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Relevance. The fact that the literature does not contain any data not only on crystallization coefficients, but also on the nature of the co-precipitation of americium (III) with calcium oxalate. The co-precipitation reaction of americium with calcium oxalate is used to concentrate trace amounts of americium due to calcium oxalate low solubility and adsorption capacity. In this relation, the study of co-precipitation of trace amounts of americium with calcium oxalate, as well as the study of the isolation of trace amounts of americium using a calcium carrier and its subsequent separation from the carrier, is of unconditional interest. Aim. Investigation of americium co-precipitation with the solid sorbent – calcium oxalate, description of the equilibrium of the sorption isotherm using Langmuir and Freundlich models. Methods. When studying the establishment of co-precipitation of americium with a carrier – calcium oxalate, the qualification of the chemical reagents used met the requirements of the grade not lower than r.g. The isotope americium-241 was used in the work, the composition of the solid phase of the carrier – calcium oxalate – corresponded to the formula CaC2O4·H2O. The concentration of americium (III) cations in the initial solution and in the filtrate was determined by gamma-spectrometric method using the SCS-07P spectrometric complex, the amount of calcium – by complexometric titration with murexide as an indicator, and the concentration of oxalate ion – by permanganatometric method. Results. It was found that the co-precipitation of americium (III) nitrate solutions with calcium oxalate is largely due to adsorption of the micro-component – americium (III) – on the surface of the existing or newly formed precipitate of the macro-component calcium oxalate. It is determined that the Langmuir equation model adequately describes sorption, since the processing of experimental data by the least squares method showed that in coordinates C/A=f(C) the sorption isotherm is described by the equation of a straight line with a high correlation coefficient of more than 0.95.

The results of experimental determination of the forms of uranium and radionuclides 90Sr, 137Cs, 154Eu, 238Pu, 239+240Pu, 241Am, and 244Cm in the bottom sediments of the premises 001/3 of the "Shelter" object are presented. By the sequential extraction procedure, the following amounts are determined: water-soluble, exchange, carbonate, and acid-soluble forms of uranium, fission products (90Sr, 137Cs, 154Eu), and transuranium elements (238Pu, 239+240Pu, 241Am, 244Cm) in the bottom sediments in the premises 001/3 on a mark of -2.60 m of auxiliary systems of the reactor compartment of the "Shelter" object. The concentration of uranium in the bottom sediments of room 001/3 is 3.1 ± 0.5 g/kg. Specific activity of 90Sr, 137Cs in the bottom sediments is within the range of 6·108 - 1·109 Bq/kg, and 239+240Pu and 241Am within the range of 6·105 - 8·106 Bq/kg. Radionuclides 90Sr, 137Cs, 154Eu, 238Pu, 239+240Pu, 241Am, 244Сm in the bottom sediments are in different chemical forms that will define their different potential mobility. Uranium and 137Cs in the bottom sediments of premises 001/3 mainly are in exchange forms. The amount of water-soluble forms of uranium and cesium is 1.5 - 3 %. The basic amount of 90Sr, more than 60 %, is carbonate soluble in a weak acid at рН 4.8. More than 65 % of 238Pu and 239+240Pu in the bottom sediments are in acid-soluble forms. The mobility of 154Eu, 241Am and 244Cm in the bottom sediments is much higher than that of plutonium; at pH 4.8 more than 40 % of 241Am go to soluble state. The ratio between the activities of 137Cs/90Sr, 90Sr/239+240Pu, 241Am/239+240Pu, and 244Cm/239+240Pu in the bottom sediments considerably differ from the analogical relations of radionuclides in a fuel containing materials of the "Shelter" object.

Radionuclides behavior on strongly contaminated territories of 30-km Chernobyl zone was studied. Samples in two layers for determination of the possible impact of works on construction of the "Shelter" object were collected. As a result, abnormal A(241Am)/A(137Cs) ratio was observed on a number of samples. The value varies between 0.004 to 0.30. Activity of 94Nb and 60Co was observed on the number of samples. Problems with spectrometer calibration appeared, when samples from Chernobyl zone with low activity were used. Calibration on efficiency of γ-rays registration become complicated in low energy interval because of different density of the investigated samples. To solve this problem methodological researches were performed, taking into account efficiency variation of γ-rays registration in samples with big volume. For this purpose, activities of 137Cs and γ-rays with 661 keV energy were compared. 137Cs activity was defined from appearance of Kx-emission of Ba (36 keV).

