[en] Compact, low energy accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for the analysis of heavy and long lived radionuclides. In this study, we will first focus on the analytical capabilities of the compact AMS system TANDY, mainly for "2"3"6U analyses, and then present a new dual tracer approach, that combines "1"2"9I and "2"3"6U. The measured "1"2"9I/"2"3"6U ratios of samples collected in the North Sea in 2009 are in reasonable agreement with the expectations from documented or estimated releases from the two major nuclear reprocessing plants located at Sellafield (GB) and La Hague (F), suggesting that the "1"2"9I/"2"3"6U ratio can be used as a water mass tag in the North Atlantic region. However, our results indicate that, in contrast to "1"2"9I, additional contributions of bomb produced "2"3"6U cannot be neglected in the North Sea region. This complicates the simple and straight forward use of the "1"2"9I/"2"3"6U ratio as a quantitative tool for the calculation of transport times of North Sea water in the Arctic Ocean.