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Chemical stabilities of SrZrO3, BaZrO3, and Sr0.5Ba0.5ZrO3 in LiCl molten salt were investigated to evaluate dissolution properties of Sr and Ba in grey phases of spent nuclear fuels during oxide reduction. Sr in SrZrO3 was partially insoluble in LiCl, even in the presence of metallic Li, while Ba in BaZrO3 was almost extracted. In contrast, both Sr and Ba in solid-solution phase (Sr0.5Ba0.5ZrO3) well dissolved in LiCl. Pre-treatment of the spent nuclear fuels before the oxide reduction should be carefully designed to prevent formation of the insoluble Sr-based compounds for efficient Sr separation. [ABSTRACT FROM AUTHOR]

Sorption of iodine on Beishan granite was studied by batch method. Great difference exists in the sorption behaviors of I− and IO3−. Under acidic condition, the sorption of IO3− improves dramatically, and IO3− could partly convert to I−. However, the sorption of I− is close to zero at all studied pH. Humic acid can slight improve the sorption of IO3−, but greatly improve the sorption of I− in acidic condition. The postulated sorption mechanisms of IO3− are electrical interaction and followed by reduction. [ABSTRACT FROM AUTHOR]

U(VI)-containing wastewater has potential radiation hazard to the environment, but contains valuable uranium resource. Based on the reduction of U(VI) and the difference in solubility between U(VI) and U(IV), here we construct a TiO-based photoelectrochemical cell to remove U(VI) and recover uranium from aqueous solution. By irradiating TiO photoanode at E = 0.45 V versus SCE, U(VI) can be simultaneously removed from aqueous solution and recovered as solid uranium compounds on a FTO glass cathode. Since ethanol can act as hole scavenger to protect the formed U(IV) and provide CO as reductant, ethanol adding improved the U(VI) reduction efficiency of TiO-based photoelectrochemical cell. [ABSTRACT FROM AUTHOR]

The 3D structure of hydrazine derivatives was optimized and their energy was calculated by density functional theory with B3LYP method and 6-311 + (3 d, 3 p) basis set. The results show that the reaction relationship between the structure of hydrazine derivatives and Np(VI) could be explained by two quantitative structure-activity relationships equations. In Eq. 1, the lowest unoccupied molecular orbital energy is a major factor affecting the reduction rate, and it is negatively correlated with the reaction rate. In Eq. 2, the molecular dipole moment and hydrophobic parameters are the most important factors affecting the reduction rate. The molecular dipole moment is negatively correlated with the reaction rate, but the hydrophobic parameter is positively correlated with the reaction rate. [ABSTRACT FROM AUTHOR]

The process of plasma chemical conversion of isotopic enriched MoF in RF (13.56 MHz) capacitive-coupled and arc discharges was investigated. In both types of discharges the formation of metal (bulk) and powder nano-dispersed molybdenum as well as of fluoromolybdens of MoF fluorides was found. The mechanism of plasma chemical reduction of MoF by hydrogen under considered experimental conditions was suggested. The isotopic and impurity composition of prepared nano-powder and bulk samples of Mo as well as of their structure was determined. [ABSTRACT FROM AUTHOR]

Uncertainties associated with short lived (half-lives less than 1 day) fission product yields listed in databases such as the National Nuclear Data Center's ENDF/B-VII are large enough for certain isotopes to provide an opportunity for new precision measurements to offer significant uncertainty reductions. A series of experiments has begun where small samples of U are irradiated with a pulsed, fission neutron spectrum at the Nevada National Security Site and placed between two broad-energy germanium detectors. The amount of various isotopes present immediately following the irradiation can be determined given the total counts and the calibrated properties of the detector system. The uncertainty on the fission yields for multiple isotopes has been reduced by nearly an order of magnitude. [ABSTRACT FROM AUTHOR]

Batch contact experiments with several porous carbon materials showed that carbon solids spontaneously reduce the oxidation state of plutonium in 1-1.5 M acid solutions, without significant adsorption. The final oxidation state and rate of Pu reduction varies with the solution matrix, and also depends on the surface chemistry and surface area of the carbon. It was demonstrated that acidic Pu(VI) solutions can be reduced to Pu(III) by passing through a column of porous carbon particles, offering an easy alternative to electrolysis with a potentiostat. [ABSTRACT FROM AUTHOR]

This project is focused on developing a geochronology tool enabling age dating of coastal marine sediments in the 100-1000 year age range. The technique employs the Si/P radio-chronometer with an ultra-low-background gas proportional beta detector with a background count rate approaching 10 counts per day (cpd), which will require significant decontamination of radiogenic nuclides present in the original sediment samples. This paper describes the multiple physical and chemical separation methods employed to maintain a high final chemical yield of P while reducing the radiogenic contributions. The final purified P samples had, on average 100 ± 7 % chemical yields with no quantifiable gamma emissions present. [ABSTRACT FROM AUTHOR]

