[en] Following the development and successful application, of an in vivo x-ray fluorescence technique to measure lead in the tibia shaft, the method was extended to include a simultaneous measurement of the lead concentration in calcaneus. This method, in which the 88 keV γ-rays from ¹⁰⁹Cd excite the lead K series x-rays, can now be used to obtain the lead concentration in both cortical (tibia) and trabecular (calcaneus) bone. As with the tibia measurement, the lead x-ray signal is normalized to a concentration in bone by means of the coherently scattered photon signal. The accuracy of this procedure was tested by comparing the results of x-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS) measurements on 44 bone samples - a section of tibia shaft and the calcaneus from each of 22 subjects. The mean differences (XRF-AAS) in lead concentration (μg Pb (g bone ash)^-1) were; for the tibia -1 +/- 2 (SEM), and for the calcaneus 2 +/- 5

[en] Effect of γ-radiation on non-isothermal decomposition kinetics of bis(diethylene triamine)cobalt(II) nitrate and bis(diethylene triamine)zinc(II) nitrate have been studied in nitrogen atmosphere at a heating rate of 10 deg C/minute. The data were analyzed by Coats- Redfern, Freeman-Caroll and Horowitz-Metzeger methods. The result showed that irradiation enhanced thermal decomposition in both the complexes. Activation energy and associated kinetic parameters are lowered upon irradiation and the extent of lowering is higher in cobalt complex compared to zinc complex. Order of the reaction for each step was found to be unity. The mechanism for deamination and decomposition is controlled by R₂ function except for the deamination of unirradiated cobalt complex where the process is governed by R₃ function. (author)

[en] Base damage and phosphate release have been determined simultaneously from gamma irradiated aqueous solutions of DNA in O₂ and N₂. Base damage (bd) was determined by the decrease in optical density at 255 nm in a Cary 14 spectrophotometer. Inorganic phosphate (Psub(i)) was estimated by a modified Berenblum and Chain method. Gamma irradiation was from a Co-60 gamma cell at a dose rate of 4 krad/min and upto a total dose of 320 krad. DNA solutions used were in the concentration range of 20 μg/ml to 200 μg/ml of salmon sperm DNA in neutral aqueous solution. An inverse correlation was found between bd and Psub(i) for all concentrations of DNA. This was seen both in O₂ and N₂. Oxygen enhancement ratio (defined as ratio of yield in O₂ to that in N₂) was more than 1 for bd and at corresponding doses OER for Psub(i) was less than 1. The OER value for Psub(i) changes at higher doses where bd gets saturated. These results show that there is a competition for radiation produced damaging species, between these two sites (viz. base and sugar-phosphate parts of DNA molecule). In general Psub(i) released was about 10% of bd for a given dose both in O₂ and N₂. (author)

[en] The formation and properties of metal-silicon interfaces are of great technological interest in semiconductor, high temperature material, and corrosion applications. Si can be deposited and diffused on metal surfaces to increase corrosion resistance in aqueous acidic environments, oxidation resistance at high temperatures, and erosion resistance. Siliconization of steel to increase its oxidation resistance is performed above 900 C to permit diffusion of Si into the metal. However, the deposition of Si on metals has not been studied in depth. Recently, the authors developed a new coating technique based on chemical vapor deposition (CVD) that allows deposition of Si at much lower temperatures than conventional CVD or pack siliconization techniques. The authors have been able to deposit silicon on W, Fe, and Cu from 350 to 850 C. This paper describes some of the preliminary findings on the metal-Si interfaces formed at these low temperatures

[en] Thermal decomposition, X-ray diffraction pattern, infrared (IR) spectrum and antibacterial property of tris(1,2-diaminoethane)nickel(II)oxalate were studied before and after γ-irradiation. Irradiation enhanced thermal decomposition. From X-ray diffraction studies, unirradiated and irradiated samples of the complex are found to be tetragonal. A change in lattice parameters was observed upon irradiation. Position and intensity of IR bands of -NH₂ and >C=O group were found to be changed upon irradiation. Antibacterial studies showed that irradiation induced activity towards B. cereus. (author)

