Radionuclide chemical species determination in waste management studies

The bio-geochemical processes of actinides potentially released to the environment from nuclear waste repositories are mainly determined by their chemical form. Results of direct and indirect determinations of soluble and colloidal species of radionuclides are reported. Experimental investigations on americium speciation in sea water are compared with model calculations. Americium pseudocolloids smaller than 0.45 m were identified. The application of the Specific Interaction Theory to activity coefficient correction is shown for the chloro- and sulphate complexes of americium. Analytical techniques for direct speciation studies are briefly reviewed.     

Study on activity of radium,radon and physicochemical parameters in ground water and their health hazards around Tumkur industrial area

Journal of Radioanalytical and Nuclear Chemistry - The activity of radium (226Ra), radon (222Rn) and physicochemical parameters in ground water around study area were estimated by standard...     

Application of thermal analysis in screening for chemical process hazards

The testing of substances and reaction mixtures for the prevention of process hazards poses special problems, which may be solved, to some extent, by commercial DTA and DSC equipment. The standard equipment specially designed for dynamic, isothermal and constant volume tests and the testing procedure is described. Finally, the principle of an evaluation method is briefly outlined.     

Combined time- and space-resolved Raman spectrometer for the non-invasive depth profiling of chemical hazards

A time-resolved inverse spatially offset Raman spectrometer was constructed for depth profiling of Raman-active substances under both the lab and the field environments. The system operating principles and performance are discussed along with its advantages relative to traditional continuous wave spatially offset Raman spectrometer. The developed spectrometer uses a combination of space- and time-resolved detection in order to obtain high-quality Raman spectra from substances hidden behind coloured opaque surface layers, such as plastic and garments, with a single measurement. The time-gated spatially offset Raman spectrometer was successfully used to detect concealed explosives and drug precursors under incandescent and fluorescent background light as well as under daylight. The average screening time was 50 s per measurement. The excitation energy requirements were relatively low (20 mW) which makes the probe safe for screening hazardous substances. The unit has been designed with nanosecond laser excitation and gated detection, making it of lower cost and complexity than previous picosecond-based systems, to provide a functional platform for in-line or in-field sensing of chemical substances.     

Radionuclide fractionation in a forest soil profile

Two alternative approaches, a sequential extraction scheme and the calculation of the variation of the distribution coefficient of radiocaesum in different K–Ca–NH₄ scenarios, were used to study the behaviour and fractionation of this radionuclide in a forest soil profile. The first approach was applied to samples originating from an experiment in which the original L (litter) layer was replaced by an L layer contaminated with a radioactive aerosol, allowing a downward migration of radiocaesium. The samples belonged to different stages after the contamination. The second approach was applied to samples contaminated with soluble radiocaseium. The results indicate that radiocaesium behaviour is quite similar in the Hand A layers, and that the mineral matter seems to govern the behaviour of radiocaesium in case of direct condensed deposition or when radiocaesium is released from structural components of the organic matter phase.     

Improvement of sample preparation in the chemical sampling of gold ore deposits

A procedure used in the chemical sampling of gold ore deposits for assessing the representative mass of samples and analytical weighed portions is improved. It is shown that the coefficient K used to assess the representative sample mass and characterizing the nonuniformity of the gold distribution in the gold ore sample can go beyond the limits established by the regulations of the Ministry of Natural Resources of the Russian Federation.     

Instrumental neutron activation analysis of a sulfide ore and some ore benefication products

Samples of a pyritic lead-zinc ore and some benefication products were examined by instrumental activation analysis using Ge(Li) gamma-spectrometry. The following elements were determined using thermal neutron activation: Sc, Cr, Co, Zn, As, Se, Ag, Sb, Ir, Au and Th. The technique is especially favourable for the determination of cobalt, arsenic, antimony and gold, but selenium, silver and thorium can also be determined in most fractions. Activation with epithermal neutrons will improve conditions for the determination of As, Sb, Se, Ag, Au and Th.     

Natural iron ore as an oxygen carrier for biomass chemical looping gasification in a fluidized bed reactor

Chemical looping gasification (CLG) of biomass was performed in a thermogravimetric analyzer (TG) reactor together with a fluidized reactor with natural iron ore oxygen carrier under inert atmosphere. TG experiments indicated that iron ore can provide oxygen source for biomass conversion in the form of lattice oxygen. In the fluidized bed experiments, the influences of reduction temperature on CLG of biomass were emphatically investigated in terms of gas distribution and solid characters. The gas yield and carbon conversion increased, but the tar content decreased in the temperature range of 1,013–1,213 K. In this temperature range, the conversion of oxygen carrier increased from 24.11 to 53.59 %. X-ray diffraction analysis shows that more FeO was generated with temperature increasing. Scanning electron microscope analysis indicates that sintering was observed at elevated temperature. An optimum mass ratio of biomass/oxygen carrier (B/O) of 0.67 was obtained with aim of achieving maximum gasification efficiency of 76.93 %.     

