluxes varied between 0.04 and 0.85 Bq·m⁻²·d⁻¹, and the average was 0.51 Bq·m⁻²·d⁻¹; ²¹⁰Po fluxes varied between 0.002 and 0.133 Bq·m⁻²·d⁻¹, and the average was 0.061 Bq·m⁻²·d⁻¹. There were positive correlations between the deposition fluxes of ⁷Be, ²¹⁰Pb or ²¹⁰Po and the amount of precipitation. The residence time of aerosols varied between 6.0 and 54.0 days with a mean of 27.1 days, which were calculated by ²¹⁰Po/²¹⁰Pb fluxes ratios.     

Determination of <Superscript>151</Superscript>Sm and <Superscript>147</Superscript>Pm using liquid scintillation tracer methods

The long-lived rare earth isotopes ¹⁵¹Sm (90 years, β _max = 76.3 keV) and ¹⁴⁷Pm (2.62 years, β _max = 224.6 keV) are low-yield fission products that generally require lengthy separation procedures to isolate and count by their beta emissions. We will describe novel liquid scintillation counting techniques using radioactive tracers to determine radiochemical yields from an environmental matrix. The recovery of ¹⁵¹Sm is determined from the alpha decay (2.25 MeV) of ¹⁴⁷Sm in the natural Sm carrier and is in excellent agreement with the gravimetric recovery. The ¹⁴⁷Pm recovery is determined by the use of ¹⁴⁵Pm (17.7 years, EC) tracer, custom-produced at LANL using an isotopically enriched target of ¹⁴⁴Sm. We have determined the ¹⁴⁵Pm recovery both from the 37.4 keV k_α1 X-ray, and the electron-capture emissions by LSC. A comparison of these recovery methods is presented.