F. Yiou, G.M. Raisbeck, Z.Q. Zhou, Campus Orsay, France

L.R. Kilus, University of Toronto,

Nuclear Instruments and Methods 92 (1994) 436-439

Using the technique of accelerator mass spectrometry (AMS). we have measured 129I in samples of seaweed and seawater taken at various distances along the coasts from the nuclear fuel reproessing facilities at La Hague France and Sellafield. Great Britain, as well as in the North Sea and in the North Atlantic. The deduced seawater 129I/127I ratios, which vary 4 orders of magnitude. demonstrate the modest sized samples required for such measurements; less than 1 ml from the English Channel or Irish Sea, less than 1 litre in tile North Atlantic. It thus should be possible to monitor not only surface circulation but also deep water formation in this latter area, which is believed to have considerable climatic influence. Given its high sensitivity for detection, and the well defined temporal and spatial distribution of its source function. 129I is a potentially attractive addition to the available suite of oceanographic tracers.