Radiation-induced separation of solid solution in Fe-Ni invar

Radiation-induced solid solution separation (RISSS) in the Fe-34.7 at.% Ni invar alloy was investigated by residual resistivity and linear thermal expansion coefficient (TEC) measurements. The alloy was irradiated with 5 MeV electrons at 245-570 K and isochronous annealed. It was found that RISSS leads to an increase of 20% in the residual resistivity and an increase of 10⁻⁵ K⁻¹ in the TEC for an electron irradiation dose of 5 × 10¹⁸ cm⁻². The kinetics of RISSS are the same, but the irradiation efficiency coefficient increases approximately by a factor of 10 when the irradiation temperature rises in the range of 240-570 K. Vacancy clusters, which are formed under irradiation, retard the decomposition. It was shown that dissociation of the vacancy clusters at temperatures of 320-500 K was followed by the free migration of the formed vacancies, and leads to further RISSS.     

On the question of the nature of radiation damage in fissionable materials

This article gives a survey of the theory of radiation damage in materials irradiated by fast particles. An attempt is made to describe the processes of phase transformations under neutron irradiation of fissionable materials with the aid of diffusion equations. In this way an expression for the coefficient of diffusion D is obtained. The possible result of the effect of thermal spikes on the structure of the eutectoid a + is investigated for an annealed uranium-molybdenum alloy.     

Absorption of molecular forms of iodine from the gaseous phase by protective paint coatings

Conclusion Under the conditions of an accident, with molecular iodine present in the vapor-gas phase absorption of the molecular iodine by organosilicate coatings and especially by epoxy coatings can play a significant role in keeping the volatile forms of iodine in the containment vessel. At 90–100°C an OS-51-03 coating can absorb about 0.1 μg/cm² of molecular iodine and epoxy coatings, up to 3 μg/cm². The area of such coatings in the containment zone can run to tens of thousands of square meters, hence the coatings can absorb up to 550 g of iodine (in the case of coatings of three to five layers). Studies must be carried out, however, on the effect that the presence of water vapor, β and γ radiation, and aging of the coatings affect the efficiency of the absorption and containment of the molecular iodine. VNIPIéT. Translated from Atomnaya énergiya, Vol. 80, No. 6, pp. 442–446, June, 1996.     

Method of estimating the critical parameters of a body of arbitrary shape made from fissionable material

In this paper we consider an approximation method for determining the critical parameters of a body of arbitrary shape (or a group of bodies) made from fissionable material. In contrast with the variational method, the method described here is extremely simple and gives an error which is favorable from the point of view of safety as applied to fissionable materials; hence it is useful for engineering calculations.The method has been applied to fast neutron systems where the single-velocity approximation gives good accuracy.We wish to express our gratitude to B. D. Stsiborskii and M. L Kuvshinov for calling our attention to the experiment with the two interacting spheres; we also wish to thank V. A. Davidenko, Yu. N. Babaev and N. A. Dmitriev for discussion of the present work and a number of valuable comments.     

Comparative tests of the efficiency of sorption-filtering materials for removing radioactive iodine from gaseous emissions

Tests of how effectively CH ₃ ¹³¹ I and radioactive iodine are removed from air for the ventillation system of the VVRts reactor are performed. Carbon-fiber materials such as Busofite and fiber materials filled with impregnated OU-A carbon are studied as sorbtion-filtering materials.It is shown that these materials absorb iodine with approximately the same efficiency. The front layer traps I₂. CH₃I becomes distributed on several layers of the sorbing assembly. Iodine desorption from Busofite and the fiber material with OU-A is negligible (2%) over 114–3000 h. Recommendations are given for the composition of the fiber materials for removing iodine from air.Translated from Atomnaya Énergiya, Vol. 97, No. 6, pp. 457–464, December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Isoparaffin diluents in solvent extraction technology for the recovery of fissionable materials -improving the technical reliability and nuclear safety of the process

Institute of Petrochemical Synthesis of the Russian Academy of Sciences. A. A. Bochvar All-Union Scientific Research Institute of Inorganic Materials. Translated from Atomnaya Énergiya, Vol. 72, No. 5, pp. 473–481, May, 1992.     

Decomposition of a metastable solid solution in uranium-molybdenum alloy

The process leading to the decomposition of a metastable solid solution (γ² phase) in uranium alloys with 13.6 and 20 at.% molybdenum under isothermal holding conditions at the temperature of the phase regions α+γ′ and α+γ of the phase diagram was examined. The proces was studied by the methods of metallography and x-ray crystallographic analysis. The changes in the microstructure and phase composition of the alloys as a function of the temperature and holding time were indicated. The decomposition process was represented in the form of C-shaped diagrams of the isothermal transformation of the γ² phase, which characterize the structural changes occurring in the aloy in the direction of the equilibrium state. It was found that the process occurs in stages, 6 figures, 7 references. Deceased. Federal Science Center of the Russian Federation—A. A. Bochvar All-Russia Scientific-Research Institute of Standardization in Machine Building. Translated from Atomnaya énergiya, Vol. 88, No. 1, pp. 43–48, January, 2000.     

Spectra of neutrons produced by 14-Mev neutrons in fissile materials

Measurements have been made of the energy distribution of neutrons produced in the passage of 14-Mev neutrons through layers of Th²³², U²³³, U²³⁵, U²³⁸ and Pu²³⁹. It is shown for all nuclides which were investigated that the secondary-neutron spectrum consists of two components; fission neutrons and evaporation neutrons. The dependence of the coefficients in the secondary neutron spectrum on the nuclear constants of the corresponding nuclides are determined, thus making it possible to find these coefficients without an experimental investigation of the neutron spectra.The authors wish to express their thanks to V. A. Davidenko for his interest in the work and discussion of the results, to A. G. Shlygin for taking part in the initial stages in the work, to Iu. A. Vasil'ev, G. S. Malkiel' and E. I. Sirotinin for exposing the plates in the accelerator, and to L. S. Andreev, L. V. Evseev, N. F. Nikolaev and V. A. Chernyshov for scanning the plates.     

用时间分辨反射率技术研究硅的固相外延

用时间分辨反射率技术实时测量了Ｓｉ＋、Ａｓ＋注入单晶硅的固相外延生长速率和外延层厚度，并与背散射沟道方法测得的非晶层厚度进行了比较。介绍了测量原理，分析了实验结果．     

On the development of a model for predicting phase separation phenomena in dividing two-phase flow

A model to predict the dividing flow characteristics for annular flow in a T-junction is proposed consisting of mixture and vapour phase continuity equations, two pressure change correlations and a closure relationship. The pressure change from the inlet through the run of the T is modelled by way of a balance of axial momentum at the junction based on a separated flow assumption. The branch pressure change is modelled using a balance of mechanical energy for the branching flow consisting of reversible and irreversible components. The closure relationship links the phase separation characteristics with the junction pressure changes. It involves a balance between pressure and inertia forces within the junction volume defining a dividing surface for each phase between the run and branch flows. The branch quality is then determined using a well-defined inlet flow distribution. The model is capable of predicting the experimentally observed phase separation characteristics from three independent studies of annular/steam—water and air-water flow in dividing T-junctions.     

Radiation embrittlement of the materials of fuel assemblies in the temperature range corresponding to maximum swelling

Translated from Atomnaya Énergiya, Vol. 69, No. 4, pp. 223–226, October, 1990.