Determination of 129I in biomonitors collected in the vicinity of a nuclear power plant by neutron activation analysis

Neutron activation analysis (NAA) was used to determine ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in bovine thyroid, moss, and river sediment samples collected in the vicinity of the Temelín nuclear power plant (NPP) in south Bohemia. The NAA procedures comprised pre-irradiation separation of ¹²⁹I by combustion of the samples in the stream of oxygen at 1,000 °C and trapping the liberated iodine in a LiOH/(NH₄)₂SO₃ solution. Post-irradiation separation of ¹³⁰I produced by the reaction ¹²⁹I(n,γ)¹³⁰I was carried out by extraction of elementary iodine with chloroform followed by precipitation of PdI₂. Nondestructive, epithermal NAA was used to determine ¹²⁷I employing the ¹²⁷I(n,γ)¹²⁸I reaction. The results showed that mean values of ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in the bovine thyroids varied from 22 to 61 mBq kg^?1 (dry mass) and 2.8 × 10^?9 to 5.4 × 10^?9, respectively. These values are close to the lower end of results reported from various regions non-polluted with ¹²⁹I. No significant differences were found between ¹²⁹I concentrations and the ¹²⁹I/¹²⁷I ratios in the bovine thyroids collected prior to the start and after several years of operation of the NPP. The mean value and standard deviation of ¹²⁹I in mBq kg^?1, dry mass and the ¹²⁹I/¹²⁷I ratio in moss Pleurozium schreberi were 23 ± 16 and 2.3 × 10^?9, respectively, whereas values of ¹²⁹I in the river sediments were below 8–10 mBq kg^?1 (dry mass) after several years of the NPP operation.     

To the relation between energies of molecular soliton and extended states in chains

A standard statement is that in the interacting electron (exciton) — phonon systems in molecular chains and on the level of the standard quantum mechanics, the formation of localised solition states is energetically more advantageous than the formation of extended (plane--wave-like or polaron) states (see e.g. /1/ for a review). The question about validity of this statement is not yet finally settled /2/. We are going to question this assertion using trivial variational arguments here. For arbitrary localized standing-soliton state (having its energy lower than the states describing running solitons irrespective of technique used to derive them), we are able to prove the existence of an intermediate or large polaron state whose energy is still lower. Hence, the energy arguments are not sufficient to explain the anomalous soliton stability.     

Preparation and characterization of a new set of IAEA reference air filters using instrumental neutron activation analysis, proton-induced X-ray emission and Rutherford backscattering

A new set of reference air filters was prepared for proficiency testing of laboratories involved in air pollution studies organized by the International Atomic Energy Agency (IAEA). The set consists of one filter loaded with airborne particulate matter (APM) and one blank filter. Target values and their standard deviations were established using instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE) with proven accuracy. Rutherford backscattering (RBS) was used to help in deriving the necessary corrections in PIXE. Losses of individual elements from APM due to the wet deposition procedure were evaluated.     

Mössbauer study of thermal conversion of FeSO4·7H2O

The aim of this study was to identify intermediary products and study of the oxidation level of FeSO₄·7H₂O in the temperature region from 200 to 600°C. The knowledge of the reaction process in this temperature region is important for the optimisation of the technology used in the red pigment manufacture.     

Verification of k 0-NAA results at the LVR-15 reactor in Řež with the use of Au+Mo+Rb(+Zn) monitor set

Long-time experience in neutron flux monitoring on irradiation in the LVR-15 research reactor in ?e? proved that Au+Mn+Rb and Au+Mo+Rb(+Zn) monitor sets for short and long irradiation, respectively, are more suitable in our conditions than the most frequently used Au+Zr set. The advantages of the former monitor set have been described previously, in the present work we discuss the advantages of the latter monitor set for long irradiations in varying active core configurations of the LVR-15 reactor. The successful application of the Au+Mo+Rb(+Zn) monitor set has been verified by comparative determination of the neutron flux parameters α (epithermal flux distribution parameter), f (thermal-to-epithermal neutron flux ratio), and F _c,Au (comparator factor) using this and the Au+Zr monitor set, and by analyses of certified reference materials, namely NIST SRMs 1547 Peach Leaves, 2711 Montana Soil, and 1633b Trace Elements in Coal Fly Ash.     

Nitrogen assay in winter wheat by short-time instrumental photon activation analysis and its comparison with the Kjeldahl method

The nitrogen content in winter wheat from various crops grown organically or conventionally was determined by instrumental photon activation analysis. The method utilizes measurement of the annihilation gamma line at 511 keV from the short-lived photoactivation product ¹³N, corrected for interference contributions from other positron emitting nuclides. Results compared well to those obtained by the Kjeldahl method. A positive impact of conventional agriculture on higher crude protein content in grain was found. Analysis of whole kernels and their germination and growth after irradiation were also tested.

     

INAA and petrological study of sandstones from the Angkor monuments

We determined 35 major, minor and trace elements in sandstone samples taken from building blocks of 19 Angkor temples and from an old and a new quarry using INAA. We also characterized the sandstone samples with conventional microscopy and electron microprobe analysis. Using cluster analysis, we found no straightforward correlation between the chemical/petrological properties of the sandstones and a presumed period of individual temples construction. The poor correlation may result either from the inherent inhomogeneity of sandstone or just reflect the diversity of quarries that supplied building blocks for the construction of any particular temple.     

Fast decomposition of biological and other materials for radiochemical activation analysis: A radiochemical study of element recoveries following alkaline-oxidative fusion

Recoveries of selected elements were studied for fast decomposition of biological and other materials using alkaline-oxidative fusion in a mixture of NaOH and Na₂O₂ at 850–900 °C. The procedure yields total mineralization of samples within 2 to 3 minutes. It is especially suitable in radiochemical activation analysis (RAA) for the determination of elements forming short-lived radionuclides. Recoveries of the elements F, Si, S, Cl, Ti, V, Mn, Ge, As, Br, Mo, Ru, In, Sb, I, Re, Os, and U determined using radiotracers were in the range 95–100%, while those for Se and Hg were significantly lower and highly variable.