Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Mixing of atmospheric <Superscript>210</Superscript>Pb and <Superscript>7</Superscript>Be and <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr fission products in four characteristic soil types

Depth distribution of atmospheric ²¹⁰Pb and ⁷Be and ⁹⁰Sr and ¹³⁷Cs fission products was measured in two types of aeolian soils (desert dust and volcanic ash), irrigated paddy soil and strongly acidic soil. The depth dependence of ²¹⁰Pb, ⁷Be and ¹³⁷Cs show that these radionuclides have been diffused as solid soil particles in surface soil layers. In aeolian soil layers, about 50% of ⁹⁰Sr were diffused in surface soil layer and the remaining 50% had penetrated to deeper layers. The half of the fission particles containing ⁹⁰Sr were shown to have decomposed over the past 35 years.     

Complex amidoboranes M<Superscript>2</Superscript>[M<Superscript>1</Superscript>(NH<Subscript>2</Subscript>BH<Subscript>3</Subscript>)<Subscript>4</Subscript>] (M<Superscript>1</Superscript> = Al,Ga; M<Superscript>2</Superscript> = Li,Na, K,Rb, Cs)

Structural, spectral, and thermodynamic characteristics of complex amidoboranes M²[M¹(NH₂BH₃)₄] (M¹ = Al, Ga; M² = Li, Na, K, Rb, Cs) were calculated by the B3LYP/def2-SVPD quantum-chemical method. The procedure for the synthesis of these compounds by reactions of alkali metal amidoboranes with aluminum and gallium chlorides was suggested and experimentally tested. Reaction products were characterized by the NMR and IR spectroscopy and X-ray phase analysis.     

A comparative study on the separation of radioyttrium from Sr- and Rb-targets via ion-exchange and solvent extraction techniques,with special reference to the production of no-carrier-added <Superscript>86</Superscript>Y, <Superscript>87</Superscript>Y and <Superscript>88</Superscript>Y using a cyclotron

The radiochemical separation of ⁸⁸Y from proton irradiated ^natSrCO₃ and alpha-particle irradiated ^natRbCl, of ⁸⁶Y from proton irradiated ⁸⁶SrCO₃, and of ⁸⁷Y from alpha-particle irradiated ^natRbCl were studied at no-carrier-added levels by two techniques, namely, ion-exchange chromatography using Dowex 50W-X8 and Dowex 21K resins, and solvent extraction using HDEHP. Out of all those methods, the ion-exchange chromatography using Dowex 50W-X8 (cation-exchanger) was found to be the best: the separation yield was high, the chemical impurity in the separated radioyttrium (inactive Sr or Rb) was low (0.5 μg) and the final product was obtained in the form of citrate. The optimized separation method using Dowex 50W-X8 was applied in practical production of ⁸⁶Y and ⁸⁸Y via proton irradiations of ⁸⁶SrCO₃ and ^natSrCO₃, respectively, at 16 MeV as well as of ⁸⁷Y and ⁸⁸Y via α-particle irradiation of ^natRbCl at 26 MeV. The tangible experimental yields of ⁸⁶Y and ⁸⁷Y amounted to 150 and 5.7 MBq/μA·h, respectively. The yields of ⁸⁸Y obtained were 0.06 MBq/μA·h and 1 MBq/μA·h for alpha-particle and proton irradiations, respectively. Each yield value corresponds to more than 70% of the respective theoretical value.     

Global fallout levels of <Superscript>99</Superscript>Tc and activity ratio of <Superscript>99</Superscript>Tc/<Superscript>137</Superscript>Cs in the Pacific Ocean

Summary Global fallout levels of ⁹⁹Tc and ¹³⁷Cs of surface seawater in the Pacific Ocean were measured. The ⁹⁹Tc concentrations ranged from 0.62 to 3.33 mBq^. m^-3and 5 of 6 samples showed less than 1 mBq^. m^-3except one sample taken in the Great Barrier Reef, Australia. The ¹³⁷Cs concentrations ranged from 2.13 to 3.14 Bq^. m^-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in the South Pacific. The ⁹⁹Tc/¹³⁷Cs activity ratios ranged from 2.5^. 10^-4to 2.9^. 10^-4, which is very close to that calculated theoretically from the fission yield.     

