Satyabrata Mishra

Destruction of soluble organics generated during the dissolution of sintered uranium carbide by mediated electrochemical oxidation process

Abstract The destruction of soluble carbonaceous compounds formed during the dissolution of sintered uranium mono carbide pellets in 11.5 M nitric acid at 65 °C has been investigated by employing mediated electrochemical oxidation (MEO) method, in which process 0.05 and 0.01 M Ag(II) and 0.1 and 0.06 M Ce(IV) were used as the regenerable catalysts. The current density and temperature of the process for maximum destruction efficiency were optimized to be 25 mA/cm2 and 75 °C respectively. The electro-oxidation behaviour of the mediator ions Ag(II) and Ce(IV) with respect to their concentration in the removal of organics and the dependence of temperature on the stabilities of the two electrochemical catalysts were compared. The effect of fission product elements in a synthetic dissolver solution on the performance of Ag(II) mediator in oxidizing the carbon content was discussed. The destruction efficiency of MEO process in eliminating the soluble organics was ascertained to be better than that of direct electrochemical oxidation method as well as prolonged oxidation of the organics with concentrated nitric acid.

Effect of Radiolysis in Altering the Physiochemical and Metal Retention Properties of Solvent-Diluent-Acid Systems

Systematic studies were performed on radiolytic degradation of Tri-n-Butyl Phosphate diluted with n-Dodecane or Normal Paraffin Hydrocarbon in the presence/absence of nitric acid as a function of absorbed gamma dose. Viscosity and phase disengagement time increased with absorbed dose but interfacial tension decreased gradually. The extent of damage caused during radiolysis was estimated by Zr retention in the organic phase. The effectiveness of carbonate wash in restoring the quality of the solvent was evaluated. Comparison of the IR spectra for the neat and the degraded samples revealed the formation of nitro alkanes at absorbed dose above 20 MRad.

Evolution in physiochemical properties of alternate PUREX solvent on hydrolytic and chemical treatment

ABSTRACT Physiochemical properties such as density, viscosity, interfacial tension (IFT) and phase disengagement time (PDT) were measured after subjecting tri-iso-amyl phosphate (TiAP)-based solvent systems to hydrolytic treatment at 40 and 50°C, for 400 h. The change in viscosity between the degraded and fresh solvent was significant compared with the change in density, which could be due to the formation of intermediate compounds susceptible to hydrogen bonding. The marginal variation in the IFT values even after accelerated treatment and the absence of any new class of compounds after treatment, as evidenced by FTIR spectral analysis, revealed that the solvent exhibited good thermal and chemical stability.

Feasibility studies of using N,N-dihexyloctanamide (DHOA) for fast reactor fuel reprocessing applications

Abstract N,N-dihexyloctanamide (DHOA) is being considered as a promising extractant in the aqueous reprocessing of spent nuclear fuels. In view of rise in temperature of the solvent during reprocessing of fast reactor fuel, the present study aimed at evaluating the physical properties such as density, viscosity, and interfacial tension and Pu(IV) extraction behavior in 1.1 M DHOA/n-dodecane as a function of temperature and duration of heating. The influence of nitric acid in altering the physical properties with respect to temperature was evaluated. Physical properties and extraction behavior of the solvent changed to a remarkable extent with temperature. Quantitative amount of Pu(IV) could be back-extracted from loaded, solvent in three contacts at 313 K. FT-IR studies were carried out to evaluate the thermal stability of the solvent. Thus, the performance of the solvent, 1.1 M DHOA/n-dodecane is satisfactory at higher temperatures also.

Thermophysical properties of tri-n-butylphosphate-ionic liquid mixture

Thermophysical properties such as viscosity, density, energy of activation and coefficient of thermal expansion were measured for the solvent phase composed of tri-n-butylphosphate (TBP), 1-butyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([C4mim][NTf2]) and 1.1 M TBP/[C4mim][NTf2]. The results were compared with that of nitric acid equilibrated [C4mim][NTf2] and 1.1M TBP/[C4mim][NTf2]. Thermal stability of the ionic liquid phase was assessed by using differential scanning calorimetric (DSC) technique. Other important physical properties such as refractive index and surface tension of the ionic liquid phase composition were evaluated before and after acid saturation.Thermophysical properties such as viscosity, density, energy of activation and coefficient of thermal expansion were measured for the solvent phase composed of tri-n-butylphosphate (TBP), 1-butyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([C4mim][NTf2]) and 1.1 M TBP/[C4mim][NTf2]. The results were compared with that of nitric acid equilibrated [C4mim][NTf2] and 1.1M TBP/[C4mim][NTf2]. Thermal stability of the ionic liquid phase was assessed by using differential scanning calorimetric (DSC) technique. Other important physical properties such as refractive index and surface tension of the ionic liquid phase composition were evaluated before and after acid saturation.

Development and Characterization of Porous Silicon Nitride Tubes

As the porous aluminous porcelain diaphragm tubes in the electrolytic cells, employed in the aqueous reprocessing of spent nuclear fuels, undergo leaching in concentrated nitric acid, corrosion resistant 600 mm long silicon nitride tubes were developed indigenously by reaction bonding of pre-formed silicon green tubes in nitrogen atmosphere. The process parameters for the fabrication were optimized to produce tubes with density, porosity and liquid permeability in the range 2.2-2.5 kg.dm–3, 20-25% and 10–5-10–6 cm.s–1 respectively. The performance of the fabricated tubes was evaluated by using them as the diaphragm tubes in the electrolytic destruction of 4 M nitric acid and the efficiency of the process was compared with that for a cell in which a commercially available silicon nitride tube was used as the diaphragm material. Though performance of both the tubes was comparable, the resistance offered by the indigenous tube to the flow of current through it was much lower than that of the other tube.