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Study on the cementation of the regenerated activity (from spent resin using ferric as regenerant) containing ferric in cement matrix showed that compressive strength and leaching behaviour are better when the ferric strength was < 5 N. The diffusion coefficient of Cs from the cement matrix was found to be in the range 2.4 × 10−5 cm2/day and 5.9 × 10−5 cm2/day with ferric solutions of strength in the range 0.5–3 N. When bentonite and vermiculite were included in the cement matrix, the diffusion coefficient of Cs was found to be in the range 6.2 × 10−7 cm2/day to 1.26 × 10−5 cm2/day with ferric strength in the same range.

Volume reduction studies were carried out on low level radioactive plastic wastes containing polyethylene, PVC and neoprene by melt densification. The optimized temperature for melting of plastics was between 170 and 180 °C. Based on laboratory scale studies. Plant scale studies were planned and conducted. The volume reduction factors obtained were around 30, which was 6-10 times higher than that of the conventional compaction process. Thermogravimetry and infrared spectroscopy were used to investigate the thermal and structural properties of the given materials. The effect of the presence of salts like potassium permanganate and hydrazine sulphate on the thermal properties of the materials was also evaluated. Leaching studies were also performed on melt-densified specimens in the laboratory. The average leach index was observed to be around 9, which was higher than the minimum stipulated value.

Polyvinyl acetate based strippable polymer has been developed for surface decontamination. Stainless steel, mild steel, polyvinyl chloride and rubber have been selected as candidate materials for the radioactive decontamination studies. The ease of strippability and homogeneity of the polymer coating has been studied using infrared spectrophotometer. Decontamination of used radioactive respirator has been carried out and the peels obtained have been subjected to leaching and incineration studies. The infrared spectrophotometric studies also have been counducted to study the interaction between polyvinyl acetate and ions, like cesium, strontium and cobalt.

An attempt has been made to synthesize ceramic titania and zirconia membranes by sol-gel process by filtering respective viscous colloidal sol through microporous alumina support and gelling followed by sintering at 400°C and 470°C respectively. The static charge on the pores of the so formed membranes and the pore size distribution determine the applicability in filtering colloidal solution. The mean pore size from SEM were found to be 0.65 μm and 0.54 μm for titania and zirconia membranes respectively with 1.47 × 107/cm2 as pore density for both. The filtration characteristics during membrane layer formation showed that the membrane layer formation started after 35 minutes in the case of titania membrane and 40 minutes in the case of zirconia membrane. From the gravimetric estimation of water content of the membranes the thickness of the membrane was found out to be 3 μm and the porosity was found out to be 0.30 for both the cases. The particle charge density was estimated from the zeta potential and the particle size. The pore charge density was estimated from the particle charge density, pore density, pore diameter and the thickness of the membrane layer. The membrane pore charge density was found to vary between 3 to −1 μ Coulombs/cm2 in the case of titania membrane and 7 to −0.5 μ Coulombs/cm2 in the case of zirconia membrane in the pH range 1–12.

The growth of Sb-based crystals (InSb, GaSb etc) was undertaken using resistive heater furnace by vertical directional solidification (VDS) technique. Crystal—melt interface shape during the growth was shown to convert from concave to convex along the crystal axis of the ingots. Many antimonide (Sb) crystals of 8 mm to 18 mm diameter were grown by optimized growth parameters. The forced convection and absence of conducting support to ampoule showed improvement in crystal quality of as grown ingots. Crystals showed preferred orientation and self-seeding. Results on interface shape and crystallinity of ingots were found to be in good agreement with the experiments.

