Zafar Yasin

Nitrate ion transport across TBP-kerosene oil supported liquid membranes coupled with uranyl ions

The role of nitrate ions in uranyl ions transport across TBP-kerosene oil supported liquid membranes (SLM) at varied concentrations of HNO3 and NaNO3 has been studied. It has been found that nitrate ions move faster compared to uranyl ions at the uranium feed solution concentrations studied. The nitrate to uranyl ions flux ratio vary from 355 to 2636 under different chemical conditions. At low uranium concentration the nitrate ions transport as HNO3 · TBP, in addition to as UO2(NO3)2 · 2TBP type complex species. The flux of nitrate ions is of the order of 12.10 · 10−3 mol · m−2 · s−1 compared to that of uranium ions (4.56 · 10−6 mol · m−2 · s−1). The permeability coefficient of the membrane for nitrate ions varies with chemical composition of the feed solution and is in the order of 2.5 · 10−10 m−2 · s−1. The data is useful to estimate the nitrate ions required to move a given amount of uranyl ions across such an SLM and in simple solvent extraction.

Comparison of Fission Induced by Protons and Pions

The goal of the present work is to compare properties of fission induced by nucleons and pions. Three different methodologies are used to make this comparison. Firstly, it is shown that pion-induced fission cross sections are not much different in magnitude from proton induced fission cross sections at the same kinetic energy. Secondly, across the pion-nucleon (3,3) resonance so prominent with free nucleons, it is observed that there is no significant change in the reaction mechanism in the case of pions. Thirdly, it is noted that an empirical expression used for evaluations of proton induced fission cross sections is also valid for positive pion-induced fission cross sections, at least for actinide nuclei. Nuclear fission is an important, interesting and complex nu- clear reaction, with relevance in areas ranging from nuclear structure models to accelerator-driven systems (ADS). There is need in basic and applied nuclear physics to understand the properties of fission induced by nucleons and pions, and cross sections for fission induced by nucleons and pions have applications in advanced nuclear reactor technologies, in medicine, for effects on electronics, etc. In ADS using high energy protons, pions are created from the primary proton reactions, and are then part of complex cascades of reactions. Hence, fission induced by nucleons and pions are both im- portant, and fission reactions may have a significant effect on spallation target performance and may contribute to the prod- uction of radioactive or chemically hazardous materials in targets (1). Fission induced by pions is not as much studied as fission induced by nucleons. Hence, the goal of the present work is to compare properties of fission induced by nucleons and pions. Three different methodologies are used to make this comparison. Firstly, it is shown that pion-induced fission cross sections are not much different in magnitude from proton induced fission cross sections at the same beam kinetic en- ergy. Secondly, across the pion-nucleon (3,3) resonance so prominent with free nucleons, it is observed that there is no significant change in the reaction mechanism in the case of pions. Thirdly, it is noted that an empirical expression used for evaluations of proton induced fission cross sections is also valid for positive pion-induced fission cross sections, at least for actinide nuclei. Fission cross sections computed using a cascade-exciton model code for 209 Bi and 238 U are also compared with available experimental data. Proton and pion induced fission cross sections are com- puted using the cascade-exciton model code CEM95. Three stages are incorporated in CEM95; cascade, preequilibrim and compound nucleus stages. A change in the ratio of the level density parameter for fission and neutron emission channels (af /an) is taken into account with change in the incident energy of the projectile to account for the change in the excitation energy of the compound nucleus. Other parameters

Separation and analysis of aluminium(III) by cation exchange ion chromatography

A method for the determination of aluminium(III) ions based on separation by cation exchange column chromatography and detection by conductivity detector has been developed. It is fast and reliable, and can be used for the separation and analysis of aluminium(III) ions from other metal ions like Mg(II), Mn(II), Zn(II), Co(II), Ca(II), Sr(II), rare earth elements like Lu(III), Tm(III), and Gd(III), which are eluted at different times and so do not interfere. Effect of p-phenylene diamine concentration present in the eluent, presence of other metal ions and effect of various anions present in the injection sample on the separation and analysis of aluminium(III) ions have also been studied.

Cascade-exciton model analysis of mass dependence of pion-induced fission

The cascade-exciton model has been used to observe the dependence of pion induced fission cross sections on the mass of the target. The analysis has been performed at energies 80 MeV, 100 MeV and 150 MeV for both the positive and negative pions. It has been shown that a single value of the ratio af/an can satisfactorily reproduce the experimental findings when compared with the available experimental data in the literature. The general trend of the fission cross sections with mass (fissility parameter) is seen to be low and slowly changing for the lighter nuclei, and it will steeply rise for the heavy nuclei.

Fission studies of gold induced by (1665 MeV) π− using a CR-39 detector

The fission cross section and fission probability of 197Au, induced by (1665 MeV) π−, have been studied using CR-39 track detectors. A 4π-geometry was used to count track statistics. A beam of negative pions of 1665 MeV was produced at AGS of Brookhaven National Laboratory, USA, and allowed to fall normally on the stack. Two detectors from the stack were scanned for fission fragment tracks after etching in 6N NaOH at 70 °C. The statistics of fission fragment tracks in both detectors were obtained. It was found that there was a marked asymmetry of registered tracks with respect to the forward and backward hemispheres. This asymmetry could be partly accounted for on the basis of momentum transfer to the struck nucleus. On the basis of counting statistics fission cross section was measured, and fission probability was determined by dividing the fission cross section with the reaction cross section. The fission cross-section and fission probability were compared with the computed values using the cascade-exciton model code CEM95.

Mass dependence of pion-induced fission cross sections on the level density parameter

Fission probabilities and fission cross sections strongly depend on the mass number of the target and energy of the projectile. In this research work, a cascade-exciton model (using CEM95 computer code) has been implemented to observe the dependence of pion-induced fission cross sections and fission probabilities on the target mass and ratio of the level density parameter in fission to neutron emission. The analysis has been performed for both the positive and negative pions as the projectile at 80, 100 and 150 MeV energies. The computed cross sections satisfactorily reproduced the experimental findings when compared with the available experimental data in the literature. We observed a smooth dependence at 150 MeV, and a sharper dependence at 80 and 100 MeV pion energy, in the fissility region above 29.44.

Cascade-exciton model analysis of level density parameter dependence in proton induced fission cross sections of some sub-actinide nuclei

Fission cross sections strongly depend on the ratio of the level density parameter in fission to neutron emission, af/an. In this work, a cascade-exciton model implemented in the code CEM95 has been used to observe this effect for proton induced fission cross sections of tungsten, lead and bismuth. The method was employed using different level density parameter ratios for each fission cross section calculation. The calculated fission cross sections are compared with the available experimental data in the literature. It has been observed that a change of the ratio of the level density parameter, af/an, is necessary with the incident energy of the proton, to best estimate the fission cross sections in CEM95.

Dependence of Nucleon and Pion-Induced Fission Cross Sections on the Level Density Parameter in the Cascade-Exciton Model

A new method is used to compute the fission cross sections in which a change of the ratio of the level density parameter in fission to neutron emission channels is taken into account with the change of the incident energy of the projectile. It is shown that fission cross sections induced by nucleons and pions depend on the ratio of the level density parameter in the fission and evaporation modes, i.e. af/an, respectively. We are unable to describe well the cross sections for fission without using this new method. The computed values exhibit reasonable agreement with the experimental data found in the literature across a wide range of beam energies.