Analysis and Alternate Selection of Nanopowder Modifiers to Improve a Special Protective Coating System

This paper presents a practical approach for rational choice of silica nanopowders as modifiers to control and improve the performance of protective coating systems operating in harsh environmental conditions. The approach is based on the multiparameter analysis of nanoparticle reactivity of similar silica synthesized by using chemical and physical methods. The analysis indicates distinct adsorption centers due to the differences in the particles formation; the features of the formation and adsorption mechanisms lead to higher diffusion capacity of the nanoparticles, synthesized by physical methods, into a paint material and finally result in stronger chemical bonds between the system elements. The approach allows reducing the consumption of paint materials by 30% or more, at least 2-3 times increasing of the coating adhesion and hence the system life. Validity of the approach is illustrated through the data obtained from comparative modeling, factory testing, and practical use of modified systems

Электрохимическое осаждение I125 на серебряные подложки для микроисточников

A technique for plating of I125 on silver matrices by electrochemical plating at alkaline pH was developed and approved. The direct covering of I125 showed to be impossible and to take place only after pre-treatment of matrices by reagents with reductive and chelating properties. According to results of set of experiments the hydrazine hydrate was chosen as activating agent. The developed method includes preparatory activation of surface of silver matrices by processing with 0,01 mM hydrazine solution and then plating of I125 from NaI125 solution in 0,05 M alkaline solution with I125 volumetric activity of 50 mCi/ml (plating voltage of 950 mV). Radioactivity of samples made by developed method with time of coating for 30 or 60 min accounted for 1,12±0,12 mCi and 1.43±0.14 mCi, respectively. Thus, the developed method is efficient technique for plating of I125 on silver matrices, has replicable results and may be used for manufacturing of microsources. Разработан и апробирован метод осаждения I125 на серебряные подложки путем электрохимического нанесения из щелочной среды. Показано, что прямое нанесение I125 невозможно и происходит только после обработки подложек реагентами, обладаю- щими восстановительными и комплексообразующими свойствами. По результатам серии экспериментов в качестве активиру- ющего агента выбран гидразингидрат. Разработанная методика включает предварительную активацию поверхности серебряных подложек обработкой 0,01 мМ раствором гидразингидрата, а затем осаждение I125 из раствора NaI125 в 0,05 М растворе щелочи с объемной активностью I125 50 мКи/мл (потенциал нанесения 950 мВ). Активность образцов, полученных согласно предложенной методике при времени нанесения 30 или 60 мин, составила 1,12±0,12 мКи и 1,43±0,14 мКи, соответственно. Таким образом, пред- ложенный метод является эффективным способом осаждения I125 на серебряные подложки, дает воспроизводимые результаты и может быть использован при организации производства микроисточников.

The analysis of impact of irregularity in radionuclide coating of scaffold on the distribution of absorbed dose produced by grid of microsources

The impact of irregularity in radionuclide coating of scaffold on the distribution of absorbed dose produced by grid of microsources was analyzed. On engineering software MATHCAD the program for calculation of absorbed dose produced by grid of microsources was created. To verify this algorithm the calculation model for MCNP code was established and represented the area consisted of soft biological tissue or any other tissue in which the grid of microsources was incorporated. Using the developed system the value of possible systematic irregular coating of radioactivity on the microsource’s core was analyzed. The distribution of activity along the surface of microsource was simulated to create distribution of absorbed dose rate corresponding to experimental data on radiation injury. The obtained model of microsource with irregular distribution of activity was compared to conventional microsource with core coated regularly along the entire area of the silver stem by main dosimetry characteristics. The results showed that even for extremely irregular distribution of activity the distribution of dose rate produced by microsource in the tumor area was not substantially different from dose-rate field obtained for microsource with regularly coated activity. The differences in dose rates (up to 10%) in areas which were the nearest to the center of the grid were significantly lower than its decline from center to periphery of the grid. For spatial distribution of absorbed dose for specific configuration of microsource set and tracing of curves of equal level by selected cut-off the program SEEDPLAN was developed. The developed program represents precisely enough the spatial distribution of selected configuration set of microsources using results of calculation data for absorbed dose around the single microsource as basic data and may be used for optimal planning of brachytherapy with microsources. </p

Electrochemical plating of I125 on silver matrix for microsources

A technique for plating of I125 on silver matrices by electrochemical plating at alkaline pH was developed and approved. The direct covering of I125 showed to be impossible and to take place only after pre-treatment of matrices by reagents with reductive and chelating properties. According to results of set of experiments the hydrazine hydrate was chosen as activating agent. The developed method includes preparatory activation of surface of silver matrices by processing with 0,01 mM hydrazine solution and then plating of I125 from NaI125 solution in 0,05 M alkaline solution with I125 volumetric activity of 50 mCi/ml (plating voltage of 950 mV). Radioactivity of samples made by developed method with time of coating for 30 or 60 min accounted for 1,12±0,12 mCi and 1.43±0.14 mCi, respectively. Thus, the developed method is efficient technique for plating of I125 on silver matrices, has replicable results and may be used for manufacturing of microsources. </p