A method has been developed for the removal of cesium from the aqueous radioactive waste using a composite ion-exchanger consisting of Copper-Ferrocyanide Powder (CFC) and Polyurethane (PU) Foam. Polyvinyl acetate has been used as a binder in the preparation of CFC-PU foam. The physical properties of CFC such as density, surface area, IR stretching frequency and lattice parameters have been evaluated and also its potassium and copper(II) content have been estimated. Optimization of loading of CFC on PU foam has been studied. The CFC-PU was viewed under microscope to find out the homogeneity of distribution. Exchange capacities of the CFC-PU foam in different media have been determined and column studies have been carried out. Studies have been undertaken on extraction of cesium from CFC foam and also on digestion of spent CFC-PU foam and immobilization of digested solution in cement matrix. The cement matrices have been characterized with respect to density, bio-resistance and leaching resistance.

Hexacyanoferrates (HCFs) are known to be efficient sorbents for the removal of Cs from aqueous solutions. But the powdery precipitate of HCF is unsuitable for use in columns. To make it amenable to column application, it has been coated on polyacrylic fibres by in situ precipitation. In batch and column experiments, the fibres coated with Cupric ferric hexacyanoferrate provided good removal of137Cs from radioactive effluents. Leaching of Cs from the fibres was found to be only 14% in demineralised water medium. The Cs-loaded fibres could easily be incinerated to a smaller volume for further conditioning.

We have successfully grown high mobility undoped and Te doped InSb crystals of size 10–12 mm dia. and 60 mm length under inert argon atmosphere in closed quartz ampoules, by vertical directional solidification (VDS) technique. The crystals showed predominantly (220) orientation along the growth axis. The surface defects, such as voids were reduced drastically by selecting proper lowering rate, rotational speed and cone angle of the ampoule. The high mobility and quality crystals were obtained with the ampoule conical angle less than 20°, lowering rate 5mm/h, and rotational speed 10 rpm.

Studies have been carried out on the immobilization of spent ion-exchange resins produced in nuclear power plants in urea-formaldehyde matrix. The matrices were prepared by incorporating different types of ion-exchange resins in the pH range of 4.5 to 5.0, using boric acid as a catalyst. Characterization of the matrices was carried out with respect to dimensional changes, compressive strength, and leach resistance. The cumulative percentage weight loss and volume change were observed to decrease with the increase in boric acid concentration before attaining a plateau. The diffusion coefficients were in the order of 10−16 M/s, and the compressive strengths were in the range of 0.83 to 12 MPa. Infrared spectral studies on the urea-formaldehyde matrices revealed that the rate and the extent of cure depended on the type of resin. © 1994 John Wiley & Sons, Inc.

Fluoride in wastewater is normally introduced through industrial processes and manufacturing. The toxicity of fluoride is well understood and considerable work has been done on the defluoridation of well waters and wastewaters. The present paper describes a two-stage method that utilizes lime in the first stage for the removal of the bulk of fluoride and zirconium in the second stage as an agent for polishing. This method brings down the fluoride to a level less than 0.2 mg/L from an initial concentration in excess of 100 mg/L. The fluoride from zirconium hydroxide precipitate generated in the second stage could be quantitatively removed by a dilute solution of sodium hydroxide, thus affording recycling of zirconium, which makes this method cost effective.

The Calutron‐Bernas ion source has been modified for high‐dose ion implantation (>1016 ions/cm2). The modified ion source has stable arc, uniformly bright illumination, and dense plasma. It consists of a hairpin‐shaped tungsten (W) filament as a hot cathode at one end, and a disk‐type graphite anode at the other end about 8 cm away; both the electrodes are fitted in an arc discharge chamber made of graphite only. The anode potential of 150–200 V and filament current of about 60 A initiates a stable bright arc. A magnetic field (0.1–0.5 kG) along the cathode‐anode axis enhances the electron ionizing efficiency, helps in collimating the electrons, and contributes also in the plasma confinement near the aperture. The operational life of W filament (1.2 mm diam) in an ambient of oxygen or nitrogen at pressure 10−3–10−4 Torr varies from 25 to 35 h. Further, a needle valve or an in‐built minioven is used, respectively, when the feed material is a gas/liquid or a solid charge. The gas/vapors is/are admitted at a...