In this work, luminescent triangular silver nanoparticles were synthesized by radiolytic reduction method. The results showed that by variation of irradiation dose, morphology of silver nanoparticles can be converted from spherical to triangular. These shape variations mainly arise from competition between adsorption rate of polymer chains on (111) facets and reduction rate of the Ag ions along (110) facets during increasing dose. Furthermore, the dramatically enhanced photoluminescence spectra were observed from triangular Ag nanoparticles. This unusual behavior can be explained by excitation of dipolar and quadrupolar resonance in triangular nanoparticles which increase the electric fields at the surface. [ABSTRACT FROM AUTHOR]

We propose a method for the decontamination and waste volume reduction of cesium-contaminated soil. The soils were solidified with an interpolyelectrolyte complex solution and classified into several size fractions by wet sieving. Gamma-ray spectrometry of these fractions showed that the distribution ratio of the activity concentration of coarse soil particles decreased, whereas that of soil particles under 0.075 mm increased relative to reference samples. Results showed that the fine soil particles, on which radioactive cesium accumulates, were removed from the surface of the coarse soil particles during sieving and washing, and remained in the washing water. [ABSTRACT FROM AUTHOR]

The aim of this work is to find the optimal procedure for Po leaching from sediment samples. An improved method is described, the optimization consisting in a substantial reduction of leaching time. The method was tested on IAEA standard reference materials and compared with the classical procedure. The repeatability was estimated by analyzing seven duplicates of IAEA 385 Irish Sea sediment. However, the results are satisfactory only when the method is applied for sediments with high organic content. For silicates, a mixture of three acids was used for a complete digestion. [ABSTRACT FROM AUTHOR]

This work presented the electrochemical study of cerium(III) on the insert electrode (Mo) in NaCl-KCl molten salt in the temperature range 954-1,007 K. The electrochemical methods such as cyclic voltammetry and square wave voltammetry were used for investigating the reduction of Ce(III). The results obtained showed that CeCl could be reduced into cerium metal in a quasi-reversible one-step process exchanging three electrons (Ce(III)+3 e → Ce(0)) at the operating temperatures on a molybdenum cathode. The diffusion coefficients of Ce(III) ions at different temperatures were determined by cyclic voltammetry. The validity of the Arrhenius law was also verified and the activation energy for diffusion was found to be 46.0 kJ mol. The apparent standard potentials of the redox couple (Ce(III)/Ce(0)) at several temperatures was calculated. The thermodynamic properties of cerium trichloride have also been investigated. [ABSTRACT FROM AUTHOR]

The extraction and reduction behavior of Mo and W, lighter homologs of Sg, was studied in continuous on-line experiments at the JAEA tandem accelerator to develop a new chemistry assembly consisting of a membrane degasser (MDG), a flow electrolytic column (FEC), and the continuous liquid-liquid extraction apparatus (SISAK). Extraction yields of Mo and W from 0.1 M HCl/0.9 M LiCl into 4-isopropyltropolone (hinokitiol, HT) in toluene were investigated. In the reduction experiment, Mo(VI) was successfully reduced to a lower oxidation state while W(VI) showed no reduction under the given conditions. [ABSTRACT FROM AUTHOR]

Quench effects can cause a serious reduction in counting efficiency for a given sample/cocktail mixture in liquid scintillation counting (LSC) experiments. This paper presents a simple experiment performed in order to test the influence of quenching on the LSC efficiency of H. The aim of this study was to investigate the behavior of several quench agents with different quench strengths (nitromethane, nitric acid, acetone, dimethyl-sulfoxide) added in different amounts to tritiated water in order to obtain standard sets for quench calibration curves. The OptiPhase HiSafe 2 and OptiPhase HiSafe 3 scintillation cocktails were used in this study in order to compare their quench resistance. Measurements were performed using a low-level LS counter (Wallac, Quantulus 1220). [ABSTRACT FROM AUTHOR]

Solvent extraction of macro amounts of Mo(V) and Mo(VI) from HCl using Aliquat 336 in chloroform was performed for the electrochemistry of Sg. The extraction reaction attained equilibrium with a shaking time of 10 s in higher than 8 M HCl. The D values of Mo(V) obtained by the electrochemical reduction of Mo(VI) were in good agreement with those obtained by the extraction of MoCl, and the D values of Mo(V) were higher than those of Mo(VI). These results suggested that the reduction behavior of Sg might be studied by electrochemical reduction combined with the present solvent extraction. [ABSTRACT FROM AUTHOR]

