backAfter the reactor accident in Fukushima which was caused by an earthquake and a subsequent tsunami in March 2011, some public concern grew with regard to additional radiation exposure. Indeed, traces of artificial radioactive substances which had their origin in Japan were detected by the German trace survey stations. The measured values, however, were uncritical and did not cause significant dose contributions due to the radionuclides deposited.
At PTB, the weekly and monthly measurements performed normally were supplemented by daily measurements in the period when the air masses were passing which contained the radionuclides released in Fukushima. The results of the daily measurements were reported to the public in coordination with the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety.
In brief, we would like to tell to you the daily processes, as performed under situations as the Fukushima accident.
Instead of dust sampling from "Monday to Monday", every day a fresh filter is fixed on the high-volume aerosol sampler. By that, the sensitivity of the measurement is decreased, but the time resolution is increased. That can be of higher importance, e. g. when a situation is rapidly varying.
Differing from the routine operation, when a sample taken from the dust sampler is left for some hours, the measurement of the daily sample is started as soon as possible. During the waiting time, the short-lived natural radionuclides of the natural decay chains of uranium and thorium would decay which hamper the detection of the artificial radionuclides. If the natural radionuclides are allowed to decay prior to the measurement the sensitivity of the measurement for artificial radionuclides will be increased. One says the "limit of detection becomes better". If the measurement result is intended to show rapid changes in the situation the measurement should be started as soon as possible.
A plausibility check is performed on the measurements and, then, they are forwarded to the coordinating laboratory at the Federal Office for Radiological Protection (Bundesamt für Strahlenschutz, BfS) as soon as possible. There, the measurements from all over Germany are compiled, radiologically assessed and, finally, reported to the public on the 
internet site of BfS. PTB and the German Meteorological Services (Deutscher Wetterdienst, DWD) also report their own results on their internet sites and refer to the radiological assessment based on the compiled data on the BfS internet site.