Environmental Carbon-14 Monitoring in Marine Ecosystems Near Nuclear Power Plants – A Methodological Intercomparison of Accelerator Mass Spectrometry, Liquid Scintillation Counting, and SCAR Spectroscopy

Sammanfattning

Environmental monitoring of Carbon-14 around nuclear power plants (NPPs) has traditionally prioritized gaseous emissions, leaving waterborne liquid discharges unmonitored due to low nominal volumes (<0.5%) and analytical challenges using traditional techniques. However, liquid releases do not experience as effective dilution as gas releases, instead discharging directly into coastal ecosystems where Carbon-14 accumulates in marine organisms, raising localized specific activities above regional background levels. This thesis presents a methodological intercomparison evaluating three analytical technologies for marine monitoring: Accelerator Mass Spectrometry (AMS), Liquid Scintillation Counting (LSC), and laser-based Saturated-Absorption Cavity Ring-down Spectroscopy (SCAR). Biological and environmental samples collected near the Ringhals NPP cooling water outlets were analyzed across five international facilities in Lund (Sweden), Debrecen (Hungary), Mangalore (India), Borås (Sweden), and Florence (Italy). The technologies were evaluated based on, for example, precision, sample throughput, investment costs, labor requirements, and automation. Findings confirm that while AMS offers superior precision, its high capital costs make it impractical for routine industrial use. Traditional LSC has low investment barriers but suffers from throughput limitations due to intensive manual chemistry and long decay-counting times. The more recent addition to the market, SCAR spectroscopy, effectively bridges this gap; by analyzing carbon dioxide gas directly and eliminating graphitization, it delivers near-AMS precision, high automation, and rapid turnaround times for a fraction of the capital investment. The study concludes that routine liquid emission monitoring using automated systems like SCAR is fully justified under the ALARA principle to ensure transparency, public safety, and institutional trust.