Cesium, americium and plutonium isotopes in ground level air of vilnius

Systematic observations of radionuclide composition and concentration in the atmosphere have been carried out at the Institute of Physics in Vilnius since 1963. Increases in activity concentration of radionuclides in the atmosphere were observed after nuclear weapon tests and the Chernobyl NPP accident. At present the radiation situation in Lithuania is determined by two main sources of radionuclides, forest fire and resuspension products transferred from highly polluted region of the Ukraine and Belarus. The activity concentrations of ¹³⁷Cs were measured in two to three days samples while plutonium and americium in monthly samples. The extremely high activity concentrations of ²³⁸Pu, ^239,240Pu, ²⁴¹Am determined in the atmosphere during the Chernobyl accident can be explained by transport of “hot particles” of different composition. Activity concentration in 1995–2003 of ²⁴¹Am and ^239,240Pu isotopes ranged from 0.3 to 500 and from 1 to 500 nBq/m³, respectively. ²³⁸Pu/^239,240Pu activity ratio in measured samples differs from 0.03 to 0.45. A decrease in ²⁴⁰Pu/²³⁹Pu atomic ratio from 0.30 to 0.19 was observed in 1995–2003.     

Speciation of radionuclides of the Chernobyl origin in aerosol and soil samples

Speciation of^134,137Cs,⁹⁰Sr,²³⁴U,²³⁸U,²³⁸Pu,^239,240Pu and²⁴¹Am was investigated in aerosol samples collected after the Chernobyl accident and in the Chernobyl soil. Sequential extraction experiments have shown a wide range of association of radionuclides, depending on sources, transformation perculiarities and radionuclide nature. Changes in speciation of¹³⁷Cs and⁹⁰Sr at various temperatures in the Chernobyl soil were analyzed. It was found that at 200°C–700°C a transformation of speciation of¹³⁷Cs took place and more available physico-chemical forms of Cs were formed. After heating at 900°C, up to 94% of¹³⁷Cs was found in the residual form and was not extractable even with 7 M HNO₃. Heating of the soil to 450°C and 900° C resulted in the formation of less available forms of⁹⁰Sr.     

Determination of Separated Plutonium,Americium and Curium in Environmental Samples by Sequential Extraction Techniques

A simple, reliable and practical radiochemical method for sequential isolation and determination of plutonium, americium and curium in a wide variety of environmental samples including soils, river sediments and water was developed. The isotopes determined are: ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ²⁴⁴Cm. The methods involve leaching of soil or sedimental samples with concentrated nitric acid using a pressure digestion technique. Subsequent concentration and separation of nuclides of interest from major matrix elements and other interfering alpha-emitters are carried out by coprecipitation with ferric hydroxide and solvent extractions. Sources suitable for alpha-spectrometry are prepared by electrodeposition from acidic ammonium chloride solution. ²⁴²Pu and ²⁴³Am are used as tracer isotopes of plutonium and americium-curium elements, respectively. Some results of analysis of soils, sediments and water are given. The alpha peaks from ²³⁸Pu, ^239,240Pu and ²⁴²Pu as well as ²⁴¹Am, ²⁴⁴Cm, ²⁴²Cm and ²⁴³Am are well resolved. The entire analytical procedures for plutonium, americium and curium are completed in less than sixteen hours.     

Alphaspektrometrische Isotopenverdünnungsanalyse von Plutoniumisotopen in Kernbrennstofflösungen

In einer bestrahlten Kernbrennstofflösung wurde die Plutoniumaktivität mit Hilfe der Isotopenverdünnungsanalyse bestimmt. Dabei wurde ²³⁸Pu als Tracerisotop verwendet. Die Abtrennung des Plutoniums wurde durch Extraktion und die Aktivitätsmessung mit Hilfe der Alphaspektrometrie unter Verwendung von Si-Halbleiterdetektoren vorgenommen. Die Störung durch ²⁴¹Am wurde durch gammaspektrometrische Messung berücksichtigt. Die Genauigkeit der ²³⁸Pu-Aktivitätsmessung und die der Messung der Gesamtaktivität beträgt ungefähr 1,5%. Die Bestimmung des ²³⁹Pu zu ²⁴⁰Pu Verhältnisses war nur mit einem groβen Fehler möglich, entsprechend der nahezu gleichen Alphaenergien dieser Isotope und der komplizierten Peakform. ²⁴¹Pu wurde durch alphaspektrometrische Differenzmessung der nachgebildeten ²⁴¹Am Aktivität bestimmt.

