Electrical-percolation effects in epoxy resin/ion-exchange resin/polyaniline anticorrosion composite materials

A new type of epoxy–polyelectrolyte anticorrosion protective material based on epoxy resin, ion-exchange resin, and polyaniline has been studied. Electrical-percolation transitions are observed after submerging stainless-steel plates coated with epoxy–polyelectrolyte compositions in a solution of NaCl. Conductivity data processed within a percolation model show that the modification of ion-exchange resin by polyaniline strongly influences the coating model parameters owing to changes in physicochemical and morphological properties of ion-exchange resin. It is established that the electrochemical response to the action of an aqueous salt solution can be controlled by variation of the material composition.     

Simulation of the VVER-1000 pump start-up experiment of the OECD V1000CT benchmark with CATHARE and TRAC-PF1

In the framework of joint effort between the Nuclear Energy Agency (NEA) of OECD, the United States Department of Energy (US DOE), and the Commissariat a l'Energie Atomique (CEA), France a coupled three-dimensional (3D) thermal-hydraulics/neutron kinetics benchmark for VVER-1000 was defined. The benchmark consists of calculation of a pump start-up experiment labelled V1000CT-1 (Phase 1), as well as a vessel mixing experiment and main steam line break (MSLB) transient labelled V1000CT-2 (Phase 2), respectively. The reference nuclear plant is Kozloduy-6 in Bulgaria. The overall objective is to assess computer codes used in the analysis of VVER-1000 reactivity transients. A specific objective is to assess the vessel mixing models used in system codes. Plant data are available for code validation consisting of one experiment of pump start-up (V1000CT-1) and one experiment of steam generator isolation (V1000CT-2). The validated codes can be used to calculate asymmetric MSLB transients involving similar mixing patterns. This paper summarizes a comparison of CATHARE and TRAC-PF1 system code results for V1000CT-1, Exercise 1, which is a full plant point kinetics simulation of a reactor coolant system (RCS) pump start-up experiment. The reference plant data include integral and sector average parameters. The comparison is made from the point of view of vessel mixing and full system simulation. CATHARE used a six-sector multiple 1D vessel thermal-hydraulic model with cross flows and TRAC used a six-sector, 18-channel coarse-mesh 3D vessel model. Good agreement in terms of integral parameters and inter-loop mixing is observed.     

Design and experience of HEU and LEU fuel for WWR-M reactors

Thin-walled WWR-M5 fuel elements were designed and manufactured and have been used successfully for 16 years; they contain twice as much uranium-235 as the WWR-M2 and WWR-M3 fuel elements. The fuel elements have been optimized with regard to their neutron physics and thermal-hydraulic parameters and fuel consumption has been minimized. The mean specific power in the core of the WWR-M reactor was raised to 230 kW l⁻¹, the measured maximum volume thermal specific power was 900±100 kW l⁻¹ and the surface specific power was 136±15 W cm⁻². The WWR-M5 fuel elements enable the power of the WWR-M pooltype reactor to be raised to 30 MW while simultaneously increasing the number of cells in the core available for experimentation by a factor of approximately two and reducing fuel element consumption. Reactor tests of WWR-M fuel elements with reduced fuel enrichment (36 and 21%) were carried out for a meat uranium density up to 2–3 g cm⁻³. Conversion of WWR-SM-type reactors to these fuel elements did not lead to a loss in reactivity and enabled their power to be increased to 20–30 MW.     

Pressure vessel steel fracture toughness in the regime from room temperature to 400°C

The fracture toughness of steels that are susceptible to dynamic strain aging shows a minimum at temperatures higher than the upper shelf starting temperature. This phenomenon is caused simultaneously by strain aging and plastic deformation. The first aim of the present work is to analyze the effect of dynamic strain aging on the fracture toughness values of three pressure vessel steels in the temperature range between room temperature and 400°C. Fracture mechanics tests were carried out on A533 GB, A516 G70 and 304L steels to obtain the following parameters: J_IC, CTOD_m and the J-R curves. These values were compared against those available in the present references, and good agreement was found. Charpy V notch tests were also carried out on A516 G70 steel at the same test temperatures as for the fracture mechanics tests to analyze the effect of the strain rate. The critical wide stretch zones of the 304L steel specimens were also measured to verify another author's hypothesis about a toughness drop at the upper shelf temperature.     

Measuring the mechanical recoil impulse of a polymeric target upon impact of a high power electron beam

A method for measuring the mechanical recoil impulse of a target produced by the relativistic electron beam of the Calamary accelerator is described. A detector based on a piezoelectric sensor is used in measurements. Results of measurements are presented for the mechanical recoil impulse produced by the relativistic electron beam with an energy as high as 300 keV, a current of up to 30 kA, and a duration of ~100 ns that is incident on an epoxy target. The energy flux density on the target surface is varied in the range of 1–10 GW/cm². The maximum measured impulse value is 0.32 N · s at an energy flux density of 10 GW/cm² (an energy fluence of 810 J/cm2).     

Magnetic properties of a low-density Bi-based HTSC

The preliminary results of the investigation of magnetic properties of a novel low-density superconducting material Bi_1.8Pb_0.3Sr₂Ca₂Cu₃O_x with a low density and microfoam structure are presented. The temperature, magnetic field, and time dependences of magnetization M have been measured. The experimental hysteresis loops M(H) are well described in the framework of the Val’kov-Khrustalev theory developed for type II granular superconductors.     

Electrodeposition, composition and structure of Zn—Cr alloys

The effect of polyethylene glycol (PEG 1500) as additive and of deposition conditions on Zn—Cr alloy electrodeposition from an acidic sulfate electrolyte at room temperature, without agitation was investigated. PEG polarizes the overall cathodic reaction and inhibits Zn deposition. Cr codeposition with Zn starts at a cathodic potential of about –1,95 V vs Hg/Hg₂SO₄, which is reached at current density of about 20 A dm^–2 in galvanostatic conditions. Zn—Cr alloy coatings containing up to 28 at % Cr were obtained depending on the plating conditions. SEM observations showed an island-like structure, formed by the local growth of crystals, which covered the surface during further deposition. In the first stages of electrodeposition the powder diffraction spectra contain lines of b.c.c. -(Zn,Cr) phase (a 3.02 Å). After 30 s deposition time weak lines of Zn-based phase (a 2.67 Å, c 4.90 Å) appear, and become clearly visible in coatings deposited for 90 s. The average Cr content in the alloy coatings decreases with advancing deposition. The as-plated surface contains C in organic compounds and Zn(OH)₂. After 50 min sputtering, Zn and a mixture of Cr, Cr₂O₃ and Cr₇C₃ were found. The presence of organic C and O, probably from inclusions of PEG, were also detected.     

Experimental investigation and thermodynamic simulation of the uranium oxide–zirconium oxide–iron oxide system in air

The behavior of melts and the phase composition of crystallization products of six compositions in the uranium oxide-zirconium oxide-iron oxide system in air have been investigated. It has been revealed that crystallized samples containing 20–50 wt % uranium oxide and 25–80 wt % iron oxide (the rest is zirconium oxide) consist of five crystalline phases and involve two types of eutectic structures. The possible factors responsible for this phenomenon have been considered.