Specific Activity Values Research Articles

Tandem column isolation of zirconium-89 from cyclotron bombarded yttrium targets using an automated fluidic platform: Anion exchange to hydroxamate resin columns

The development of a tandem column purification method for the preparation of high-purity 89Zr(IV) oxalate is presented. The primary column was a macroporous strongly basic anion exchange resin on styrene divinylbenzene co-polymer. The secondary column, with an internal volume of 33 μL, was packed with hydroxamate resin. A condition of inverted selectivity was developed, whereby the 89Zr eluent solution for the primary column is equivalent to the 89Zr load solution for the secondary column. The ability to transfer 89Zr from one column to the next allows two sequential column clean-up methods to be performed prior to the final elution of the 89Zr(IV) oxalate. This approach assures delivery of high purity 89Zr product and assures a 89Zr product that is eluted in a substantially smaller volume than is possible when using the traditionally-employed single hydroxamate resin column method. The tandem column purification process has been implemented into a prototype automated fluidic system. The system is configured with on-line gamma detection so column effluents can be monitored in near-real time. The automated method was tested using seven cyclotron bombarded Y foil targets. It was found that 95.1 ± 1.3% of the 89Zr present in the foils was recovered in the secondary column elution fraction. Furthermore, elution peak analysis of several 89Zr elution profile radiochromatograms made possible the determination of 89Zr recovery as a function of volume; a 89Zr product volume that contains 90% of the mean secondary column elution peak can be obtained in 0.29 ± 0.06 mL (representing 86 ± 5% of the 89Zr activity in the target). This product volume represents a significant improvement in radionuclide product concentration over the predominant method used in the field. In addition to the reduced 89Zr product elution volume, titrations of the 89Zr product with deferoxamine mesylate salt across two preparatory methods resulted in mean effective specific activity (ESA) values of 279 and 340 T Bq·mmole−1 and mean bindable metals concentrations ([MB]) of 13.5 and 16.7 nmole·g−1. These ESA and [MB] values infer that the 89Zr(IV) oxalate product resulting from this tandem column isolation method has the highest purity reported to date.

The Pear Aroma in the Austrian Pinot Blanc Wine Variety: Evaluation by Means of Sensorial-Analytical-Typograms with regard to Vintage, Wine Styles, and Origin of Wines

The perceived pear aroma in wines was associated with various short- and medium-chain ester compounds. A consumer study confirmed this assumption. In total, eight ester compounds from a series of 100 aromatic substances were associated with the pear aroma. In this study, a valid stable isotope dilution assay headspace solid-phase microextraction gas chromatography mass spectroscopy (SIDA-HS-SPME-GC-MS) method was developed for the analysis of these compounds, and 102 Austrian Pinot blanc wines of vintages 2013–2016 were analysed. They were assessed with regard to vintage and origin influences as well as wine styles. However, an attempt was made to capture the synergies of these compounds for the pear aroma. With the detection of ethyl (E,Z)-2,4-decadienoate and methyl (E)-geranoate, two volatile compounds were measured which had not previously been detected in Austrian wines. The eight analysed esters were perceived very differently. Therefore, specific odour activity values for the various sensations could be calculated with a mathematical combination of the analyses and the results of the sensory studies. A vintage influence on the sensorial descriptor “overripe pear” and a relationship between wine style and total pear aroma were determined.

Inhibition kinetics of ammonium oxidizing bacteria under Cu(II) and As(III) stresses during the nitritation process

Nitritation processes with ammonium oxidizing bacteria (AOB) frequently suffer inhibition from heavy metals in municipal wastewater treatment. In the present study, two frequently detected heavy metals, Cu(II) and As(III), were selected to assess their inhibition effect during the nitritation process. Specific ammonium conversion rate (SACR), specific oxygen uptake rate (SOUR), and specific nitrite production rate (SNPR) in batch tests were first applied to evaluate nitritation kinetics, and simulated by the classic Haldane substrate inhibition kinetic model. The presence of Cu(II) stress imposed a more pronounced inhibition on nitritation process than As(III) with half inhibition concentrations of 6.7 and 86.6 mg L−1, respectively. The kinetic result showed that Cu(II) acts as an uncompetitive inhibitor on nitritation process with reduced affinity (KS) and specific activity (Vmax) values. The difference in the inhibition kinetics between Cu(II) and As(III) can be accounted by the oxidation of As(III) to As(V) and subsequent competition by dissolved oxygen under nitritation condition. Our result indicated that the SNPR method exhibits great performance in describing and modelling the inhibition kinetics of heavy metals on nitritation process.