Radionuclides behavior on strongly contaminated territories of 30-km Chernobyl zone was studied. Samples in two layers for determination of the possible impact of the works on construction of the “Shelter” object were collected. As a result, abnormal A(241Am)/A(137Cs) ratio was observed on a number of samples. The value varies between 0.004 to 0.30. Activity of 94Nb and 60Co was observed on the number of samples. Problems with spectrometer calibration appeared, when samples from Chernobyl zone with low activity were used. Calibration on efficiency of γ-rays registration become complicated in low energy interval because of different density of the investigated samples. To solve this problem methodological researches were performed, taking into account efficiency variation of γ-rays registration in samples with big volume. For this purpose, activities of 137Cs and γ-rays with 661 keV energy were compared. 137Cs activity was defined from appearance of Kx-emission of Ba (36 keV). [ABSTRACT FROM AUTHOR]

Assessment is given of area and behavior of large wildfire in the Chornobyl Exclusion Zone (ChEZ) which has been burning during April 27 - 29, 2015. Levels of radionuclide contamination of combustible material show that expected effective dose of firefighters during one fire-line hour did not exceed 0.64 μSv in case of external exposure and 0.37 μSv in case of internal exposure. It is shown that the expected effective dose of internal exposure of firefighters during suppression of wildfires in ChEZ was below the dose from external exposure. At the moment exposures of 90Sr and 241Pu (along with 238-240Pu and 241Am) make the most significant contribution to the internal dose of firefighters during forest and grassland fires suppression in the ChEZ.

Assessment of area and behavior of large wildfire in the Chornobyl Exclusion Zone (ChEZ) which has been burning during April 27 - 29, 2015. Levels of radionuclide contamination of combustible material show that expected effective dose of firefighters during one fire-line hour did not exceed 0.64 pSv in case of external exposure and 0.37 pSv in case of internal exposure. It is shown that the expected effective dose of internal exposure of firefighters during suppression of wildfires in ChEZ were below the dose from external exposure. At the moment exposure of 90Sr ad 241Pu (along with 238-240Pu and 241Am) make the most significant contribution to the internal dose of firefighters during forest and grassland fires suppression in the ChEZ. [ABSTRACT FROM AUTHOR]

Quantitative parameters of 90Sr, 137Cs, 239Pu and 241Am transfer from solid phase of soil to gastric, intestine juice of cows as well as to imitating solutions have been estimated on the base of results of laboratory incubation experiments. A prevailing role of enzyme complex and microflora of gastrointestinal tract in radionuclides transfer from solid phase of soil to solution has been shown.

Based on the requirements to x-ray equipment and its modern characteristics, the authors validate the 5-130 keV range for radiation registration in radiation control of x-ray examination rooms. Experimentally derived graphic representation of the sensitivity of S2010 dosimeter in this energy interval shows that the error of measurements of radiation less than 26 keV is exceedingly over 25%, recorded in the certificate. Experimentally determined angular anisotropy for the 109Cd radiation shows that a corporal angle of 0.04 pi sr corresponds to a relative sensitivity of 0.8. The narrow aperture of the pickup necessitates its careful orientation during measurements. The proper background of the dosimeter is 0.05 mR/h in the 4 to 14 keV range and 0.01 mR/h in the 14 to 140 keV range with the external background equal to 1.5 microR/h.

Records of pollution by plutonium and americium 241 of skin wounds and burns in the personnel of the Mayak plant in 1948-1992 are analyzed. Traumas occurred in 286 (7.2%) workers, mechanical injuries were 84.1% of these. A high incidence of wound contamination was recorded in the workers engaged in mechanical processing of plutonium. Altogether 34.1% of injuries had alpha-radiators in residual amounts after debridement, though their levels did not surpass the minimal levels of radionuclide detection.

From the analysis of the results of examination of 96 dogs it is concluded that the estimate of a relative danger of breathing transuranium radionuclides with different metabolism rates (polymeric 239Pu and monomeric 241Am), according to degree of leukopenia is more reliable when it is compared with a mean weighed dose per whole organism than the dose per individual "critical" organ.