Stress-corrosion cracking of a monel 400 tube

A bent Ni-Cu Monel 400 alloy tube, which operated as part of a pipeline in a petrochemical distillery installation, failed by through-thickness cracking. The pipeline was used to carry a stream of gaseous hydrocarbons containing hydrochloric acid (HCl) into a reaction tower. The tower provided a caustic solution (NaOH) to remove HCl from the stream, before the latter was directed to a burner. Metallographic examination showed that the cracks were intergranular and were frequently branched. Although nominal chemical composition of the component was found within the specified range, electron dispersive analysis by X-ray (EDXA) indicated significant segregation of sulfur and chlorine on grain boundaries. Failure was attributed to hypochlorous-acid (HClO)-induced stress-corrosion cracking (SCC). The HClO was formed by the reaction of HCl with atmospheric O₂, and the oxygen entered the tube during shutdowns/startups of the installation. Residual stresses, originating from the in situ bend forming of the tube during assembly of the line, provided a driving force for crack growth, and the segregation of sulfur on grain boundaries enhanced the susceptibility of the material to cracking.     

Carbon nanotube field emitters for planar emission vacuum micro-and nanoelectronics

The design and manufacturing technology of carbon nanotube field emitters for novel devices of planar emission vacuum micro-and nanoelectronics are described. Prototypes of diode structures with such emitters are obtained in which the threshold field strength amounts to ～2 V/μm and the direct to reverse current ratio exceeds 10⁵. The obtained small scatter of characteristics points to the possibility of creating integrated circuits possessing high operation speed and a working temperature range expanded from ?60 to +30°C.     

Producing a compact long-lived plasma formation

A method of producing compact long-lived plasma formations (plasmoids) is described. The method is based on the effect of capture of a high-current relativistic electron beam under conditions of significant overcompensation of space charge of the beam by positive background ions. Requirements are formulated which are placed on the parameters of a plasma-beam system for the realization of this method, and numerical estimates are given of the overall electric charge and energy content of the electron component of a plasmoid. The dynamics of forming a plasmoid are investigated experimentally.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 843–849.Original Russian Text Copyright © 2004 by B. V. Alekhin, A. E. Dubinov, V. S. Zhdanov, V. G Kornilov, K. E. Mikheev, V. D. Selemir, N. V. Stepanov, V. I. Chelpanov, and O. A. Shamro.     

New Generation of Microfuel-Based Fuel Elements for VVÉR Reactors

The results of development work on a new generation of fuel elements based on microfuel for VVÉR reactors using the basic data from post-reactor investigations and bench tests in experiments simulating LOCA for existing fuel elements with ceramic fuel are presented. It is shown that cermet fuel elements will make it possible to realize most fully the advantages of such fuel, specifically, to develop a sealed first loop and to simplify and reduce the cost of safety, automatic control, radiation protection, coolant puification, and other systems. For example, cermet fuel elements in VVÉR-1500 reactors can improve safety under various operating conditions, maneuverability, vibrational strength, fuel assembly lifetime, and geometric stability of fuel elements.     

Measurement of the Total Range and Specific Energy Deposition of a Beam of Uranium Ions in Porous Carbon Targets

Experimental results on the total range and specific energy deposition of a beam of uranium ions in foam carbon targets with various densities are presented. The chaotic arrangement of graphite grains in a porous target is modeled theoretically and the influence of the porosity on ion stopping is investigated.     

Laboratory wear tests and clinical observations of the penetration of femoral heads into acetabular cups in total replacement hip joints: I: Charnley prostheses with polytetrafluoroethylene acetabular cups

A quarter of a century has now elapsed since the late Professor Sir John Charnley introduced his low friction arthroplasty of the hip based on a stainless steel femoral component and an unfilled polytetrafluoroethylene (PTFE) acetabular cup. The advantages of the very low friction resulting from the use of PTFE and a femoral head of diameter 22 mm were unfortunately outweighed by a very rapid penetration of the femoral head into the acetabular cup. Charnley abandoned the use of PTFE after some 3 years and 300 operations and subsequent measurements revealed a penetration rate of 2.26 mm year^?1. In 1962 he adopted ultrahigh molecular weight polyethylene as the socket material and this material is now used almost exclusively in total replacement joints.In this paper we report further laboratory wear studies of PTFE on stainless steel in disc machines and compare the laboratory wear factors with those deduced from clinical observations. Charnley's clinical penetration rates have been analysed in terms of Paul's loading cycles for steady walking and measurements of the walking activity of elderly patients by Wallbridge and Dowson.It is shown that the wear factor for PTFE and stainless steel is about 3 × 10^?5mm³N^?1m^?1 and that there is excellent agreement between the mean value obtained from a variety of laboratory experiments involving environments of atmospheric air, distilled water, bovine synovial fluid and Ringers' solution with various counterface roughnesses and the wear factors derived from clinical observations.     

Experimental Study of the Deformation of Instantaneous Neutron Spectra from the Fission of <Superscript>235</Superscript>U Nuclei in Fast-Reactor Core Materials

The results from studies of the deformation of the instantaneous neutron spectra resulting from the fission of ²³⁵U nuclei in the material of structural elements of a fast reactor core are presented. The neutron spectra at and near the center of the reactor core were measured using neutron activation and fission neutron detectors.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 15–25.Original Russian Text Copyright © 2005 by Sevast’yanov, Koshelev, Maslov.