The BSH has developed a quick method for the determination of activity concentrations of Cs-137/134. At locations where a semiconductor spectrometer for an accurate determination of activity concentrations is not available, this method allows a quick determination of the Cs activity concentration of a sample.
A water sample is taken at the location of the accident and transported by helicopter or car to the BSH laboratory for analysis. Cs-137/134 is selectively enriched using an ion exchange process on potassium hexacyanocobalt(II)-ferrate (II) (KCFC). The sea water sample (40 l) is passed through an ion-exchange column packed with 10 g KCFC (400 ml/min).
The enriched KCFC flows into a measuring dish and is subjected to spectrometric analysis using an NaI detector.
The above spectrum shows a strongly magnified Cs-137 peak (662 keV). (Compare daily spectrum, without Cs enrichment, at monitoring station "Kühlungsborn" under "
Measuring data") . It represents 1986 Chernobyl fallout and is negligibly small as compared to natural potassium-40 (1460keV). The net peak area is proportional to the activity level.
Since March 1999, the BSH Rostock has routinely used the above method to analyze water samples taken at the Kühlungsborn promenade pier. By analyzing Baltic Sea water at regular intervals, it is possible to detect any inputs of artificial radionuclides by direct comparison.
The red-coloured Cs net peak area in the spectrum of 31 January 2017 shows an activity concentration of
18 mBq/l in Baltic Sea water.
Data series since March 1999:
Activity concentration of Cs-137 in the Baltic Sea (Kuehlungsborn)