Primary and secondary measurements of 222Rn.
In the past few years, a primary measurement system has been established at the PTB allowing absolute measurements of 222Rn. The activity can be determined by counting the emitted alpha particles in a defined solid angle after condensing the radon at a cold point under vacuum conditions. This primary measurement system is connected to a solid 226Ra source, where 222Rn can be produced up to an activity of about 2MBq. After the measurement, radon can be completely transferred into a glass bulb or a stainless steel cylinder for use as a transfer standard. The results of the measurements, the uncertainties and the realization of the primary measurement system are described. For quality assurance and fast determination of radon activity, a secondary measurement system with an NaI(Tl) detector is also used. Together, both systems provide a reliable tool for the production of gaseous 222Rn activity standards with relative uncertainties of less than 1%.
Dersch
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Physikalisch-Technische Bundesanstalt, Bundesallee 100, Braunschweig 38116, Germany.
D000512:Alpha Particles; D005740:Gases / Q000032:analysis* / Q000592:standards*; D006207:Half-Life; D011786:Quality Control; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods* / Q000592:standards*; D011886:Radon / Q000032:analysis* / Q000592:standards*; D017687:Radon Daughters / Q000032:analysis / Q000592:standards; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D005740:Gases; D017687:Radon Daughters; D011886:Radon