Characterization and inhibition effects of some metal ions on carbonic anhydrase enzyme from Kangal Akkaraman sheep.

In this work, the carbonic anhydrase (CA) enzyme was purified from Kangal Akkaraman sheep in Sivas, Turkey with specific activity value of 6681.57EU/mg and yield of 14.90% with using affinity column chromatography. For designating the subunit molecular mass and enzyme purity, sodium dodecyl sulfate polyacrylamide gel electrophoresis method was used and single band for this procedure was obtained. The molecular mass of CA enzyme was found as 28.89kDa. In this study, the optimum temperature and optimum pH were obtained from 30 and 7.5. Vmax and Km values for p-nitrophenylacetate substrate of the CA were determined from Lineweaver-Burk graphs. Additionally, the inhibitory results of diverse heavy metal ions (Hg+ , Fe2+ , Pb2+ , Co2+ , Ag+ , and Cu2+ ) on sheep were studied. Indeed, CA enzyme activities of Kangal sheep were investigated with using esterase procedure under in vitro conditions. The heavy metal concentrations inhibiting 50% of enzyme activity (IC50 ) and Ki values were obtained.

Effect of Fukushima Accident on Fishes and Fish Like other Foods Collected from the Bay of Bengal and Karnaphuli River, Bangladesh

An experiment was carried out to assess the radiological exposure due to the intake of fishes and fish like foods from some common estuary (Karnaphuli River) and Marine (Bay of Bengal) contaminated by Fukushima Reactor Accident, if any, by using gamma spectroscopy. The analysis was done to estimate the radioactivity concentrations due to natural radionuclides namely 238U, 232Th and 40K and artificial radionuclide 137Cs in Karnaphuli estuary and Chittagong city adjoining Bay of Bengal fish and fish-like samples. The activity concentration for 238U in all the samples ranged from 0.10615 ± 0.0000 to 2.4767 ± 0.0005 Bq.kg-1 with the mean of 0.6109 ± 0.0001 Bq.kg-1. The Activity of 232Th ranged from 0.0009 ± 0.0000 to 0.0273 ± 0.0000 Bq.kg-1 with the mean of 0.0074 ± 0.0000 Bq.kg-1. The activity concentration for 40K was found to be in the range from 1.5516 ± 0.0311 to 74.8658 ± 0.2532 Bq.kg-1 with the mean of 24.9533 ± 0.0702 Bq.kg-1. The artificial radionuclide 137Cs was not found in any of the samples. The specific activity values for most of the sample were within the permissible limits. The average effective dose and internal hazard index due to consumption of those fishes and fish-like foods was found to be 0.1 mSv.y-1 and 0.0085 ± 0.0000 mSv.y-1 respectively. The research work showed that the consumers of concerned fishes and fish-like foods of the Chittagong area have no risk of radioactivity ingestion even though no amount of radiation is assumed to be totally safe.
 The Chittagong Univ. J. Sci. 40(1) : 75-96, 2018

Measuring Radiological Parameters in Some Samples of Local and Imported Paints Buildingsin Najaf, Iraq

Exposure of the natural radioactivity available in soil and construction materials around the world occupies great concern because of the health risks associated with it. In this work, samples were collected from various markets in Najaf city, Iraq .The measurements of the paints samples have been carried out using gamma ray spectroscopy NaI(Tl) with that (“3×3”). The average value of specific activities were for238U, 232Th and 40K in different types of paints and dyes were 44.19±4.73Bq/Kg, 30.17±3.64 Bq/Kg and 478.84±10.34 Bq/Kg respectively. It is show that, the average value in samples under study were higher than the corresponding global values documented in (UNSCEAR2000) publications. All radiological parameters (Activity of Radium equivalentRaeq and out annual effective dose AEDout)were lower than the permissible limits except absorbed dose rate were higher than worldwide average (UNSCEAR, 2000).

