Evaluation and assessment of 25 years of environmental radioactivity monitoring data at Tarapur (India) nuclear site.

The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between (137)Cs in discharge canal seawater and station discharged activity and correlation of (137)Cs, (60)Co, and (131)I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of (137)Cs and (131)I in seawater versus biota are discussed. A good correlation between (137)Cs in seawater and (137)Cs in liquid waste discharged was observed (R(2) = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of (137)Cs, (131)I and (60)Co (R(2) = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean (137)Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg(-1) in soil, 0.91-0.016 Bq L(-1) in milk and 0.28-0.036 Bq kg(-1) in vegetation. Similarly, the mean (90)Sr in these matrixes decreased from 3.9 to 0.26 Bq kg(-1); 0.37-0.011 Bq L(-1) and 0.34-0.022 Bq kg(-1) respectively. Cesium-137 of about 700 microBq m(-3) was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.