Volume 107, Issue 3

Many commercial processes exist for converting uranium from ore to the desired uranium compound for use in nuclear power or nuclear weapons. Accurately determining the processing history of the uranium ore concentrates (UOCs) and their calcination products, can greatly aid a nuclear forensics investigation of unknown or interdicted nuclear materials. In this study, two novel forensic signatures, based on nuclear materials synthesis, were pursued. Thermogravimetric analysis – mass spectrometry (TGA-MS) was utilized for its ability to discern UOCs based on mass changes and evolved gas species; while scanning electron microscopy (SEM), in conjunction with particle segmentation, was performed to identify microfeatures present in the calcination and reduction products (i.e. UO 3 , U 3 O 8 , and UO 2 ) that are unique to the starting UOC. In total, five UOCs from common commercial processing routes including: ammonium diuranate (ADU), uranyl peroxide (UO 4 ), sodium diuranate (SDU), uranyl hydroxide (UH), and ammonium uranyl carbonate (AUC), were synthesized from uranyl nitrate solutions. Samples of these materials were calcined in air at 400 °C and 800 °C. The 800 °C calcination product was subsequently reduced with hydrogen gas at 510 °C. The starting UOCs were investigated using TGA-MS; while SEM quantitative morphological analysis was used to identify signatures in the calcination products. Powder X-ray diffractometry (p-XRD) was used to identify the composition of each UOC and the subsequent calcination products. TGA-MS of the starting UOCs indicate temperature-dependent dehydration, volatilization, and reduction events that were unique to each material; thus making this a quantifiable signature of the initial material in the processing history. In addition, p-XRD, in conjunction with quantitative morphological analysis, was capable of discriminating calcination products of each processing history at the 99 % confidence level. Quantifying these nuclear material properties, enables nuclear forensics scientists to better identify the origin of unknown or interdicted nuclear materials.

The new abilities of the method of standard sets of nuclides (SSN) supplemented by the procedure of statistical testing for geochemical studies and nuclear dating are presented. The method allows one move from point-like to probabilistic dating procedures when both the age of the sample and the statistical errors of its determination can be estimated. Low background γ-spectrometric experiments were carried out for samples of rocks of the Carpathian Mountains and calculations for their dating by using the SSN of the series 238 U were made. The dependence of the reliability of nuclear dating on the quality of the low background experiment is discussed too.

A method has been developed for quantification of trace rare earth (Ce, Dy, Er, Eu, Gd, Ho, La, Nd, Pr, Sm, Tb and Yb) impurities in alumina and aluminum by inductively coupled plasma mass spectrometry (ICP-MS) after matrix separation. The matrix separation was achieved by selective precipitation of trace elements. Due to its refractory nature a microwave digestion method was developed and optimized for the quantitative dissolution of Al 2 O 3 . The analytical methodology was validated by recovery studies with standard addition as well as with an independent γ-spectrometry technique using 152,154 Eu tracers. The observed recovery in the synthetic samples was in the range of 93–100% with precision within 6.1–11.6 (%RSD), while the same in the case of radio tracer technique were found to be >98% and <2% (RSD), respectively. The method detection limit was found within 0.5–8.3 μg kg −1 , respectively. The procedure is simple, organic waste free and suitable for routine analysis.

Blends of rubber-rubber have desired properties intermediated between two rubber matrices. On the other hand, polymer-clay nanocomposites have attracted the attention of many researchers and experimental results are presented in a large number of recent papers and patents because of the outstanding mechanical properties and low gas permeability that are achieved in many cases. Polymer-clay nanocomposites are a new class of mineral-field polymer that contain relatively small amounts (<10%) of nanometer-sized clay particles. In this study, new nanocomposite materials were produced from the blend of polybutadiene rubber (BR) and ethylene propylene diene monomer rubber (EPDM), BR/EPDM (50/50) as matrix and organically modified vermiculite clay (VMT) by quaternary alkylammonium in different contents (3, 6, 9 and 12 phr) as the filler by using rubber mill then, the rubber nanocomposite sheets were irradiated at doses of 25, 50, 75, 100 and 150 kGy using γ-radiation technique as a crosslinking tool. The prepared composites can be characterized by using various analytical techniques including X-ray diffractometer (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) as well as mechanical properties measurements.