Environmental assessment of risks associated with the Ordovician Dictyonema shale in the eastern part of the Baltic Klint

The results of research considered in this article made it possible to expand the understanding of the environmental risks associated with the highly radioactive bituminous argillites of the Baltic Sea region. The natural patterns of the distribution of natural radionuclides 226Ra, 232Th and 40K are established along the strike and thickness of layers. The average value of the effective specific activity (ESA) for all samples in the Koporka River valley amounted 1270 Bq/kg. The minimum value of ESA was 650 Bq/kg (the closest to the seam roof level), and the maximum value was 3750 Bq/kg (the second from the seam floor level). Conversion to mass fractions of natural radionuclides (NRN) showed that the average content of uranium in the sample amounted up to 90.7 g/t, thorium up to 11.4 g/t and of potassium up to 4.1%. The high heterogeneity of the content distribution of NRN along the strike of the Dictyonema shale seam was confirmed by studies of separate outcrops of highly radioactive rocks along the banks of the Tosna River. In general, the level of the argillites radioactivity has abnormally high value and exceeds the natural background more than ten times. The average annual values of the effective dose amounted from 5,8 to 10,7 mSv/year, that should be classified as the territories of emergency ecological danger and zones of ecological disaster.

Opportunities and perspectives of agricultural development in radiation-polluted territories

Based on the analysis of research results and scientific publications of domestic and foreign scientists, the opportunities and perspectives of agricultural development in radioactive contaminated territories of Polissya were substantiated. The value of specific activity of 137Cs is considered and it is established that all cultures have an increased accumulation of it.

РАДІОАКТИВНЕ ЗАБРУДНЕННЯ 137СS МОХОВО-ЛИШАЙНИКОВОГО ПОКРИВУ В УМОВАХ СВІЖОГО СУБОРУ

Досліджено сучасне радіоактивне забруднення мохово-лишайникового покриву в умовах свіжого субору в лісах Українського Полісся. Щільність радіоактивного забруднення ґрунту в межах пробної площі варіювала у широких діапазонах – від 315 до 708 кБк/м2. Виявлено значні коливання величин питомої активності та показників інтенсивності надходження 137Cs для всіх досліджуваних видів зелених (брієвих) мохів та епігейних лишайників. Так, на пробній площі для дикрану багатоніжкового середній вміст 137Сs становив 11538±1022 Бк/кг; для плевроцію Шребера – 9312±679 Бк/кг. З'ясовано, що радіоактивне забруднення дикрану багатоніжкового істотно вище, ніж у плевроцію Шребера (в 1,2 раза). Концентрація 137Cs у лишайниках загалом змінювалась в широкому діапазоні – від 3975 до 9182 Бк/кг. Найменші значення вмісту 137Cs встановлено у кладонії м'якої, а найбільші – у кладонії дюймової. Коефіцієнт накопичення 137Cs для лишайників був у діапазоні від 3,2 до 6,5, а для зелених (брієвих) мохів – від 3,8 до 7,7. Коефіцієнт переходу 137Cs у лишайниках родини Кладонієвих змінювався від 11,8 до 24,4 м2·кг-1·10-3. За інтенсивністю накопичення 137Cs епігейні лишайники можна розмістити таким чином: кладонія дюймова > кладонія струнка > кладонія оленяча > кладонія м'яка. Щодо зелених мохів, то для дикрану багатоніжкового середній показник коефіцієнта переходу становив 29,2±0,9 м2·кг-1·10-3, майже в 2 рази більше, ніж для плевроцію Шребера – 16,3±0,06 м2·кг-1·10-3. Значення концентрації 137Сs у мохово-лишайниковому покриві має тісний лінійний зв'язок з величиною щільності радіоактивного забруднення ґрунту.

