Radiological survey in Tejo River (Portugal)

Nuclear and Technological Institute/Radiological Protection and Safety Unit, E.N. 10, 2685-953 Sacavém, Portugal

Corresponding author: madruga@itn.pt

Abstract

The Tejo River flows between Spain and Portugal discharging in the Atlantic Ocean. In its Spanish section receives discharges from three nuclear power plants (NPP) being the Almaraz NPP located nearby the Portuguese border. This paper summarizes and analyses the radionuclide concentrations in surface water, sediments and fish in Tejo River from the years 2001 to 2005. The surface waters, following radiochemical procedures, were analysed for total and residual beta, ¹³⁷Cs and ⁹⁰Sr by beta measurements using proportional counters and for ³H by liquid scintillation counting, after isotopic enrichment. Radionuclide concentrations were determined in sediments and fish by gamma spectrometry. The results obtained for ¹³⁷Cs and ⁹⁰Sr in surface waters are low and of the order of magnitude of the background. Regarding the ³H, the activities are higher than those obtained for other rivers. The levels of artificial and natural radionuclides in fish are below the minimum detectable activity with the exception to ⁴⁰K. For sediments, the ²²⁸Ra, ²²⁶Ra and ¹³⁷Cs concentrations increase with the decreasing of the sediment size. An opposite behaviour was observed for ⁴⁰K. The data show that the radioactivity levels in Tejo River are low and within the values measured in other Portuguese rivers except for ³H in water which values are higher due to the influence of the Almaraz NPP.