Improvement of the Procedure for Monitoring Iodine Radionuclides in Off-Gases from Nuclear Power Facilities

The paper deals with improvement of the procedure for monitoring volatile species of iodine radionuclides by using new Siloksid high-performance selective granulated mineral sorbents based on porous silicon dioxide impregnated with silver nitrate. The scheme of measuring the volume activity of iodine radionuclides in gaseous process media, air of working rooms, off-gases, and open air is described.     

Anisotropy of clays in diffusion transport of radionuclides

Comprehensive analysis of physicochemical and mineralogical properties of clays as surrounding rocks for radioactive waste repositories is performed with emphasis on the clay anisotropy. The results of a long-term experiment on diffusion transport of radionuclides in an experimental sample, a Cambrian clay monolith, are reported, and the anisotropy of the clay monolith with respect to diffusion properties along and perpendicular to the stratification plane is considered in detail.     

Thermostabilization of the Frequency of a Proton Relaxometer Based on Nuclear Magnetic Resonance with a Magnetic System on Permanent Magnets

Two variants of automatic correction of temperature variations of a constant magnetic field in the system of a permanent magnet NMR relaxometer are described. In the first version, the magnetic flux correction in the magnetic circuit of the system is used with a magnetic shunt, which is moved by a stepping motor. In the second version, the field is corrected by the current in the coils placed on the magnetic circuit of the magnetic system. Correction of the field is carried out automatically during the tuning of the resonant frequency of the device. The proposed methods make it possible to correct the relative change in the magnetic field within 1%, which covers possible temperature variations of the magnetic field in the entire range of room temperatures when using magnets based on neodymium–iron–boron and samarium–cobalt alloys (NdFeB and SmCo).

     

Synthesis and magnetic properties of M<Subscript>0.08</Subscript>Ti<Subscript>0.91</Subscript>V<Subscript>0.09</Subscript>O<Subscript>2 + δ</Subscript> · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (M = Cr,Mn, Fe,Co, Ni) nanopowders

Using sol-gel synthesis and ion exchange, we have prepared titanium vanadium oxide nanopowders doped with transition-metal ions: M_0.08Ti_0.91V_0.09O_{2 + δ} · nH₂O with M = Cr, Mn, Fe, Co, and Ni. The valence state of the ions in the nanopowders and their morphology and structure have been studied by scanning electron microscopy, X-ray diffraction, IR spectroscopy, and X-ray photoelectron spectroscopy. The M _x Ti_0.91V_0.09O_{2 + δ} · nH₂O oxides dried in air or calcined at 400°C in air are shown to be paramagnets. Vacuum annealing of Co_0.08Ti_0.91V_0.09O_{2 + δ} · nH₂O at 700°C gives rise to a significant ferromagnetic contribution.     

Calculation of Solidification Process of Continuous Cast Bar

In this paper, it presents the results of calculation of solidification process of copper continuous cast bar by cross section size 120 mmx70 mm with application of ProCast 2010 software. The estimation of mould design effect on solidification process of continuos copper cast bar is completed at various speeds of casting. Profiles of liquid metal cavities and temperature allocations in the cast bar at various casting speeds are defined. The analysis of received liquid metal cavity profiles shows that a new mold construction allows significantly decrease of the length of the liquid metal cavity during continuous copper casting at HAZELET casting machine and the increase of maximum casting speed from 10 to Ii m/min. Adequacy of the results of copper continuous cast bar solidification process calculation is confirmed by the experimental data.     

Cascade synthesis of a state observer with nonlinear correcting influences

For the synthesis problem for an invariant tracking system for a nonlinear automated control object under incomplete measurements, we develop a decompositional procedure of observer state synthesis with sigmoidal correcting influences in order to get current estimates of the unmeasured state variables and existing uncertainties. This observer in the pre-limit situation possesses the advantages of an observer with discontinuous correcting influences operating in sliding mode; in particular, it lets us estimate external influences without introducing their dynamical model. Unlike a sliding mode observer whose order has been extended due to filters over discontinuous correcting influences, the dimension of this observer equals the dimension of the control object, and in a microprocessor implementation this observer ensures better quality (smoothness) of the signals being estimated.     

Application of NMR relaxometry for determining the concentration of nanopowder magnetite in aqueous media

The use of the effect of a decrease in the transverse relaxation time T ₂ of the NMR signal of water protons in the presence of magnetic particles has been suggested for the quantitative estimation of the concentration of magnetite (Fe₃O₄) nanopowder in water. A calibration dependence of the relaxivity T ₂ ^?1 on the iron concentration has been obtained for model suspensions of magnetite nanoparticles with sizes of approximately 20 nm in the concentration range of 0.15–70 mg/L. For comparison, the concentration dependences of T ₂ ^?1 for aqueous solutions of Fe(NO₃)₃ · 9H₂O and FeSO₄ · 7H₂O and paramagnetic salts Ni(NO₃)₂ · 9H₂O, Cr(NO₃)₃ · 9H₂O, and CuSO₄ · 5H₂O have been studied to show that they correlate with their paramagnetic susceptibilities.