Temperature Dependence of the Oxygen Reduction Reaction Activity and Local Structural Analysis of Pt/C Catalyst

Introduction For the widespread commercialization of Polymer Electrolyte Fuel Cell (PEFC), reducing the amount of platinum used for cathode catalyst material is important by improving the oxygen reduction reaction (ORR) activity. Convection voltammetry using rotating disc electrode (RDE) is one of the usable ways for evaluating ORR activity of cathode catalyst materials for PEFCs. However, the correlation between ORR activity and the electronic as well as local structure of these materials casted on RDE is not fully clear yet. In this paper, we report the temperature dependency of ORR activity of TEC10V30E Pt/C catalysis (T.K.K.) from 25oC to 60 oC, combining RDE measurements and Operando X-ray absorption spectroscopic measurements (XAS). We investigated the correlation with the electronic structure / local structural parameters of the Pt/C catalyst and investigated the factors that govern the oxygen reduction reaction activity on the RDE surface from the viewpoint of temperature dependency. Experimental Electrochemical parameters obtained by electrochemical characterization using platinum-supported carbon (Pt/C) as a cathode catalyst and precisely temperature-controlled RDE and temperature variable Operand XAS on RDE surface. A model electrode was prepared by applying a catalyst ink prepared from TEC 10 V 30 E Pt / C (TKK) to the surface of glassy carbon RDE. The electrochemical cell was constructed using a model electrode fabricated in the working electrode, a Pt mesh for the counter electrode, a reversible hydrogen electrode for the reference electrode, and 0.1 M HClO 4 aq for the electrolyte. Electrochemical surface area was calculated by CV measurement under N 2 saturation condition and area specific activity value was determined by LSV measurement under N2 and O2 saturated conditions. Measurements were carried out at 10, 25, 40, 50, 60 ºC. For this model electrode, operand XAS measurement of Pt LIII -edge and Pt LII -edge were carried out by using the beamline BL37XU in SPring-8 (Japan). The measurements were performed by a fluorescent method using a temperature variable type Operand cell that can directly measure the electrocatalyst applied to RDE (Fig. 1). The number of Pt 5d orbital vacancies was calculated from the obtained XANES spectrum, and the local structure of Pt was analyzed from the EXAFS spectrum. The oxygen reduction activity performance in the electrochemical measurement was evaluated from the area specific activity value at 0.9 V of the Pt / C catalyst at 10, 25, 40, 50, 60 ºC. The oxygen reduction activity of the model electrode is determined by the electrochemical parameters related to the oxygen reduction reaction such as the oxygen coverage. Result According to RDE results, the reaction rate of ORR specific activity was determined for Pt/C from 25 oC to 60 oC. Linear sweep voltammetry showed the coverage of oxygen species at Pt surface dramatically increased at high temperature in 1.1 V (vs. RHE). This oxygen species could reduce the ORR by blocking active sites for additional O2 adsorption. We also found the rapid increase of Pt 5d orbital vacancy by X-ray absorption spectra with the temperature, indicating that Pt was more easily oxidized at 60℃ than 25 oC. Fig. 1. Schematic view of operando XAS cell for measuring ORR activity of Pt/C catalyst casted on RDE under controlling temperature. Figure 1

Temperature Dependence on Oxygen Reduction Reaction for Carbon-Supported Pd-Core/Pt-Shell Electrocatalysts