Fission studies in the reaction of <Superscript>19</Superscript>F with <Superscript>209</Superscript>Bi at 99.2 MeV

Fission product yield studies in the reaction of 99.2 MeV ¹⁹F with ²⁰⁹Bi have been carried out for the first time using gamma-ray spectrometry. The cross sections for the production of fission products have been determined. The yield distribution of fission products was found to be symmetric and broad with FWHM around 22 mass units and peak near mass 111. The average number of neutrons emitted per fission has been found to be around 6.7. The comparison of the fission products yield distribution of ²⁰⁹Bi using projectiles like ⁴He, ¹²C, ¹⁶O, and ¹⁹F have shown that the mass of symmetric peak increases as the mass of the compound nucleus increases. The high fission yield around mass 112 has been attributed to the presence of deformed neutron shells. The total fission cross section and width of the mass distribution have been found to be low in case of ¹⁶O induced fission as compared to the ⁴He, ¹²C, and ¹⁹F induced fission of ²⁰⁹Bi.     

Determination of potassium traces in foodstuffs by natural <Superscript>40</Superscript>K radiation

Summary After the Chernobyl accident in April 1986, Mexico imported from one European country a shipment of 28,000 tons of milk powder contaminated with the fission product ¹³⁷Cs. Since then, the local authorities of Public Health have established as a compulsory condition to obtain through gamma-spectroscopy a certificate of no radioactive contamination either to imported or exported foodstuffs. But at the same time, the absence of long-lived, gamma-emitters fission products is certified, it is also possible to find the concentration of the important trace element K in foodstuffs, by the peak of 1461 keV from ⁴⁰K, invariably present in the gamma-spectra. Taking advantage of the fact that it does not require any previous manipulation of the sample, this paper describes the general procedure in milk powder or any other foodstuff.     

Synthesis,structure formation,and thermal expansion of A<Superscript>+</Superscript>M<Superscript>2+</Superscript>MgE<Superscript>4+</Superscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The compounds AMMgE(PO₄)₃ (A = Na, K, Rb, Cs; M = Sr, Pb, Ba; E = Ti, Zr) were synthesized by the sol–gel procedure followed by heat treatment and studied by X-ray diffraction, differential thermal and electron microprobe analysis, and IR spectroscopy. The phosphates crystallize in the kosnarite (KZr₂(PO₄)₃, space group \(R\bar 3\)) and langbeinite (K₂Mg₂(SO₄)₃, space group P2₁3) structural types. The structure of KPbMgTi(PO₄)₃ was refined by full-profile analysis (space group P2₁3, Z = 4, a = 9.8540(3) Å, V = 956.83(4) ų). The structure is formed by a framework of vertex-sharing MgO₆ and TiO₆ octahedra and PO₄ tetrahedra. The K and Pb atoms fully occupy the extra-framework cavities and are coordinated to nine oxygen atoms. A variable-temperature X-ray diffraction study of KPbMgTi(PO₄)₃ showed that the compound expands isotropically and refer to medium-expansion class (linear thermal expansion coefficients α _a = α _b = α _c = 8 × 10^–6°C^–1). The number of stretching and bending modes of the PO₄ tetrahedron observed in the IR spectra is in agreement with that predicted by the factor group analysis of vibrations for space groups \(R\bar 3\) and P2₁3. A structural transition from the cubic langbeinite to the rhombohedral kosnarite was found for CsSrMgZr(PO₄)₃. In the morphotropic series of ASrMgZr(PO₄)₃ (A = Na, K, Rb, Cs) the kosnarite–langbeinite transition occurs upon the Na → K replacement. The effect of the sizes and electronegativities of cations combined in AMMgE(PO₄)₃ on the change of the structural type was analyzed.     

