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Abstract  

Safety assessment of low and intermediate level waste (LILW) repositories requires the understanding of radionuclides sorption–desorption mechanisms, mainly the degree of interaction between radionuclides and mineral surfaces. Among the different radionuclides that are part of the Portuguese radwastes’ inventory 137Cs is one of the most important from the radiological point of view due to its high radiotoxicity. The clay component of natural geomaterials termed rañas, originated from an area located in the NE Mainland of Portugal, was studied for their potential as effective barriers. These geomaterials (grains-size fractions <63 μm, <36 μm) were characterized in terms of cationic exchange capacity (CEC), frayed edge sites (FES) and radiocaesium interception potential (RIP). Organic matter content and pH were also determined. The fractions were mineralogically analyzed by X-ray diffraction and by instrumental neutron activation analysis (INAA) for chemical elemental composition. Smectite (montmorilonite), illite, kaolinite were identified. The capacity of FES is related to the samples granulometry as opposed to what was observed for CEC and RIP. The behavior of rañas was not similar for all samples which may be related to differences in mineralogy. Future studies with regard to the behaviour of radiocaesium are expected to clarify the possible application of these geomaterials as liner/backfill/buffer for a LILW repository.

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Abstract  

The zirconium isotope 93Zr is a long-lived pure β-particle-emitting radionuclide produced from 235U fission and from neutron activation of the stable isotope 92Zr and thus occurring as one of the radionuclides found in nuclear reactors. Due to its long half life, 93Zr is one of the radionuclides of interest for the performance of assessment studies of waste storage or disposal. Measurement of 93Zr is difficult owing to its trace level concentration and its low activity in nuclear wastes and further because its certified standards are not frequently available. A radiochemical procedure based on liquid–liquid extraction with 1-(2-thenoyl)-3,3,3-trifluoroacetone in xylene, ion exchange with Dowex resin and selective extraction using TRU resin has to be carried out in order to separate zirconium from the matrix and to analyze it by liquid scintillation spectrometry technique (LSC). To set up the radiochemical separation procedure for 93Zr, a tracer solution of 95Zr was used in order to follow the behavior of zirconium during the process by γ-ray spectrometry through measurement of the 95Zr. Then, the protocol was applied to low level waste (LLW) and intermediate level waste (ILW) from nuclear power plants. The efficiency detection for 63Ni was used to determination of 93Zr activity in the matrices analyzed. The limit of detection of the 0.05 Bq l−1 was obtained for 63Ni standard solutions by using a sample:cocktail ratio of 3:17 mL for OptiPhase HiSafe 3 cocktail.

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Two fish species, one top predator (Imparfinis mirini) and one intermediate detritivorous species (Hisonotus depres-sicauda) , were experimentally manipulated to evaluate their relative importance in structuring the periphytic community, as well as their effects on the other trophic levels. An enclosure experiment was conducted in the Potreirinho creek, a second order tributary of Paranapanema River, SE Brazil. Five treatments were used: enclosure of the predator species, enclosure of the detritivorous species, enclosure of both together, exclusion of all fish species (closed control cage), and cage open to all fish community (open control). Through direct and indirect effects, I. mirini , when alone, gave rise to a trophic cascade that resulted in a positive effect on algal resources. Through direct effects, H. depressicauda , when alone, reduced the amount of organic matter, resulting in a positive indirect effect on algae. In addition, when the two species were enclosed together, only the effects determined by the detritivorous species were present. The results indicate the important role of the intermediate detritivorous species in the maintenance of the composition and trophic structure of the analyzed community by reducing the effects caused by the top predator.

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Thin-layer chromatographic (TLC) study on nine reactive dyes, seventeen fluorescent brighteners (nine of them are triazine-stilbene derivatives and eight — derivatives of 2-aminodimethylterephthalate), and their intermediates (twenty four in number), all of them containing 4-amino-2,2,6,6-tetramethylpiperidine stabilizer fragment, was performed. These compounds were synthesized for simultaneously bleaching or coloration and stabilization of fabrics or polymers; some of them were able to copolymerize with appropriate monomers like acrylonitrile, methyl methacrylate, and acrylamide. The most suitable stationary and mobile phases for separation, ultraviolet (UV) light as detector, and TLC technique for detection were found. The TLC method was suitable and reliable for monitoring both the synthesis and the purity of the compounds.

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Attenuation specific from Vrancea intermediate-depth focus toward SE is revised at length in order to re-evaluate the seismic hazard at the nuclear power plant (NPP) Cernavoda. To this aim, we took into consideration all the strong motion data available for the region and test a large range of relationship types. Since the instrumental data are limited as magnitude and  depth intervals, the extrapolation based on the attenuation laws deduced from these data to great magnitudes is very instable and must be carefully considered. The extrapolation outside the characteristic domain of the available database leads to large deviations, especially at large magnitudes and for the relations which contain the depth as independent parameter.