Introduction Polymer electrolyte Fuel Cells (PEFCs) have been developed for the electric device applications such as residential fuel cell cogeneration system and fuel cell vehicles. PEFC cathode catalyst requires an excess amount of platinum due to the degradation of oxygen reduction reaction (ORR) activity at acidic environment and slow reaction kinetics at low temperature. Therefore, it is important to reduce the use of platinum in the catalyst and improve its catalytic activity as well as durability. Core-shell structure is one of the solutions to achieve a higher catalytic activity, higher durability and less use of platinum. However, the factor of controlling ORR activity in core-shell catalyst still has not well understood such as potential/temperature-dependent surface structures and oxidation states of platinum. Convection voltammetry using rotating disc electrode (RDE) is one of the usable ways for evaluating ORR activity of cathode catalyst materials for PEFCs. However, the correlation between ORR activity and the electronic as well as local structure of these materials casted on RDE is not fully clear yet. In this paper, we report the temperature dependency of ORR activity of TEC10V30E Pt/C catalysts (T.K.K.) and Pd-core/Pt-shell/C catalysts from 25 oC to 60 oC, combining RDE measurements and Operando X-ray absorption spectroscopic measurements (XAS). We investigated the correlation with the electronic structure / local structural parameters of the Pt/C catalyst and investigated the factors that govern the oxygen reduction reaction activity on the RDE surface from the viewpoint of temperature dependency. In this research, we synthesized the 1 mono-layer platinum shell on the carbon-supported palladium (Pt-Pd/C) by copper under potential deposition method and investigated its ORR activity at different temperatures and the state of platinum by rotating disk electrode (RDE) measurements and operando X-ray absorption fine structure (XAFS) respectively. The effect of oxygen coverage at Pt surface on ORR activity was mainly discussed. Experimental A model electrode was prepared by applying a catalyst ink prepared from TEC 10 V 30 E Pt / C (TKK) to the surface of glassy carbon RDE. The 1 mono-layer platinum shell on the carbon-supported palladium (Pt-Pd/C) by copper under potential deposition method. The electrochemical cell was constructed using a model electrode fabricated in the working electrode, a Pt mesh for the counter electrode, a reversible hydrogen electrode for the reference electrode, and 0.1 M HClO4 aq for the electrolyte. Electrochemical surface area was calculated by CV measurement under N2 saturated condition and area specific activity value was determined by LSV measurement under N2 and O2 saturated conditions. Measurements were carried out at 10, 25, 40, 50, 60 ºC. For this model electrode, operand XAS measurement of Pt LIII -edge and Pt LII -edge were carried out by using the beamline BL37XU/BL01B1 in SPring-8 (Japan). The measurements were performed by a fluorescent method using a temperature variable type Operand cell that can directly measure the electrocatalyst applied to RDE (Fig. 1). The number of Pt 5d orbital vacancies was calculated from the obtained XANES spectrum, and the local structure of Pt was analyzed from the EXAFS spectrum. The oxygen reduction activity performance in the electrochemical measurement was evaluated from the area specific activity value at 0.9 V of the Pt / C catalyst at 10, 25, 40, 50, 60 ºC. The oxygen reduction activity of the model electrode is determined by the electrochemical parameters related to the oxygen reduction reaction such as the oxygen coverage. Results and discussion According to RDE results, Pt-Pd/C has a potentially higher ORR specific activity than the conventional Pt/C at low temperature (< 50℃) while its catalytic activity has suddenly deteriorated over 60℃. Linear sweep voltammetry showed the coverage of oxygen species at Pt surface dramatically increased at high temperature in 1.1 V (vs. RHE). This oxygen species could reduce the ORR by blocking active sites for additional O2 adsorption. We also found the rapid increase of Pt 5d orbital vacancy by X-ray absorption spectra with the temperature, indicating that Pt on Pd/C was more easily oxidized over 60℃ than Pt/C.

Evaluation of phase separation in a single-stage vertical anaerobic reactor: Performance and microbial composition analysis

In order to explore whether the acidogenic phase and methanogenic phase could be separated vertically into a single-stage anaerobic reactor, a controlled double circulation (CDC) anaerobic reactor was proposed for treating traditional Chinese medicine (TCM) wastewater in this study. The results showed that most of the organic pollutants and refractory were removed in the first reaction area where most of the amount of sludge existed. The organic acids were accumulated in the first reaction area, and larger specific methanogenic activity (SMA) and coenzyme F420 values were found in the second reaction area. Bacterial and archaeal community structures in the two reaction areas of the CDC reactor were analyzed by Illumina MiSeq Sequencing, which revealed that the archaeal community showed larger difference compared with the bacterial community. Differences in the performance and microbial composition of the two reaction areas confirmed that phase separation was implemented in the CDC reactor.