Ion exchange of radium and barium in zeolites

The sorption of radium, barium and mixture of both elements has been studied in the zeolites 3A, 5A and Y. The ratio zeolite; solution was 100 mg: 10 cm³ and the pH was 3. Carrier-free radium was completely retained in all studied zeolites. When 0.0016 meq of barium/cm³ were added, the sorption of radium decreased in the zeolite 5A only and when 0.014 meq of barium/cm³, the radium sorption was reduced in all the studied zeolites. The sorption of barium was similar to that of radium. The amounts of sodium and calcium removed from the zeolites and the proton quantity fixed to them allowed us propose the ion exchange mechaniosm. The changes and ionic radii of the species exchanged did not play an important role. However, the location of the ions in the crystalline network of each zeolite is probably an important parameter for the exchange.     

Improvement of the control of analytical work in the chemical sampling of gold ore deposits

A procedure for the control of analytical work in the chemical sampling of gold ore deposits is proposed to increase the efficiency of the control of analytical work.     

Emanation studies of radium containing materials by a simple radon monitoring system

The applicability of a radon emanation system to radium determination in fine-grained solid samples has been investigated by means of a closed radon emanation system consisting of a radon monitor and an aluminium vessel. The system has been calibrated with radium-containing fine-grained samples (e.g. phosphogypsum, granite and pitchblende) and the evaluation of the calibration data included linearity, detection limits and analytical resolution of the method. The studied radon emanation system presents very good linear response (R ² = 0.99) to the radium content of the samples, the detection limit for radon is 25 Bq m^?3 and the analytical resolution 15 Bq m^?3. In addition, the relation between particle size of the materials and radon emanation has indicated that the applicability of the radon emanation system to radium determination is strongly depended not only on the mineral type but also on the particle size of the grained material.     

On the hyperfine structure and isotope shift of radium

The hyperfine structure and isotope shift of the heaviest known alkaline earth element radium (Z=88) have been studied in both the atomic Ra I and ionic Ra II spectra. The measurements, carried out by on-line collinear fast-beam laser spectroscopy, yield the hyperfine constantsA andB of the 7s and 7p _1/2 states in Ra II, of all states of the excited 7s 7p configuration and the 7s 7d ³ D ₃ state in Ra I. The data allow a consistent evaluation of the nuclear moments for eight odd-A radium isotopes. In particular, a complete analysis of the hyperfine structure of thesp configuration in the two-electron system provides a stringent test of the validity of the semi-empirical modified Breit-Wills theory. It is shown that the effective operator formalism is equivalent, if relativistic correction functions are used to reduce the number of parameters. The semi-empirical hyperfine fields are evaluated and found to agree generally with those from ab-initio calculations. The isotope shifts in thes?p,s ²?sp,sp?sd transitions are analysed semi-empirically and compared with ab-initio calculations. The consistency of the different analyses proves their validity and classifies the spectrum of Ra I as a model case for a simple and clean two-electron spectrum.     

Adsorption behavior of radium in carbonaceous slate

This paper discusses the adsorption of radium by carbonaceous slate studied by the static adsorption method. The best conditions for the adsorption are equilibrium time 23 hours, solid to liquid ratiom/v 120 g·ml^–1, pH 7.8, and temperature 30°C. The adsorption at low concentration can be described well by Freundlich isotherm.     

Use of inorganic adsorbers in radium analysis

Two new simple methods were studied for the analysis of radium in fresh waters by concentration and purification. Both methods are based on the use of an inorganic selective adsorber, namely basic lead rhodizonate, LERHO, and partially reduced tin dioxide (PRTD). The procedures were checked by using filtered fresh waters spiked with 0.1 Bq of²²⁶Ra, and in the presence of few μg/l of barium. In each experiment¹³³Ba radioisotope was added to water samples to measure the yield of the overall procedure by γ-counting. Barium and radium were adsorbed from basic solutions on LERHO packed chromatographic column in the first procedure, while batch experiments were preferred for the adsorption on PRTD. After separation,²²⁶Ra and barium were eluted from the exchangers and co-precipitated onto small filters as thin film, supported on an inactive barium sulphate substrate, to be submitted to alpha-and gamma-spectrometry. Both methods gave promising results.     

On the determination of radium by alpha-spectrometry

In order to determine radium in environmental samples by -spectrometry, the way in which some changes in the chromatographic conditions can affect the purification of the element on cation exchange columns from hydrochloric solutions have been studied. Some modifications have also been introduced in the method of electrodeposition of radium from an ammonium oxalate electrolyte.