Ultra Low-Level Liquid Scintillation Spectrometry, Application to Rapid Measurement and Decision Making

Franz Schönhofer

Federal Ministry for Agriculture, Forestry, Environment and Water Management, Department of Radiation Protection

Liquid scintillation spectrometry (LSC) is an excellent tool for counting of beta- and alpha-emitters. Development of new counters since 1983, which among other new features are equipped with active shield, MCA technique and alpha-beta separation, has led to very interesting applications not only in ultra low-level counting, but also to the use in other applications which were not possible before. This paper describes the use of ultra-low-level liquid scintillation counters for applications like fast survey measurements, using the advantages of these new instrumentation. Time, manpower, costs for chemicals etc. can be saved and in cases, when very quick decisions have to be made, for instance after accidents, the saying “Time is money” becomes an essential feature. The four instruments “Quantulus“, (Wallac Oy), which we have used both for routine purposes and to answer urgent, rather unconventional questions, have not only very low background, which cuts measurement time considerably, but from the pulse height spectra much information about the nature of the radionuclides present - and often about the absence of specific radionuclides - can be extracted.

Several examples will be given for the application of ultra low-level liquid scintillation spectrometers for instance concerning the Chernobyl accident, detection and identification of contamination, fast decision
of compliance of waste water from nuclear installations including a semi-quantitative determination and nuclide specific identification of contaminants, ground water contamination with artificial and natural radionuclides, incorporation of radionuclides, as well as fast drinking water surveillance and rapid determination of radon-222 in hundreds of samples within short time.