POTENTIALLY POSSIBLE POPULATION EXPOSURE DOSES DUE TO MINERAL NATURAL MEDICAL WATER CONSUMPTION

Mineral natural table, medical-table and medical water is usually characterized by enhanced mineralization, so annual consumption of such water for drinking and cooking is much lower than standard water consumption of adult population. The limitation of population exposure due to mineral natural table and medical-table water could be achieved by the implementation of limitation of their consumption. The aim of the investigation is to estimate potentially possible population exposure doses from mineral natural medical water consumption on an example of the water which is used for drinking therapy in the complex of sanatorium health resort treatment of patients in one of the sanatoriums of Saint-Petersburg. The data on mineral medical water radionuclides specific activity values used for patients exposure doses estimation was obtained during implemented radiochemical analysis carried out using the techniques developed in the Institute of Radiation Hygiene. Obtained results of the investigations and their analysis demonstrated that potentially possible patients’ maximal annual effective exposure doses due to implementation of mineral natural medical water for drinking therapy in the complex of sanatorium health resort treatment will not exceed definitely the reference dose level, recommended by WHO, equal to 0.1 mSv/year because of a low amount of water consumption prescribed by a physician. It is clear unreasonable to set limitations on natural radionuclides content in mineral medical water because patients take it as a medicine according to physician prescribing and the consumption of such water is connected with their therapy properties. Principle of justification of the procedures appointment has to be applied when the course of mineral medical water treatment is prescribed. The essence of the principle is to compare therapy (medical) benefits as a result of treatment with the damage to health as a result of radiation exposure. It is necessary to estimate the effective internal exposure doses due to mineral natural medical water consumption for different age groups of population for the process of justification of therapy procedures.

Assessment of radiation exposure to human and non-human biota due to natural radionuclides in terrestrial environment of Belgrade, the capital of Serbia

The main focus of this study was to assess radiation exposure to human and non-human biota due to natural radionuclides in soil of the Serbian capital. For the first time, ERICA tool was employed for calculation of gamma dose rates to non-human biota in this area. In analyzed soils, the mean values of 226Ra, 232Th and 40K specific activities were found to be 35, 43 and 490 Bq kg−1, respectively. The distribution of analyzed natural radionuclides in soils was discussed in respect to its statistically significant correlations with sand, silt, clay, carbonates, cation exchange capacity and pH value. The annual outdoor effective dose rates to the population varied from 48 to 98 μSv, and the total dose rates to terrestrial biota, calculated by ERICA tool, varied from 9.84 × 10−2 μGy h−1 (for tree) to 5.54 × 10+0 μGy h−1 (for lichen and bryophytes). The results obtained could serve as a baseline data for the assessment of possible anthropogenic enhancement of the total dose rate to human and non-human biota of the study area.

ЛИКВИДАЦИЯ ЯДЕРНОГО НАСЛЕДИЯ: РАДИАЦИОННО-ГИГИЕНИЧЕСКИЕ КРИТЕРИИ БЕЗОПАСНОСТИ ДЕЗАКТИВИРОВАННЫХ УЧАСТКОВ ТЕРРИТОРИИ, ЗДАНИЙ И СООРУЖЕНИЙ

The article presents approaches to the establishment of criteria (requirements) of radiation safety to the decontaminated areas of the territory, buildings and decommissioned facilities of use of atomic energy and other types of practical activities with sources of ionizing radiation. The main directions of further use of the decontaminated areas of the territory, buildings, and constructions, including 5 scenarios of restricted and unrestricted use, are determined; the criteria of radiation safety in the term of a dose constraint of a critical group of the population in 0.3 mSv/year living or working on decontaminated objects are established; the controlled parameters of the radiation situation and their levels, as well as the list of radionuclides subject to control are justified. The article presents the values of specific activity (Bq/kg) of residual radioactive contamination of soils and materials of buildings and structures, the radiation dose to the population in which will not exceed 0.3 mSv/year. Based on the presented data, draft sanitary rules and guidelines have been developed.

