Tests for Resistance to Cryolite: Methods and Comparative Evaluation

Methods of testing refractory and barrier (shielding) materials used in the lining of aluminum electrolyzers for resistance against corrosive attack of electrolyte components are briefly reviewed. The advantages of a method proposed by Allaire et al. [2] are emphasized vis-a-vis the conventional methods that are used to simulate performance of the aluminum electrolysis cell.     

Mononitride Fuel for Fast Reactors

Substantiation is given for the development of nuclear power based on inherently-safe fast reactors with a mononitride core. Fundamental studies and design work on the development of such reactors with lead (BREST-OD-300), lead–bismuth (SVBR-75/100), and sodium coolant (BN-800) are being performed. The development of nuclear power in our country is based on organizing a closed fuel cycle. The results of experimental investigations of the properties of mononitride fuel are correlated. Mononitride fuel meets all requirements for fast-reactor fuel.     

State of the Art and Trends in the Development of Base Plate Materials for Aluminum Electrolysis Cells

The state of the art and trends in the production and application of barrier materials intended for preventing the infiltration of corrosive components (sodium, sodium fluoride, and molten aluminum) into the heat-insulating layer of refractories for the base plate of aluminum electrolysis cells are discussed. Results for different types of barrier materials tested for cryolitic stability are given; the granular composition and pore structure of some of them are studied. Strengths and weaknesses of the barrier materials are discussed.__________Translated from Novye Ogneupory, No. 2, pp. 16 – 22, February, 2005.     

Liquid-metal plasticizer for forming fuel-element kernels

It is proposed that the possibility of fabricating fuel elements by extrusion using nonremovable liquid-metal plasticizer be investigated. Alloys of sodium with potassium and thallium are examined as plasticizers. The implementation of this method will permit fabricating fuel elements remotely using high-activity fuel produced in breeder reactors.     

Thermochemical Stability, Radiation Testing, Fabrication, and Reprocessing of Mononitride Fuel

A thermodynamic analysis and experimental investigations have shown that mononitride fuel is thermochemically stable up to 1973–2073 K, at which temperature the equilibrium vapor pressure of nitrogen does not exceed 4.5·10^–7–2.1·10^–6 MPa. It is concluded on the basis of a generalization of the data from radiation testing of mononitride fuel with burnup up to 9–10% in fast and 16.8% in thermal reactors with lineal power density from 400 to 1300 W/cm that it should operate reliably in fuel elements with helium and liquid-metal sublayers. The requirement for the impurity (oxygen and carbon) content in it is formulated. When both oxygen and carbon impurities are present simultaneously in mononitride, the mass fraction of each should not exceed 0.15%. The methods for fabricating mononitride fuel are determined by the final product of the reprocessing of irradiated fuel. Consequently, methods for fabricating mixed nitride fuel from oxides and metals are now being developed.     

Processes in refractory materials of the cathode assembly of electrolysis cells for aluminum production

One of the main causes of the failure of electrolysis cells is the destruction of barrier (refractory) materials. This work is aimed at the establishment of the main regularities of the interaction between fluorides and various barrier materials. A thermodynamic analysis of the processes running in refractory materials of the cathode assembly of electrolysis cells, as well as the results of an X-ray phase analysis of the fragments of the refractory materials, allowed one to reveal the major mechanism of their destruction, which consists of the occurrence of gas-phase reactions. On the basis thereof, recommendations were developed aimed at increasing the lifetime of the barrier materials of electrolysis cells for aluminum production.     

Non-traditional domestic refractory materials for aluminum metallurgy

The promising and most accessible natural and technogenic raw materials are considered for lining metallurgical units for producing primary and secondary aluminum. A potential form of natural raw material for use as a dry barrier mix in aluminum electrolyzers is quartz pyrophyllite rock. For lining melting and casting units of the aluminum industry with the greatest technical and economic efficiency it is desirable to use aluminothermal slags and fuzed materials of OAO Klyuchevsk Ferroalloy Plant. __________ Translated from Novye Ogneupory, No. 8, pp. 20–23, August 2008.     

High-enrichment fuel in VVER

The results of a search for the optimal water-uranium ratio for VVER with no changes to the fuel elements and assemblies are presented. It is shown that decreasing the volume of a fuel pellet while maintaining the same ²³⁵U load as a result of increasing the enrichment will decrease the specific consumption of uranium and increase the run time. The proposed modifications to the fuel can be implemented in operating reactors and advanced VVER designs.     

Statistical estimation of fast-reactor fuel-element lifetime

Conclusions On the basis of a statistical analysis, the main parameters having a significant influence on the theoretical determination of fuel-element lifetimes in the operation of power fast reactors in steady power conditions may be isolated. These include the creep and swelling of the fuel and shell materials, prolonged-plasticity lag, shell-material corrosion, gap contact conductivity, and the strain diagrams of the shell and fuel materials obtained for irradiated materials at the corresponding strain rates. By means of deeper investigation of these properties of the materials, it is possible to increase significantly the reliability of fuel-element lifetime predictions in designing fast reactors and to optimize the structure of fuel elements more correctly.Another important result of the statistical analysis is information regarding the increase in the number of unsealed fuel elements with fuel burnup. It is shown that for the given conditions of reactor operation the number of unsealed fuel elements rises almost exponentially, beginning with a burnup >7% of heavy atoms. The results of such calculations must obviously be taken into account in the cost-benefit analysis of projected new reactors and in choosing the optimal fuel burnup.Translated from Atomnaya Énergiya, Vol. 48, No. 1, pp. 16–19, January, 1980.