Non-destructive measurements of natural radionuclides in building materials for radon entry rate assessment

To control the specific activity of 226Ra in building materials of operated buildings, a non-destructive in situ method consisted in measurements of gamma spectra with a fixed geometry of the detector position in a room is suggested. The calculation of the average specific activity of natural radionuclides in building materials is carried out by comparing the calculated flux density of unscattered gamma quanta normalized to the specific activity of 100 Bq/kg, and the experimentally measured count rates in the photopeak. For the measured values of the average specific activity of 226Ra in building materials, the expected values of radon concentration in rooms were calculated. The developed method has been verified for rooms in modern multi-storey energy-efficient buildings. Concentrations of 232Th and 40K in building materials which contribute to the indoor external radiation exposure can be measured by developed method also.