[en] The effect of radiative transfer on Rayleigh-Benard convection in a fluid-saturated porous layer is studied using Goody's approach. The Milne-Eddington approximation is employed in obtaining the initial static state and linear stability analysis is performed. An equivalent single-phase two-flux model is used in deriving the equation of heat transport for transparent and opaque media. The critical Rayleigh number is obtained by the Galerkin method and radiation is shown to stabilize the system for both the transparent and opaque media. It is found that the opaque media releases heat for convection more slowly than transparent media. Radiation is shown to affect the cell size in the case of transparent media only. The results of the problem have applications in heat engine containing fluid saturated-packed bed which works on the regenerative cycle. (author)

[en] SnO₂ nanostructured thin films were deposited on ultrasonically cleaned glass substrates at different substrate temperatures using the spray pyrolysis technique. The influence of substrate temperature on structural, morphological, electrical and optical properties of thin films have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDAX), two probe method and UV-Vis spectroscopy respectively. It was found that the deposited thin films were showing a tetragonal structure with a preferred orientation along (200) direction. Scanning electron microscopy results have shown that the substrate temperature influenced the growth mechanism of the SnO₂ thin films. Optical properties of thin films were analyzed by UV-Vis spectrophotometer. Optical band gap values were determined using Tauc extrapolation at different substrate temperatures. As the substrate temperature increased from 350°C to 450°C, optical band gap was found to increase from 3.14 eV to 3.67 eV. The figure of merit has been calculated from transmission spectra and the electrical properties are analysed and discussed. (author)

[en] Highlights: • Nanostructured V2O5 thin films were deposited on glass substrates using spray pyrolysis technique. • Deposited thin films were annealed at different temperatures (350–450 °C) for 1 h. • All nanostructured thin films have observed good crystallinity and varied with annealing temperature. • The film which is annealed at a temperature of 450 °C is showing improved properties. • This optimized film will be very use full in thermo-chromic devices. -- Abstract: V₂O₅ thin films were deposited by the spray pyrolysis method on pre-cleaned glass substrates at 300 °C and also these thin films were annealed for 1 h from 350 °C to 450 °C. Ammonium vanadate (NH₄VO₃) and Triton X-100 were used as starting materials were dissolved in water solvent. Structural, Optical, morphological and electrical properties were analyzed by using X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy (SEM) and two probe method respectively. X-ray diffraction studies have shown the thin films were composed of V₂O₅ with orthorhombic structure and oriented along (100) direction at high annealing temperatures. The SEM images reveal the morphological changes in films while increase the annealing temperature. The effect of annealing temperature on optical and electrical properties of the V₂O₅ thin films have been investigated and reported.

[en] Reliable performance of nuclear fuels and critical core components has a large bearing on the economics of nuclear power and radiation safety of plant operating personnel. In view of this, Post Irradiation Examination (PIE) is periodically carried out on fuels and components to generate feedback information which is used by the designers, fabricators and the reactor operators to bring about changes for improved performance of the fuel and components. Examination of the fuel bundles has to be carried out inside hot cells due to their high radioactivity

[en] A potential criticality risk hazard exists when large quantities of fissile materials are handled in nuclear facilities. The most important aspect of criticality safety is accident prevention because of the potentially serious consequences that can result. Based on criticality analysis various methodologies are adopted to control criticality in such facilities. In spite of effective criticality control methods put in place there lies a chance of criticality emergency and hence such facilities need criticality detection and evacuation system to minimise the personal exposure in such emergency. Establishing an effective evacuation management system is also an equally important safety requirement for prompt evacuation from the facility. The criticality evacuation management system has been designed, implemented and commissioned in an important facility at Trombay. This technique has saved laying large nos. of cables and improved the reliability of annunciation system by using state of art latest components. It has self-diagnosis facility, which is very helpful for prompt diagnosis and immediate replacement in case of malfunctioning. (author)

