Radiocarbon and Other Environmental Isotopes in the Groundwater of the Sites for a Planned New Nuclear Power Plant in Lithuania

Abstract

The assessment of construction sites for the new Visaginas Nuclear Power Plant (Visaginas NPP), including groundwater characterization, took place over the last few years. For a better understanding of the groundwater system, studies on radiocarbon; tritium; stable isotopes of hydrogen, oxygen, and carbon; and helium content were carried out at the location of the new NPP, at the Western and Eastern sites, as well as in the near-surface repository (NSR) site. Two critical depth zones in the Quaternary aquifer system were characterized by different groundwater residence times and having slightly different stable isotope features and helium content. The first shallow interval of the Quaternary multi-aquifer system consists of an unconfined aquifer and semiconfined aquifer. The second depth interval of the system is related to the lower Quaternary confined aquifer. Groundwater residence time in the first flow system was mainly based on tritium data and ranges from 6 to 60 yr. These aquifers are the most important in terms of safety assessment and are considered as a potential radionuclide transfer pathway in safety assessment. Groundwater residence time in the lower Quaternary aquifers based on 14 C data varies from modern to several thousand years and in some intervals up to 10,500 yr.

Interpretation of the anomalous groundwater chemistry and 234U/238U activity ratio disequilibrium in the northern part of the baltic region

“…Database of the Department of Hydrogeology and Engineering Geology of Vilnius University (DHVU) is a synthesis of long-term collaboration between laboratories and was developed since 1976 up to 2000 by the Lithuanian Geological Institute, and continued until now at the Vilnius University with the cooperation of Estonian Geological Survey, Institute of Geology of the Taltech University and from the published papers which include chemical and isotopic data from BAB [17][18][19][40][41][42][43][44][45].…”

Calibrated geochemical ages of the Baltic Artesian Basin groundwater

“…A case study of Lithuania's mineral groundwater located in Birštonas, where brine water recharges into the freshwater aquifer area, involved radiocarbon dating (Zuzevicius et al, 2007). Radiocarbon age data were obtained for the new Visaginas Nuclear Power Plant construction site for better groundwater circulation characterisation (Mažeika et al, 2013). Middle-Upper Devonian aquifer system groundwater in Lithuania was dated with radiocarbon to evaluate the dolomitisation effect on 14 C values, to correct age by the Fontes-Garnier matrix exchange model and dilution factors derived from tritium and carbon-13 data (Mokrik et al, 2009).…”

A SIMPLE CO2 EXTRACTION METHOD FOR RADIOCARBON ANALYSES OF DISSOLVED INORGANIC CARBON IN WATER SAMPLES WITHOUT A CARRIER GAS

“…The headspace gas extraction method has been employed instead of water bubbling in several studies (Molnár et al 2013;Gao et al 2014). This extraction method is commonly used for stable carbon isotope (δ 13 C) measurements (Atekwana and Krishnamurthy 1998;Torres et al 2005;Miyajima et al 2009;Mažeika et al 2013;Meier and Sharma 2015;Sack and Sharma 2014;Takahashi et al 2019a). A water sample is injected into an acid-containing vial filled with He or N 2 gas.…”

“…The precipitation method has also been widely used, especially in studies of groundwater (Carmi et al 1971;Haynes and Haas 1980;Drimmie et al 1991;Aucour et al 1999;Alvarado et al 2013;Burg et al 2013;Mažeika et al 2013;Minami et al 2015). In this method, DIC is precipitated as carbonate material (BaCO 3 or SrCO 3 ) by adding BaCl 2 or SrCl 2 to the sample and controlling the pH using alkaline reagents.…”