Characterization of a Novel endo-β-1,4-glucanase from the Model Soft Rot Phytopathogen Pectobacterium wasabiae SCC3193

Pectobacterium wasabiae is a dreadful causal agent of potato soft rot. It relied mainly on the production a wide range of plant cell wall-degrading enzymes to cause disease. Of the different enzymes, the endo-b-1,4-glucanase may be important in pathogenesis, being responsible for hydrolyzing the cellulose. In the process of pathogen infection, cellulase secreted by the pathogen is major determinant of pathogenicity, which played an important role in softening and decomposition of cell wall. But so far, the related research very rarely. However, most characteristic of the cellulase in the soft rot bacteria was not clear so far. Here, a putative endo-b-1,4-glucanase gene from P. wasabiae SCC3193 was previously synthesized according the bias codon of yeast, heteroexpressed in Pichia pastoris, and further investigated for its characteristic. Pectobacterium wasabiae SCC3193 is a genetically well characterized model in soft rot research. SDS-PAGE analysis showed that the recombinant endo-b-1,4-glucanase (PcegAI) produced in P. pastoris has a molecular mass of approximately 30kDa. When CMC was used as substrate, it exhibited maximal activity at pH 4.0 with an optimum temperature of 40°C, and stable at pH 5-8. The Km and specific activity values for CMC are 64.5 mM and 7 ×103 U mg-1 respectively. Most metallic ions had no influence on the activity of endo-b-1,4-glucanase at a concentration of 1 mM except for Cu2+ and Mn2+. These characteristics suggested that PcegAI may play a major role in degrading of cellulose polymers. The high activity of this enzyme also has potential in biomass opening, such as the bioconversion of lignocellulosic materials and bioethanol production.

Радиационная обстановка на хвостохранилище Степногорского горно-химического комбината и прилегающих территориях. Сообщение I

Purpose: Assessment of the radiation situation at the tailing dump of the Stepnogorsk Mining-Chemical Combine (SMCC) and the settlements around.&#x0D; Material and methods: The tailing dumps of the SMCC and the settlements near located of Aksu, Kvartsytka and Zavodskaya were objects of the radioecological research. Field expedition studies were performed during the summer period and consisted in carrying out a detailed gamma survey of the territory of the investigated objects and settlements, sampling of surface waters, vegetation, surface and layered soil samples. In settlements, along with sampling and studying the gamma background, the equivalent equilibrium volume activity of radon daughters in residential and industrial premises was determined. To determine the concentrations of the studied radionuclides a background was selected, within which the levels of their global deposition were studied. To calculate the individual effective radiation dose of the population the National Radiation Protection Board methodology was used as the basis.&#x0D; Results: In the northern part of the tailing dump of the SMCC in the adjoining territory, a radioactive contamination site was found where the specific activity values for 226Ra, 232Th and 210Pb reach values of 1500–2000 Bq/kg. On the territory of the Aksu settlement, 5 local areas with the area from 25 to 1000 m2 were found, with the intensity of ambient dose equivalent of gamma radiation from 0.39 to 0.86 µSv/h. In the Zavodskaya village, two areas with increased levels of gamma radiation intensity were identified. &#x0D; Conclusion: The obtained results of field work and laboratory analytical studies testify to the negative impact of the tailing dump of the SMCC on the environment of adjacent territories, expressed in contamination of soil, water and vegetation with radionuclides. The nature of the abnormal areas on the territory of the settlements of Aksu and Zavodskaya excludes their origin from the tailing dump of the SMCC. The appearance of these areas of contamination may be due to the use of materials of the 3rd class in sanitary and hygienic standards for improvement and road construction. The probable annual effective dose for the population living in the radioactive local areas of the Aksu ~6.5 mSv/year, at the normal rate of 1 mSv/year from man-made radiation sources.

