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- Author or Editor: M. Frontasyeva x
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Abstract
Epithermal neutron activation analysis is shown to be a powerful technique for the simultaneous determination of chlorine, bromine and iodine in organic-rich soils. Examples are shown from a transect study in northern Norway where samples of surface soil were collected at distances of 0–300 km from the coastline. All three elements decreased exponentially as a function of distance from the ocean, strongly indicating that atmospheric supply from the marine environment is the predominant source of these elements in the soil. The Cl/Br and Br/I ratios also showed a regular change with distance from the ocean, and hypotheses for this behavior are offered.
Abstract
INAA is known to be a powerful technique for the simultaneous determination of chlorine, bromine and iodine. In this paper INAA using epithermal neutrons is shown to be particularly useful to elucidate marine gradients of these elements. Examples are from a transect study in northern Norway where samples of the feather moss Hylocomium splendens were collected at distances of 0-300 km from the coastline. All three elements decrease exponentially as a function of distance from the ocean in the moss samples, strongly indicating that the atmospheric supply from the marine environment is the predominant source of these elements to the terrestrial ecosystem. It is suggested that environmental studies of halogens in general and iodine in particular is a promising future area of application for INAA, when employing epithermal neutrons.
Abstract
Experience in applying conventional and epithermal neutron activation analysis for some challenging areas of life sciences and material science is reviewed. For more than 30 years of its operation the radioanalytical complex REGATA at the IBR-2 reactor in Dubna has become a source of analytical data for the environmental studies, marine geology, biotechnology and medicine, technological process of diamond and boron nitride synthesis, archaeology, nanomaterials, etc. In spite of competing non-nuclear analytical techniques (AAS, ICP-ES, ICP-MS, etc.), the reactor neutron activation analysis (NAA) as a primary (ratio) method continues to be the most powerful multielement analytical technique providing quantification of trace elements at ultralow levels. Combined with modern statistical data treatment of large arrays of data, GIS (geographic information system) technologies, electron scanning microscopy, tomography, and others, NAA serves to obtain actual, practical results resumed in the review. The perspectives of using the upgraded reactor IBR-2M for analytical investigations are discussed.
Abstract
Instrumental activation analysis (INAA) based on irradiations in a nuclear reactor with particularly high relative fluxes of resonance and fast neutrons has been shown to open new possibilities for multi-element surveys of mosses used as monitors of atmospheric deposition. Comparison is made with data obtained by inductively coupled plasma-mass spectrometry (ICP-MS) and conventional INAA. Data for 15 elements not previously investigated in routine moss studies are presented, e.g., Zr, Sn, Hf, Ta, W, Au, Th, and the rare earth elements Ce, Nd, Eu, Gd, Tb, Tm, Yb, Lu. Other elements particularly well determined by this approach are Sc, Co, As, Ag, Sb, Cs, La, Sm, Th, and the non-metallic trace elements Se, Br, and I. Advantages and drawbacks with the high fast neutron component are discussed.
Abstract
For the first time the moss biomonitoring technique has been applied to air pollution monitoring in Central Russia (Tula region). INAA at the IBR-2 reactor has made it possible to determine the content of 33 elements in mosses collected at 83 sampling site. In addition to NAA, flame AAS (atomic absorption spectrometry) was applied to determine the content of Cd, Cu and Pb. Factor analysis was applied to determine possible sources of trace element deposition in Tula mosses. The geographical distribution of factor scores and some element distribution maps over the investigated territory are presented.
Summary
In ombrotrophic bogs the surface peat layer is supplied with chemical substances only from the atmosphere. Therefore, peat cores from these bogs can be used to study temporal trends in atmospheric deposition of pollutants. In this work epithermal neutron activation analysis was applied for the first time to study the distribution of 35 elements in peat profiles from ombrotrophic bogs. The selected samples were from Finnmark county in northern Norway, one pristine site far from any local pollution source, and the other samples from strongly affected by long-term operation of a Russian copper-nickel smelters located close to the border. The elements are classified with respect to their behavior in the uppermost 40 cm of the peat, and similarities and differences between the two profiles are discussed. As compared with other more commonly used analytical techniques based on acid decomposition of the sample, ENAA has the advantage of providing the total concentrations of the elements.
Abstract
The paper discusses the possibilities of energy dispersive X-ray fluorescence spectroscopy and instrumental neutron activation analysis in the investigation of environmental pollutions. The X-ray fluorescence spectroscopy of samples was performed using the MECA-1044A analyzer (XR-500, LINC SYSTEMS, Great Britain) with a pulsed X-ray tube with a silver target as a source of excitation. Neutron activation analysis was carried out on the basis of two reactors: IBR-2 LNP JINR, Dubna, and TWR ITEP, Moscow. The optimal regimes of measurement for both methods as well as the detection limits corresponding to these regimes are given. To illustrate the perspectives of the methods, the ecological problem of the consequences of introducing into soil of the now available meliorator CaSO4·2H2O is solved in the paper. Data on absorption of trace elements in a wide range including rare-earth elements by agricultural plants are presented. This paper may be of interest for specialists in analytical chemistry and ecology.
Abstract
The results of activation studies of concrete ingredients for shielding structures of nuclear installations in the aspect of their decommissioning are given. It is shown that for the long-lived induced radioactivity of construction mineral materials irradiated for 30 years and cooled for more than one year such radionuclides as calcium, iron, cobalt, caesium and europium are responsible. Elemental content of the binding agent and raw material components for their production is obtained by neutron activation analysis. The results show that the type of the binding agent influences to a great extent the concrete shielding activity. The concentration of the above mentioned elements should be taken into account even at the stage of nuclear power plants design. It would allow one to make a prognosis on the volume and radioactivity of wastes as on the radioactivity effect felt by the staff engaged in the decommissioning.
Abstract
The content of binding agent components and aggregates of shielding concrete (portland cement, gabbro, silicate, granite, hematite, magnetite, limestone) has been studied to identify nuclides contributing to the long-lived radioactivity of concretes used in nuclear reactor shielding. Elemental content was determined by neutron activation analysis at the IBR-2 reactor of the Laboratory of Neutron Physics (JINR). It is shown that the nuclides mainly responsible for the long-lived activity are152Eu,154Eu,60Co and134Cs. Based upon the experimental data obtained, calculations of the specific activity of concrete ingredients being irradiated for 30 years by a unit neutron flux density have been performed, and diagrams of the dependence of the specific activity versus time are presented. It is recommended that the application of such media as magnetite, serpentinite, chromite to shielding structures should be abandoned. Estimations of the dose rate from concrete structures containing various aggregates for the limiting case of semi-infinite space are given. The results obtained can form the basis for the optimal choice of the materials when constructing the concrete shielding of neutron sources.
Abstract
Experience in application of radioanalytical methods, including NAA, at the IBR-2 pulsed fast reactor is reviewed. Details of the instruments dedicated to the neutron activation analysis and radiography studies are reported. Applications of resonance neutrons to environmental control, to analysis of geological samples in oil extraction regions, to testing the quality of food products, and to the investigation of high-purity materials to solve nuclear physics problems, are exemplified. Work to use isotopic neutron sources for an analysis for nitrogen in natural and synthetic materials is being carried out.