Electronic structure and quadrupole interactions in triple molybdates Li<Subscript>2</Subscript>M<Subscript>3</Subscript>Al(MoO<Subscript>4</Subscript>)<Subscript>4</Subscript>, M = Cs,Rb

Within the density functional theory the electronic structure of triple molybdates Li₂M₃Al(MoO₄)₄, where M = Cs, Rb, is studied for the first time. It is found that all molybdates studied belong to wide band insulators with a band gap of ~4 eV. Quadrupole frequencies and asymmetry parameters of the electric field gradient near magnetic ⁷Li, ²⁷Al, ⁸⁷Rb, and ¹³³Cs nuclei are calculated and experimental NMR spectra are interpreted.     

Distribution characteristics of <Superscript>14</Superscript>C and <Superscript>3</Superscript>H in spent resins from the Canada deuterium uranium-pressurized heavy water reactors (CANDU-PHWRs) of Korea

It is regarded that the spent resins from the water purification systems of moderator (MOD) and the primary coolant of the Canada deuterium uranium-pressurized heavy water reactor (CANDU-PHWR) are a unique waste, owing to their high ¹⁴C and gamma-emitting nuclides. In this work, ¹⁴C and ³H contents, anion and cation fractions and the predominant gamma-emitting nuclides of the spent resins from 4 units of CANDUPHWRs, were investigated. Also the chemical species of ¹⁴C of the spent resins were determined. For a simultaneous separation of ¹⁴C and ³H from the spent resins, the wet oxidation-16 wt% H₂SO₄ stripping process was utilized. The ¹⁴C and ³H activity concentration range of the spent resins of the nuclear power plant (NPP), 4 units of all CANDU-PHWR types, was 2.48E5 Bq/g ∼5.33E6 Bq/g, 1.29E5 Bq/g and ∼2.33E5 Bq/g, respectively. Among the analyzed spent resins, the highest ¹⁴C and ³H activity concentration was detected in units 4 and 3, respectively. It was found that more than 92% of the ¹⁴C activity concentration was retained on the anion resin and the predominant chemical species was inorganic ¹⁴C. It was revealed that the anion resin fraction of the spent resins from unit 1 and unit 2, was about 40% and that of unit 3 and unit 4 was around 60%. More than 80% of the total gamma-radioactivity concentration was associated with the cation fraction of the spent resin. The predominant gamma-emitting nuclide of the spent resin for unit 2 was ¹³⁷Cs, a fission product, and that for unit 4 was ⁶⁰Co, a corrosion product.     

Determining the activity of <Superscript>241</Superscript>Pu by liquid scintillation counting

Liquid scintillation counting (LSC) is one of the most widely used methods for determining the activity of ²⁴¹Pu. One of the main challenges of this counting method is the efficiency calibration of the system for the low beta energies of ²⁴¹Pu (E _max = 20.8 keV). In this paper we compare the two most frequently used methods, the CIEMAT/NIST efficiency tracing (CNET) method and the experimental quench correction curve method. Both methods proved to be reliable, and agree within their uncertainties, for the expected quenching conditions of the sources.     

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.     

Separation of <Superscript>133</Superscript>Xe from <Superscript>99</Superscript>Mo, <Superscript>131</Superscript>I and uranium,and removal of impurities using gas chromatography

Summary Separation and purification of ¹³³Xe from acidic solution containing uranium, ⁹⁹Mo and ¹³¹I has been developed. In the first step of this work, uranium pellets were dissolved under pressure (8-15 bar) in 8M nitric acid solution. Then¹³³ Xe and other gases were conducted to activated charcoal cold trap. Final purification of ¹³³Xe from impurities such as NO_x, radioiodine and krypton was performed by passing through a molecular sieve preparative chromatographic column using helium as mobile phase. The final recovery of ¹³³Xe from the separation-purification process was higher than 98%. Adsorption-desorption behavior of radioxenon on the charcoal and molecular sieves have also been studied and discussed.     