The effect of NaCl concentration (10.0-1,000 mM) on Ra adsorption was investigated in the presence of montmorillonite and kaolinite. A positive correlation was observed between the dissolved Ra and NaCl concentrations in the presence of these adsorbents. Distribution coefficients decreased from the order of 10 to 10 (mL g) with an increase in NaCl concentration. Although the coefficients were higher for montmorillonite than kaolinite at lower NaCl concentrations, the trend was reversed at higher NaCl concentrations (≥500 mM) owing to the sharper reduction of the coefficient for montmorillonite with the increase in NaCl concentration. The rapid reduction was ascribed to higher negative charge density of montmorillonite, which leads the Ra adsorption mechanism to approach charge-compensating ion exchange. [ABSTRACT FROM AUTHOR]

Anhydrous ytterbium chloride was obtained via solid-phase reaction from YbO with AlCl as a chlorination agent. The electrochemical behavior of the chloridized YbO was investigated on W electrodes in LiCl-KCl and LiCl-KCl-AlCl melts by cyclic voltammetry and square wave voltammetry. The results showed that the reduction/reoxidation of Yb(III)/Yb(II) was reversible and controlled by diffusion. The signals related to the formation of two Al-Yb intermetallic compounds were detected in LiCl-KCl-AlCl melt. Potentiostatic electrolysis was carried out in LiCl-KCl-AlCl-YbCl melt on W electrodes at 943 K at different potentials and AlYb, AlYb, AlLi and AlLi phases were detected in deposits. Then, the extraction of ytterbium was performed. The currents evolution was recorded by square wave voltammetry and the extraction efficiency was evaluated via inductive coupled plasma atomic emission spectrometer analysis during electrolysis. The initial extraction rate is much higher than that at longer times. The extraction efficiency was about 98.0 % for Yb(III) after potentiostatic electrolysis for 60 h at −1.84 V in LiCl-KCl-AlCl-YbCl melt. [ABSTRACT FROM AUTHOR]

The performance of a radiation shielding system for a hyper-pure germanium detector has been characterised for Terrestrial radiation sources, Cosmic muons, X-ray fluorescence and the Compton scattering of source photons. Several methods to reduce the background seen are quantified, including increasing the inner radius of the Pb cave, and increasing the thickness of the shielding. Substantial improvements in the reduction of fluorescence X-rays are found to be achievable by modifying the liner thicknesses used. Increasing the Sn liner from 1.5 to 2.5 mm will increase the shielding of Pb X-rays from 95 to 99.5 %. Reducing the Cu liner from 1.0 to 0.5 mm maintains a 99.5 % level of shielding for Sn/Cd X-rays, however it greatly reduces the amount of Compton scattering of source photons into the detector (a process that is shown to cause an order of magnitude more events in the background than X-ray fluorescence). Cosmic muons were found to increase the amount of background radiation seen, both through direct interaction and the production of secondary radiation. The Cosmic muon contribution, however, was found to produce a much smaller effect than that caused by Terrestrial radiation and Compton scattered photons/fluorescence from the source. The total level of background radiation entering the detector chamber was found to decrease up to the full 200 mm of Pb shielding simulated. [ABSTRACT FROM AUTHOR]

This paper describes the use of IBC′s AnaLigPu-02 molecular recognition technology product to effectively and selectively pre-concentrate, separate and recover plutonium from urine samples. This method uses two-stage column separations consisting of two different commercial products, Eichrom's Pre-filter Material and AnaLigPu-02 resin from IBC Advanced Technologies. By eliminating the co-precipitation techniques and the ashing steps to remove residual organics, the analysis time was reduced significantly. The method was successfully tested by adding known activities of reference solutions of Pu and Pu to urine samples. [ABSTRACT FROM AUTHOR]

The relative stability of different oxidation states of actinide elements is influenced by the nature of complexes formed and redox equilibria in aqueous/non-aqueous solutions. The reduction/stripping studies on Pu(IV) ions from loaded organic phases of 1.1 M tributyl phosphate and of 1.1 M N,N-dihexyl octanamide in n-dodecane were studied using organic soluble tert-butyl hydroquinone (TBH) and aqueous soluble reductants like acetaldoxime (AX) and hydroxyurea (HU). These studies were carried out as a function of reductant and nitric acid concentration (0.5-4 M HNO) and of time. The changes in Pu oxidation states were followed by spectrophotometry for TBH and by distribution ratio values for AX and HU as reductants. Spectrophotometric investigations using TBH as reductant showed that it was desirable to strip Pu(III) formed after reduction of Pu(IV) in the organic phase, which may otherwise be reconverted to extractable Pu(IV) by in situ generated HNO from oxidative degradation of TBH to tert-butyl quinone. Similarly, the biphasic reduction/stripping of Pu(IV) using AX and HU as reductant rate was affected adversely with increased aqueous phase acidity. This data will help in the accurate simulation of Pu separation processes using these reductants in mixer-settlers/pulsed columns or centrifugal contactors. [ABSTRACT FROM AUTHOR]