In irradiated nuclear fuel solution plutonium isotops were determined with the help of isotope dilution analysis. ²³⁸Pu was used as a tracer isotope. Plutonium was separated by extraction and the activity was measured by alphaspectroscopy using silicon detectors. Interfering ²⁴¹Am was recognized by gamma spectroscopic measurements. The accuracy of ²³⁸Pu determination and the determination of the total activity amounts to about 1-5%. For the ²³⁹Pu ratio we obtained a value with a large systematic error due to the similar alpha energies of these isotopes in the complicated shape of the peaks. The ²⁴¹Pu activity was determined by alphaspectroscopic difference measurement, and was calculated from the ingrown of ²⁴¹Am activity.     

Measurements of134Cs and137Cs by gamma spectrometry in some Italian soils following the nuclear reactor accident of chernobyl

Summary The concentration as well as the vertical distribution of¹³⁴Cs and¹³⁷Cs were determined in several soil samples subsequently to the Chernobyl accident. The soil samples were selected in some representative geomorphological situation in Apulia that is a region of Italy. Both undisturbed and cultivated soils were considered. The total deposition of¹³⁷Cs as due to the Chernobyl accident was estimated and the obtained results were also controlled by measurements of the radioactive fall-out in rain and snow during 1986 and 1987. Also the deposition of^239,240Pu during 1986 and 1987 was measured.

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Riassunto è stata determinata la concentrazione e la distribuzione verticale, di¹³⁴Cs e¹³⁷Cs in alcuni campioni di terreno successivamente all'incidente di Chernobyl. I campioni sono stati selezionati in alcune situazioni geomorfologiche rappresentative della Puglia. Sono stati presi in considerazione sia terreni indisturbati che coltivati. è stata determinata la deposizione totale di¹³⁷Cs dovuta all'incidente di Chernobyl. Questo risultato è stato valutato anche in relazione alle misure di ricaduta di¹³⁷Cs nella pioggia e nella neve durante l'ultimo quadrimestre 1986 e il 1987. Per la medesima ricaduta è stato anche misurato il^239,249Pu.

     

Characteristics of radionuclide contamination of different zones of Semipalatinsk Nuclear Test Site “Opytnoe pole”

Data on the spatial distribution of radionuclides (²⁴¹Am, ²³⁹Pu, ¹³⁷Cs and ¹⁵²Eu) formed during nuclear explosions of different types near P2 SNTS test site are presented. Radionuclide contamination induced by the explosions varies in the concentrations of individual radionuclides, their proportions and species. Examination of the variations is a crucial task to plan remediation activities as well as those aimed at decrease of radiation risk for population and prevention of repeated contamination. Concentrations of ²⁴¹Am and ^239+240Pu that are the most toxic radionuclides in the area lie in hundred thousands of Bqkg^?1. The most contaminated areas are classified by the radionuclide concentration, ratio and form present in soil.     

Present status and trends of radioecological research

Radioecology can be defined as the science concerned with the interactions between radionuclides and the environment and with the effects of radionuclides on man and biotic communities. Ecology advanced from radioecological studies because tracer radionuclides were instrumental in understanding many ecological processes. During the period of fallout from nuclear weapons testing the behaviour of the most important radionuclides (typically:⁹⁰Sr,¹³¹I,¹³⁷Cs,^239,240Pu) in the most critical pathways was studied. After the Chernobyl accident studies were extended to natural and semi-natural ecosystems and to other less common radionuclides. In principle the implementation of radiation protection criteria for man, which are based on the protection of a single individual, assures the protection of organisms other than man. In case of serious contamination scenarios there is a need for realistic evaluations of the effectiveness of the countermeasures that could be undertaken. In particular, studies on biogeochemical transfer mechanisms which control the cycling of radionuclides should be developed. With reference to future developments of the nuclear industry, some attention should be paid to the operation and the releases from, e.g., intrinsically safe reactors and fusion plants. Besides such potential new-type sources, the decontamination and possible site restoration of military installations has to be considered.     

Studies of the radionuclide content of fuel particles sampled from the chernobyl nuclear power plant’s No. 4 reactor unit

Spectroscopic studies are performed of the L _x , K _x , and ?? emanations from fuel particles sampled in 2011 inside the Chernobyl Nuclear Power Plant??s (ChNPP??s) No. 4 reactor unit. The isotope ratios for ^134,135Cs, ^154,155Eu, Pu isotopes, ^241,243Am, and ²⁴³Cm are measured. The data on ?? emitters for all radionuclides above ²⁴¹Am exhibit considerable inconsistency with the theoretically calculated values. A systematic deviation of the ⁹⁰Sr and ¹³⁷Cs ratios for the fuel component from the 1986 data is observed. Zirconium is shown to be the main radionuclide in the fuel particles.     

