Marine environmental radioactivity near nuclear power plants in northern Taiwan

Abstract

The levels and composition of environmental radioactivity at the outlets of nuclear power plants and nearby coastal environs in northern Taiwan have been investigated by gamma spectrometric analysis of seawater, algae, fish and sediment samples collected systematically in the past four years. The results show that anthropogenic radionuclides contribute very little to the total radioactivities in all types of samples. Samples from the outlet of the Second Nuclear Power Plant are more enriched in artificial nuclides, with average algae samples containing ∼4 Bq/kg of 137Cs + 54Mn + 60Co (or 3.6% of the total activity) and average sediment samples containing ∼6 Bq/kg of 137Cs + 54Mn + 60Co (or 1% of the total activity). Compared with AEC-mandated investigation levels of 137Cs, 54Mn and 60Co for various types of environmental materials, average activities of these artificial nuclides observed to date are two to three orders of magnitude lower, well within their regulatory limits. The ultimate source of 137Cs in the survey area is most likely atmospheric fallout derived from weapons tests during the 1950's and 1960's. As regards 54Mn and 60Co, they were inevitably emitted from nuclear power pants, largely during or after the period of power outages for scheduled maintenance of reactors. Thus far, we have not detected any traces of 54Mn and 60Co beyond the outlets of the first and the second nuclear power plants, suggesting that the dispersal of reactor-produced artificial nuclides is highly restricted and well controlled.