Thermohydraulic investigations of increasing the burnup of nuclear fuel in fast-neutron reactors

We present the results from experimental and calculated investigations of the effect the deformation of fuel assembly casings, fuel rod bundle, and single fuel rods in the cores of fast-neutron reactors has on their temperature conditions. It is shown that the distortion of a fuel assembly (FA) is determined to a considerable extent by temperature nonuniformities in it, which in the final analysis affects the burnup of nuclear fuel.     

Thermohydraulic studies of sodium-cooled reactor facilities

Thermohydraulic studies of reactor facilities with fast reactors are complex experimentally and computationally. Extensive experimental data are obtained on the velocity and temperature profiles, hydrodynamic resistance and heat emission, initial heat section, and interchannel mixing of the coolant in the fuel assemblies. These are used to develop engineering methods of performing thermohydraulic calculations of fuel assemblies as well as computational compute codes. The particulars of the hydrodynamics and heat transfer in intermediate heat exchangers and steam generators of reactor facilities with fast reactors are studied. This has made it possible to validate their thermohydraulic characteristics.     

Numerical simulation of the thermohydraulics of reactor fuel assemblies with blockages

Computer codes for analyzing the thermohydraulics of fuel assemblies with blocked coolant flow cross sections are examined. The computational results obtained with these codes are analyzed, and a conclusion is drawn on the basis of this analysis about the most important computational codes in this field. The results of the analysis are illustrated. An extensive literature from the worldwide practice of the thermohydraulics of blocked fuel assemblies is presented. Further work required to improve the computer codes is indicated. 7 figures. 2 tables, 65 references. State Science Center of the Russian Federation—A. I. Leipunskii Physics and Power Engineering Institute. Translated from Atomanya énergiya, Vol. 87, No. 5, pp. 342–356, November, 1999.     

Continuous-wave lasing of single-mode metamorphic quantum dot lasers for the 1.5-μm spectral region

Lasers based on InAs/InGaAs quantum dots grown on metamorphic (In,Ga,Al)As layers deposited by MBE on GaAs substrates exhibited emission near 1.5 μm with a differential quantum efficiency of about 50%. The narrow-stripe lasers operate in a single transverse mode and withstand continuous current density above 20 kA cm^?2 without significant degradation. A maximum continuous-wave output power of 220 mW is obtained. Neither current nor beam filamentation was observed up to the highest pumping levels.