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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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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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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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Abstract  

Sorption experiments for radionuclides such as 14C, 99Tc, 137Cs, 90Sr, 63Ni, and 241Am were conducted using two different groundwaters (GM-1 and SS-5) and solid materials (granodiorite and fracture-filling material) sampled from the Wolsong low- and intermediate-level radioactive waste (LILW) repository, Gyeongju, Korea. The distribution coefficients of the radionuclides, K d’s, were obtained and their sorption properties were discussed for each radionuclide. For all sorbing radionuclides, the K d values for the fracture-filling material were observed to be higher than those for granodiorite regardless of the groundwater. The K d values were increased in the sequence 99Tc < 14C < 90Sr < 137Cs < 63Ni < 241Am regardless of sorbent types implying that the sorption of radionuclides onto geological media is affected by their chemical behavior in accordance with geochemical environments. Anionic radionuclides such as 14C and 99Tc showed very low K d values both for the granodiorite and fracture-filling material. The mineralogical composition of the geological media and groundwater conditions was also observed to be important in the sorption of sorbing radionuclides, especially in the case of strongly sorbing radionuclides.

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Abstract  

An analytical procedure for the determination of activation products 238Pu, 241Pu, 239Pu/240Pu, 241Am, 237Np, and a fission product 90Sr in radioactive wastes is presented. Samples were decomposed using Fenton’s reaction. The separation was performed by anion-exchange chromatography, extraction chromatography, using TRU and Srresin, and precipitation techniques, followed by α-spectrometry and LSC counting. Tracer solutions and pure ion exchange resins were used to prepare artificial samples and trace nuclides during the analytical procedure. Some real samples of spent ion-exchange resins originating from our TRIGA Mark II research reactor were analyzed.

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Abstract  

The recoil properties of 26 radionuclides produced in the photonuclear reactions on Cu at bremsstrahlung end-point energies (E 0) of 250 to 1000 MeV have been investigated using the thick-target thick-catcher method. Kinematic properties of the product nuclei were calculated by the two-step vector velocity model. The calculated mean kinetic energies,T, of product nuclei increase with increase of the mass difference between products and target, reflecting the resonance natures and absorption mechanisms. TheT atE 0≥600 MeV were well reproduced by a calculation performed by PICA code byGabriel andAlsmiller atE 0=400 MeV, except for (γ,xn) products by giant-resonance.

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Abstract  

Two isothermal soot oxidation protocols were tested in a Perkin-Elmer TGA6: (1) the sample was heated under N2 and then the reaction gas was introduced and (2) the sample was introduced after the empty furnace was heated under the reaction gas. The first protocol is common in soot oxidation studies, it gives a measure of the volatiles and is easier to handle, but as it is shown the determined reaction rate may be falsified by the O2 concentration. Using gas analysis it was found that ∼2000 s are necessary for the complete gas change in the instrument. An instrument specific correction function involving the O2 concentration and reaction order n with respect to O2 was developed which allowed the correlation of the rates measured with both protocols.

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Abstract  

The calorimetric glass transition and dielectric dynamics of -relaxation in propylene glycol (PG) and its five oligomers (polypropylene glycol, PPG) have been investigated by the modulated differential scanning calorimetry (MDSC) and the broadband dielectric spectroscopy. From the temperature dependence of heat capacity of PPGs, it is clarified that the glass transition temperature (T g) and the glass transition region are affected by the heating rate. The kinetic changes of PG and PPGs near T g strongly depend on the underlying heating rate. With increasing the molecular mass of PPGs, the fragility derived from the relaxation time against temperature also increases. The PG monomer is stronger than its oligomers, PPGs, because of the larger number density of the —OH end group which tends to construct the intermolecular network structure. Adam-Gibbs (AG) theory could still hold for MDSC results due to the fact that the dielectric relaxation time can be related to the configurational entropy.

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A key reaction in one of the routes to efavirenz, an essential drug used in the treatment of acquired immunodeficiency syndrome (AIDS), is the ortho-lithiation reaction of N-Boc-4-chloroaniline. For the first time, we demonstrate that the reaction may be conducted using n-BuLi and show that the reaction may be performed in a flow reactor with a significantly higher yield (70%) compared to batch (28%) when using n-BuLi for the ortho-metalation reaction at a temperature of −45 °C. In addition, it was shown that tetramethylethylenediamine (TMEDA) did not need to be added to the flow reaction, which simplified the purification procedure.

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Abstract  

The use of radioanalytical techniques to study heavy ion induced nuclear reactions offers some distinct advantages over conventional physical techniques. Among these are (a) unit Z and A resultion in detecting the reaction products (b) high sensitivity for low probability events (c) lack of low energy thresholds or cutoffs in measuring reactcion product energy spectcra (d) economical use of accelerator time and (e) simple, portable experimental apparatus allowing broad survey measurements of reaction mechanisms at a variety of nuclear particle accelerators. We describe examples of these advantages from our research in nuclear chemistry.

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