Plutonium, americium and radiocaesium in the marine environment close to the Vandellos I nuclear power plant before decommissioning

The Vandellos nuclear power plant (NPP), releasing low-level radioactive liquid waste to the Mediterranean Sea, is the first to be decommissioned in Spain, after an incident which occurred in 1989. The presence, distribution and uptake of various artificial radionuclides (radiocaesium, plutonium and americium) in the environment close to the plant were studied in seawater, bottom sediments and biota, including Posidonia oceanica, fish, crustaceans and molluscs. Seawater, sediments and Posidonia oceanica showed enhanced levels in the close vicinity of the NPP, although the effect was restricted to its near environment. Maximum concentrations in seawater were 11.6 +/- 0.5 Bq m(-3) and 16.9 +/- 1.2 mBq m(-3) for Cs-137 and Pu-239,Pu-240, respectively. When sediment concentrations were normalized to excess (210)pb, they showed both the short-distance transport of artificial radionuclides from the Vandellos plant and the long-distance transport of Cs-137 from the Asco NPP. Posidonia oceanica showed the presence of various gamma-emitters attributed to the impact of the Chernobyl accident, on which the effect of the NPP was superimposed. Seawater, sediment and Posidonia oceanica collected near the plant also showed an enhancement of the plutonium isotopic ratio above the fallout value. The uptake of these radionuclides by marine organisms was detectable but limited. Pelagic fish showed relatively higher Cs-137 concentrations and only in the case of demersal fish was the plutonium isotopic ratio increased. The reported levels constitute a set of baseline values against which the impact of the decommissioning operations of the Vandellos I NPP can be studied. (C) 2000 Elsevier Science Ltd. All rights reserved.