Dynamic response analysis of corrosion products activity under steady state operation and Mechanical Shim based power-maneuvering transients in AP-1000

The advanced Mechanical Shim (MSHIM) core control strategy is a flexible power-maneuvering feature of AP-1000 reactor. This is vulnerable for variation in Activated Corrosion Products (ACPs) buildup while providing frequent power maneuver opportunities. It is therefore important to study the ACPs buildup behavior in AP-1000 reactor. A new simulation methodology is developed to analyze the specific activity due to ACPs under steady state operation and MSHIM based power-maneuvering transients. The dynamic response of coolant specific activity due to corrosion products (56Mn, 59Fe, 24Na, 60Co and 99Mo) has been analyzed under steady state full power operation. It is observed that short-lived 56Mn and 24Na are major sources of predominant and total coolant specific activity during reactor operation, whereas long lived ACPs mainly contributed after shutdown. The parametric study of MSHIM control based daily load follow operation, step load, load regulation and scram transients is also carried out. It is found that specific activity increases or decreases directly as a function of power maneuvering levels during daily load follow and load regulation transients. However, if power becomes constant followed by the decreasing power maneuvering, the specific activity retains its prior behavior and finally attains a lower constant value. For the step load transients, the specific activity value increases sharply and finally reaches a new saturation level. In all of the anticipated power maneuvering transients, the post saturation specific activity value shows direct relation with net change in power before and after the transients. The higher the difference between pre-transient and post-transient power levels, the longer it takes to achieve saturation value and vice versa. For postulated scram transients, it is observed that the specific activity due to 56Mn suddenly decreases after the transients mainly due to its short half-life and discontinuation in further production.

Oxygen reduction reaction on electrochemically deposited silver nanoparticles from non-aqueous solution

Silver was electrodeposited onto glassy carbon electrode from 0.1 mM AgClO4 acetonitrile solution containing 0.1 M LiClO4. The electrochemical deposition was carried out at constant potential of −0.5 V vs. SCE. The surface morphology was studied by scanning electron microscopy and the average particle size was determined to be 45 nm to 90 nm when increasing the deposition time from 10 s to 300 s. The rotating disk electrode (RDE) method was employed for oxygen reduction studies in 0.1 M KOH solution. It was determined that the final product for the reaction is water and the rate-determining step is the slow transfer of the first electron to O2 molecule. The specific activities (SA) and mass activities (MA) were calculated from the RDE results and the latter was independent of the deposition time. The method used to determine electroactive surface area of Ag influenced substantially the determination of SA values.

Natural radioactivity in some building materials and assessment of the associated radiation hazards

Abstract The results of the specific activities of 232Th, 226Ra and 40K measured in samples of commonly used building materials in Bosnia and Herzegovina are presented. Measurements were performed by gamma-ray spectrometer with coaxial HPGe detector. The surface radon exhalation and mass exhalation rates for selected building materials were also measured. The determined values of specific activities were in range from 3.16±0.81 Bq kg−1 to 64.79±6.16 Bq kg−1 for 232Th, from 2.46±0.95 Bq kg−1 to 53.89 ±3.67 Bq kg−1 for 226Ra and from 28.44±7.28 Bq kg−1 to 557.30±93.38 Bq kg−1 for 40K. The radium equivalent activity, the activity concentration index, the external and internal hazard indices as well as the absorbed dose rate in indoor air and the corresponding annual effective dose, due to gamma-ray emission from the radioactive nuclides in the building material, were evaluated in order to assess the radiation hazards for people. The measured specific activities of the natural radioactive nuclides in all investigated building materials were compared with the published results for building materials from other European countries. It can be noted that the results from this study are similar to the data for building materials from neighbouring countries and for building materials used in the EU Member States. The radiological hazard parameters of the building materials were all within the recommended limits for safety use.