Abstract
The Ignalina Nuclear Power Plant (INPP) in Lithuania is a rare case when lake water is used instead of river or sea water for cooling. Lake Drūkšiai with water residence time of 3–4 year and undisturbed sediment layers is a unique system to assess the impact of a nuclear facility on the aquatic ecosystem with a sufficiently high temporal resolution. We constructed a model of radiocarbon cycling processes in lake ecosystem which evaluates the 14C specific activity vertical distribution in two organic sediment fractions: alkali-soluble and alkali-insoluble. Model calculations proved that during the first 15 years of operation since 1983, 14C annual aqueous releases from the INPP were in water dissolved inorganic carbon form and varied in the range of 2.4 ÷ 3.7 × 108 Bq/year. The results of the modeling of hypothetic scenarios also showed that there was the only one episode of elevated releases from the INPP in 2000–2001, which changed the interaction between the two organic sediment fractions for the period of 2000–2006. It was caused most probably by released chemicals from INPP but not by 14C contamination. Interaction processes between both sediment fractions recovered to its original state after 2006, indicating that the released additional chemical compounds lake ecosystem have been cleaned-up.
Highlights
Radiocarbon is one of the main radionuclides discharged by nuclear industry, which, during the carbon biochemical cycle, incorporates into the tissues of living organisms and contributes to their radiation exposure. 14C produced in reactors is released directly to the environment in a gaseous form or in smaller quantities as liquid effluents [1,2]
The discharges from light-water-cooled graphite-moderated reactors (RBMK), which operated at the Ignalina Nuclear Power Plant (INPP), are of carbon dioxide form 14C [11,12] and are similar to other boiling water reactors (BWRs)
The INPP located in north-eastern Lithuania operated two RBMK-1500 units
Summary
Radiocarbon is one of the main radionuclides discharged by nuclear industry, which, during the carbon biochemical cycle, incorporates into the tissues of living organisms and contributes to their radiation exposure. 14C produced in reactors is released directly to the environment in a gaseous form or in smaller quantities as liquid effluents [1,2]. The chemical form of released radiocarbon depends on the design features of the nuclear power plant. The boiling water reactors (BWRs) and heavy water reactors (HWRs, CANDU type) as well as gas cooled reactors (HTGR, AGR, Magnox) release 14C mainly as carbon dioxide; whereas discharges from pressurized water reactors (PWRs) are dominated by hydrocarbons such as methane or ethane [1,3,4,5,6,7,8,9,10]. The discharges from light-water-cooled graphite-moderated reactors (RBMK), which operated at the Ignalina Nuclear Power Plant (INPP), are of carbon dioxide form 14C [11,12] and are similar to other BWRs. The INPP located in north-eastern Lithuania operated two RBMK-1500 units (design electric power 1500 MWe). Unit 2 was put into operation in August 1987 and shut down on 31 December 2009
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