14C in the environment of Swiss nuclear installations

Abstract

The results of a 10-yr survey of 14C content in tree leaves from the vicinity of Swiss nuclear installations are reported. The interpretation is based on the results from a reference station showing a systematic decrease from Δ14C=+350‰ in 1997 to ca+190‰ in 1987. Excess activities of up to ca 100‰ are observed in the vicinity of nuclear power plants which are compatible with release rates and dilution calculations. A higher excess of up to 1400‰ is measured in the close vicinity of a small research plant which releases the activity on top of the roof. The determined decrease of the activity with distance can be described by a power law with c-1.4 in the exponent. Additional doses of 14C to plants and population from excess 14C activities are estimated to be negligible compared to natural doses. -Authors