Tri- n-butyl phosphate (TBP) is the key complexant within the plutonium and uranium reduction extraction process used to extract uranium and plutonium from used nuclear fuel. During reprocessing TBP degrades to dibutyl phosphate (DBP), butyl acid phosphate (MBP), butanol, and phosphoric acid over time. A method for rapidly monitoring TBP degradation is needed for the support of nuclear forensics. Therefore, a Fourier transform infrared spectrometry-attenuated total reflectance (FTIR-ATR) technique was developed to determine approximate peak intensity ratios of TBP and its degradation products. The technique was developed by combining variable concentrations of TBP, DBP, and MBP to simulate TBP degradation. This method is achieved by analyzing selected peak positions and peak intensity ratios of TBP and DBP at different stages of degradation. The developed technique was tested on TBP samples degraded with nitric acid. In mock degradation samples, the 1,235 cm peak position shifts to 1,220 cm as the concentration of TBP decreases and DBP increases. Peak intensity ratios of TBP positions at 1,279 and 1,020 cm relative to DBP positions at 909 and 1,003 cm demonstrate an increasing trend as the concentration of DBP increases. The same peak intensity ratios were used to analyze DBP relative to MBP whereas a decreasing trend is seen with increasing DBP concentrations. The technique developed from this study may be used as a tool to determine TBP degradation in nuclear reprocessing via a rapid FTIR-ATR measurement without gas chromatography analysis. [ABSTRACT FROM AUTHOR]

In a contemporary salt-free flowsheet of nuclear fuel reprocessing, uranous ions are used as a reducing agent to accomplish the separation of uranium and plutonium from each other which is normally produced electrochemically. In the present study, continuous mode electrochemical reduction of uranyl ions in nitric acid medium and in the presence of hydrazine nitrate was carried out in a divided cell at three different feed flow rates and cathodic current densities for the purpose of optimizing the process conditions for better conversion efficiency. A correlation function is described as a mathematical model in which, mass transfer parameter is expressed as a function of current density and flow rate. From the multivariable nonlinear regression of the experimental data, rate parameter was determined. The electro reduction of uranyl ions was not influenced by the initial acidity. The maximum conversion rate of 87 % was obtained for the electro-reduction of 100 g/l U(VI) in 3 M nitric acid with feed flow rate as 0.3 l/h and current density as 15 mA/cm. The results for the reduction of 100 g/l uranyl ions indicate that an optimum flow rate of about 0.5 l/h and 15 mA/cm as cathodic current density may suffice for the conversion with efficiency better than 60 %. The calculated steady state concentrations for U(IV) were found to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

An electrochemical reduction of UO to U in a LiCl-KCl-LiO molten salt has been investigated in this study. A diagram showing equilibrium potentials (relative to Cl/Cl) plotted versus the negative logarithms of oxide-ion activity (pO) was constructed. The crushed UO pellets in the cathode basket of an electrolytic reducer were successfully reduced to U. The reduction of UO is proved to proceed mainly through chemical reaction with in situ generated Li and K at the cathode. The control of cathode potential is essential to prevent the deposition and subsequent vaporization of K metal at the cathode for the applications of a LiCl-KCl-LiO molten salt as an electrolyte for the metal production from its oxide sources. [ABSTRACT FROM AUTHOR]

A biamperometric methodology for the sequential determination of thorium (Th) and uranium (U) was developed. In the sample solution containing Th and U, Th was first determined by complexometric titration based on the electrochemical behaviour of EDTA maintaining a potential of ≥200 mV between the twin Pt electrodes. This was followed by the redox titrimetric determination of U employing biamperometry to detect the end point. Prior to the determination of U, EDTA was destroyed by fuming with concentrated HClO to eliminate its interference in the U determination. The method was tested for the determination of Th and U in (Th, U) O samples containing 4 mg of Th and 2-8 mg of U, with precision and accuracy of better than 0.3 %. [ABSTRACT FROM AUTHOR]

The Bothnian Sea which is located between Finland and Sweden represents an important source of fresh water to the Baltic Sea. We here present new data on the radioactive isotope I species from water samples collected in December 2009 at different depths in the Bothnian Sea. Concentrations of I (iodide) in the Bothnian Sea range from 14 × 10 to 32 × 10 atoms/L, while IO (iodate) concentrations are relatively low and fluctuating at 1 × 10 atoms/L. For nutrients data determined in the same samples as I, significant correlations could be found between I and total P, NO-N, SiO-Si, but rather poor with NH-N. The correlations suggest comparable source pathway of I and nutrient parameters, while the source of NH-N may be different. The small amounts and negligible change of IO indicate prevailing extensive reduction of iodate in the Baltic Sea. [ABSTRACT FROM AUTHOR]

