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Jakimaviciute-Maseliene V.,Nature Research Center | Mazeika J.,Vilnius Gediminas Technical University | Motiejunas S.,Radioactive Waste Management Agency
Journal of Environmental Engineering and Landscape Management | Year: 2012

The Strategy on Radioactive Waste Management of Lithuania (Radioaktyviuju... 2008) envisages evaluating the possibilities of disposal of spent nuclear fuel and long-lived radioactive waste from operation and decommissioning of Ignalina NPP in a deep geological repository. The crystalline basement and sedimentary cover of south-eastern Lithuania was selected for the current model case studies due to availability of geological and hydrogeological data from previous explorations. Groundwater flow, radionuclide (iodine-129 as mobile and long-lived one) transport and heat transfer, modelling using computer code FEFLOW was performed. The model domain of south-eastern Lithuania comprises Proterozoic-Archaean aquifer with overlaying aquifers system of sedimentary cover. The upward groundwater flow through defected canister located in tectonically damaged zone was conservatively generated. The main results of calculations are following: in case of upward groundwater flow, the maximum activity concentration of 129I in groundwater of the tectonic fracture zone above defected canister will not exceed 10-4 Bq/l; the maximum temperature in the tectonic fracture will obtain about 30-35°C and will not impact on the radionuclide transport. Location of model domain in south-eastern Lithuania does not mean any reference to the site for deep geological repository. The results show that doses obtained by human via drinking water should be below the dose constraint (0.2 mSv /year). Copyright © 2012 Vilnius Gediminas Technical University (VGTU) Press Technika.

Vaitkeviciene V.,Lithuanian Energy Institute | Vaitkeviciene V.,Vytautas Magnus University | Mazeika J.,Institute of Geology and Geography | Skuratovic Z.,Institute of Geology and Geography | And 4 more authors.
Radiocarbon | Year: 2013

Radiocarbon is one of the most significant radionuclides affecting the safety margins of near-surface repositories for the disposal of low- and intermediate-level, short-lived radioactive waste, arising from the operation and decommissioning of nuclear power plants (NPPs). One of the goals of the present study was to characterize radioactive waste from Ignalina NPP (Lithuania) (storage tanks TW18B01 and TW11B03) from the spent ion-exchange resins/perlite stream to determine the 14C-specific activity of inorganic and organic carbon compounds. The approach applied is based on classical radiochemical separation methods, including acid-stripping techniques and wet oxidation with subsequent catalytic combustion. The suitability of the method for 14C-specific activity determination in ion-exchange resin samples with a minimum detectable activity of 0.5 Bq/g by liquid scintillation counting (LSC) was demonstrated. The extraction efficiency of inorganic and organic carbon compounds based on model samples with known 14C activity was estimated. The fraction of 14C associated with organic compounds ranged from 42% to 63% for storage tank TW18B01 and from 30% to 63% for storage tank TW11B03. The specific activity of inorganic 14C was estimated as 12.6 Bq/g with a relative standard deviation (RSD) of 29% for storage tank TW18B01, and 177.5 Bq/g with a RSD of 35% for storage tank TW11B03. Based on volume and density data, the total 14C activity for radioactive waste stored in tanks TW18B01 and TW11B03 was estimated as 3.59E + 10 Bq (±32%) and 4.15E + 11 Bq (±28%), respectively. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.

Jakimaviciute-Maseliene V.,Vilnius University | Jakimaviciute-Maseliene V.,Nature Research Center | Mazeika J.,Nature Research Center | Motiejunas S.,Radioactive Waste Management Agency
Progress in Nuclear Energy | Year: 2016

About 100 000 m3 of solid conditioned Low and Intermediate Level Waste, generated during operation and decommissioning of the Ignalina nuclear power plant, are to be disposed of in a near-surface repository. In this study a computer code FEFLOW 5.0 was applied for simulating the transport of the most mobile radionuclides (3H, 14C, 59Ni and 94Nb) within moisture through an unsaturated vault of the near-surface repository in Stabatiškė Site. HYDRUS-1D analysis was used to assess the radionuclide transport in the repository and to estimate initial activity concentrations of radionuclides transported from the cemented waste. Radionuclide release from the vaults in the unsaturated conditions after closure of the repository and consequent contaminant plume transport has been assessed taking into account site-specific natural and engineering conditions and based on a normal evolution scenario. The highest value of 14C activity concentration (about 3.3·108 Bq/m3) in the moisture of soils below engineering barriers is predicted after about 7300 years after repository closure. The predicted maximum activity concentrations of the others modeled mobile radionuclide 3H (after 100 years after repository closure), 94Nb (after 300 000 years) and 59Ni (after 173 000 years) at the groundwater table are 1.1·105, 3.7·104 and 2.4·106 Bq/m3, respectively. © 2015 Elsevier Ltd. All rights reserved.

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