High sensitive beta- and gamma ray spectroscopy and its implications on radiation protection

The background components of NaI(Tl)- and germanium-detectors and proportional counters are described and the measures, which have to be taken to minimize them. Besides careful selection of the detector and shielding materials, of importance are the design of the anticoincidence system and the suppression of Rn and its daughters. Sensitivities of mBq, respectively a few mBq/kg for γ-spectroscopy and a few decays per day with proportional counter measurement can be achieved. Examples of environmental incorporation and accidental neutron dose monitoring are given to demonstrate the advantages of extreme low level counting in health physics. (orig.)