Oxygen measurements in stagnant lead-bismuth eutectic using electrochemical sensors

Sensors are the major part of an active oxygen control system (OCS) to be used in ADS reactors employing lead bismuth eutectic (LBE). We tested Pt/air and Bi/Bi₂O₃ probes based on yttria-stabilized zirconia (YSZ) solid electrolytes. The sensors were calibrated by evaluating the electromotive force (EMF) - temperature dependencies in oxygen un-/saturated stagnant LBE compared to the van’t-Hoff’s isotherm. Also, probe kinetics while changing the H₂/H₂O ratio was studied. Typical, reproducible curves are presented confirming attainment of oxygen equilibrium between the fluids. The sensor outputs are deterministic, predictable. Exceptional small drifts were due to interfacial kinetics, not to the sensors behavior. Simultaneous testing of several probes in one melt was performed. The sensors seemed to be qualified for large scale use.     

Prospective Power-Reactor Fuel Cycles Based on Water-Free Reprocessing of Spent Fuel

A pyroelectrochemical process for reprocessing spent fuel and fabricating granular oxides UO₂, PuO₂ or (U, Pu)O₂ from chloride melts has been developed at the Scientific-Research Institute of Nuclear Reactors for a prospective nuclear fuel cycle. The basic equipment has been developed. The basic results of a comprehensive study of fuel elements with vibrationally compacted (U, Pu)O₂ fuel for fast reactors are presented. The performance of the reactors remains high up to 30% burnup in standard BOR-60 reactor fuel assemblies and 32% burnup in experimental fuel elements. An assessment is made of the effectiveness of the pyroelectrochemical methods and vibrational compaction technology for plutonium utilization.     

The concept of work compatibility: An integrated design criterion for improving workplace human performance in manufacturing systems

In this paper, we present the concept of work compatibility as an integrated work design criterion that simultaneously improves human health and safety, productivity, and work quality in manufacturing systems. In this respect, we have modeled work compatibility as a work design parameter that mathematically integrates the energizing (i.e., system resources) and the demand (i.e., system requirements) forces in the work system. A mathematical equation has been derived for the work compatibility matrix. Furthermore, an operating zone has been developed in which there is a region of optimality for the employee to function on practical grounds with a good degree of efficiency and sustainability. An application example is provided to demonstrate the potential of work compatibility to improve productivity and quality along with improvement in worker safety and health. © 2004 Wiley Periodicals, Inc. Hum Factors Man 14: 379–402, 2004.     

A comparison between classical robust stability conditions

The paper is focused on the comparison between some classical robust stability conditions for continuous‐time linear time‐invariant systems. Such conditions are given as lemmas in the paper, since their statements include some generalizations, needed in order to better compare (and use) them. The analysis is carried out by comparing pairwise the families of systems whose stabilization through a given compensator is guaranteed by each of the considered robust stability conditions. Some properties of the families are formally derived and stated, and some very simple examples arc exhibited in order to illustrate the presented properties and comparisons. A theorem, representing an extension of one of the considered conditions, is proposed in order to overcome some difficulties arising in the use of the classical result. Copyright © 2004 John Wiley & Sons, Ltd.     

Confocal surface profiling utilizing chromatic aberration

A new method for surface profiling in the confocal microscope utilizing chromatic aberration is presented. An expression for the integrated spectral intensity in the new profilometer is derived and chromatic aberration in the confocal microscope is explained. Estimates of the minimum resolvable depth and the maximum depth that can be profiled are given utilizing a ratiometric signal detection scheme. Examples of ratio images illustrating the new surface profiling technique are presented, showing the scheme to be both simple to implement and effective.     

In-situ comprehensive calibration of a tri-port nano-electro-mechanical device

We report on experiments performed in vacuum and at cryogenic temperatures on a tri-port nano-electro-mechanical (NEMS) device. One port is a very nonlinear capacitive actuation, while the two others implement the magnetomotive scheme with a linear input force port and a (quasi-linear) output velocity port. We present an experimental method enabling a full characterization of the nanomechanical device harmonic response: the nonlinear capacitance function C(x) is derived, and the normal parameters k and m (spring constant and mass) of the mode under study are measured through a careful definition of the motion (in meters) and of the applied forces (in Newtons). These results are obtained with a series of purely electric measurements performed without disconnecting/reconnecting the device, and rely only on known dc properties of the circuit, making use of a thermometric property of the oscillator itself: we use the Young modulus of the coating metal as a thermometer, and the resistivity for Joule heating. The setup requires only three connecting lines without any particular matching, enabling the preservation of a high impedance NEMS environment even at MHz frequencies. The experimental data are fit to a detailed electrical and thermal model of the NEMS device, demonstrating a complete understanding of its dynamics. These methods are quite general and can be adapted (as a whole, or in parts) to a large variety of electromechanical devices.     

Design and construction of a high temperature and pressure electrodeless conductivity probe

An electrodeless conductivity probe has been designed and tested at temperatures up to 250 degrees C and pressures of 4.13 MPa (600 psi). A unique pressure seal permits temperature cycling. Design of the electronics permits accurate measurement of conductivities at various elevated temperatures in spite of the change of magnetic properties of the toroids with temperature. The design of the probe can be adapted for insertion, in-line, or bypass operation.     

The Effect of Coolant Concentration on the Machinability of Nickel-Base, Nimonic C-263, Alloy

This paper investigates the effect of coolant concentration on tool performance when machining nickel-base, C-263, alloy with triple coated (TiN/TiCN/TiN) carbide insert at various (3–9%) coolant concentrations and under different cutting speed conditions. Tool life, tool-failure modes, wear rates, component forces and surface finish generated during machining were recorded, analyzed and used to formulate mechanisms responsible for tool wear at the cutting conditions investigated. Analysis of the recorded data shows that tool performance during machining is dependent on coolant concentration. 6% coolant concentration gave the best overall performance as effective combination of cooling and lubrication functions were achieved during machining. Increasing coolant concentration to 9% reduced tool performance due to a reduction of the tool-chip contact length area and the consequent increase in compressive stresses at the tool-chip and tool-workpiece interfaces. This action often leads to pronounced chipping of the tool cutting edge during machining. Friction coefficient between the workpiece material and substrate increases once the coating layer(s) is broken as a result of the direct contact between the tool substrate and the work material. This action increases mechanical wear of the tool, which in turn leads to a significant increase in the cutting force with negligible effect on the feed forces during machining.     

聚变驱动次临界堆双冷嬗变包层结构设计与分析

给出聚变驱动次临界堆液态金属LiPb/He气双冷嬗变包层参考结构概念,采用了低活化铁素体/马氏体RAFM钢(如CLAM)作为结构材料、简单液态金属流道、两个独立氦气冷却系统以及燃料球/颗粒等设计方案。重点分析了嬗变包层第一壁、重金属区与裂变产物嬗变区的结构设计特点。     

Unstable oscillation of tubular cantilevered beams conveying a compressible fluid

This paper is concerned with establishing the conditions of stability of a cantilevered tube conveying a compressible fluid. Solutions to Niordson's eigenvalue problem associated with the equations of motion are computed using Muller's method. The effects on critical velocity of compressibility which are accommodated by specifying the tube aspect ratio and fluid sonic velocity are parametrically studied. Aspect ratio is found to have a more pronounced effect on critical velocity than sonic velocity over the parameter range that was considered.