[en] In the present work, gas sensing properties of the screen printed ceria and ruthenate-sensitized BaSnO${}_3$ (BSO) with La doping heterostructure sensors towards the detection of ammonia and formaldehyde gases at room temperature were studied. Adhered, porous screen printed films with different morphologies were obtained by depositing the LaxBa${}_x$Ba${}_{1-<!--\; ???\; -->x}$SnO${}_{3-<!--\; ???\; -->\mathrm{\delta <!--\; ??\; -->}}$ (x = 0 and 0.05) powder particles prepared by the polymerized complex method. Ceria and ruthenate sensitization for screen printed LaxBa${}_x$Ba${}_{1-<!--\; ???\; -->x}$SnO${}_{3-<!--\; ???\; -->\mathrm{\delta <!--\; ??\; -->}}$ (x = 0.05) film was processed through dip-coating in the 0.03 M aqueous solution of CeCl${}_3$ and RuCl${}_3$, respectively. La-doped BaSnO${}_3$ (LBSO) sensor with smaller crystallites, needle-like morphology and high concentration of oxygen vacancies exhibited superior gas response of 65 and 29 towards 50 ppm of ammonia and formaldehyde gases, respectively. Superabundant sensitization of ceria and ruthenate reduced the oxygen vacancy and structural open porosity in the LBSO sensor; therefore, the ammonia gas response was decreased from 65 to 14 and 3, respectively, whereas the formaldehyde gas response was reduced to less than 1/6th times the LBSO sensor. Limit of detection of LBSO sensors was estimated to be ~ 1 and ~ 2 ppm against ammonia and formaldehyde, respectively. The presence of fluorite structured phase ceria with high oxygen atoms storage capacity facilitates the rapid oxidization of analyte gases and caused the expeditious response (75 s) and recovery (60 s) in CeOx-sensitized LBSO sensor. This study might give a new insight into the development of doped and sensitized BSO-based gas sensors operating at ambient conditions.

[en] Facility ventilation system on once through basis is normally recommended and followed for highly radioactive plutonium laboratories generating particulate matter. However recirculatory ventilation system is economical from the point of view of both capital and operational costs. Further, significant energy saving will also be achieved. The present paper discusses the philosophy related to recirculatory ventilation system from engineering and radiation safety points of view and highlights the modifications required to be made in the once through ventilation system suitable for operation in recirculatory mode. (author). 4 refs., 4 tabs., 3 figs

[en] The growth of Gadolinium doped ceria thin films with controlled surface structure for device quality applications presents a significant problem for experimental investigation. In the present study gadolinium doped cerium oxide thin films were prepared by pulsed laser deposition (PLD) and were studied for their surface structure evaluation in relation to the optimized operating conditions during the stage of film preparation. The deposition was made with gadolinium concentration of 10 mole% to ceria pellets. The films were deposited on quartz substrate in the presence of oxygen partial pressure of 1.5 x 10^-3 torr using KrF Excimer laser with laser energy 220 mJ at a substrate temperature 700℃. The effect of annealing temperature on 10 mole% GDC thin film was investigated. The film thickness was measured by using AMBIOS make XP-l stylus profiler. As prepared and annealed thin films were characterized for crystallinity, particle size and orientation by using G.I.XRD. The films were characterized using atomic force microscopy (AFM). The AFM results gave a consistent picture of the evolution of GDC film surface morphologies and microstructures in terms of surface roughness, grain distribution and mean grain size. The optical transmittance spectra was used to determine the optical constants such as optical band gap, refractive index, extinction coefficient of as prepared and annealed thin films. (author)

[en] RLG is an important and exclusive radiological facility at Trombay for carrying out R and D and pursuing the Department's high priority objectives involving a variety of radioactive materials in considerable quantities. Since commissioning, about five decades ago, RLG has grown a lot as a facility in size as well as volume and in importance of its activities. Support systems play all important role for safe operations in such a facility. The challenges experienced in expanding the facility and in providing utility and safety support to the facility during this long period are compiled for future reference in developing such facilities

[en] A facile co-precipitation technique is used to fabricate ZnO and AZO (Al-doped ZnO) nanoparticles. It is analyzed and investigated that the effect of Al doping concentration has altered the structural and morphological properties of the nanoparticles. Increasing the concentration of doping has reduced the average crystallite size considerably in the range 18–24 nm. With the increased microstrain, we observe that bond length decreases for AZO nanoparticles. FESEM images indicate that morphology varies from the hexagonal crystalline phase of ZnO structure to the spherical shape of AZO samples. The UV–Vis spectroscopic studies showed that Al was incorporated into ZnO lattice as Al³⁺ due to the decreasing optical band gap of nanoparticles. The gas sensing responses of ZnO and AZO nanoparticles have been studied at optimum temperature with a low concentration of ammonia gas. The sensing studies revealed that the response of gas mainly relies on the size of the particles.