Исследование влияния неравномерности нанесения на подложку радионуклида на распределение поглощенной дозы, создаваемой решеткой микроисточников

The impact of irregularity in radionuclide coating of scaffold on the distribution of absorbed dose produced by grid of microsources was analyzed. On engineering software MATHCAD the program for calculation of absorbed dose produced by grid of microsources was created. To verify this algorithm the calculation model for MCNP code was established and represented the area consisted of soft biological tissue or any other tissue in which the grid of microsources was incorporated. Using the developed system the value of possible systematic irregular coating of radioactivity on the microsource’s core was analyzed. The distribution of activity along the surface of microsource was simulated to create distribution of absorbed dose rate corresponding to experimental data on radiation injury. The obtained model of microsource with irregular distribution of activity was compared to conventional microsource with core coated regularly along the entire area of the silver stem by main dosimetry characteristics. The results showed that even for extremely irregular distribution of activity the distribution of dose rate produced by microsource in the tumor area was not substantially different from dose-rate field obtained for microsource with regularly coated activity. The differences in dose rates (up to 10%) in areas which were the nearest to the center of the grid were significantly lower than its decline from center to periphery of the grid. For spatial distribution of absorbed dose for specific configuration of microsource set and tracing of curves of equal level by selected cut-off the program SEEDPLAN was developed. The developed program represents precisely enough the spatial distribution of selected configuration set of microsources using results of calculation data for absorbed dose around the single microsource as basic data and may be used for optimal planning of brachytherapy with microsources. Изучено влияние неравномерности нанесения радионуклида на подложку на распределение поглощенной дозы, создаваемой решеткой микроисточников. На инженерном программном комплексе MATHCAD разработана программа расчета мощности поглощенной дозы, создаваемой решеткой из микроисточников. Для верификации данного алгоритма создана расчетная модель для кода MCNP, представляющая собой область, состоящую из мягкой биологической ткани или любой другой ткани, в которую введена решетка микроисточников. При помощи разработанной системы было проанализировано значение возможного систематического неравномерного нанесения активности на сердечник микроисточника. В работе моделировалось распределение активности по поверхности микроисточника для создания распределения мощности поглощенной дозы, соответствующей экспериментальным данным радиационного поражения. Полученная модель микроисточника с неравномерным распределением активности сравнивалась по основным дозиметрическим характеристикам со стандартным микроисточником, использующим сердечник с активностью, нанесенной равномерно по всей площади серебряного стержня. Полученные результаты доказывают, что даже при очень неравномерном распределении активности распреде- ление мощности дозы, создаваемое в окрестности опухоли решеткой микроисточников, практически не отличается от поля мощности дозы, полученного для микроисточников с равномерно распределенной активностью. Различия в мощности дозы (до 10%) в ближайших к центру решетки областях существенно меньше, чем спад ее от центра к периферии решетки. С целью получения пространственного распределения поглощенной энергии для заданной конфигурации набора микроисточников и построения кривых равного уровня по заданным срезам создана программа SEEDPLAN. Разработанная программа достаточно точно отображает пространственное распределение для заданной конфигурации набора микроисточников, используя в качестве исходных данных результаты расчетов поглощенной энергии вокруг одиночного микроисточника, и может быть использована при оптимальном планировании брахитерии, использующей микроисточники.

Electrochemical plating of I125 on silver matrix for microsources

<p>A technique for plating of I125 on silver matrices by electrochemical plating at alkaline pH was developed and approved. The direct covering of I125 showed to be impossible and to take place only after pre-treatment of matrices by reagents with reductive and chelating properties. According to results of set of experiments the hydrazine hydrate was chosen as activating agent. The developed method includes preparatory activation of surface of silver matrices by processing with 0,01 mM hydrazine solution and then plating of I125 from NaI125 solution in 0,05 M alkaline solution with I125 volumetric activity of 50 mCi/ml (plating voltage of 950 mV). Radioactivity of samples made by developed method with time of coating for 30 or 60 min accounted for 1,12±0,12 mCi and 1.43±0.14 mCi, respectively. Thus, the developed method is efficient technique for plating of I125 on silver matrices, has replicable results and may be used for manufacturing of microsources.</p><p> </p

Neutron-induced fission cross section of U-234 and Np-237 measured at the CERN Neutron Time-of-Flight (n_TOF) facility

A high-resolution measurement of the neutron-induced fission cross section of U-234 and Np-237 has been performed at the CERN Neutron Time-of-Flight facility. The cross sections have been determined in a wide energy range from 1 eV to 1 GeV using the evaluated U-235 cross section as reference. In these measurements the energy determination for the U-234 resonances could be improved, whereas previous discrepancies for the Np-237 resonances were confirmed. New cross-section data are provided for high neutron energies that go beyond the limits of prior evaluations, obtaining important differences in the case of Np-237