Time filter

Source Type

Debrecen, Hungary

Molnar M.,Institute of Nuclear Research | Palcsu L.,Institute of Nuclear Research | Futo I.,Institute of Nuclear Research | Svingor E.,Institute of Nuclear Research | And 4 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2010

To obtain reliable estimates of the quantities and rates of the gas production in L/ILW a series of measurements was carried in the last 7 years in Hungary. The typical gas production rates were 0.05-0.2 STP litre gas/day for CO2 and CH4 generation, and less for H2. No explosive gas mixture was indicated in the L/ILW drums during the investigated storage period. Compositions of headspace gases in closed L/ILW vaults were in agreement with gas generation processes observed in L/ILW drums. The stable carbon isotope measurements show that the main source of the CO2 gas is the degradation of organic matter and indicates microbial degradation processes as the main sources of CH4. Typical tritium activity concentrations were <10 Bq/l gas in the drums and <1,000 Bq/l gas in the vaults. Typical 14C activity values of the headspace gases were <2.0 Bq/l gas in the drums and <1,000 Bq/l gas in the vaults. © 2010 Akadémiai Kiadó, Budapest, Hungary. Source

Janovics R.,Hertelendi Laboratory of Environmental Studies | Molnar M.,Hertelendi Laboratory of Environmental Studies | Futo I.,Hertelendi Laboratory of Environmental Studies | Rinyu L.,Hertelendi Laboratory of Environmental Studies | And 4 more authors.
Radiocarbon | Year: 2010

An automatic water sampling unit was developed to monitor the radioactive emission (radiocarbon and other corrosion and fission products) from nuclear facilities into the groundwater. Automatic sampling is based on the principal of ion exchange using built-in resin columns in the submerging samplers. In this way, even the short-term emissions can be detected. According to our experiments, the 14C activity concentrations and the δ13C values of the samples made by the ion exchange method are systematically underestimated compared to the real values. The carbonate adsorption feature of the sampling unit was studied under laboratory and field conditions. For this purpose, a test method was developed. The observed sampling efficiencies and additionally some carbon contamination for the sampling method itself have to be taken into consideration when we estimate the amount of 14C contamination introduced into the groundwater from a nuclear facility. Therefore, a correction factor should be made for the 14C anion exchange sampling. With the help of this correction, the results converge to the expected value. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona. Source

Molnar M.,ETH Zurich | Molnar M.,Hungarian Academy of Sciences | Hajdas I.,ETH Zurich | Janovics R.,Hungarian Academy of Sciences | And 4 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2013

Two new methods for the sample preparation of groundwater for C-14 measurements with accelerator mass spectrometry (AMS) were developed and tested. Both methods are simple and do not require vacuum for the extraction of CO 2 from water. A double needle with flow controlled He carrier gas is used for air flushing out before the reaction and also for the CO2 transfer out from the septa sealed reactor test tube. The extracted CO 2 was either graphitized or directly measured with an AMS equipped with a gas ion source. The processing blank and the reproducibility of the applied methods are satisfactory and allow precise groundwater C-14 analyses. The feasibility of field sampling directly into the reaction tubes was demonstrated using very old (1-20 pMC) groundwater samples. The C-14 content of as little as 1 mL of water sample could be measured with 1% precision (for a modern sample) within 20 min with the gas ion source of a MICADAS type AMS system. The preparation of the samples can be performed while measurements are already running and therefore require no additional time. © 2012 Elsevier B.V. All rights reserved. Source

Molnar M.,Hertelendi Laboratory of Environmental Studies | Major I.,Debrecen University | Haszpra L.,Hungarian Meteorological Service | Svetlik I.,Nuclear Physics Institute of Czech Republic | And 2 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2010

A field unit was installed in the city of Debrecen (East Hungary) during the summer of 2008 to monitor urban atmospheric fossil fuel CO2. To establish a reference level simultaneous CO2 sampling has been carried out at a rural site (Hegyhátsál) in Western Hungary. Using the Hungarian background 14CO2 observations from the rural site atmospheric fossil fuel CO2 component for the city of Debrecen was reported in a regional "Hungarian" scale. A well visible fossil fuel CO2 peak (10-15 ppm) with a maximum in the middle of winter 2008 (January) was observed in Debrecen air. Significant local maximum (~20 ppm) in fossil fuel CO2 during Octobers of 2008 and 2009 was also detected. Stable isotope results are in agreement with the 14C based fossil fuel CO2 observations as the winter of 2008 and 2009 was different in atmospheric δ13C variations too. The more negative δ13C of atmospheric CO2 in the winter of 2008 means more fossil carbon in the atmosphere than during the winter of 2009. © 2010 Akadémiai Kiadó, Budapest, Hungary. Source

Rinyu L.,Hungarian Academy of Sciences | Molnar M.,Hungarian Academy of Sciences | Molnar M.,ETH Zurich | Major I.,Hungarian Academy of Sciences | And 5 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2013

The original sealed tube zinc reduction graphitization process was first developed for rapid low-precision measurements of biomedical tracer samples and later also applied for high precision measurements of not too old samples. In this study we tested the MICADAS (mini radiocarbon dating system [1]) radiocarbon measurements of targets prepared by sealed tube graphitization process. We found the optimal iron catalyst and reagents (TiH2 and Zn) amount whereby we can reach a relatively low background level, and minimized the overall δ13C fractionation during the graphitization. Repeated measurements of normalization standards and real samples with known 14C activities were very well reproduced. Finally, we demonstrated the applicability of the sealed tube graphitization on real environmental samples covering a wide range of 14C concentrations. © 2012 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations