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Generation and investigation of defined thoron decay product reference fields for the calibration of thoron decay product measuring instruments

10.05.2006

Within the scope of a research project which will be funded until the end of 2006 by the Federal Office for Radiation Protection with a total amount of 305000,- EUR, a reference field for thoron decay products will be established at PTB.

As an extension to a research project concluded in 2003 (“Manufacture and investigation of defined thoron decay product reference fields for the calibration of thoron decay product measuring instruments “), a reference field for thoron decay products shall be established by the end of 2006 at PTB within the scope of a research project funded by the Federal Office for Radiation Protection.

Due to the considerably shorter half-life compared to that of radon (222Rn), little attention has so far been paid to the exposure by thoron emanation (220Rn) from the ground. Measurements in living and working rooms, however, show that - in addition to the decay products of radon – decay products of thoron also occur in relevant concentrations. Moreover, in the case that the activity concentrations of radon and thoron are identical, the potential alpha energy concentration of the thoron decay products is larger by a factor 13.4 than that of radon decay products. This is why thoron decay products must in specific situations and applications also been taken into account when the radiation exposure by radon isotopes is determined and evaluated.