A k-RNAA procedure was developed to determine I in a mixed resin sample. CH extraction and (NH)SO back-extraction were used to separate I in ashed samples. The I target sample for irradiation in the reactor was prepared by heating the (NH)SO back-extraction solution to reduce its volume and then to dry it in a quartz ampoule. No MgO and LiOH were needed during the target sample preparation. After irradiation, the nuclide I was purified by combining hydrated antimony pentoxide column and CH extraction separations. A k-factor was determined for the reaction of I ( n, 2 n) I and used for iodine chemical yield determination. The apparent I concentrations of five nuclear reaction interferences were calculated. The relative standard deviation of three I determinations was found to be 3.5 %. The I content in the analyzed resin was found to be 1.36 × 10 g/g (8.63 × 10 Bq/g) with a relative uncertainty of 9.1 %. The detection limit of I was calculated to be 7.4 × 10 g (4.7 × 10 Bq) in a k-RNAA of a blank sample. [ABSTRACT FROM AUTHOR]

One of the most effective methods for reducing exposure is the use of air cleaners. In this study, a dose mitigation of a commonly-used Japanese air cleaner under conditions in which aerosols are continuously supplied was investigated. Although the values of the EERC during an operation of air cleaner decreased, values of the f increased with the use of air cleaner. An effective dose was calculated on the basis of our experimental results, resulting in the dose mitigation of about 40 % by the air cleaner. Air cleaners can be regarded as an effective tool for the dose mitigation under with conditions in which aerosols are continuously supplied. [ABSTRACT FROM AUTHOR]

Tc is an important radionuclides related to repository safety assessment. The mobility pertechnetate (TcO) can be reduced to immobility technetium(IV) hydrous oxides (TcO· nHO) by Fe(II)-bearing minerals. In China, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for the HLW repository, which is contained some FeO. The diffusion behavior of Tc was investigated in GMZ bentonite by through- and out-diffusion methods. The effective diffusion coefficient ( D), the accessible porosity (ε), apparent diffusion coefficient ( D) and distribution coefficient ( K) were decreased with the increasing of dry density. The D values were (2.8 ± 0.2) × 10 m/s and (3.5 ± 0.2) × 10 m/s at dry density of 1,600 and 1,800 kg/m, respectively. It was indicated that the dominating species was TcO during the diffusion processing. While, out-diffusion results showed that part of TcO may be reduced by Fe(II). The relationship of D and ε could be described by Archie's law with exponent n = 2.4 for Tc diffusion in GMZ bentonite. Furthermore, the relationship between D and dry density (ρ) was exponential. [ABSTRACT FROM AUTHOR]

A spectrophotometric method is developed for the determination of dissolved tri- n butyl phosphate (TBP) in aqueous streams of Purex process used in nuclear fuel reprocessing. The method is based on the formation of phosphomolybdate with added ammonium molybdate followed by reduction with hydrazine sulphate in acid medium. Orthophosphate and molybdate ions combine in acidic solution to give molybdophosphoric (phosphomolybdic) acid, which upon selective reduction (with hydrazinium sulphate) produces a blue colour, due to molybdenum blue. The intensity of blue colour is proportional to the amount of phosphate. If the acidity at the time of reduction is 0.5 M in sulphuric acid and hydrazinium sulphate is the reductant, the resulting blue complex exhibits maximum absorption at 810-840 nm. The system obeys Lambert-Beer's law at 830 nm in the concentration range of 0.1-1.0 μg/ml of phosphate. Molar Absorptivity was determined to be 3.1 × 10L mol cm at 830 nm. The results obtained are reproducible with standard deviation of 1 % and relative error less than 2 % and are in good agreement with those obtained by ion chromatographic technique. [ABSTRACT FROM AUTHOR]

Au (β = 0.96 MeV (98.6 %), γ = 0.412 MeV (95.5 %) and T = 2.7 days) is a radionuclide with very appealing characteristics. Au has been widely used to treat the uterus, bladder, cervix, prostate, melanoma, breast, skin and other cancers. In the present study, cationic Au and nonionic Au are prepared following thermal neutron irradiation of commercially available natural gold compounds in Tehran Research Reactor via the Au(n,γ)Au reaction. The prospects in the production of pure Au and Au for radionuclide therapy are discussed and effect of reduction on the activity of radioactive gold is evaluated. Au particles were synthesized via NaBH reduction of aqueous solutions of hydrogen tetrachloroaurate trihydrate. Then two quartz tubes were charged with cationic Au and nonionic Au. After irradiation by thermal neutrons, the samples were analyzed for a period of 1 month by liquid scintillation counter and high purity germanium detector. As a result, Au reduction process had no significant effect on the activity of the Au sample. In conclusions, natural gold thermal neutron activation cross section is reasonably high for medical application. [ABSTRACT FROM AUTHOR]