To develop a possible PET blood pool imaging agent, a series 68 Ga-dextran carboxylate derivatives were prepared. Dextran carboxylates with different degree of oxidations (DO) were prepared through stepwise dextran oxidation using NaIO 4 and CH 3 COOOH. The products were characterized by FT-IR and GPC, followed by solubility and toxicity tests on Hella cells (viability=98.6, 97.4 and 95.6% for 3 dextran carboxylates with DOs: 8.3, 24.6 and 39.8%, respectively. The products were labeled with 68 Ga (radiochemical purity>98%; ITLC) followed by stability tests in final solution as well as in presence of cycteine and human serum. Two stable tracers (DOs; 24.6 and 39.8%) were adminstered intravenously into wild type rat tail vein separately demonstrating suitable retention in circulation as expected from blood pool imaging agents. Liver and spleen also contained activities. The major excretion was through urinary pathway esp. for derivative with DO. 39.8%. Unlike 68 Ga-dextran, lungs showed lower uptake. The dextran carboxylate with the highest 39.8% showed the best characteristics for a blood pool agent, though more studies including PET imaging in larger mammals are required.

Coal-fly-ash is one of the major byproducts of coal-based power plant in which naturally occurring radioactive materials (NORMs) are drastically enriched compared to those of feed coals. Thus, improper management of fly-ash may introduce additional radioactivity to the surrounding environment and cause radiological risk. So, in order to study the distribution of radionuclides in soil around a coal-based power plant and to evaluate their radiological risk, soil, coal and fly-ash samples were analyzed by using a HPGe detector for U-238, Ra-226, Th-232 and K-40 radioactivity concentrations. Furthermore, soil minerals were also studied by X-ray diffractometer to assess the mineralogical provenance of the radionuclides. Mean radioactivity concentrations (in Bq·kg −1 ) of U-238, Ra-226, Th-232 and K-40 in soil samples are 102.9±41.4, 63.6±7.4, 103.4±13.9 and 494.2±107.5, respectively which are comparatively higher than the typical world mean value. Elevated levels of radioactivity are likely due to the presence of illite, kaolinite, monazite, rutile and zircon minerals in the soil samples rather than technogenic contributions from the power plant. Furthermore, mean soil contamination factor (CF) are close to unity and mean pollution load index (PLI) is below unity while the average radium equivalent activity (Ra eq in Bq·kg −1 ), external hazard index (H ex ), absorbed γ dose rate (D in nGyh −1 ), annual effective dose rate (E in mSv·y −1 ) and excess lifetime cancer risk (ELCR in Sv −1 ) are 249.5±21.7, 0.67±0.06, 114.2±9.4, 0.20±0.02, 4.9×10 −4 ±0.4×10 −4 , respectively, which are within the permissible limit. Thus, in terms of radioactivity concentrations and associated environmental and radiological indices, the effect of the power plant is insignificant.

Bi 2 O 3 –B 2 O 3 –Li 2 O–K 2 O–MoO 3 glass system has been synthesized using melt-quenching technique. γ ray shielding properties have been evaluated in terms of mass attenuation coefficient at photon energies 356, 662 and 1173 keV. These shielding parameters are also compared with standard nuclear radiation shielding material “barite concrete” at the same photon energies. Most of our prepared samples show better γ ray shielding properties as compared to barite concrete at the same photon energies. Density, molar volume, XRD, FTIR and Raman studies have been employed to study the structural properties of the prepared glass system. Different structural groups such as [BO 3 ], [BO 4 ], [MoO 4 ] and [MoO 6 ] have been detected in the amorphous network. The presence of non-bridging oxygens, bridging oxygens and change of coordination number has been discussed. The optical absorption spectra are recorded in the wavelength range 200–800 nm and optical band gap is calculated which has shown strong dependence on Bi 2 O 3 /B 2 O 3 ratio. The samples have also been tested for their durability by measuring dissolution rate properties using distilled water at 90°C. It has been concluded that increase in the content of Bi 2 O 3 in the composition improves durability and γ ray shielding properties of the samples.

As the utilizing of porphyrins and metalloporphyrins in high dose dosimetry becomes more prevalent, research on structural effects of these molecules on dosimetric characteristics and physicochemical properties of their film dosimeters becomes more and more essential. The present study emphasizes dosimetry (measuring radiolytic bleaching of two novel film dosimeters with spectrophotometric methods against 60 Co γ-rays exposure in dose range of 0–100 kGy) and evaluating substituent effects on the radiation response of the film dosimeters (role of organic groups and changing the metal core of porphyrins). With casting of solutions of polycarbonate (PC) containing 0.5 wt.% 5,10,15,20-Tetrakis(2,4,6-trimethoxyphenyl) porphyrin (TTMPP) and 5,10,15,20-Tetraphenyl-21H,23H-porphine manganese (III) chloride (Mn-TPP), two novel radiochromic films with the thickness of 20 μm were fabricated. The presence of porphyrin fragments has been observed in the UV–Vis spectra after γ radiation. Due to the changes of the metal core and substituents of the dye ring, meaningful shifts of maximum absorbance of Soret bands of porphyrins and different radiation response of film-dosimeters were observed. The results were compared with the other polycarbonate/porphyrin film dosimeters. The results indicate that the radiation-induced decoloration of PC/Porphyrin films can be reliably tuned and used in high dose dosimetry.