[en] The polycrystalline samples of Pb(Li_1/4La_1/4Mo_1/2)O₃ have been prepared by solid state reaction technique. Preliminary x-ray structural analysis of the compound indicates the formation of single phase compound in the orthorhombic crystal system at room temperature. The surface morphology and particle/grain distribution have been studied by scanning electron microscopy (SEM). Studies of dielectric constant (ε) and dielectric loss (tan δ) of the compound as a function of frequency (100 Hz to 10 kHz) and temperature (-100 deg to 150 degC) show that the compound has ferroelectric phase transition at 95 degC. (author). 13 refs., 6 figs

[en] The polycrystalline samples of Pb(Li_1/4Dy_1/4W_1/2)O₃ have been synthesized by high-temperature solid-state reaction techniques. Room temperature x-ray diffraction (XRD) studies of the compound provided preliminary structural data, and hence formation of a single phase desired material was confirmed. Detailed studies of dielectric constant(ε) and loss(tan δ) as a function of frequency (100 Hz to 10 kHz) at room temperature (298 K) and also as a function of temperature (liquid nitrogen to 403 K) at 10 kHz suggest that the compound undergoes a ferroelectric phase transition of diffuse type. (author). 17 refs., 5 figs., 1 tab

[en] Polycrystalline samples of Pb(Li_1/4Y_1/4X_1/2)O₃ (where X tungsten and molybdenum) were prepared by solid state reaction technique. Preliminary x-ray studies of these compounds suggest the formation of single phase compound. Detailed dielectric studies (dielectric constant (ε) and dielectric loss (tan δ)) as a function of temperature (-150 degC to 450 degC) and frequency (200 Hz to 10 kHz) suggest that one of these compounds, Pb (Li_1/4Y_1/4W_1/2)O₃ undergoes ferroelectric phase transition of diffuse-type, whereas Pb(Li_1/4Y_1/4Mo_1/2)O₃ shows a strong dielectric anomaly, relating to ferroparaelectric phase transition at 317 degC. (author). 22 refs., 3 figs., 1 tab

[en] Preliminary x-ray structural analysis of polycrystalline Pb(Li_0.25Gd_0.25Mo_0.5)O₃ (PLGM) ceramics, prepared from solid-state reaction technique, provides single phase orthorhombic structure at room temperature (20 degC). Study of scanning electron microscopy (SEM) gives the surface morphology of the sintered pellet (i.e. grain distribution, porosity etc). Detailed dielectric studies in the wide range of temperatures (viz. liquid nitrogen to 200 degC) and frequency in the range 400 Hz-10 kHz show the ferroelectric phase transition at 107 degC. (author)

[en] The polycrystalline samples of Pb(Li_1/4Sm_1/4 W_1/2)O₃ (hereafter PLSW), which belongs to a ferroelectric oxide family of the perovskite structure were prepared by high-temperature solid-state reaction technique. Preliminary x-ray analysis of the sample provided lattice parameters: a=7.0542 A, b=8.0538 A and c = 12.2448 A and also formation of single phase compound. Detailed studies of dielectric constant and loss as function of temperature and frequency and electrical conductivity show structural phase transition at 84 degC which is quite different from the other members of the family. (author). 16 refs., 5 figs., 1 tab

[en] The performance of a full reactor core simulator depends on the input parameters and nuclear data specifically to nuclear reaction cross section. The source of variation of homogenized cross section depends on the random variation of reactor state parameters that will be in dynamic equilibrium with various feedbacks e.g., fuel and coolant temperature, coolant density, etc. To validate the simulation model of PHWR 37-fuel element cluster, the IAEA-CRP lattice benchmark with natural uranium oxide fuel is analysed using the computer code DRAGON. In this benchmark exercise, all the basic cell data are similar to a typical PHWR data. The DRAGON code solves the neutron transport equation to estimate neutron flux in multi-group structure, neutron multiplication factor and associated homogenized cross section of the given system. The main objective of this study is to estimate variation of the neutron multiplication factor, two group cross-sections and isotopic composition change of ²³⁵U and ²³⁹Pu with burnup

[en] Ion irradiation induced modifications of a periodic Pt/C multilayer system containing Fe impurity have been analyzed by X-ray techniques suitable for exploring nanometer depth scales with sub-nanometer depth resolution. The multilayer stack with 15 Pt/C layer pairs (period 4.23 nm, total thickness 63.45 nm) was fabricated on a glass substrate. A 2 MeV Au²⁺ ion beam was rastered on the sample to obtain uniformly irradiated strips with fluences from 1 x 10¹⁴ to 1 x 10¹⁵ ions/cm². These strips were analyzed with X-ray standing wave and X-ray reflectivity experiments. Ion induced atomic displacements across multilayer interfaces are known [Appl. Phys. Lett. 79 (2001) 467]. Here additionally we identify irradiation induced redistribution of Fe impurity atoms, which cannot be explained simply by atomic displacements due to ion-atom collision. With increasing ion fluences more Fe atoms migrate from C- to Pt-layers. This behaviour has been explained in terms of radiation induced enhanced diffusion and Fe-Pt and Fe-C phase diagrams

[en] Spent fuel of uranium-plutonium mixed oxide (MOX) from sodium cooled Fast Breeder Test Reactor (FBTR) was analyzed for at.% burn-up by preferential evaporation method. A sequential pattern of analysis of fission monitor Nd and heavy elements, U and Pu provided an un-interfered isotopic composition. Concentrations of individual elements were determined by isotopic dilution mass spectrometry. The proposed method provides at.% burn-up with an uncertainty of about 4% (compared to ASTM method), is less time consuming, does not involve any chemical separation, reduction in radioactive waste and substantial reduction in the radiation exposure to analyst. (author)

[en] Of late Monte Carlo (MC) technique is widely employed in all branches of computational science although it was initially experienced only with neutron transport problems. This has become possible with availability of faster computers with large memory on one hand, and on the other hand due to development of suitable analytical methods to judge the accuracy of the results. The present paper intends to share the experience on MC modeling of some of the reactor physics problems related to VVER type of light water reactors, KAMINI research reactor and photo-neutron flux estimations for a thorium bundle immersed in heavy water. State-of-art computer codes namely, MCNP and KENO-VI module of SCALE computer code package, both based on MC principles were used to analyse the above problems. Yet another problem addressed in this paper is time dependent neutron source term estimation due to use of thoria bundle immersed in heavy water. Computational model of thoria (ThO₂) bundle similar to the configuration of 19 pin PHWR bundle has been made using MCNP code to estimate the photo neutron flux as well as dose rates when it is completely immersed in heavy water pool. The photon emitted by ²⁰⁸Tl isotope formed in the decay chain of ²³²Th is the main cause for the production of photo-neutrons in heavy water

[en] The chemical bonding of contaminants like carbon and oxygen on the surface of Ta and Ta₂O₅ films due to Ar⁺ ion bombardment during sputter etching, has been studied using Auger electron spectroscopy and slow electron energy loss spectroscopy. Finger printing of C KLL peak shows that the energy separation between the major positive-going and negative-going excursions, which is 23 eV in the pure graphitic form, reduces to 6 eV indicating the carbide formation after ion bombardment. It is assumed that the chemical reaction is initiated by an increase in π electrons in the graphite due to ion bombardment. The carbide formation is found to be much less effected in Ta₂O₅ films which has been attributed to the absence of free d electrons of Ta in the oxide