Published online by Cambridge University Press: 06 June 2009
The Angra dos Reis nuclear power plant site is located 130 km south from Rio de Janeiro city. Seawater is used as cooling water for both units; the cooling water is pumped from Itaorna Bay and discharged into Piraquara de Fora Bay, together with the liquid effluents from the two NPPs. Piraquara de Fora Bay belongs to a large bay system, Ilha Grande Bay and, therefore, conservative radionuclides in seawater will reach this bay with the tidal movement and, at the end, exported to open sea. Radium isotopes behave conservatively in seawater and can be applied as natural tracers to carry out dispersion studies. Two transets involving eight sampling points each were performed in Ilha Grande bay and 228Ra, 226Ra, 224Ra and 223Ra determination realized. The results have shown that the conservative radionuclide dispersion is controlled by eddy diffusion with negligible net offshore advection. The calculated eddy diffusion coefficient was 26 km2 ⋅ d-1 and 25 km2 ⋅ d-1, based on 223Ra and 224Ra respectively.