Determination of Actinide Traces in Reactor Water

In reactor water from primary coolant ²³⁹Np, ²³⁸U, ²³⁸Pu and ^239,240Pu was determined using isotope dilution and isotope dilution activation analysis. An example of crud and reactor water from a power station was also investigated by gamma spectroscopy and activation analysis. For localization and characterization methods of cladding failure the usefulness of analyti?al determination of actinides in reactor water is emphasized.     

Transmutation of 129I, 237Np, 238Pu, 239Pu, and 241Am using neutrons produced in target-blanket system ‘Energy plus Transmutation’ by relativistic protons

Target-blanket facility ‘Energy + Transmutation’ was irradiated by proton beam extracted from the Nuclotron Accelerator in Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction yields (residual nuclei production yields) have been determined using γ-spectroscopy. Neutron field's energy distribution has also been studied using a set of threshold detectors. Results of transmutation studies of ¹²⁹I, ²³⁷Np, ²³⁸Pu, ²³⁹Pu and ²⁴¹Am are presented.      

Photofission of americium isotopes in the energy range 6–12 MeV

By means of the reference method, the cross sections for the fission of the ²⁴¹Am, ^242m Am, and ²⁴³Am isotopes were measured at the microtron of the Institute of Physics and Power Engineering (Obninsk). These measurements, which employed the cross section for ²³⁸U photofission as a reference, covered the energy range 6–12 MeV scanned with a variable step of 50 to 200 keV. Data on ^242m Am photofission in the energy range 6–12 MeV and ²⁴³Am photofission in the region between 6 and 7 MeV were obtained for the first time. New results for ²⁴¹Am reveal that the cross sections for ²⁴¹Am photofission from previous studies of the present author were exaggerated. The new results for this isotope comply well with data of other authors. It is not confirmed that the fissility of ²⁴¹Am is less than the fissility of ²⁴³Am. The energy dependences of the fissilities of the americium isotopes from photofission data are compared with those that were obtained for these fissilities from data on direct reactions like ²⁴⁰Pu(³He, df)²⁴¹Am. The results of this comparison show that the observed fission thresholds and the plateaulike dependences at energies above 7.5 MeV from the two types of studies comply well. The present data show evidence that, in the energy region around 6 MeV, the photofission cross section has a maximum, which is associated, in all probability, with the low-energy resonance structure in the cross section for dipole photoabsorption.     

Rapid methods for the determination of long-lived radionuclides in environmental samples by ICP-SFMS and radioanalytical techniques

Two improved sample preparation methods for the determination of americium and plutonium (Method 1) and plutonium (Method 2) from environmental samples by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and alpha spectrometry are presented. Both procedures involve a rapid CaF₂ co-precipitation step for pre-concentration and matrix removal followed by extraction chromatographic separations. The average recovery after sample preparation was better than 85 % for both americium and plutonium. The method developed also focused on the elimination of possible interferences in the mass spectrometric analysis caused by molecular ions (e.g. ²⁰⁸Pb¹⁶O ₂ ⁺ or ²³⁸U¹H⁺) by employing suitable matrix separation prior to ICP-SFMS analysis of the desolvated sample. Isotopes with alpha energies similar to the analytes that may cause interferences in alpha spectrometric analysis were also separated. For ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴¹Am detection limits of 15, 9.2, 14 and 23 fg g⁻¹, respectively were achieved by ICP-SFMS, and 0.1 mBq obtained by alpha spectrometry. The methods developed are especially applicable for monitoring purposes of anthropogenic transuranium elements, as the analysis (sample preparation and ICP-SFMS measurement) can be carried out within 6 hours for one batch of samples.     

137Cs and 40K activity concentration measurements and elemental analysis in lichen samples collected from the Giresun province of northeastern Turkey

About 21 years after the Chernobyl accident, ¹³⁷Cs and ⁴⁰K activity concentration measurements using gamma-ray spectroscopy and elemental analysis using energy dispersive X-ray spectroscopy were performed in five different lichen species collected from the Giresun province of northeastern Turkey. Being a symbiosis of algae and fungi, lichens are mostly used for environmental measurements since the fungal partner is responsible for the uptake of necessary nutrients or harmful substances, such as heavy metals of radionuclides. The gamma activity results showed that ¹³⁷Cs, an artificial radionuclide released from the Chernobyl power plant accident, is still eminent in the environment of the province. The mean activity concentrations of ¹³⁷Cs and ⁴⁰K ranged from 24 to 254 with the mean value of 102 Bq kg^?1 and from 345 to 2103 with the mean value of 1143 Bq kg^?1 in dry weight. The results of the elemental analyses showed potassium, calcium, titanium, iron, tin, and barium in different concentrations.     

