Permeability of fluorine and some fluorine-containing gases through nonporous fluorine-stable polymers

The experimental coefficients of permeability of fluorine, hydrogen fluoride, and uranium and tungsten hexafluorides through nonporous films consisting of certain fluorine resistant polymer materials are presented. It is shown that the membrane method of removing hydrogen fluoride from fluorine and uranium and tungsten hexafluorides is attractive. __________ Translated from Atomnaya énergiya, Vol. 102, No. 6, pp. 367–370, June, 2007.     

Chemical absorbent for catching halogen-containing gases discharged from isotope separation plants

The results of industrial tests of a cascade of chemical absorbents for catching spent halogen-containing processes gases during discharge into the atmosphere are discussed. It is noted that the volume of the discharged gases decreases as a result of CO₂ absorption. The HF and Cl₂ content in passing gas can serve as a criterion for the completion of each catching step; Cl₂ detection after the last step is a service life criterion for all chemical absorbents of a facility without exception. The average catching efficiency is 99.7 and 98.5% with respect to fluorine- and chlorine-containing components, respectively. An approximate calculation of the near-ground concentration of HF and Cl₂ is performed. The gases discharged by the isotope separation plant at the Siberian Chemical Combine were purified at the level of the maximum admissible concentration for the working zone and not at the level of the technical norm established individually for each industrial enterprise. Equipping nuclear fuel cycle enterprises with such systems will make it possible to decrease environmental contamination considerably.     

Multidimensional effects in laminar filmwise condensation of water vapour in binary and ternary mixtures with noncondensable gases

This paper is dealing with the multidimensional modelling of gravity driven water vapour free convection condensation from binary and ternary mixtures of condensable and noncondensable gases. In the case of ternary mixtures, a special attention is paid to the influence of the light gas on the transport phenomena in the gaseous phase. Two solution methods have been applied: an analytical solution employing the boundary layer similarity approximation and a numerical solution of multi-fluid, multi-component formulation of the conservation equations. It has been demonstrated that the two methods are equivalent when applied to binary mixtures in simple geometries. However, to capture the spatial effects and the ternary mixture phenomena the latter method must be used.     

Radiation vulcanization of fluorine copolymers

Irradiation of rubberlike fluorine copolymers gives a rubber with poor physicochemical properties, but with fillers it is possible to obtain rubbers with valuable technical properties. The surface activity of the filler has a strong effect on the properties of the rubbers obtained. The most valuable properties are those of radiation rubbers that contain active channel black. They have a higher resistance to heat aging, are more stable to solvents and static deformation than the usual peroxide rubbers. In contrast to polytetrafluoroethylene and polytrifluorochloroethylene, rubberlike fluorine copolymers of the Kel-F type are cross-linked under the action of ionizing radiation. The degree of cross-linking of the fluorine copolymers is determined by their composition and the irradiation dose and medium. The presence of oxygen promotes a greater degree of cross-linking.     

偕胺肟基超高分子量聚乙烯纤维对含氟含铀溶液中铀的吸附性能研究

铀浓缩过程中产生的含氟含铀废水中铀浓度较高,需将铀浓度降至可排放的限定值以下,以避免污染水生生态系统,进而对人体健康造成威胁。采用电子束预辐射接枝法将丙烯腈与甲基丙烯酸接枝于超高分子量聚乙烯纤维(Ultra-high Molecular Weight Polyethylene,UHMWPE)上,并通过胺肟化反应制备出偕胺肟基(Amidoxime,AO)吸附材料。利用红外光谱、X射线光电子能谱、扫描电镜对改性前后UHMWPE纤维的化学结构及表面形貌进行表征,评估AO基UHMWPE纤维对模拟含氟含铀废水中铀酰离子的吸附性能。试验结果表明:AO基UHMWPE纤维对铀酰离子的吸附行为遵循准二级动力学模型和Langmuir等温吸附模型;铀饱和吸附容量可达151.98 mg?g-1(铀初始浓度:40 mg?L~(-1);氟离子浓度:10 g?L~(-1);吸附剂:0.2 g?L~(-1);吸附时间:21 d),与理论饱和吸附容量(153.85 mg?g-1)基本吻合;增加吸附剂的用量(1.5 g?L~(-1))可使铀酰离子的去除率达到99.93%,残余铀酰离子浓度为28μg?L~(-1),符合国家排放标准(50μg?L~(-1))。     

Thermophysical properties of pure gases and mixtures at temperatures of 300-30 000 K and atmospheric pressure:thermodynamic properties and solution of equilibrium compositions

The equilibrium compositions and thermodynamic properties(density,enthalpy,etc at constant pressure)of plasma of pure gases and mixtures under local thermodynamic nonequilibrium have been calculated in this paper.The homotopy Levenberg-Marquardt algorithm was proposed to accurately solve nonlinear equations with singular Jacobian matrices,and is constructed by the Saha equation and Guldberg-Waage equation combined with mass conservation,the electric neutrality principle and Dalton's partial pressure law,to solve the problem of dependence on the initial value in the process of iteration calculation.In this research,the equations at a higher temperature were solved and used as the auxiliary equations,and the homotopy control parameters'sequence of the homotopy equations was selected by equal ratios.For auxiliary equations,the iterative initial value was obtained by assuming that there were only the highest-valence atomic cations and electrons at this temperature,and the plasma equilibrium composition distribution with the required accuracy was ultimately solved under the current conditions employing the Levenberg-Marquardt algorithm.The control parameter sequence was arranged according to the geometric sequence and the homotopy step was gradually shortened to ensure continuity of the homotopy process.Finally,the equilibrium composition and thermodynamic properties of pure N2,Mg(30％)-C02(70％)and Mg(40％)-CO(50％)-N2(10％)mixture plasma at atmospheric pressure were calculated and the calculation process of some specified temperatures was shown and analyzed.The calculation accuracy of equilibrium composition is higher than other findings in the literature.The results for the thermodynamic properties are in good agreement with data reported by the literature.     

Calculation of a square cascade with losses of the working material in the steps and pipelines during separation of multicomponent isotopic mixtures

A method is proposed for calculating the stationary mass transfer of a multicomponent isotopic mixture in a square cascade with arbitrary enrichment and losses at the separation steps and in the pipelines of the cascade. The method, which is based on successive approximation of the cascade separation factor, makes it possible to reduce computational time substantially compared with the conventional method of quasilinearization. __________ Translated from Atomnaya énergiya, Vol. 104, No. 1, pp. 17–23, January, 2008.