Colloidal Cu-Al nanoparticles were prepared in an aqueous polyvinyl alcohol solution containing copper chloride and aluminum chloride as precursors, isopropanol as a scavenger of hydroxyl radicals, and distilled water as a solvent. The gamma irradiations were carried out in a Co gamma source chamber with different doses up to 120 kGy. The formation of Cu-Al nanoparticles has been observed initially by the change in color of the colloidal samples from colorless to brown. The nanoparticles properties were characterized by transmission electron microscopy, energy dispersive X-ray spectrometry, and UV-Vis spectrophotometer. At a constant Cu/Al molar ratio, size of the nanoparticles can be well controlled by varying the precursors concentration and radiation dose. The average particle diameter increases with increase of precursors concentration and decreases with increase of dose. This is owing to the competition between nucleation process, aggregation process, and ions association in the formation of nanoparticles during irradiation. [ABSTRACT FROM AUTHOR]

Two types of ammonium uranyl nitrate (NH)UO(NO)·2HO and NHUO(NO), were thermally decomposed and reduced in a TG-DTA unit in nitrogen, air, and hydrogen atmospheres. Various intermediate phases produced by the thermal decomposition and reduction process were investigated by an X-ray diffraction analysis and a TG/DTA analysis. Both (NH)UO(NO)·2HO and NHUO(NO) decomposed to amorphous UO regardless of the atmosphere used. The amorphous UO from (NH)UO(NO)·2HO was crystallized to γ-UO regardless of the atmosphere used without a change in weight. The amorphous UO obtained from decomposition of NHUO(NO) was crystallized to α-UO under a nitrogen and air atmosphere, and to β-UO under a hydrogen atmosphere without a change in weight. Under each atmosphere, the reaction paths of (NH)UO(NO)·2HO and NHUO(NO) were as follows: under a nitrogen atmosphere: (NH)UO(NO)·2HO → (NH)UO(NO)·HO → (NH)UO(NO) → NHUO(NO) → A-UO → γ-UO → UO, NHUO(NO) → A-UO → α-UO → UO; under an air atmosphere: (NH)UO(NO)·2HO → (NH)UO(NO)·HO → (NH)UO(NO) → NHUO(NO) → A-UO → γ-UO → UO, NHUO(NO) → A-UO → α-UO → UO; and under a hydrogen atmosphere: (NH)UO(NO)·2HO → (NH)UO(NO)·HO → (NH)UO(NO) → NHUO(NO) → A-UO → γ-UO → α-UO → UO, NH UO(NO) → A-UO → β-UO → α-UO → UO. [ABSTRACT FROM AUTHOR]

Valency control of neptunium is an important issue in the partitioning of high level liquid waste (HLLW) from power-reactor spent fuel treatment. The redox behavior of neptunium in HLLW is quite different from that in nitric acid because of the effect of the large amount of ions in HLLW. In order to remove neptunium from HLLW, we studied the reduction of neptunium in synthetic HLLW (SHLLW) to maintain its valency at IV so that it can be extracted by TRPO extractant in the well developed Chinese TRPO process. Five different reductants were tested and the reduction behavior was investigated. The influence of some active elements in SHLLW was studied. The mechanism that the reductants react with neptunium through Fe element was supposed and proved by experiments. The reduction rate of Np(V) was highly enhanced by Fe element. Finally, a hybrid reductant was suggested and good reduction efficiency was obtained. [ABSTRACT FROM AUTHOR]

Spent fuel discharged from Fast Breeder Test Reactor (FBTR) in Kalpakkam is being reprocessed by modified plutonium uranium reduction extraction (PUREX) process using 30% TBP (tributylphosphate) as extractant in the presence of heavy normal paraffin (HNP) as diluent. Partitioning of uranium (U) and plutonium (Pu) is carried out using oxalate precipitation method. Uranium oxide product obtained by this method contains appreciable amount of plutonium which has to be recovered. Recovery of plutonium from this uranium oxide product is carried out by reducing Pu to inextractable Pu(III) using hydroxyurea (HU) and then uranium is extracted into 30% TBP. A small amount of Pu which is extracted in the organic phase is stripped back to aqueous phase by scrubbing with scrubbing agent containing 0.1 M HU in 4 M nitric acid. Similarly U and Pu are co-extracted into 30% TBP and then Pu is removed by scrubbing with 0.1 M HU in 4 M nitric acid. Further decontamination from Pu is obtained in the stripping stages. By this method Pu contamination in the uranium oxide is brought from 7300 ppm to 0.4-3 ppm (wt/wt). This uranium product obtained can be handled on table top. [ABSTRACT FROM AUTHOR]

