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  • Author or Editor: J. Molnár x
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Abstract  

Thermic detectors are seldom used in analytical laboratories, in spite of their advantageous properties. Their theoretical basis provides simple relations and useful equations for the design and construction of thermic liquid analyzers. In this paper a home-made detector system was used for the continuous determination of hydrochloric acid. The results were in accordance with the theoretical considerations.

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Abstract  

The nucleating efficiency and selectivity of different β-nucleating agents was characterised and compared by differential scanning calorimetry, (DSC) and temperature-modulated DSC (TMDSC). The nucleating agents were the calcium salts of pimelic and suberic acid (Ca-pim and Ca-sub), linear trans-γ-quinacridone (LTQ), a commercial nucleator NJ Star (NJS) and an experimental product (CGX-220). The efficiency and the selectivity of Ca-sub and Ca-pim are extremely high. NJS is efficient above a critical concentration, which is connected with its partial dissolution in polypropylene melt. LTQ and CGX-220 possess strong overall nucleating ability and moderate selectivity. Using TMDSC, we found that three consecutive processes take place during the heating of β-nucleated samples cooled down to room temperature: reversible partial melting of the β-form, irreversible βα-recrystallisation, and the melting of the α-modification formed during βα-recrystallisation or being present in samples prepared with non-selective β-nucleators. Melting of the α-phase contains both reversible and irreversible components.

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Abstract  

The γ-ray spectrum analysis code HYPERMET-PC has been significantly upgraded since its introduction in the firstk 0-Users Workshop (1992). Some aspects of the implemented procedures in the new version 5.0, such as the novel approach to handle tandem LFC spectra and the benefit of using ortho-normal polynomials for fitting efficiency curves will be outlined. Having realized the importance of quality assurance in applied γ-ray spectrometry, additional utilities have been incorporated for checking system parameters: nonlinearity, energy resolution, etc. The new Nuclide Identification routine makes the program suitable for qualitative analysis both of NAA and PGAA type.

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Abstract  

The introduced method to determine the individual activities of the short-lived radon daughters in air is based on simultaneous α- and β-counting of the sampled air collected on a filter. The measured curves of gross-α and gross-β intensities were decomposed by sum of exponentials and the individual activities of the progenies were assessed. Furthermore, computer simulations were carried out supplemented with aerosol measurements to describe the physical processes of radon progenies in air during the experiments and to verify the suitability of the method.

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Abstract  

An IBM PC controlled nuclear electromigratic measuring system was developed to determine ion mobilities of different radioactive isotopes. The software and interface are shown in detail.

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Abstract  

In this paper, the development of a new-type of resin is presented, which contains selective complexing and scintillating molecules in a chemically bonded form. The resin material is produced via radiation polymerization of a solution of 2-(4-allyloxy-phenyl)-5-phenyl oxazole, 5-(allyloxy-phenyl)-2-[4-(5-phenyl-oxazole-2-il)-phenyl] oxazole, diethylene glycol dimethacrylate (DEGMA), styrene and the allyl derivative of a 18C6 crown ether-dicarbolic acid complexing agent. The product is a macroporous polymer matrix that shows fluorescent properties and ion binding capacity excellent for radioanalytical purposes.

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Abstract  

We studied the long-term (190 hours) behaviour of [Zn(propyltetrazole)6](BF4)2 single crystal under high-vacuum (HV) conditions (10–8 torr) with a depth-sensitive technique of positron annihilation spectroscopy (PAS). The obtained data indicate the slow formation of a new near-surface structure which is formed by the decomposition of the [Zn(propyltetrazole)6]2+ ions. The assumption of such a decomposition process was confirmed by additional mass spectroscopic measurements.

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Abstract  

A simple and effective method has been developed for the determination of the transuranium isotopes in primary coolant samples of WWER-440 type reactors. Membrane filters containing undissolved particles from about one liter coolant were destroyed by mineral acids, then americium-curium isotopes and neptunium-plutonium isotopes were coprecipitated sequentially with NdF3 based on their different redox behavior. Alpha-spectra were determined by silicon semiconductor detectors connected to multichannel analyzers. Activity ratios measured in a reactor unit with a failed fuel element were compared with calculated values of the same type of reactor under similar conditions. Parameters of the defective fuel (burnup, original enrichment) could be estimated.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: G. Molnár, T. Belgya, L. Dabolczi, B. Fazekas, Zs. Révay, Á. Veres, I. Bikit, Z. Kiss, and J. Östör

Abstract  

Prompt gamma-activation analysis (PGAA) is an important complementary technique to conventional instrumental activation analysis that can be successfully used in a number of cases when INAA is not applicable. Therefore, a PGAA facility has been constructed at the recently refurbished and upgraded Budapest Research Reactor. It occupies the end position of a new curved themal guide of 30 m length and 2.5×10 cm2 cross section which provides a clean beam of low energy neutrons. The sophisticated HPGe-BGO -ray spectrometer system can be operated in Compton-suppression and pair-spectrometer modes simultaneously. The octal splitting of the main BGO improves efficient pair mode operation when coincidences between pairs of opposite segments and the HPGe detector are required separately. Gamma-gamma coincidence measurements will also be possible when the new multiparameter data acquisition system is completed. One of the main tasks at the new facility will be the accumulation of new spectroscopic data for detector calibration and standardisation, as well as for the construction of a more accurate prompt -ray library for the chemical elements. Various applications are planned, such as the determination of hydrogen in fullerenes and of toxic trace elements in environmental samples.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Ormai, A. Fritz, J. Solymosi, I. Gresits, E. Hertelendi, Z. Szúcs, N. Vajda, Zs. Molnár, and P. Zagyvai

Abstract  

In the execution of disposal of low and intermediate level radioactive wastes, it is important to evaluate accurately the kind and quantity of each radionuclide in the wastes. For such an evaluation, correlation of non-gamma-emitting nuclides based on gamma-emitting nuclides is recommended and regarded as a practical method. This method necessitates a completion of a highly accurate and reliable nondestructive assay system of gamma-emitting nuclides for practical use. In 1992, in support of the new waste disposal program in Hungary, Paks NPP initiated a waste characterization program to determine the radiological properties of its radwastes. A segmented gamma scanning system has been set up to measure the gamma-emitting nuclides in 200 litre low level drums following in-drum compaction. In the framework of the program a radiochemical analysis sub-program was started to determine the long-lived non-gamma emitting radionuclides, mainly those listed in the US regulatory document (10CFR61). The radionuclides of interest have been3H,14C,90Sr,55Fe,59Ni,99Tc,129I and TRUs. Sample preparation techniques and measurement methods have been selected and used. Newly developed or adopted methods have been tested on real liquid radwaste streams such as concentrates, ion-exchange resin and sludge. The measurements taken so far have revealed brand new information and data on radiological composition of waste of WWER-type reactors. In the next stage of the characterisation program attempt will be made for providing correlation factors between the gamma and non-gamma-emitting radionuclides in different waste streams. Short description of the methods and results on waste inventory are given by highlighting the problem areas.

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