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VERMI Workshop on "Source Preparation in Radionuclide Metrology"


In November 2007, a three-day meeting was held in Braunschweig with participants of the LNE-LNHB (France), NPL (Great Britain), IRMM (European Commission) and PTB (Germany) in the scope of the Virtual European Radionuclide Metrology Institute (VERMI). VERMI was called into being by the aforementioned institutes, above all, to sustain the knowledge gained over decades in the field of radionuclide metrology in Europe. Several workshops have already been organised by VERMI for this purpose, including block events in Paris, Geel and Varna each lasting for several days, which included an intensive training programme focussing on the areas of primary and secondary standard measuring procedures.

This workshop organised at the PTB was exclusively dedicated to the preparation of radioactive sources. Source preparation plays a fundamental role in activity measurements as preparation techniques and the characteristics of the sources significantly influence the uncertainties of the activity. The sources for the classical coincidence measurements are e.g. produced by dropping weighed amounts of a radioactive solution onto a very thin foil. During production, an absorption of ionising radiation within the source which is as low as possible, as well as a distribution of the activity over the active source surface which is as uniform as possible, are usually aimed at. The source characteristics depend very much, among other things, on the pre-treatment of the support, the drying up process and chemical aspects.

An intensive exchange of experience which was especially supported by joint practical experiments took place within the workshop. In the frame of demonstrations in the lab, important details could be debated and the participants' various approaches to routine source production could be discussed. Experiments with a sample dryer supplied by IRMM as well as the discussion on the advantages and disadvantages of freeze drying were focal points.

Other topics were: the production of thin sources using electrolytic separation, sources for liquid scintillation counting, weighing procedures, the characterisation and evaluation of sources e.g. by autoradiography and microscopy, chemical questions and uncertainties. Producing samples in environmental radioactivity and producing radioactive gas sources were also discussed.

Apart from the above, laboratory tours and a lively exchange of experience between all those involved - who, above all, would like the contact to continue and have other similar meetings - took place in the scope of the event.