Comparative study of incorporation of Cl and F into SiO2 during the MCVD process

We report the results of examination of incorporation of chlorine and fluorine into silica as revealed from secondary ion mass spectroscopy (SIMS) and Raman spectroscopy measurements. The samples were preform-like rods made by the MCVD process. SIMS spectra were used for quantitative analysis of Cl concentration in glass. The concentrations of F were obtained from the Raman spectra. Both spectroscopic methods indicated the presence of Si---Cl groups in SiO₂ synthesized from chlorine-rich vapour gaseous blend. The difference in structural roles of Cl and F in chemically deposited silica manifests itself in the efficiency of their bonding to Si and in interaction with intrinsic structural defects.     

Kinetics of Aperiodic Cascade Boosters: Speed of Operation and Safety

The results of Monte-Carlo calculations of simple spherically symmetric systems, simulating an aperiodic booster, are presented. The purpose of the calculations is to give a clear demonsration of the specific features of the kinetics of cascade reactor systems and the possibilities which the application of the cascade principle in an aperiodic booster adds to increasing safety and improving the time parameters of the pulses. Another goal is to determine the materials for the moderator which are best from the standpoint of optimizing the parameters of the booster. It is shown that for the same total number of fissions the neutron pulses in a cascade booster are generated under conditions of much greater subcriticality and are much shorter in duration than for a single-section booster. The best pulse parameters are obtained in cascade boosters with tungsten, lead, and molybdenum neutron moderators.     

Substantiation of the Radiochemical Characteristics of Liquid Radioactive Wastes That Determine Safe Operation of Deep Waste Disposal Sites

The qualitative and quantitative radiochemical composition of liquid wastes is substantiated. This makes possible further safe operation of deep waste disposal sites at the Mining-Chemical Plant and the Siberian Chemical Plant. The toxicity and temperature in a formation with the wastes removed are used as the assessment criteria, satisfaction of which guarantees that the wastes will remain localized within the assigned boundaries of the waste-disposal formation site. It is concluded that the standard limit should be imposed on the specific activity of the long-lived group of radionuclides – ⁹⁰Sr and ¹³⁷Cs – rather than on the total specific activity of the wastes placed in deep disposal sites. For maximum specific activity of ⁹⁰Sr and ¹³⁷Cs of 37 GBq/dm³ and total specific activity not exceeding 185 GBq/dm³ for buried wastes with radionuclide composition characteristic of modern radiochemical production operations, it is impossible for potentially dangerous radiation and thermochemical processes to occur in the waste-disposal formation site. The recommended limit permits reducing substantially the volume of buried wastes and therefore the region over which the wastes propagate in the deep disposal site.     

Structural and mechanical properties and effective permeability of fissured materials

The article investigates the dependences of porosity and of the permeability tensor of an elastic fissured medium on the characteristics of its state of stress and the pressure of the permeating liquid.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 5, pp. 818–826, November, 1985.     

Use of biocompatible calcium-phosphate glass ceramic BGC in surgical treatment of maxillary cysts

The possibility of using the granulated form of biocompatible material made of calcium-phosphate glass ceramic BGC for treatment of maxillary cysts was demonstrated.