The kinetics of reduction reactions between N, N-dimethylhydroxylamine (DMHAN) and plutonium(IV) in nitric acid solution have been studied spectrophotometrically. The kinetic equation of the reaction is determined to be -d[Pu(IV)]/d t = k[Pu(IV)][DMHAN]/[H] at the beginning, where, the rate constant of the reaction ( k) is 10.5 ± 1.8(mol/L) s at 14.5 °C. By regressing of the time-concentration curve of the reaction, The complete rate equation is calculated as $$ - {\frac{\rm{d[Pu(IV)]}}{{{\rm{d}}t}}} = {\frac{{k [{\rm{Pu(IV)]}}^{ 2} [ {\rm{DMHAN]}}^{ 1. 1 8} / [ {\rm{H}}^{ + }]^{ 2. 2 2} }}{{ 8. 1 2 [ {\rm{Pu(III)]}} + 9 5. 9 [{\rm{Pu(IV)]}}}}} $$ with the reaction constant k about 1,000(mol/L) s at 14.5 °C and an ionic strength (μ) of 4.0 mol/L. [ABSTRACT FROM AUTHOR]

The reduction of ammonium pertechnetate by sodium borohydride in 0.1 M NaOH/glacial acetic acid has been studied. The reduction products (solids and solutions) have been characterized by UV-Visible spectroscopy, Scanning Electron Microscopy/Energy-dispersive X-ray emission spectroscopy (SEM/EDS), and X-ray absorption fine structure (XAFS) spectroscopy. UV-Visible spectra of the solution, after reduction, exhibit bands at 350 and 500 nm that have been attributed to the formation of polymeric Tc(IV) species. SEM/EDS on the solid (X-ray amorphous) indicates the absence of metallic Tc and the presence of oxygen. EXAFS measurements further indicate that the precipitate exhibits a [Tc(μ-O)Tc] core structure. XANES is consistent with the formation of Tc(III) and/or Tc(IV). Results infer that reduction of aqueous Tc(VII) by borohydride in the presence of acetic acid does not produce metallic Tc, but a mixture of various oxidation states of Tc near Tc(III) and Tc(IV). [ABSTRACT FROM AUTHOR]

The results concerning the reduction of U(VI) adsorbed on anion exchange resin as uranyl chloro complexes and sulfate complexes with V(III) in HCl and HSO solution are presented. The reduction of uranyl sulfate adsorbed on anion exchange resin (UOSO) in 0.05 M sulfuric acid was carried out, the reaction rate being first order with respect to both concentrations: [U(VI)] and [V(III)]. From Arrhenius plot the activation parameters of the reaction between U(VI) and V(III) in sulfuric acid solution were determined: E = 34.9 ± 0.9 kJ/mol; Δ Η = 35.5 ± 0.9 kJ/mol and Δ S = −165.7 ± 3 J/K mol. The reduction reaction rate makes possible the utilization of this reaction for displacement of the uranium adsorption band in a U separation column packed with anion exchange resin. [ABSTRACT FROM AUTHOR]

Both single stage and multi-stages experiments on stripping plutonium with N, N-dimethylhydroxylamine (DMHAN) as reductant with methylhydrozine (MMH) as supporting reductant were carried out. The effect of contact time, temperature, acidity, concentration of DMHAN on back-extraction rate of plutonium was investigated in the single stage experiment. The results demonstrated that the reaction of stripping Pu(IV) in the organic phase (30% TBP-kerosene) 1BF solutions by DMHAN exhibits excellent stripping efficiency. Under the given conditions, the back-extraction rate of plutonium reaches 90% within 2 min. Higher temperature, lower acidity and the increased concentration of DMHAN benifit the stripping reaction. The concentration profile of HNO, uranium and plutonium were determined in a multi-stages mixer-settler after the steady state of the back-extraction, and the multi-stages results show that the plutonium can be separated effectively from uranium. The recovery of plutonium and uranium reach 99.995% or over 99.99% respectively. The separation factor of U from Pu (SF) is about 2 × 10. [ABSTRACT FROM AUTHOR]

The present study involves the screening of silver nanoparticles containing carbonized yeast cells isolated from coconut cell sap for efficient adsorption of few long lived radionuclides like Cs, Co, Ru, Pu and Am. Yeast cells containing silver nanoparticles produced through biological reduction were subjected to carbonization (400 °C for 1 h) at atmospheric conditions and their properties were analyzed using fourier transform infra-red spectroscopy, X-ray diffraction, scanning electron microscope attached with energy dispersive spectroscopy and transmission electron microscope. The average size of the silver nanoparticles present on the surface of the carbonized silver containing yeast cells (CSY) was 19 ± 9 nm. The carbonized control yeast cells without silver exposure (CCY) did not contain any particles on its surface. The efficiency of CSY and CCY towards the radionuclide adsorption was studied in batch mode at fixed contact time, concentration, and at its native pH. CSY was efficient in removal of Pu (76.75%) and Ru (54.73%) whereas CCY showed efficient removal only for Am (62.89%). Both the adsorbents did not show any retention with respect to Co and Cs. Based on the experimental data, decontamination factor and distribution coefficient ( K) were calculated and, from the values, it was observed that these adsorbents have greater potential to adsorb radionuclides. [ABSTRACT FROM AUTHOR]

