I-129 in the oceans: origins and applications

The quantity of the long lived (half-life 15.7 million years) radioactive i sotope I-129 in the pre-nuclear age ocean was similar to 100 kg. Various nu clear related activities, including weapons testing, nuclear fuel reprocess ing, Chernobyl and other authorized or non-authorized dumping of radioactiv e waste have increased the ocean inventory of I-129 by more than one order of magnitude. The most important of these sources are the direct marine dis charges from the commercial reprocessing facilities at La Hague (France) an d Sellafield (UK) which have discharged similar to 1640 kg in the English C hannel, and similar to 720 kg in the Irish Sea, respectively. We discuss ho w this I-129 can be used as both a 'pathway' and 'transit time' tracer in t he North Atlantic and Arctic oceans, as well as a parameter for distinguish ing between reprocessed and non-reprocessed nuclear waste in the ocean, and as a proxy for the transport and dilution of other soluble pollutants inpu t to the North Sea. (C) 1999 Elsevier Science B.V. All rights reserved.