JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2012 | Volume:- | Issue:2 (60-1)|Papers Count:10

Due to the extensive use of nuclear energy and its replacement for fossil fuels in recent decades, the radioactive waste production has increased enormously. The vast majority of the radioactive wastes products, are in the liquid form and consequently their treatment is of great importance. In this paper, tin oxide with nano-structure has been synthesized as an absorbent by the homogenous sedimentation method in the presence of urea, so as to adsorb uranium (VI) and thorium (IV) ions. The results obtained from the XRD, SEM and nitrogen adsorption/desorption analyses on the tin oxide sample showed the cassiterite structure with an average particle size of 30 nanometer and a specific surface area of 27.5 m2/g. The distribution coefficients of uranium and thorium were studied by means of batch method. The effects of different variables such as pH and time of contact between the exchanger and solution were investigated and the optimum conditions for sorption of these ions were determined.

Development of oral therapeutic radiopharmaceuticals is a new concept in radiopharmacy. Due to the interesting therapeutic properties of 177Lu and oral bioavailability of maltolate (MAL) metal complexes, 177Lu-maltolate (177Lu-MAL) was developed as a possible therapeutic compound for ultimate oral administration. The specific activity of 2.6-3 GBq/mg was obtained by irradiation of natural Lu2O3 sample with thermal neutron flux of 4×1013 n.cm-2.s-1 for Lu-177. The product was converted into chloride form which was further used for labeling maltol (MAL). At optimized conditions a radiochemical purity of about >99% was obtained for 177Lu-MAL shown by ITLC (specific activity, 970-1000 Mbq/mmole). The stability of the labeled compound as well as the partition coefficient was determined in the final solution up to 24h. Biodistribution studies of Lu-177 chloride and 177Lu-MAL were carried out in wild-type rats for post-oral distribution phase data. Lu-MAL is a possible therapeutic agent in human malignancies for the bone palliation therapy so the efficacy of the compound should be tested in various animal models.

Hydrogeochemistry has been used in recent years as a successful exploration drilling for sedimentary deposits, with a particular interest for the uranium. Like any other exploration activity, hydrogeochemistry needs to identify and investigate the region, especially the hydrogeological one. Ferdows region is one of the priority areas for uranium exploration, where the identification and exploration activities in the prospecting phase have begun since 1388. Because of the detection of uranium mineralization in the area and existence of sedimental uranium mineralization conditions, the hydrogeochemical exploration activities in the area is on the agenda. In this respect, 19 water samples by standard methods were taken and after analysis of metals, carbonates and ions processing and interpretation of results indicated that uranium transfer capability in the region was is extremely limited and the probability of mineralization is low. However, due to high levels of uranium tracers in these areas, the possibility of vein type mineralization of uranium in the upstream is existing and needs to be investigated further.

Biosorption technology is one of the novel technologies used for removal and recovery of radioactive metals from aqueous solutions. Scheduled researches are required for this technique. In this research, biosorption of uranium, lead and cadmium by immobilized baker’s yeast on calcium alginate was investigated. Equilibrium parameters in single systems and binary systems (uranium-lead and uranium-cadmium) were studied. The obtained results in single systems showed that the uranium uptake capacity is higher than that of lead and cadmium. Also, according to the observations in binary systems, the uranium uptake capacity was decreased by interferences of lead or cadmium ions. Nevertheless, uranium uptake capacity in these binary systems is high (more than 130 mg g-1 in uranium-lead and 200 mg g-1 in uranium-cadmium binary systems). The equilibrium isotherms were modeled by Langmuir, Freundlich and combination Langmuir-Freundlich models in single systems and the competitive Langmuir, modified extended Langmuir, extended Freundlich and combination Langmuir-Freundlich models in binary systems. According to the results, the Freundlich model in single systems and the extended Freundlich model in binary systems were found to be better than the others.

Uranium is leached from the uranium ore of the second anomaly of Saghand by the Acidithiobacillus ferrooxidans bacteria in an internal airlift bio-reactor. This study has been made to find the effect of aeration rate as well as its optimal value. The experiments have been carried out at 4 aeration rates to find the best recovery results in the least possible time duration. The results showed that the most percentage of the uranium recovery is in the superficial gas velocity of 0.010 m/s. The recovery at this aeration rate has an efficiency of more than 95% in 11 days. Also, the best range for aeration study in the airlift bio-reactor is calculated with a minimum value of 0.0065 m/s which is the critical value of the uranium particle suspension as well as the maximum value of 0.015 m/s. The stress on the bacteria increases the recovery time process in velocities of more than 0.015 m/s.

By considering the chaos theory, the condition for stability of nuclear reactor is studied. By considering the enrichment fuel as a control parameter, the lyapunov exponent is used for the study of the critical condition. This study, as an example, will focus on the special type of spherical ZPR-III nuclear reactor.

Poly-vinylidene fluoride (PVDF) films were prepared and irradiated by 10MeV electrons at different doses ranging from 50 to 300kGy with a dose rate of 10kGy/s. The FTIR results indicated that no major phase content change was observed. The optical absorption spectra indicated that the electron irradiation results in shifting of the absorption peak, appearance of a new peak and increasing the band gap (Eg). These changes may be due to the breaking of polymer chains and creation of new defects. The X-ray diffraction analysis of samples indicated that the crystallinity did not show any major changes. Concerning the gel fraction measurements, it was observed that gel fraction increases with increasing the dose, where it is an indication of the formation of cross-linked films.

This paper is dealing with the reactor parameter determination experiments performed at the light water subcritical reactor (LWSCR) in Esfahan. The parameter determination methods are derived from a theory based on neutron source position. The LWSCR reactor system is modeled by Monte Carlo calculations (MCNP4C), WIMSD5B and CITATION, and the criticality safety and neutron flux distribution problems are presented and analyzed. The analysis of the multiplication factors obtained by MCNP4C are in fairly good agreement with the results obtained by WIMSD5B and CITATION. For the flux distribution calculations, the MCNP4C results differ from the experimental observations by less than 12% and by ~5% for the WIMSD5B and CITATION.