Investigation of the internal friction increase caused by temperature changes in polycrystalline uranium specimens

The increase in the internal friction with time in heating at different rates was measured with respect to the damping of torsional vibrations during the heating of specimens. Specimens of -phase quenched, - and -phase annealed, and recrystallized polycrystalline uranium were investigated. It is shown that the rate of the internal friction rise in specimens gradually decreases in time and that the internal friction increment attains a limiting value, the magnitude of which is approximately proportional to the specimen heating rate. The internal friction increment is related to stresses which arise in the specimen due to the anisotropic thermal expansion coefficient when the temperature changes. The reduction in internal stresses, which is either due to an increase in the grain size to a magnitude comparable to the diameter of the specimen under investigation or the formation of a predominant orientation in specimens, results in a reduction of the internal friction increment. During the heating process, also macroscopic shearing deformation occurs in the specimen. Such an increase in internal friction in heating was also observed in a thermally anisotropic metal, such as zinc; it was not observed in metals with isotropic thermal expansion coefficients — aluminum and molybdenum.     

Internal friction in uranium

Studies have been made of the temperature dependence of internal friction and the shear modulus in uranium. The internal friction in uranium depends on the heat treatment and is reduced after annealing in the ß and regions. During polymorphous transformations the internal friction changes its value isothermally. The transitions ß and ß are accompanied by a reduction in the internal friction and ß and ß by an increase in the internal friction. Each polymorphous modification of uranium in the temperature ranges for its existence has its own value of internal friction.     

High-temperature internal friction in polycrystalline Zirconium and Zircaloy-4

The data on the high-temperature internal friction of zirconium and zirconium alloys are reviewed and new results on zirconium and Zircaloy-4, measured at low and at intermediate frequencies, are presented. It is shown that the damping spectrum of pure zirconium, for annealed polycrystals, shows a peak probably related to relaxation of grain or subgrain boundaries. The data on Zircaloy-4 show two peaks: one near the grain-boundary peak in the pure metal and another one at a higher temperature. Possible mechanisms for these peaks are discussed. Finally, the high-temperature internal friction background of zirconium and zirconium alloys is analyzed and, for Zircaloy-4, the apparent activation enthalpy is found to be related to the grain size.     

Coefficient of static friction of the uranium dioxide-zirconium alloy pair under irradiation

Moscow Engineering Physics Institute. Translated from Atomnaya Énergiya, Vol. 71, No. 5, pp. 463–466, November, 1991.     

The oxidation of polycrystalline uranium dioxide in air at room temperature

The nature of the interaction between interstitial impurities and substitutional solutes in vanadium is investigated experimentally by measuring the internal friction. The nature of the interaction can be explained in terms of the chemical affinity. Substitutional atoms, whose oxide or nitride formation energy is greater than that of vanadium act as attractive centers to oxygen or nitrogen. On the other hand, substitutional atoms with formation energy smaller than that of vanadium act as non-interactive or repulsive centers. Iron, copper, nickel, chromium, and manganese are non-interactive or repulsive to oxygen; iron, nickel, beryllium, copper, chromium, and manganese are non-interactive or repulsive to nitrogen. The region around the substitutional iron forbidden to oxygen is estimated to extend to the second nearest neighbour sites. Titanium, aluminum, and beryllium are attractive to oxygen and aluminum and titanium to nitrogen. Binding energies estimated are 0.26 ± 0.4 eV for titanium and oxygen, 0.14 eV for aluminum and oxygen, and 0.27 eV for beryllium and oxygen.     

Properties of uranium vacancies in uranium monocarbide

From the excess resistivity obtained by quenching from temperatures between 1300 and 1600 °C a formation energy of 1.7 eV is determined. The quenchedin resistivity recovers with an activation energy of 2.2 eV in the temperature region between 400 and 600 °C. These two values are attributed to the formation and migration activation energies of uranium vacancies, respectively. It is further shown that uranium monocarbide remains single-phase, if the deviation from stoichiometry does not exceed more than a few tenths of one percent and if gases (mainly oxygen) are in solid solution.     

The effect of neutron irradiation on the internal friction of zinc monocrystals and polycrystals

By an investigation of the effect of neutron irradiation on the internal friction of zinc polycrystals and monocrystals, we determined the value of the critical stress amplitude _cr before and after irradiation.It was shown that the value of _cr, which may be related to the beginning of the motion of dislocations, increases as a result of irradiation. The increase of _cr in irradiated zinc is explained by the fact that the dislocations are held fixed as a result of interaction with point defects.In addition, we studied the effects of the orientation of the basal plane (0001) with respect to the longitudinal axis of the zinc monocrystal specimen on internal friction and on _cr. The results of the investigations of the effect of orientation on internal friction and on _cr are compared with well-known representations of slippage obtained from static studies of monocrystals in tension along one axis.The authors express their gratitude to S. T. Konobeevskii for his comments on the results of the work.     