PET with Ga from the TiO- or SnO- based Ge/Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity (Ge vs. Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of Ge activity is produced by eluting the Ge/Ga generators and residues from PET chemistry. Since clearance level of Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce Ge activity in solution from >10 kBq/g to <10 Bq/g; which implies the solution can be discarded as regular waste. Most efficient method to reduce the Ge activity is by sorption of TiO or FeO and subsequent centrifugation. The required 10 Bq per mL level of Ge activity in waste was reached by FeO logarithmically, whereas with TiO asymptotically. The procedure with FeO eliminates ≥90% of the Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate Ge activity sorption on TiO, FeO or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore Ge activity containing waste could directly be used without further interventions. Ge activity containing liquid waste at different HCl concentrations (0.05-1.0 M HCl), was recirculated at 1 mL/min. With Zeolite in the recirculation system, Ge activity showed highest sorption. [ABSTRACT FROM AUTHOR]

Oxidation of Pu(III) in 1 bp solution to Pu(IV) was studied using the salt-free oxidant NO. It was proved that the reductants N,N-dimethylhydroxylamine (DMHAN) and monomethyl-hydrazine (MMH) present in 1 bp solution of CIAE-APOR process can be oxidized and removed from the solutions also by NO before the oxidation of Pu(III). The effects of the acidity, the temperature and the amount of NO added on the oxidation of DMHAN and MMH were studied. [ABSTRACT FROM AUTHOR]

Nitrofurantoin (NFN) radiolabeling with technetium-99m (Tc) was investigated using different concentration of the NFN, sodium pertechnetate (NaTcO), reducing agent (SnCl) at different pH ranges (5.1-6.00). The suitability of the Tc-NFN was evaluated in terms of the radiochemical purity (RCP) yield, in vitro stability in saline, serum, in vitro binding with E. coli, biodistribution in E. coli infected model rat (ERT), and scintigraphic accuracy in E. coli infected model rabbit (EBT). The superlative radiochemical succumb at 2.5 mg NFN, 125 μL of SnCl (1 μg/μL in 0.01 N HCl), 2.5 mCi of NaTcO, at pH 5.2 at 30, 60, 90, and 120 min after reconstitution was 64.50 ± 0.11, 97.50 ± 0.16, 94.25 ± 0.10, 92.15 ± 0.14 and 90.75 ± 0.0.13%. The complex was found stable in saline and serum for 90% up to 120 min and showed 50-65% in vitro binding with E. coli. The absorption of the Tc-NFN, primarily at E. Coli infected (ECT) muscle of ERT was lower but after 60 min it went up to 7.25 ± 0.17%. The absorption in the blood, liver, spleen, stomach, intestines, inflamed muscle (N.T1) and normal muscle (N.T2) went down while in the kidney and urine it went up with time. The ratio of the ECT/N.T1 was 7:1 and N.T2/N.T1 was 2:1. The Whole Body Static (WBS) imaging of the ERB confirmed the suitability of the Tc-NFN as radiotracer. The superlative radiochemical succumb, significant in vitro stability in saline and serum, in vitro binding with E. coli, ideal biodistribution and scintigraphic accuracy confirmed the viability of the Tc-NFN as radiotracer for infection. [ABSTRACT FROM AUTHOR]

The structure changes and the degree of reduction of UO after mechanoactivation in agate and stainless steel vessels in different media are studied. Clearly expressed reduction of U(IV, VI) oxide, accompanied by oxygen release as a result of mechanochemical activation is observed. The highest degree of reduction is reached when mechanoactivation is performed in suspension with nonpolar organic solvents. The presence of acetaldehyde as a reducing agent did not cause valuable increase of the reduction process. Quantitative evaluation of the mechanochemically induced changes in the crystal structure of UO is done. Decrease of the crystallite sizes of both the UO and the reduced form, provoked by the mechanochemical treatment is observed for all the samples. No other uranium-contained compounds, formed during the mechanoactivation in the different media and mixtures were found. [ABSTRACT FROM AUTHOR]

The spontaneous reduction of Eu to Eu was examined when EuCl was added into a pyroprocessing media of LiCl molten salt at 923 K. The amount of Eu was calculated by measuring the total charge consumed to oxidize Eu ions to Eu ions. The concentration ratio of Eu to Eu was estimated to be about 0.40 in the media. In addition, it is confirmed that the reduction of Eu to Eu is caused by the oxidation power of Cl to Cl. The coexistence of Eu and Eu in the LiCl molten salt system was examined by UV-Visible and luminescence spectroscopy. The molar absorptivities of Eu and Eu, calculated from UV-Visible absorption spectra, were 423 and 1954 M cm, respectively. [ABSTRACT FROM AUTHOR]

Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide consecration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order. [ABSTRACT FROM AUTHOR]