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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.


Plausinaitis D.,Vilnius University | Naujalis E.,Lithuanian Academy of Sciences | Prokopchik A.,Ignalina Nuclear Power Plant | Budreika A.,Company LOKMIS
Current Analytical Chemistry | Year: 2014

A simple and fast on-line chromatographic procedure has been developed for separation of 134Cs, 135Cs, 137Cs and 87Sr ions from interfering isotopes of 134Ba, 135Ba, 137Ba and 87Rb. This analytical method offers the possibility to measure the chromatograms of Rb, Cs, Sr and Ba isotopes using ICP-MS technique in isocratic conditions in one run. For the separation, the oxalic acid neutralized with ammonia could be used as the main component of the mobile phase. For specialized ion chromatography (IC) column IonPac CS5A and standard HPLC column Zorbax SCX300, an optimal concentration of oxalic acid has been fixed at 0.1 mol/L and eluent pH range has been fixed at 4.5-5.5. Under these conditions, the retention time of all four elements did not exceed 15 minutes. Our observations demonstrate that the sample injection volume can be increased up to 1 mL. The application of the method for the determination of 134Cs, 135Cs, 137Cs and some isotopes of Rb, Sr and Ba in sample from spent nuclear fuel storage has been demonstrated. Activity of 134Cs and 137Cs calculated from ICP-MS data is comparable to the gamma spectroscopy data. © 2014 Bentham Science Publishers.


Kaliatka A.,Lithuanian Energy Institute | Uspuras E.,Lithuanian Energy Institute | Vaisnoras M.,Lithuanian Energy Institute | Krivoshein G.,Ignalina Nuclear Power Plant
Nuclear Engineering and Design | Year: 2010

The main problem in nuclear energy is providing of safety at all stages of lifetime of nuclear installations in conditions of normal operation, accidents and at shutdown. Ignalina NPP, located in Lithuania, is one of the latest with RBMK reactors at highest capacity. Ignalina NPP has two units, both are closed for decommissioning now (in 2004 and 2009). Both units are equipped with RBMK-1500 reactors, the thermal power output is 4200 MW, the electrical power capacity is 1500 MW for each. In RBMK-1500 reactor the fuel assemblies remain for long time inside reactor core after the final shutdown. The paper discusses possibility of heat removal from the RBMK-1500 core at shutdown condition by natural circulation of water (1) and air (2) inside the fuel channels. In first case the decay heat from fuel assemblies is removed due to natural circulation of water and the piping above reactor core should be cooled by means of ventilation in the drum separator compartments. To warrant free access of air in to fuel channels (in the second case) the reactor cooling system should be completely dry out and the pressure headers and the steam discharge valves in steam lines should be opened. If mentioned conditions will be fulfilled, the reactor core will be cooled by natural circulation of water or air and fuel rods remain intact. © 2010 Elsevier B.V. All rights reserved.


Mazeika J.,Scientific Research Institute | Lujaniene G.,Scientific Research Institute | Petrosius R.,Scientific Research Institute | Orysaka N.,Ignalina Nuclear Power Plant | Ovcinikov S.,Ignalina Nuclear Power Plant
Open Chemistry | Year: 2015

On a first attempt, the determination of 14C and 36Cl activity concentrations in basic operational waste (spent ion-exchange resins and perlite mixture), in decommissioning waste (construction concrete, sand, stainless steel and serpentinite) and irradiated graphite from the Ignalina NPP has been performed. The samples for measurement of the specific activity of 14C and 36Cl were obtained from the selected places, where the highest values of the dose rate and the activity concentrations of gamma emitters were found. The performed study of the total 14C and 36Cl activity concentrations was based on estimated chemical forms of 14C (inorganic and organic compounds) and 36Cl as Cl-ion. The tested methods used in this study were found to be suitable for estimation of activity concentrations of measured radionuclides. © 2015 Jonas Mažeika et al., licensee De Gruyter Open.


Marao A.,Lithuanian Energy Institute | Kaliatka T.,Lithuanian Energy Institute | Uspuras E.,Lithuanian Energy Institute | Krivosein G.,Ignalina Nuclear Power Plant
Energetika | Year: 2010

Before transferring fuel rods from the reactor core to the spent fuel pool, the state of the fuel rods after operation should be determined. The state of a fuel rod could be estimated by employing deterministic analysis. In this work, the state of the RBMK-1500 fuel rod after normal operation was evaluated using the numerical method. Recently, analysis of the processes in RBMK-1500 fuel rods has been performed only by RBMK designers. In the last years, specialists of the Lithuanian Energy Institute started modelling the process in fuel rods of the Ignalina Nuclear Power Plant (NPP) as well, using the FEMAXI-6 code adapted to the specific features of the RBMK-1500 fuel rod. The calculation results obtained using the adapted FEMAXI-6 code were compared with calculations performed by specialists from the Kurchatov Institute. A comparison of the results shows that the adapted FEMAXI-6 code is suitable for the analysis of processes in fuel rods of the RBMK-1500. The processes during the whole life of fuel rods were analyzed using the adapted FEMAXI-6 code. For this analysis, a fuel rod from the fuel channel with an average initial power (2.5 MW) was selected. The state of a fuel rod after operation was evaluated using numerical analysis. The obtained results can be used for the analysis of processes in fuel rods stored in spent fuel pools. © lietuvos mokslu{ogonek} akademija, 2010.


Kaliatka A.,Lithuanian Energy Institute | Uspuras E.,Lithuanian Energy Institute | Vaisnoras M.,Lithuanian Energy Institute | Krivoshein G.,Ignalina Nuclear Power Plant
Energetika | Year: 2010

The main problem in nuclear energy is providing safety at all stages of the lifetime of nuclear installations in conditions of normal operation, accidents and at shutdown. In the RBMK-1500 reactor, the fuel assemblies remain for a long time inside the reactor core after its final shutdown. The decay heat from reactor the core is removed mainly by natural circulation of water in the reactor cooling system. This paper discusses the reliability of this reactor cooling mode in different accident conditions. © lietuvos moksl? akademija, 2010.

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