Radionuclide purity assessment and calibration of <Superscript>90</Superscript>Y(<Superscript>177</Superscript>Lu) glass particles using gamma-ray spectrometry

Intra-hepatic administration of radioactive glass microspheres is a treatment for patients with primary liver cancer and hepatic metastases. The purpose of this study was radionuclide purity assessment of new glass particles containing two radionuclide, ⁹⁰Y as a therapeutic source and also ¹⁷⁷Lu as a source of diagnostic gamma. For the mixed source, activity measurement using a dose calibrator cannot be used and we need new calibration methods. YAS (Yb) and YAS compositions were sol–gel derived glass particles and production of ⁹⁰Y (¹⁷⁷Lu) and ⁹⁰Y particles was performed using the Tehran Research Reactor. The radionuclide purity was carried out using γ-spectrometry with HPGe detector. A non-destructive spectroscopic assay was employed due to a newly updated low uncertainty positron branching ratio of ⁹⁰Y that emit 511 keV annihilation radiations. In another method, a new calibration of ⁹⁰Y using a non-destructive spectroscopic assay of ⁸⁸Y were investigated. Potential radionuclide impurity include: ⁸⁸Y, ¹⁵²Eu, ⁶⁰Co with activity 100, 50 and 5 Bq per 1 mg of that are not harmful for patients due to delivering radioactive particles about 20–50 mg in ⁹⁰Y(¹⁷⁷Lu) glass microspheres. Among of radionuclide impurity, ¹⁵²Er with a half life of 13.54 years and ⁸⁸Y with a half life of 106.65 days was important in the residual delivery device. For calibration of ⁹⁰Y with monitoring of 511 keV, errors were12.2–21%. In calibration of ⁹⁰Y using gamma spectroscopic assay of ⁸⁸Y, there was an error less than 14%. Spectroscopic assay of ⁸⁸Y can be performed easily and has more repeat for our purpose.     

Radiochemical measurement of <Superscript>237</Superscript>Np in a solution of mixed radionuclides: Experiences in chemical separation and alpha-spectrometry

A radiochemical procedure is described for the measurement of 0.1 Bq ²³⁷Np in a solution containing similar activity concentrations of Th, U, Pu and Am as well as activity concentrations of ⁶⁰Co, ⁹⁰Sr and ¹³⁷Cs one hundred times higher. A tracer of ²³⁹Np (milked from ²⁴³Am) was used as an isotopic spike for chemical yield determination. The relationship between gamma-counting geometries for ampoule (liquid) and NdF₃ (solid) ²³⁹Np sources was established so that Np chemical yields could be measured by a comparative method. Efficiencies of alpha-spectrometers for ²³⁷Np in NdF₃ sources were measured by a bootstrap technique. Two sets of experiments were designed and used to test out the procedure.     

Soil-to-plant transfer factors of fallout <Superscript>137</Superscript>Cs and native <Superscript>133</Superscript>Cs in various crops collected in Japan

In order to compare the soil-to-plant transfer factors (TFs) of fallout ¹³⁷Cs and those of native stable ¹³³Cs, concentrations of these isotopes were determined in various crops and the associated soils collected throughout Japan. The results showed that TF-¹³⁷Cs was 11 times higher than TF-native ¹³³Cs for brown rice, while those values were almost the same for leafy vegetables. Possibly, fallout ¹³⁷Cs would be more mobile and more easily adsorbed by plants than native ¹³³Cs in the soil because a part of the ¹³³Cs is in a soil structure where it is hard to replace with ¹³⁷Cs. However, ¹³⁷Cs and native ¹³³Cs have reached an approximately isotopic equilibrium in the bioavailable fraction in the soils, therefore, the TF-native ¹³³Cs can be used for long-term transfer of ¹³⁷Cs in the environment.     

