Further results in search for transuranium elements in effluents discharged to air from nuclear power plants

In this work we present data on transuranium nuclides ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ²⁴⁴Cm in effluents discharged to air (activity concentrations and annually discharged activities of individual radionuclides) from 7 stacks in 2004–2009. In the effluents discharged to air from one stack low activities of transuranium nuclides were observed throughout the studied period. Transuranium nuclides had been discharged to air from this stack also in previous years since 1996 when defect in the cladding of a fuel element and consequent contamination of the primary circuit occurred. In the effluents discharged to air from another stack transuranium nuclides were observed only in some monitoring periods of studied years. We could not prove the presence of transuranium nuclides in the effluents of the other stacks up to 2006. The transuranium nuclides in discharged effluents were registered in the second half-year of 2006. In 2007–2008 especially low activities of ²⁴¹Am were found in these effluents.     

NAA for optimization of radiation shielding of nuclear power plants

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.     

Agent for chemical dissolution of oxide layers grown on heat transfer surfaces of carbon steel components of nuclear and classifical power plants

Inhibited buffer-complexing ferrous citrate+citric acid solutions, 2.5<pH<3.5, at 363±5K, is used to dissolve a compact magnetite layer grown on low alloyed steel in a nuclear plant generator. The average rate of oxide dissolution is 40 m/h. Similarly, a compact duplex layer of magnetite covered by hematite formed on a carbon steel pipe of a classical heat exchanger dissolves in less than 10 h. The mean rate of metal uniform corrosion ranges between 1 and 9 mg/cm² h depending on pH, inhibitors and citrate ion concentration.     

Assessment of the EPDM seal lifetime in nuclear power plants

An EPDM seal was qualified for use in nuclear power plants (NPPs). The primary function of the seal is to prevent leakage of unwanted fluids and gases during long-term normal operation, as well as during postulated accidents which may occur at the end of the planned service lifetime. Tested samples were compressed between two massive metal plates (the same compression as under regular service conditions) and exposed to an accelerated ageing procedure to simulate up to 10 years of operation, including accident simulation. Mechanical properties, compression set and a gas leakage test were carried out. The minimum necessary compression to keep the required tightness under all conditions during normal service and during accident conditions was found and the service lifetime was assessed for two seal thicknesses.     

A study on kinetics of ignition reaction of B4C/KNO3 and B4C/KClO4 pyrotechnic smoke compositions

Journal of Thermal Analysis and Calorimetry - Presented herein is a study on the ignition reaction kinetics and mechanism of B4C/KNO3 and B4C/KClO4 pyrotechnic smoke compositions using the...     

C4/C5烃催化裂解制低碳烯烃的研究进展

从催化剂类型、裂解工艺、催化裂解的影响因素和裂解机理4个方面对国内外C4／C5烃催化裂解制低碳烯烃的研究进行了综述。催化裂解制低碳烯烃催化剂主要采用ZSM-5分子筛系列催化剂，在此基础上发展了酸改性或水热改性高硅ZSM系列分子筛及介孔MCM41分子筛。总结了国内外C4／C5烃的裂解工艺，认为影响催化裂解的主要因素是裂解原料、催化剂类型及工艺条件。目前，裂解机理主要是自由基与碳正离子机理相结合的机理。并简述了本课题组目前有关C4烷烃催化裂解的主要研究进展。     

C4/C5烃催化裂解制低碳烯烃的研究进展

从催化剂类型、裂解工艺、催化裂解的影响因素和裂解机理4个方面对国内外C4/C5烃催化裂解制低碳烯烃的研究进行了综述。催化裂解制低碳烯烃催化剂主要采用ZSM-5分子筛系列催化剂,在此基础上发展了酸改性或水热改性高硅ZSM系列分子筛及介孔MCM-41分子筛。总结了国内外C4/C5烃的裂解工艺,认为影响催化裂解的主要因素是裂解原料、催化剂类型及工艺条件。目前,裂解机理主要是自由基与碳正离子机理相结合的机理。并简述了本课题组目前有关C4烷烃催化裂解的主要研究进展。     

Quantitative determination of site occupancy of multi-rare-earth elements doped into Ca2SnO4 phosphor by electron channeling microanalysis

X-ray fluorescence analysis based on electron channeling effects in transmission electron microscopy (TEM) was performed on Ca₂SnO₄ phosphor materials doped with Eu³⁺/Y³⁺ at various concentrations, which showed red photoluminescence associated with the ⁵D₀-⁷F₂ electric dipole transition of Eu³⁺ ions. The method provided direct information on which host element site dopant elements occupy, the results of which were compared with those of X-ray diffraction (XRD)-Rietveld analysis. The obtained results indicated that while it is not favorable for a part of Eu³⁺ to occupy the smaller Sn⁴⁺ site, this is still energetically better than creating Ca vacancies or any other of the possible charge balance mechanisms. The local lattice distortions associated with dopant impurities with different ionic radii were also examined by TEM-electron energy-loss spectroscopy (TEM-EELS). The change in PL intensity as a function of dopant concentration is discussed based on the experimental results, although the general concept of concentration quenching applies.     

