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  • Author or Editor: V. Nazarov x
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Abstract  

Experience in the application of radioanalytical methods, including NAA, at the IBR-2 pulsed fast reactor is reviewed. Details of the instruments dedicated to neutron activation analysis and radiography studies are reported. Applications of resonance neutrons to environmental monitoring, studying of water ecosystems, analysis of geological samples in oil extraction regions, and investigation of high-purity materials are exemplified.

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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.

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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.

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Abstract  

An intercomparison of data obtained for a moss reference material (Hylocomium splendens) used as biomonitor of atmospheric deposition by different multi-element techniques is presented. In total 43 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Zr, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ta, W, Au, Th, U) were determined using inductively coupled plasma-mass spectrometry (ICP-MS), conventional instrumental neutron activation analysis (INAA), epithermal neutron activation analysis (ENAA) and as well as shorttime neutron activation analysis without and with a6LiD-converter. Advantages and drawbacks of each method are discussed. The introduction of moss reference materials for atmospheric multi-element deposition studies involving nuclear analytical techniques is strongly recommended.

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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.

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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.

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Abstract  

Experience in the use of epithermal neutron activation analysis (ENAA) in the monitoring of atmospheric deposition by means of moss, lichens and pine needles is summarized. It is shown that 45 elements (Mg, K, Ca, Al, Cl, Sc, V, Cr, Mn, Fe, Co, Ni (using (n,p)-reaction), Zn, Cu, As, Se, Br, Rb, Sr, Zr, Mo, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ta, W, Au, Th and U, as well as Ir and Re in pine needles in the presence of anthropogenic pollution by the nickel mining plant) are reliably determined. Examples of the use of lichens, moss and pine needles as biomonitors of atmospheric deposition in Franz Josef Land the Kola peninsula and in the Tver region are given.

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Abstract  

The present paper based on experimental results contains discussions and suggestions on the possible use of fine-powder Al2O3 and SiO2 with their original content of microimpurities of up to 40 elements, as multielement standards for neutron activation analysis. For example, activation analysis of As, Au, Ba, Cr, Cs, Fe, Ga, K, Ni, Sb, Sc, Se, Sr, Ta, Th, Ti, U, W, Zn, Zr and the REE La, Ce, Nd, Sm, Eu, Tb, Tm, Yb contained in SiO2 powder off MERCK reagents showed their concentrations to be 0.1 to 5% of those in IAEA standard SL-1. In Al2O3 this level is even lower, approximately 10 times and more for the majority of the above-mentioned elements. As Al2O3 and SiO2 are good sorbents for the majority of elements, additional introduction of some elements may allow more methods of analysis. The homogeneity of Al2O3 and SiO2 samples both in the original state and after introduction of some elements was determined by neutron activation analysis, and the SD did not exceed 1% for an Al2O3 sample weight of 0.1 g, and 2% for SiO2.

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Abstract  

The determination of impurities in high-purity solvents, (acetone, isopropanol, trichloroethylene and trichlorotrifluoroethane) used in the production of integrated circuits was carried out by reactor neutron activation analysis. A special vacuum evaporation technique was used for the preconcentration of the solvents. The results showed that sodium and iron are the main impurity components in the solvents and on the other hand the quality of the solvents satisfies the specifications required by high-technology standards. The suspended solid particles in solvents were counted by a Microscopic Image Analysis System (MIAS).

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Abstract  

A measuring technique based on the alpha particles being released from the10B(n, α) nuclear reaction and using the time-of-flight technique at a periodically pulsing reactor was developed. Non-destructive determination for the range distribution of boron impurities in ion-implanted silicon have been performed. Projected ranges obtained in the energy region 20–80 keV are compared to calculated results and to other experiments. Examples are shown for some typical boron distributions before and after annealing the sample.

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