Erfassung des Proteinstoffwechsels mit dem Isotop 15N bei Herz-Kreislauf-Erkrankungen

From the set of experiments, where transfer factors for transuranic elements in soil-plant system and basic soil parameters were determined, Romney's and Eriksson's experiments were undergone a multiple correlation and regression analysis. Effect of soil properties on soil-to-wheat grain and soil-to-wheat straw in Romney's experiments was studied. Different uptake of transuraniums by wheat grain and wheat straw was found. Conclusions for uptake of ^239,240Pu by wheat in Romney's experiment were different from results obtained in Eriksson's experiment for ²³⁸Pu.     

237Np separation from environmental matrices by extraction chromatography method

Aliquat-336 anchored on hydrophobized silica gel was used for effective separation of ²³⁷Np from soil matrices and from model solutions. Alpha spectrometry for ²³⁷Np determination was used. The interfering radionuclides present in environmental samples such as ²³⁴U, ²³²Th, ²³¹Pa and ^239+240Pu were removed by separation with nitric acid solutions containing formic acid and ferrous sulfamate as reducing agents. Spiking samples with ^238,234U, ²³²Th and ²³⁸Pu were used to check separation effectiveness. A separation yield of ²³⁷Np from soil matrices was checked by measuring of added known amount activity and was found to be about 15%. The yield of separation for model solutions was about 56%. Different parameters of eluant on recovery of ²³⁷Np from column were studied.     

Particularization of α contamination using CR-39 track detectors

Solid-state nuclear track detectors (SSNTDs) have found wide use in various domains of science and technology, e.g. in environmental experiments. Measurement of α activity on sources in an environment, such as air, is not easy because of the short penetration range of the α particles. Furthermore, the measurement of α activity by most gas ionization detectors suffers from the high background induced by the accompanying gamma radiation. SSNTDs have been used successfully as detecting devices as passive system to detect the α contamination of different surfaces. This work presents the response of CR-39 (for two types) to α particles from two sources, ²³⁸Pu with energy 5 MeV and ²⁴¹Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity and energy resolution are studied.     

Mössbauer Study of Iron-Containing Atmospheric Aerosol Collected During the Chernobyl Accident

During the Chernobyl accident a large quantity of radionuclides was released into the troposphere and contaminated a wide geographical area. The present study concentrates on atmospheric iron. The Mössbauer measurements were performed on the atmospheric aerosol collected during the accident on 27–30 April 1986 in Warsaw and in Legnica, Poland. Results were compared with the data obtained for samples collected at the same sites just before the accident. The observed increase in iron concentration determined by Mössbauer effect could be explained by the enrichment of natural iron in ⁵⁷Fe isotope in ⁵⁶Fe(n,)⁵⁷Fe reaction.     

Particularization of alpha contamination using CR-39 track detectors

Solid-state nuclear track detectors have found wide use in various domains of science and technology, e.g. in environmental experiments. The measurement of alpha activity on sources in an environment, such as air is not easy because of short penetration range of alpha particles. Furthermore, measurement of alpha activity by most gas ionization detectors suffers from high background induced by the accompanying gamma radiation. Solid state nuclear track detectors (SSNTDs) have been used successfully as detecting devices and as a passive system to detect alpha contamination on different surfaces. This work presents the response of CR-39 (for two types) to alpha particles from two sources, ²³⁸Pu with energy 5 MeV and ²⁴¹Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity and energy resolution are studied.      

Measurement of cross sections for the reactions 241Am(n, 2n) and 241Am(n, 3n)

The cross sections for the reactions ²⁴¹Am(n, 2n)²⁴⁰Am and ²⁴¹Am(n, 3n)²³⁹Am are measured for several neutron-energy values in the range 13.42–14.86 MeV. An upper limit on the cross section for the reaction ²⁴¹Am(n, α)²³⁸Np is also obtained.     

Evaluation of 242Cm and 244Cm decay data

The decay data evaluation results are presented for the ²⁴²Cm and ²⁴⁴Cm radionuclides decaying to the levels in ²³⁸Pu and ²⁴⁰Pu, respectively. The evaluated data have been obtained using information published up to 2005. The text was submitted by the author in English.