[en] The effect of gamma irradiation on single crystal and powdered samples of diaquamalonatomanganese(II) was investigated. Thermal, spectral and surface morphological studies were also performed using the powdered samples before and after irradiation. Single crystal as well as PXRD studies showed that both unirradiated and irradiated samples are orthorhombic. Changes in lattice parameters upon irradiation are different in powder and single crystal of the same material. Thermal decomposition profiles of unirradiated and irradiated samples are found to be similar. Upon irradiation significant changes were observed in spectral features. AFM studies revealed morphological changes and enhanced roughness in the irradiated sample. (author)

[en] Throughout the world, occupational exposures at nuclear power plants have been steadily decreasing over the past decade due to technological advances, improved plant designs, improved water chemistry and plant operational procedures, as well as other factors. However, with the aging of the nuclear plants, the task of maintaining occupational exposures low has become increasingly difficult. At MAPS,the first indigenously built Indian PHWR- the cumulative efforts put in modifications/improvements in design over the years, supplemented by refinements in work practices contributed to substantial reduction of unproductive doses for different jobs. The Operation Section had put sustained efforts which resulted in the reduction of annual collective dose for that Section and also in the reduction of stack emissions of ⁴¹Ar and ³H. In this paper, focus is made on various design improvements supplemented by refinements in work procedures and better practices to meet the ALARA objective at MAPS. (author)

[en] Irradiation induced decomposition of some transition metal sulphates and alkali metal sulphates were investigated by E.Johnson. The objective of our study is to extend such studies to metal amine complexes containing sulphate as anion. Metal amine complexes of the type (MLn)SO₄ were prepared and characterised. The samples were irradiated to varying doses upto 900 kGy using ⁶⁰Co gamma rays. NH₃ and SO₃^2- in the irradiated samples were estimated spectrophotometrically. Infrared spectra of the samples were recorded before and after gamma irradiation

[en] During manufacturing of Mixed Oxide Fuel (MOX) pellets for Advance Heavy Water Reactor (AHWR-LEU), around 30% rejected MOX pellets are generated in every cycle. These rejected MOX pellets are dissolved in nitric acid for recovery of U/Th. The recovered U/Th is recycled for production of MOX pellets. MOX pellets of varying compositions are used in AHWR fuel. Dissolution of MOX pellets in nitric acid is a challenging task because of its low surface area and longer dissolution times. High normal nitric acid is used in order to increase rate of dissolution, which in turn results in generation of high free acidity solution which influences the precipitation characteristics of Uranium (VI) by oxalic acid. Oxalic acid precipitation helps in generation of nitric acid which can be used for dissolution there by effectively facilitating nil effluent generation. Precipitation by oxalic acid unlike ammonia has advantage of zero liquid effluent discharge by complete recycle of oxalate filtrate to dissolution section. In the present work, the effect of various parameters like free acidity, residence time, concentration of oxalic acid, initial concentration of uranium and thorium etc. on the precipitation of U(VI) and Th(IV) in nitrate media by oxalic acid was carried out. The precipitated powder was subjected to various morphological evaluations like particle size etc. Study of various parameters on the co-precipitation of uranium and thorium by oxalic acid was carried out. It was observed that complete precipitation (> 99.9%) of thorium as oxalate does not depend on free acidity range (1- 6 N). Excess oxalic acid is not required for complete precipitation of thorium oxalate. The precipitation of uranyl oxalate varies with initial free acidity of solution. Uranyl oxalate precipitation does not take place at and above 5 N of free acidity

[en] Some of the aqueous streams from reprocessing plant contain dissolved Tributyl Phosphate (TBP). This will lead to the formation of red oil in further reprocessing steps. The separation of dissolved organics using non-ionic macro porous polymeric resin is an emerging technique in the field of nuclear fuel reprocessing. Experiments were conducted for the removal of TBP from aqueous solution (3M HNO₃) using Amberlite XAD-4 resins. In the present study, Tulsion ADS 1700, a non-ionic polymeric adsorbent resin was used for the removal of TBP from aqueous (3 M HNO₃) solution