MUA型微量铀分析仪测定801矿铀的不确定度评定

测量不确定度是一个合理表征测量结果分散性的参数,体现着测量质量的高低。分析了用MUA分析仪测量801矿铀含量过程中不确定度的来源并计算各不确定度分量,得出合成标准不确定度和扩展不确定度,结果表明:MUA分析仪测量801矿铀的测量不确定度小,可信度高,其测量不确定度来源的主要因素为重复性实验不确定度。     

A study of chemical parameters of the internal gelation based sol-gel process for uranium dioxide

Internal gelation process is one of the important sol-gel routes for the preparation of spherical particles of fuel materials. Successful preparation of defect free fuel particles has been reported only with a narrow range of feed solution compositions. Investigations have been carried out to study the gelation behaviour of solutions containing uranyl nitrate, hexamethylene-tetramine (hexa) and urea with a view to defining the regions of possible interest to the process. A gelation field diagram has been constructed defining regions where a single phase gel can be readily obtained. A number of compositions from this gelation field diagram have been used for the preparation of UO₂ microspheres and it was observed that good spherical particles could be obtained with uranium concentrations ranging from 0.7 to 1.5 molar. The mole ratio (hexa, urea)/uranium for obtaining good particles decreased with increasing uranium concentration.     

Electrodeposition of metallic uranium at near ambient conditions from room temperature ionic liquid

The electrochemical behavior of U(IV) in the room temperature ionic liquid (RTIL), N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf₂), was investigated to evaluate the feasibility of using the RTIL for non-aqueous reprocessing application. In this context, the rate of dissolution of uranium oxide (UO₂) in HNTf₂ was studied at 353 K. The dissolution of UO₂ in HNTf₂ was rapid; nearly 50% of UO₂ dissolved within 3 h and more than 95% dissolved in 25 h. The resultant solution was dried, diluted with MPPiNTf₂ and the electrochemical behavior of U(IV) in MPPiNTf₂ was studied at 373 K at platinum, glassy carbon and stainless steel electrodes. The cyclic voltammograms of U(IV) in MPPiNTf₂ at platinum and glassy carbon electrodes consisted of four cathodic waves occurring at a peak potentials of −0.7 V (Fc/Fc⁺), −1.4 V, −2.2 V and −2.7 V. Controlled potential electrolysis of a solution of U(IV) in MPPiNTf₂ at −2.8 V (Fc/Fc⁺) resulted in the deposition of metallic uranium, which was confirmed by X-ray diffraction and scanning electron microscopy.     

Diffusion in uranium alloys with zirconium and titanium

Moscow Engineering-Physics Institute. Translated from Atomnaya Énergiya, Vol. 72, No. 1, pp. 30–33, January, 1992.     

热液型铀矿床可能的铀源——以俄罗斯斯特列措夫铀矿田为例

位于俄罗斯外贝加尔地区的斯特列措夫铀矿田为世界上最大的火山岩型铀矿田,也是俄罗斯最大的铀资源所在地。研究表明,斯特列措夫诸多铀矿床铀源主要源于组成破火山口地层大约1/3的强烈蚀变的流纹岩和由海西期黑云母花岗岩构成的破火山口基底。华南地区为我国重要的热液型铀矿床产地,斯特列措夫铀矿田铀源的研究对我国华南地区开展铀矿找矿勘探工作和成矿研究具有一定的指导意义。     

Economy of uranium resources in a three-component reactor fleet with mixed thorium/uranium fuel cycles

The potential for minimizing uranium consumption by using a reactor fleet with three different components and mixed thorium/uranium cycles has been investigated with a view to making nuclear power a more sustainable and cleaner means of generating energy. Mass flows of fissile material have been calculated from burnup simulations at the core-equivalent assembly level for each of the three components of the proposed reactor fleet: plutonium extracted from the spent fuel of a standard pressurized water reactor (first component) is converted to ²³³U in an advanced boiling water reactor (second component) to feed a deficit of multi-recycled ²³³U needed for the Th/²³³U fuel of the light/heavy water reactor (third component) which has a high breeding ratio. Although the proposed fleet cannot breed its own fuel, we show that it offers the possibility for substantial economy of uranium resources without the need to resort to innovative (and costly) reactor designs. A very high fleet breeding ratio is achieved by using only currently existing water-based reactor technology and we show that such three-component systems will become economically competitive if the uranium price becomes sufficiently high (>300 $/kg). Another major advantage of such systems is a corresponding substantial decrease in production of plutonium and minor actinide waste.