Assessment of parameters for simulation of thermal ageing of materials in nuclear power plants using DSC

Summary Simulation of thermal ageing is an important part of qualification of materials designed for the use in nuclear power plants (NPP). According to standards, the simulation of long-term service thermal ageing is performed isothermally at elevated temperature using Arrhenius methodology. The samples or equipment are aged in thermal chamber, to bring them to the same state as after long-term service time. To proceed a reliable simulation, the testing parameters should be taken very carefully and the accelerator factors should not be too high. The testing temperature and time and the activation energy are the most important parameters. Determination of these factors and the limitations of their use in practice are discussed.     

Flash X-ray tube for X-ray photoelectron studies of melts

A flash X-ray tube designed for studies of nonequilibrium processes in melts is described. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1160–1162, November–December, 1998.     

Spontaneous reductive decomposition behavior of hydrogen permanganate in water for chemical decontamination of nuclear power plants

The spontaneous reductive decomposition behavior of HMnO₄ in water as a function of the initial HMnO₄ concentration and reaction temperature was investigated. The decomposition of HMnO₄ was fast in the early stage of the reaction and thereafter slowed down significantly, regardless of the initial HMnO₄ concentration. The loss of HMnO₄ by spontaneous reductive decomposition increased with increasing reaction temperature. Based on the experimental results and the classical nucleation theory, a mathematical model was developed using a combination of two first-order reactions representing the nucleation and crystal growth of MnO₂ to predict the spontaneous reductive decomposition behavior of HMnO₄.     

13C nuclear magnetic resonance studies of cellulose acetate

¹³C-NMR spectra of ring carbons and O-acetyl carbonyl carbons of cellulose acetate (CA) in dimethyl sulfoxide-d₆ were analyzed. The CA samples with the degree of substitution (DS) ranging from 0.84 and 1.91 were prepared by homogeneous acetylation of cellulose with acetic anhydride in a 10% LiCl/dimethyl acetamide solvent. It was found that the use of these low DS samples permitted easier assignments not only of the ring carbon but also of the O-acetyl carbonyl carbon signals. The assignments were confirmed by comparing with the ¹H-NMR spectra of the samples obtained by complete acetylation of the corresponding CA samples with acetyl-d₃ chloride. Two methods for determining the distribution of O-acetyl groups of CA, i.e., the relative DS at the three different types of hydroxyl groups, were developed. One is based on the measurements of the relative intensities of the signals for the ring carbons and the other is based on the measurements of the relative intensities of the signals for the O-acetyl carbonyl carbons.     

Solubility of AlPO4 in cryolite melts

The solubility of aluminium orthophosphate in cryolite melts was determined. Part of the binary phase diagram of the system Na₃AlF₆-AlPO₄ was investigated. The eutectic point was determined to be at 43.7 mass% (or 57.2 mol%) AlPO₄ and (696 ± 1) °C. It is suggested that in pure molten cryolite melts the orthophosphate ion dissociates partly into a metaphosphate ion and an oxide ion.     

Radioisotope X-ray fluorescence analysis of some elements in fly ash of Afsin-Elbistan power plants

Energy dispersive X-ray fluorescence technique was used for the determination of As, Sr, Mo, Ba, In and Ce in fly ash Afsin-Elbistan power plants using the standard addition method. An annular²⁴¹Am source was employed for excitation of the K shell of the elements.     

HV-4B型碳硫分析仪的故障及维修

介绍HV-4B型碳硫分析低度的常见故障、故障产生的原因及排除方法。     

Determination of plutonium,americium and curium in airborne effluents of nuclear power plants

A radiochemical method has been developed for the determination of²³⁸Pu,^{239, 240}Pu,²⁴¹Am,²⁴²Cm and²⁴⁴Cm in airborne effluents of nuclear power plants. The method involves conversion of transuranium elements to acid-soluble forms, dissolution, purification, electrodeposition and alpha spectrometric determination. Final recovery ranged from 69.0 to 75.4% for plutonium and from 26.8 to 68.3% for americium and curium.     

Recombination of hydrogen and oxygen in the technical gaseous waste of nuclear power plants

The recombination of hydrogen and oxygen in technical gaseous waste of nuclear power plants in enlarged scale experiment has been studied on the basis of our previous work.¹ The catalyst and its best operating conditions for recombination of hydrogen and oxygen determined in a small scale experiment were demonstrated and tested. The results show that the data obtained in an enlarged scale experiment agreed well with that of in a small scale test. The recombination rate of H₂ and O₂ was higher than 98.3% and 99.98% respectively. After recombination, the residual concentrations of H₂ and O₂ in waste gas were O₂<3 ppm, H₂<400 ppm. The Pd-Al₂O₃ catalyst and operating conditions determined for gaseous waste processing of nuclear power plants were satisfactory.