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Abstract  

Partitioning of minor alpha-emitting actinides, especially U, Pu and Am from medium active alkaline waste is possible from intermediate level liquid wastes (ILLW) produced during spent fuel reprocessing following Purex process. This paper deals with the efficient removal of alpha-activity from ILLW by solvent extraction process. Counter current batch extraction with O/A ratio 2:1 as well as multistage mixer settler has demonstrated that most of the alpha-activity was removed from the alkaline effluents using 20% Versatic-10 (V-10) in dodecane after giving 3 to 4 contacts, thus converting alkaline waste as non-alpha waste. Under the optimum conditions (pH 9.0-9.5 and VA-10), both Pu(IV) and Am(III) are highly extractable whereas U(VI) is relatively poorly extracted. To assess the applicability of this process for regular treatment of the waste, a feasibility study on pilot plant scale using six stage mixer settler was operated to treat the ILLW. The results indicated that almost >99.90% alpha-emitting actinides are removed. Dilute nitric acid (0.5M HNO3) served as the most efficient strippant for all these actinides. This facilitate an easy regeneration of the extractant which can be recycled. This method is useful in obtaining alpha-free wastes and had positive impact on ease and safety aspects during subsequent waste treatment and long term storage.

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Abstract  

A simple and rapid separation procedure was systemized for the determination of 99Tc, 90Sr, 94Nb, 55Fe and 59,63Ni in low and intermediate level radioactive wastes. The integrated procedure involves precipitation, anion exchange and extraction chromatography for the separation and purification of individual radionuclide from sample matrix elements and from other radionuclides. After separating Re (as a surrogate of 99Tc) on an anion change resin column, Sr, Nb, Fe and Ni were sequentially separated as follows; Sr was separated as Sr (Ca-oxalate) co-precipitates from Nb, Fe and Ni followed by purification using Sr-Spec extraction chromatographic resin. Nb was separated from Fe and Ni by anion exchange chromatography. Fe was separated from Ni by anion exchange chromatography. Ni was separated as Ni-dimethylglyoxime precipitates after the removal of 134,137Cs and 110mAg by Cs-phosphotungstate and AgCl precipitation, respectively. Finally, the radionuclide sources were prepared by precipitation for their radioactivity measurements. The reliability of the procedure was evaluated by measuring the recovery of chemical carriers added to a synthetic radioactive waste solution.

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The correlations between seismic activities and tidal periodicities are investigated at three seismic zones: Vrancea (Romania), Bucaramanga (Colombia) and Hindu Kush (Afganistan). The epicenter of earthquake nests distribution is characterized by intermediate-depth. In this paper, we study the influences of the principal lunar and solar semidiurnal tidal components M2 and S2 on seismic activities. The tidal phase is determined by HiCum stacking method according to the earthquake occurrence time and location. The stacking function could be shifted in time and space domain which provides the possibility to evaluate the seismic activities and tidal periodicities at both. The tidal phase distribution was tested by two independent methods Schuster and Permutation. The null hypothesis between seismic activities and selected tidal periodicities is rejected when the statistical p -values obtained by the two tests reach less than 5% level. As a result of the shift stacking function in time axis, a systematic temporal pattern related to the decrease of the p -values seems to be preceding occurrence of the larger earthquakes. A “tidal tomography” map is obtained when stacking function is shifted in 3D geometry following the epicenters distribution.

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Abstract  

New (radio)halogen derivatives of 1-allylterguride have been prepared by method of destannylation-halogenation. 1-Alylterguride shows relatively high binding affinity, which can be used in the case of its radiolabeled derivatives with imaging methods like PET or SPET in studies of properties of receptor's binding places and ligand affinity. The (radio)halogenation was performed via organotin precursors: 1-tributylstannyl-3-chlorprop-1-ene and 2-tributylstannyl-3-chloroprop-1-ene, which were prepared from appropriate alcohols. Linkers of the tin group were used for alkylation of N1 of terguride both under microwave irradiation and under conventional heating. In the last step (destannylation-halogenation), fluoro-, bromo- and iododerivatives as well as 125I iodo- and 82Br bromoderivatives of 1-allylterguride were obtained.

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The formation of benzynes derivatives from ortho-trimethylsilyl triflates using tetra-n-butylammonium fluoride (TBAF) as the benzyne-forming trigger was achieved in a straightforward flow reactor at room temperature. These benzynes were immediately trapped in Diels—Alder reactions to deliver the desired cycloadducts.

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