The thermal decompositions of nickel(II), copper(II), cobalt(II) and manganese(II) perchlorates were studied by thermal analysis and kinetic measurements. Anhydrous perchlorates could not be prepared by heating and outgassing the samples in vacuum; oxides were obtained as the main solid decomposition products. In the case of cobalt and manganese perchlorates, oxidation of the metal ions was observed during the decomposition. In most cases the decompositions of the perchlorates followed the Avrami-Erofeyev kinetics. A correlation was found between the stabilities of the perchlorates and the effective field strengths of the cations.
Iodine isotopes formed in the course of fission in nuclear reactors may be present in the primary coolant in different oxidation states, i.e., in different chemical forms. It is important to know the chemical forms and their proportions in order to asses the environmental effect of the emitted iodine and the performance of air filters used in the primary circuit for binding iodine species, since both depend on the chemical forms in which it is present. Volatile components were separated from water samples taken separately from each block of the nuclear power station by purging with inert gas, then the aerosol, iodine vapour and alkyl iodides were selectively bound on the filter system of the KOMBI sampler. I
, I–, IO–, IO
left in the aqueous phase after purging were separated by consecutive physical and chemical procedures (extraction, isotope exchange, reduction). The results of the investigations have shown that the water technology used in the Nuclear Power Plant in Paks is appropriate with respect to the radioiodine balance. Iodine was found to be the predominant species, and no volatile iodine species were found to be present in the primary coolant. Volatile iodine species sometimes appearing in emissions may be formed from leaching waters due to secondary effects.
The retention of the radioactive noble gases takes place on the charcoal adsorber by dynamic adsorption, meanwhile their radioactivity decrease according to their half-life-times. For the optimal operation of the adsorber units the on-line control and analysis of the retention properties would be required. Therefore a procedure has been developed for the determination of the retention times and the dynamic adsorption coefficients for the specific noble gas isotopes. The method is based on the continuous analysis of the in- and out-flow of the adsorber system by -ray spectroscopy using semiconductor detectors. After the successful laboratory test, the procedure was installed and the retention properties of a charcoal based radioactive gas adsorber system were determined. For the evaluation of the data, a theoretical model was developed, which was used for the calculation of the dynamic retention coefficients of the noble gas isotopes.
A quantitative method for the analysis of -emitters in infinitely thin and thick samples was described in Part I. The calculation of errors in intensity, intensity ratio and activity concentration is discussed here in detail. Different definitions of detection sensitivity are compared and evaluated on the basis of the relative statistical error associated therewith. Dependence between the relative error of the net signal and the required measurement time is deduced and illustrated.
A method for determining bulk or surface activity concentration of -emitters in infinitely thick or thin samples using energy selective detectors without any prior chemical separation or qualitative analysis was introduced in Part I. In addition to that method, a correction procedure is often required in order to compensate for the -sensitivity of the -detector. A system or two — preferably identical —detectors positioned to the front and rear side of a sample has been established. The rear side detector is shielded against -radiation. The -response of both detectors is determined as a function of -energy using monoenergetic calibration standards. Response pulses are selected to form 8 or 16 energy intervals, and separate series of correction coefficients are then computed for each interval and standard energy using the ratio of the respective counts. When a sample having mixed - and -radiation is evaluated, an effective
-energy is first calculated from the pulse height distribution of the rear side detector, the appropriate series of correction coefficients is selected and finally net -counts are generated from the counts of the front side detector. Sensitivities in natural and elevated -background are presented.
The activity concentration of bulk and surface samples contaminated with -emitting radioisotopes is difficult to measure without the a priori knowledge of the nature of the non-gamma emitting components. Beta-emitters cannot be identified from any measured spectral distribution. The counting efficiency of the measuring system changes significantly with -energy so it cannot be assumed to have a single value obtained with a standard source with known energy. Application of an energy selective -detector is introduced for determining bulk and surface activity concentration. Samples of infinitely thick or infinitelythin nature are to be prepared. The distribution of -energy deposited in the detector is registered as counts in 8 or 16 energy intervals. No information is needed on the qualitative composition of the sample. Normalised integral distributions (intensity ratios) are derived from the count rates of the intervals. These distributions are then compared to calibrated intensity ratios obtained with suitable standard sources. An average (effective) counting efficiency is generated from this comparison by a special algorithm. Activity concentration of an unknown sample is then obtained using this average efficiency. Calibration and sensitivity data are presented for different types of bulk and surface samples.
Investigations on the disintegration rate of fission products of238U and239Pu are presented. The intensity of the - and -radiation of fission products were measured continuously in an interval of 1–1300 hours following the fission, offering the possibility for determining the general and specific characteristics of the individual fission products. A universal measuring procedure was elaborated for the rapid in situ determination of the dosimetric features of fission products, which is suitable for the accurate evaluation and prediction of external absorbed dose even in case of fission products of various origin and unknown composition.
Authors:L. Szeredi, G. Palkovics, N. Solymosi, L. Tekes and J. Méhesfalvi
The prevalence of gastric Helicobacter infection in finishing pigs and the influence of this infection on gastric lesions was studied. Stomachs of 89 finishing pigs from 27 randomly selected herds were sampled at the slaughterhouse. Forty cases (Group A) were selected based upon the presence of gross pathological lesions in the pars oesophagea, and further 49 cases were obtained at random (Group B). Three samples of gastric tissue (junction of pars oesophagea and pars cardiaca, fundic area, and pyloric area) were collected from each stomach for histological and immunohistochemical examination. Helicobacter antigen was detected in 76 cases (85.4%). No association was found between the presence of Helicobacter in the stomach and the occurrence of gross pathological lesions in the pars oesophagea or gastritis detected on histological examination. However, a significant association was found between the occurrence of Helicobacter in the pyloric area and the presence of erosions/ulcers in the pars oesophagea (OR: 7.01, p = 0.022) in Group B. A significant association was also evident between the presence of Helicobacter and glandular lesions (dilatation of the glands + glandular abscess + degeneration of glandular epithelial cells). In conclusion, Helicobacter infection seems to be a contributing factor to pathological changes in the stomach of finishing pigs.
Authors:I. Gresits, S. Tölgyesi, L. Nagy and J. Solymosi
A radioisotope-excited energy-dispersive X-ray fluorescence system has been constructed and used for the analysis of blood samples for trace elements. The possibility of determination of trace elements in blood by X-ray fluorescence based on comparison with standard reference materials has been outlined and the applicability of the method demonstrated by the analysis of blood samples. The method enables fast, non-destructive direct analyses to be carried out without lengthy sample pretreatment on a routine basis.