Improvement of <Superscript>137</Superscript>Cs analysis in small volume seawater samples using the Ogoya underground facility

¹³⁷Cs in seawater is one of the most powerful tracers of water motion. Large volumes of samples have been required for determination of ¹³⁷Cs in seawater. This paper describes improvement of separation and purification processes of ¹³⁷Cs in seawater, which includes purification of ¹³⁷Cs using hexachloroplatinic acid in addition to ammonium phosphomolybdate (AMP) precipitation. As a result, we succeeded the ¹³⁷Cs determination in seawater with a smaller sample volume of 10 liter by using ultra-low background gamma-spectrometry in the Ogoya underground facility. ¹³⁷Cs detection limit was about 0.1 mBq (counting time: 10⁶ s). This method is applied to determine ¹³⁷Cs in small samples of the South Pacific deep waters.     

Contribution to the external gamma dose rate from <Superscript>137</Superscript>Cs and <Superscript>40</Superscript>K activity concentrations determined in the vertical profile of sandy beaches

Sampling sites, located along the Calabria and Basilicata Regions coastal beaches (south of Italy), were selected to assess the external gamma dose rate in air, 1 m above ground, and to estimate the fraction attributable to the radiocesium and radiopotassium contents along the vertical sand profile. Mean values for the gamma dose rate were: 76±30 nGy·h⁻¹. ¹³⁷Cs and ⁴⁰K deposition densities in sand samples were determined for each sampling site (mean values 0.24±0.22 kBq·m⁻² and 178±88 kBq·m⁻², respectively). The ¹³⁷Cs external dose rate contribution was assessed using a Monte Carlo simulation code. The method gives an estimation of the contribution to the external gamma dose rate of each sand layer along the vertical profile. The dose rate associated with the ¹³⁷Cs content in sand was 0.16±0.14 nGy·h⁻¹. The cosmic radiation and ⁴⁰K contributions to the external gamma dose rate were estimated using the UNSCEAR methodologies. The values obtained were 34±3 nGy·h⁻¹ and 18±9 nGy·h⁻¹, respectively.     

The Sorben-Tec system for rapid dosimetric evaluation of <Superscript>137</Superscript>Cs in drinking water

The Sorben-Tec system was developed for rapid evaluation of ¹³⁷Cs in drinking water using a domestic personal dosimeter or beta-radiometer. Linear calibration curves were obtained for dosimetric and beta-radiometric measurement of caesium. In case of 20 L drinking water sample, detection limits of ¹³⁷Cs were found to be 12.3 and 2.0 Bq L^?1 for dosimetric and beta-radiometric measurement respectively. This system is recommended for using by non-professionals who are living at radioactively contaminated areas or near nuclear power plants.     

Relationships among <Superscript>137</Superscript>Cs, <Superscript>133</Superscript>Cs,and K in plant uptake observed in Japanese agricultural fields

Plant uptake of radiocesium (¹³⁷Cs) was investigated in consideration of the relationships with naturally existing ¹³³Cs and potassium (K). We first determined plant-unavailable fraction of ¹³⁷Cs in soil by batch sorption and sequential extraction methods with a radiotracer. Then, using the data obtained from the batch sorption and extraction methods, we clarified the relationships of plant-available and plant-unavailable fractions between ¹³⁷Cs, ¹³³Cs, and K in soil. Additionally, ¹³⁷Cs concentrations in crop were estimated using ¹³⁷Cs in soil and several factors, i.e. fixation ratio of ¹³⁷Cs in soil, cation exchange capacity, and K concentration in crop. The results implied that the fixation ratio of ¹³⁷Cs in soil was a very important key to understanding ¹³⁷Cs plant uptake.