1. Department of Geosciences, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden
2. International Atomic Energy Agency, Department of Safeguards, 1220 Vienna, Austria
3. Strålsäkerhetsmyndigheten, Swedish Radiation Safety Authority, SE-171 16 Stockholm, Sweden
4. Department of Medical Physics, Department of Medical and Health Sciences, Linköping University, SE-581 83 Linköping, Sweden