In situ gamma spectroscopy to characterize building materials as radon and thoron sources

Abstract In situ gamma spectroscopy is widely utilized to determine the outdoor gamma dose rate from the soil and to calculate the natural and artificial radionuclide concentration and their contribution to the dose rate. The application of in situ gamma spectroscopy in indoor environments can not supply quantitative information about activity concentration of radionuclides in building materials, but this technique can provide interesting information about building materials as radon source. In fact, a method based on analyses of gamma spectra data has been developed by the authors to provide, in field, quantitative estimation of disequilibrium in 226 Ra and 228 Ac sub-chains due to 222 Rn and 220 Rn exhalation. The method has been applied to data of gamma spectroscopy measurements carried out with HPGe detector (26%) in seven dwellings and one office in Rome. The first results of the data analysis show that, as regards especially the 226 Ra sub-chain disequilibrium, different building materials (tuff, concrete, etc.) can show very different characteristics. If, in addition to the spectrometric data, other indoor environment parameters (indoor γ dose rates, room dimensions, wall thickness, etc.) (Bochicchio et al., Radiat Prot Dosim 1994;56(1–4):137–140; Bochicchio et al., Environ Int 1996a;22:S633–S639) are utilized in a room model, an evaluation of 226 Ra, 228 Ac and 40 K activity concentration and an indication of the exhalation features, by means of estimation of exhaled 222 Rn activity concentration, can be achieved.